Applications of Research from the U.S. Geological Survey 

Program, Assessment of Regional Earthquake Hazards 

and Risk Along the Wasatch Front, Utah

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1519

Contributions from Utah Geological Survey, Utah Division of Comprehensive 

Emergency Management, University of Utah, and Utah State University

f

vum: 

-
COVER PHOTOGRAPH Oblique aerial view looking east at theWasatch fault zone below Spanish Fork 

Peak near Mapleton, Utah. The fault is the high west-facing curvilinear scarp. The flat bench at the 

base of the faceted range front is the Bonne ville shoreline. Geological studies at this location indicate 

that the most recent large magnitude surface faulting earthquake occurred about 650 years ago. 

(Photograph by Woodward-Clyde and Associates, 1969.)
Applications of Research from the 

U.S. Geological Survey Program, 

Assessment of Regional Earthquake 

Hazards and Risk Along the 

Wasatch Front, Utah

Edited by PAULA L. GORI

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1519

Contributions from 

Utah Geological Survey, 

Utah Division of Comprehensive 

Emergency Management, 

University of Utah, and 

Utah State University

This report documents how pertinent 

information about earthquake hazards 

along the Wasatch Front, Utah, was 

transferred to researchers, public 

officials, design professionals, land-use 

planners, and emergency managers as 

part of the U.S. Geological Survey's 

effort to mitigate the effects of 

earthquake hazards.

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1993
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade, product, or firm names in this publication is for

descriptive purposes only and does not imply endorsement by the

U.S. Government

Library of Congress Cataloging in Publication Data

Applications of research from the U.S. Geological Survey program, assessment of regional earthquake hazards and risk along the 

Wasatch Front, Utah/edited by Paula L. Gori.

p. cm. (U.S. Geological Survey professional paper ; 1519) 

Includes bibliographical references.

1. Earthquake hazard analysis Wasatch Eange (Utah and Idaho) 2. Seismology Wasatch Eange (Utah and Idaho) 

3. Natural disasters Utah. 4. Faults (Geology) Wasatch Eange (Utah and Idaho) 5. Geology, Stratigraphy. 

6. Geology Wasatch Eange (Utah and Idaho) I. Gori, Paula. II. Series. 

QE535.2.U6A66 1993

551.2'2'09792201-dc20 91^180

CIP

For sale by U.S. Geological Survey, Map Distribution

Box 25286, Bldg. 810, Federal Center

Denver, CO 80225
PREFACE

In 1983, the U.S. Geological Survey (USGS) targeted the Wasatch Front, 

Utah, for a multiyear program that focused on earthquake hazards research and 

hazards reduction. This report represents the transfer of pertinent information 

about earthquake hazards along the Wasatch Front to researchers, public 

officials, design professionals, land-use planners, and emergency managers as 

part of the USGS effort to mitigate the effects of earthquake hazards. An earlier 

report, USGS Professional Paper 1500, "Assessment of Regional Earthquake 

Hazards and Risk Along the Wasatch Front, Utah, A-J and K-Z," contained the 

results of much of the research and experiences of the program from 1983 to 1988. 

This report contains the results of research and experiences undertaken during 

the later phases of the Wasatch Front program.

Professional Paper 1500 defined the nature of the earthquake hazards in the 

Wasatch Front, including tectonic framework and earthquake potential, groundshaking hazards and the estimated losses, and the use of earthquake hazards 

information for urban and regional planning. This Professional Paper complements the first report by presenting examples of how the research and experiences were applied at the local level.

Application of scientific information to further earthquake hazards reduction 

was one of the goals of the USGS program in the Wasatch Front. Presented in 

this report is an explanation of how new information was incorporated into policy 

and practice and how new information about the earthquake hazards was 

specifically applied in Utah. This report, therefore, is a compendium of information developed at the local level to reduce the earthquake hazards of surface-fault 

rupture, landslides and debris flows, liquefaction, and tectonic subsidence with an 

explanation of the methodologies followed to encourage the organization and 

application of scientific information. The authors who have contributed to this 

report represent the many disciplines and levels of government that participated 

in this multidisciplinary cooperative program.

Paula L. Gori, Editor

in
CONTENTS

Page

Preface.............................................................................. Ill

Interactive Workshops: Essential Elements of the Earthquake

Hazards Research and Reduction Program in the

Wasatch Front, Utah

By Paula L. Gori....................................................... 1

Introduction.................................................................. 1

Utah Regional Earthquake Hazards Assessment Program.... 2

The Role of Interactive Workshops................................... 3

Interactive Workshops in Utah ........................................ 5

Conclusion.................................................................... 10

References ................................................................... 11

Appendix A.................................................................. 12

Reducing Earthquake Hazards in Utah: The Crucial

Connection Between Researchers and Practitioners

By William J. Kockelman........................................... 16

Introduction and Purpose................................................ 16

Acknowledgments.......................................................... 22

Toward the Connection in Utah ....................................... 22

Translation for Practitioners............................................ 26

Examples of Successful Translation in Utah....................... 30

Transfer to Nontechnical Users........................................ 40

Examples of Successful Transfer in Utah........................... 45

Evaluation and Revision ................................................. 64

Conclusion.................................................................... 67

References ................................................................... 68

Public Perceptions of the Implementation of Earthquake

Mitigation Policies Along the Wasatch Front in Utah

By Gary E. Madsen, Loren R. Anderson, Jerold H.

Barnes, and Genevieve Atwood ................................... 75

Introduction.................................................................. 75

Acknowledgments.......................................................... 76

Methodology................................................................. 76

Results of the Surveys ................................................... 76

Application of Research Findings to Implementation of

Earthquake Hazard Reduction on the Wasatch Front.... 80

References ................................................................... 80

A Data Base Designed for Urban Seismic Hazards Studies

By Arthur C. Tarr ..................................................... 82

Introduction.................................................................. 82

Acknowledgments.......................................................... 82

Summary of Methods ..................................................... 82

Data Base Management System....................................... 83

Benefits and Costs of a Data Base Management System....... 84

Design Objectives.......................................................... 84

Data Base Design Considerations ..................................... 84

Example of Relational Organization.................................. 85

Data Files in the Data Base ............................................ 87

Implementation of the Data Base ..................................... 88

References ................................................................... 88

Appendix A: Urban Hazards Data Base File Structures....... 89

A Mapping of Ground-Shaking Intensities for Salt Lake 

County, Utah 

By Philip C. Emmi................................................

Introduction..............................................................

Acknowledgments......................................................

Measurement of Ground Shaking..................................

General Model for the Assessment of Ground-Shaking 

Hazards .............................................................

Points of Departure Data and Relationships .................

Comparison of Alternative Methods..............................

References ...............................................................

Appendix A: Abbreviated Description of the Modified 

Mercalli Intensity Scale ........................................

Appendix B: The Interpretation of Technical Statements 

of Risk............... ................................................

Appendix C: Use of Computer Mapping and GIS

Methodologies.....................................................

Wasatch Front County Hazards Geologist Program

By Gary E. Christenson .........................................

Introduction..............................................................

Acknowledgments......................................................

Description of the Program .........................................

Accomplishments.......................................................

Evaluation and Suggestions.........................................

Conclusions...............................................................

References ...............................................................

Surface-Fault Rupture: A Guide for Land-Use Planning, 

Utah and Juab Counties, Utah 

By Robert M. Robison ...........................................

Introduction..............................................................

Acknowledgments......................................................

Characteristics of the Wasatch Fault Zone .....................

Consequences of Surface-Fault Ruptures and Reduction 

of Hazards..........................................................

Use of Special Study Zone Maps ..................................

Scope of Site Investigations.........................................

References ...............................................................

Landslide Hazards: A Guide for Land-Use Planning, Davis 

County, Utah 

By Robert M. Robison and Mike Lowe ....................

Introduction..............................................................

Acknowledgments......................................................

Landslide Characteristics............................................

Consequences............................................................

Landslide Susceptibility..............................................

Reducing Landslide Hazards .......................................

Summary of Methods Used in Map Preparation ..............

Recommended Use of Maps for Land-Use Planning and 

Development.......................................................

Page

91

91

91

91

95

96

100

106

109

111

112

114

114

115

115

117

119

119

120

121

121

122

122

125

125

125

128

129

129

129

129

130

131

131

131

133
VI CONTENTS

Page

Landslide Hazards: A Guide for Land-Use Planning, Davis

County, Utah Continued 

Scope of Site Investigations........................................... 136

References ................................................................. 137

Rockfall Hazards: A Guide for Land-Use Planning, Salt Lake

County, Utah

By Craig V. Nelson.................................................. 138

Introduction................................................................ 138

Acknowledgments........................................................ 138

Characteristics of Rockfalls ........................................... 138

Effects of Rockfalls...................................................... 138

Evaluating Rockfall Susceptibility .................................. 139

Reducing Rockfall Hazards............................................ 139

Use of Rockfall Hazard Special Study Area Maps ............. 140

Scope of Site Investigations........................................... 141

Summary................................................................... 142

References ................................................................. 142

Debris-Flow Hazards: A Guide for Land-Use Planning, Davis

County, Utah

By Mike Lowe......................................................... 143

Introduction................................................................ 143

Acknowledgments........................................................ 144

Nature and Causes of Debris Flows................................ 144

Effects of Debris Flows ................................................ 144

Debris-Flow Hazard Reduction...................................... 145

Summary of Methods Used in Map Preparation................ 148

Recommended Use of Maps in Land-Use Planning............ 148

Scope of Site Investigations........................................... 149

References................................................................. 150

Liquefaction Hazards: A Guide for Land-Use Planning, Davis

County, Utah

By Mike Lowe......................................................... 151

Introduction................................................................ 151

Acknowledgments........................................................ 151

Liquefaction Hazards: A Guide for Land-Use Planning, Davis

County, Utah Continued 

Nature of the Liquefaction Hazard ................................. 152

Reduction of Liquefaction Hazards ................................. 153

Information for Davis County on Liquefaction Potential..... 154

Recommended Use of Maps in Land-Use Planning............ 155

Scope of Site Investigations........................................... 156

References................................................................. 156

Tectonic Subsidence Hazard: A Guide for Land-Use Planning, 

Utah and Juab Counties, Utah 

By Robert M. Robison ............................................. 158

Introduction................................................................ 158

Acknowledgments........................................................ 158

Characteristics of Tectonic Subsidence ............................ 158

Mitigation................................................................... 159

Use of Hazard Maps..................................................... 162

Scope of Site Investigations........................................... 162

References ................................................................. 162

Hazards from Earthquake-Induced Ground Failure in

Sensitive Clays, Vibratory Settlement, and Flooding 

Due to Seiches, Surface-Drainage Disruptions, and 

Increased Ground-Water Discharge, Davis County, Utah 

By Mike Lowe......................................................... 163

Introduction................................................................ 163

Acknowledgments........................................................ 163

Ground Failure Due to Loss of Strength in Sensitive

Clays................................................................... 163

Subsidence Caused by Vibratory Settlement in Granular

Materials.............................................................. 164

Flooding Caused by Seiches in Great Salt Lake ................ 165

Flooding Due to Surface-Drainage Disruptions During

Earthquakes......................................................... 166

Increased Ground-Water Discharge Due to Earthquakes.... 166

Conclusions and Recommendations ................................. 166

References................................................................. 166

ILLUSTRATIONS

FIGURE 1. Five components needed for an effective comprehensive earthquake hazard reduction program .................................. 17

2. Example of a table showing average recurrence intervals ..................................................................................... 30

3. Part of a cadastral map of Salt Lake County showing a surface-fault rupture zone and the potential liquefaction areas... 32

4. Map showing three levels of ground shaking on alluvium relative to bedrock ........................................................... 33

5-8. Parts of topographic maps showing:

5. Utah County, areas with high, moderate, low, and very low potential for liquefaction corresponding to the

probability of exceeding a critical acceleration .................................................................................. 34

6. Davis County, Utah, potential for earthquake-induced landslides and liquefaction ........................................ 35

7. Salt Lake and Tooele Counties, mountain spur areas susceptible to rockfalls ............................................... 37

8. Northern Juab Valley, Utah, potential consequences of tectonic deformation along the Nephi segment of the

Wasatch fault.............................................................................................................................. 38

9. Topographic map of Ogden/Pineview, Utah, study area showing inundation area from a failure of Pineview Dam .......... 39

10. Part of a final performance report on educational, advisory, and review services over a 6-month period....................... 46

11-17. Illustrations of transfer techniques:

11. Part of the table of contents from a workshop proceedings ....................................................................... 48

12. Typical cover of a serial publication that addresses geologic hazard and resource issues ................................ 49

13. Typical article reporting on the status of the Utah Earthquake-Hazard Reduction Program in the

Wasatch Front Forum.......... ........................................................................................................ 50

14. Example of materials provided to students, teachers, and the general public under an outreach program by

the Utah Museum of Natural History.............................................................................................. 51

15. Example of a general fact sheet widely distributed in Utah ..................................................................... 53
CONTENTS VII

FIGURES 11-17. Continued Page

16. Typical press release by the USGS Public Affairs Office ......................................................................... 54

17. Typical local newspaper coverage of earthquake hazard reduction activities................................................ 55

18. Status of geologic hazard maps and texts being produced by county geologists as of June 1988.................................. 56

19-22. Examples of transfer and/or reduction techniques:

19. Letter addressing a specific issue in Utah............................................................................................. 58

20. Guidelines for evaluating a hazard and preparing reports in Utah............................................................. 60

21. Matrix with recommendations for site-specific stability analysis for critical facilities and other land uses

in several hazard zones................................................................................................................ 62

22. Topical outline for geologic hazards ordinances in areas with and without geologic hazards maps ................... 63

23. Rankings by key public and private decisionmakers as to the relative seriousness of 18 State and local issues for

three States and three cities..................................................................................................................... 67

24. Cross section of hypothetical seismic ground response study area ......................................................................... 83

25. Relationships of terms used in three different representations of data in a data base................................................ 85

26. Seismic stations and boreholes in a hypothetical area where seismic response studies are conducted........................... 85

27. Tables showing station and borehole data.......................................................................................................... 86

28. Examples of many-to-one and one-to-many pointer relationships among records in hypothetical STATION,

RESPONSE, and EVENT relations .......................................................................................................... 87

29. Relationships of data files in the geotechnical data base....................................................................................... 87

30. The S16°E component horizontal accelerogram recorded at Pacoima Dam and the velocity and displacement

seismograms derived from it; 1971 San Fernando, Calif., earthquake............................................................... 93

31. Derivation of the harmonic oscillator response at 0.33-Hz and 2.0-Hz frequency from a velocity seismogram and the

role in the construction of a pseudo-relative velocity response spectrum........................................................... 94

32. Velocity seismograms for three Salt Lake City locations exemplifying site amplification during low-amplitude ground

motions initiated by a low-strain event that induced linearly elastic relative site responses ................................. 96

33, 34. Graphs suggested by various authors to show functional relationships between MMI and the logarithm of peak 

horizontal acceleration measured in: 

33AandS. Units of gravity .................................................................................................................... 99

34. Centimeters per second.......................................................................................................... 99

35-37. Graphs showing:

35. A functional relationship between ground-motion amplification ratios and intensity increments for nearby 

soil sites that can be added to estimates of MMI at the reference rock site to obtain MMI estimates 

for soil sites............................................................................................................................... 100

36. A comparison of curves defining the relationship between ground-motion amplification ratios and rock-site

intensity increments.................................................................................................................... 100

37. A comparison of estimates of MMI with a 10 percent chance of being exceeded over a 10-, a 50-, and a 250-yr

exposure period by valley location within Salt Lake County, Utah...................................................... 101

38. Maps showing microzonations of MMI for the urbanizable area of Salt Lake County, Utah........................................ 103

39, 40. Graphs showing estimated loss to:

39. Selected structures as a function of MMI.............................................................................................. 110

40. Selected lifelines as a function of MMI ................................................................................................. 110

41. Functions describing the probabilities with which events of different intensity might occur over various exposure

periods.................................................................................................................................................. Ill

42. Illustration of a graphic overlay technique using a geographic information system ................................................... 113

43. Location map................................................................................................................................................ 116

44. Map showing the location of Utah and eastern Juab Counties, Utah...................................................................... 122

45. Schematic diagram of the Wasatch fault zone showing the relation of the epicenter to the focus and the trace of the

surface-fault rupture................................................................................................................................ 122

46. Sketch showing schematic diagram of a normal fault showing features typical of the Wasatch fault zone near the

ground surface........................................................................................................................................ 123

47, 48. Maps showing:

47. Boundaries and names for the Wasatch fault zone segments .................................................................... 124

48. The Wasatch fault zone at the mouth of Rock Canyon, Utah.................................................................... 126

49. Schematic diagram of recommended minimum setback distances relative to fault scarps in areas where trenching

studies are not performed......................................................................................................................... 127

50. Block diagram of a rotational landslide.............................................................................................................. 130

51. Location map for figures 52, 53, and 54............................................................................................................. 132

52-54. Maps showing:

52. Landslide inventory for the Centerville and northern Bountiful area of southern Davis County, Utah ............ 133

53. Landslide hazards for the Centerville and northern Bountiful area of southern Davis County, Utah............... 134

54. Earthquake-induced landslide potential for the Centerville and northern Bountiful area of southern Davis

County, Utah............................................................................................................................. 135

55, 56. Location maps of:

55. The August 14, 1988, San Rafael Swell, Utah, earthquake ...................................................................... 139

56. The July 3, 1984, Dead Horse Point rockfall.......................................................................................... 140
VIII CONTENTS

Page

FIGURE 57. Article from the Utah Geological and Mineral Survey Survey Notes, spring 1987..................................................... 141

58. Example of the output model generated by the computer program ROCKFALL for a rockfall event on a

generalized slope..................................................................................................................................... 141

59. Portion of the rockfall hazards special study area map in the Draper Quadrangle, southeast of Salt Lake City,

Utah..................................................................................................................................................... 142

60, 61. Location maps for:

60. Debris basins in Davis County............................................................................................................ 147

61. Figure 62 ........................................................................................................................................ 148

62. Example of a debris-flow hazard special study zone map for the east Layton area of northern Davis County, Utah....... 149

63-66. Diagrams showing:

63. Tilting of a building due to liquefaction and loss of bearing strength in the underlying soil............................ 152

64. Liquefaction-induced ground oscillation ................................................................................................ 152

65. Lateral spread ................................................................................................................................. 153

66. Flow failure..................................................................................................................................... 153

67-71. Maps showing:

67. Location for figure 68........................................................................................................................ 154

68. Liquefaction-potential map for the Centerville and northern Bountiful area of southern Davis County............ 155

69. Location of Utah and northeastern Juab Counties.................................................................................. 159

70. Surface rupture and tectonic subsidence accompanying a hypothetical earthquake along the Wasatch

fault zone.................................................................................................................................. 160

71. Area of potential tectonic subsidence in part of Utah Valley .................................................................... 161

TABLES

TABLE 1. Rankings by local government planners and building officials as to potential damage from earthquake hazards in Salt Lake

Valley............................................................................................................................................................ 77

2. Perceptions of the likelihood of a future damaging earthquake in the Salt Lake Valley: Comparison of local technical

officials and public residents.............................................................................................................................. 77

3. Concern of public residents about a future serious earthquake occurring in Salt Lake Valley ............................................. 78

4. Policies to reduce earthquake risks in the Salt Lake Valley: Comparison of local technical officials and public

residents........................................................................................................................................................ 79

5. Estimates of Modified Mercalli Intensity for the edge and center of the Jordan River Valley, Utah, using six different

methods of estimation....................................................................................................................................... 101

6. A cross classification of surficial geologic units with site amplification factors .................................................................. 102

7. Percentage of time spent on various tasks by the county geologists ............................................................................... 118

8. Data for the Wasatch fault zone in Utah and northeastern Juab Counties ....................................................................... 124

9. Relationship between ground displacement and damage to structures............................................................................. 131

10. Earthquake-induced landslide potential categories, soil moisture levels considered, probability of exceedence of critical

acceleration needed to cause failure during 100-yr period, and possible magnitudes of displacement.............................. 136

11. Recommended requirement for site-specific investigations of slope stability for various classes of facilities proposed within

Davis County, Utah......................................................................................................................................... 136

12. Recommended requirement for site-specific investigations of seismic slope stability for various classes of facilities in

different earthquake-induced landslide-potential zones ........................................................................................... 136

13. Historical Davis County debris flows ........................................................................................................................ 143

14. Alluvial-fan sedimentation intensity scale................................................................................................................... 145

15. Matrix indicating recommended report requirements for debris-flow hazards, Davis County, Utah ..................................... 148

16. Ground slope and expected failure mode resulting from liquefaction............................................................................... 152

17. Relationship between ground displacement and damage to structures............................................................................. 153

18. Criteria used to evaluate liquefaction potential........................................................................................................... 156

19. Matrix indicating recommended report requirements for liquefaction hazards, Davis County, Utah..................................... 156
APPLICATIONS OF RESEARCH FROM THE

U.S. GEOLOGICAL SURVEY PROGRAM,

ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND 

RISK ALONG THE WASATCH FRONT, UTAH

INTERACTIVE WORKSHOPS: ESSENTIAL ELEMENTS OF THE 

EARTHQUAKE HAZARDS RESEARCH AND REDUCTION PROGRAM

IN THE WASATCH FRONT, UTAH

By PAULA L. GORI

ABSTRACT

Interactive workshops provided the forum and stimulus necessary to 

foster collaboration among the participants in the multidisciplinary, 

5-yr program of earthquake hazards reduction in the Wasatch Front, 

Utah. The workshop process validated well-documented social science 

theories on the importance of interpersonal interaction, including 

interaction between researchers and users of research to increase the 

probability that research will be relevant to the user's needs and, 

therefore, more readily used.

INTRODUCTION

Communication and collaboration between researchers 

and users of research are essential in a complex, multidisciplinary, multiyear program. The program of earthquake hazards research and reduction focused in the 

Wasatch Front, Utah, was such a program. In the early 

planning phase of the program, it was evident immediately that, if hazards reduction was to be successful, 

researchers from the U.S. Geological Survey (USGS), 

the Utah Geological Survey1 (UGS), the University of 

Utah, and other State and academic institutions, as well 

as officials from State and local governments, Federal 

agencies, and private organizations, would need to play 

active roles in the 5-yr research and implementation 

program. Coordination of USGS efforts would be a 

complex undertaking in and of itself, with researchers

Manuscript approved for publication April 15, 1991.

1The Utah Geological Survey was previously called the Utah Geological and 

Mineral Survey (UGMS).

from Menlo Park, Calif.; Golden, Colo.; Reston, Va.; and 

Salt Lake City, Utah, representing many different parts 

and tasks of the agency.

At the onset of the program in 1983, representatives 

of the major institutions in the program (USGS, UGS, 

Utah Federal Emergency Management Agency 

(FEMA), Utah Comprehensive Emergency Management (GEM), and University of Utah) endorsed a strategy of convening annual, interactive workshops to 

review progress of the program and to recommend 

further research and implementation activities. Proceedings of annual workshops were chosen as vehicles to 

communicate findings of researchers and experiences of 

public officials and professionals to others who were 

unable to attend.

The annual workshop was not a new experience for 

USGS or FEMA. Both agencies had, since 1980, convened earthquake-related workshops responding in part 

to an Office of Science and Technology report that stated, 

"It is crucial, then, that Federal agencies that produce 

hazards information collaborate with program and local 

officials as they develop policies and procedures. Furthermore, research shows that, whenever possible, 

interaction among Federal, State, and local officials 

should take place on a face-to-face basis" (Office of 

Science and Technology Policy, p. 182). Prior success 

with the process of convening interactive workshops and 

the shortage of travel funds for non-Utah-based participants mandated the use of large, annual workshops to 

communicate findings and experiences, recommend
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

future research and implementation activities, galvanize 

support for earthquake-related policy, and energize the 

participants and communities in the program.

This paper evaluates the effectiveness and importance 

of the workshop process in the overall program by 

providing an assessment of the role and value of the 

interactive workshops in the 5-yr program of hazards 

research and hazards reduction in the Wasatch Front 

area. The assessment will be valuable to (1) USGS in its 

long-term planning of future multidisciplinary focused 

research and implementation programs, (2) participants 

in the ongoing Utah program, and (3) other institutions 

that will be undertaking long-term, complex programs 

that involve information transfer. This paper is not an 

evaluation of the focused research and implementation 

program in the Wasatch Front area. That evaluation will 

be best undertaken at a later date, upon completion of 

the program and after sufficient time has elapsed to allow 

for implementation of earthquake hazards information 

and research into public and private policy.

This paper shows that interactive workshops during 

the Utah program provided the forum and stimulus 

necessary to foster collaboration between participants in 

the program, energized the participants, and reduced the 

time necessary to implement a complex interdisciplinary 

program of earthquake hazards reduction. The next 

section describes the Utah Regional Earthquake Hazards Assessment Program. Literature regarding the 

effectiveness of workshops in facilitating collaboration 

between users of research and researchers is reviewed, 

and the workshop process and the results of interviews 

and surveys of participants in the program are described 

in context. In the final section, conclusions are drawn 

from interviews and surveys, and observations are made 

about the usefulness and importance of interactive workshops to the focused earthquake hazards research and 

reduction program in the Wasatch Front, Utah.

UTAH REGIONAL EARTHQUAKE HAZARDS 

ASSESSMENT PROGRAM

More than 80 percent of Utah's 2 million people are 

located along the Wasatch Front. A large earthquake 

centered near Salt Lake City has the potential to cause 

extensive damage to buildings, lifelines, and public facilities. The October 28, 1983, Borah Peak, Idaho, magnitude (Ms) 7.3 earthquake demonstrated that large earthquakes occur in the Intermountain Seismic Belt, where 

the Wasatch Front is situated.

In 1983, USGS targeted the Wasatch Front for the 

5-yr Utah Regional Earthquake Hazards Assessment 

Program. The goals of the program were to (1) accelerate 

the development of a knowledge base on seismic sources,

size, frequency of occurrence, and physical effects of 

earthquakes in a 10-county area along the Wasatch 

Front, including Salt Lake, Davis, Juab, Weber, 

Wasatch, Summit, Morgan, Cache, Utah, and Box Elder 

Counties, and (2) foster implementation of earthquake 

hazards mitigation measures (Hays and Gori, 1984, p. 

17-22). The goals were to be tackled simultaneously by 

subdividing the effort into the following five components:

1. Development of information systems for use in earthquake hazards evaluations, risk assessment, and 

implementation of loss reduction measures.

2. Synthesis of new and existing geological and geophysical data needed for the evaluation of earthquake 

hazards.

3. Development of ground-motion models and maps of 

the ground-shaking hazard.

4. Development of models for loss and casualty estimates for urban areas.

5. Implementation of measures to mitigate earthquake

hazards.

To carry out these objectives successfully, the program required the participation of a diverse set of 

institutions. The major institutions that participated in 

the program were

U.S. Geological Survey 

Geologic Division 

Mapping Division

Federal Emergency Management Agency 

National Headquarters 

Region VIII

Utah Geological Survey

Utah Division of Comprehensive Emergency 

Management

University of Utah 

Utah State University

Numerous other organizations and individuals participated in the program from its inception in 1983, including 

but not limited to county and city planners; State, 

county, and local government officials; engineers; consulting geologists; and representatives from USGS Division of Water Resources, U.S. Bureau of Reclamation, 

U.S. Corps of Engineers, local utilities, private colleges 

and universities, and the media.

The major participants agreed on six strategies to 

meet their shared goals of increasing the level of understanding of the seismic hazards in the Wasatch Front and 

implementing earthquake hazards mitigation measures. 

The six strategies were as follows: 

1. USGS and UGS would foster strong partnerships

with universities, the private sector, units of local

government, and other State and Federal agencies.
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM

2. Results of past research studies would be used to the 

fullest extent possible.

3. Ten counties along the Wasatch Front would be 

studied. Although Salt Lake, Davis, Utah, and Weber 

Counties would receive primary attention because of 

their population density, potential risk, and the availability of information from prior and ongoing research 

studies, Cache, Box Elder, Summit, Wasatch, and 

Juab Counties would also be studied.

4. Each year, a workshop would be held in Salt Lake 

City to review the year's progress and recommend 

future research.

5. Proceedings of the workshops, which would include 

papers documenting results from all research projects 

in the Wasatch Front, would be published as USGS 

open-file reports. A USGS professional paper, including the major research findings, would be published at 

the conclusion of the program.

6. Knowledge gained from earthquakes such as the one 

at Borah Peak, Idaho, in October 1983 would be used 

to improve the methodology currently used to evaluate earthquake hazards and to assess risk in the 

Wasatch Front area. Earthquakes in other parts of 

the world that share a similar tectonic setting would 

be investigated to provide insight into the characteristics of ground-shaking and the physical effects that 

might occur in a major earthquake (Hays and Gori, 

1984, p. 21-22).

Especially significant is the fact that planners of the 

Regional Earthquake Hazards Assessment Program 

decided early in the process to convene annual workshops in Salt Lake City to review accomplishments each 

year and to plan future activities. In fact, three of the six 

strategies depended on workshops. Strategy 1, formation of partnerships, relied on the workshop process 

because only through an interactive process could strong 

partnerships be initiated and maintained. Workshops 

provided that arena and, as will be discussed below, 

helped form bonds between participants. Strategy 4 

called for annual workshops to be convened, and strategy 

5 suggested that proceedings from the annual workshops 

be used to disseminate research results and results from 

hazard mitigation activities. Therefore, workshops were 

designated from the beginning of the program to fulfill 

important functions.

The Regional Earthquake Hazards Assessment Program constituted a major effort of the USGS Office of 

Earthquakes, Volcanoes, and Engineering and of UGS 

and resulted in programmatic changes. A large number 

of scientists from the USGS Branch of Geologic Risk 

Assessment and scientists from other branches conducted research on the Wasatch Front area during the 

program. UGS, with funds from USGS and the State, 

substantially increased its efforts of earthquake hazards

assessment, mapping, and information dissemination 

during the program. Similarly, FEMA and GEM 

increased attention on and funding for earthquake hazards. During the program, the Office of Earthquakes, 

Volcanoes, and Engineering funded universities and 

private firms through its external research program to 

conduct research in the Wasatch Front area in tandem 

with its internal research program. FEMA funded State 

and local organizations to implement loss reduction activities in the area. As an indication of how many were 

intimately involved in the program, 60 individuals contributed one or more articles to the USGS professional 

paper on Assessment of Regional Earthquake Hazards 

and Risk Along the Wasatch Front Utah.

A major scientific contribution of the Regional Earthquake Hazards Assessment Program was a refinement of 

the explanation for seismicity along the Wasatch Front 

to include a greater understanding of the Wasatch fault 

and its 12 segments that had been identified. Scientists 

also identified the "characteristic" earthquake for the 

region to be similar to the 1983 Borah Peak, Idaho, 

magnitude (Ms) 7.3, earthquake and concurred that 

moderate, but potentially damaging earthquakes, without surface rupture (M=5.5-6.5), might occur anywhere 

within the Wasatch Front on known or unknown faults. 

Researchers had stressed the possibility of a large earthquake centered near Salt Lake City causing numerous 

injuries, loss of life, and extensive damage to buildings, 

lifelines, and public facilities as a result of (1) peak 

ground acceleration expected to be 0.2-0.4 g, (2) surface 

fault rupture, (3) tectonic deformation, (4) landslides 

including rockfalls and rockslides, and (5) liquefaction. At 

the close of the 5-yr program of focused research, the 

participants drafted a consensus document that specified 

the extent of the earthquake hazards and types of 

mitigation measures that were appropriate to minimize 

damage and losses from future earthquakes. Federal, 

State, and local governments, as well as private institutions and individuals, had begun to act on the information 

provided from the program. By 1989, the program 

moved into a second phase, which emphasized implementation of loss reduction measures at the State, local, and 

individual level, although the participants recognized the 

need to continue assessing and mapping the earthquake 

hazards.

THE ROLE OF INTERACTIVE WORKSHOPS

The USGS, in planning for the Regional Earthquake 

Hazard Assessment Program, followed the welldocumented assumption that interaction between 

researchers and users of research increases the probability that research will be relevant to the user's needs
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

and, therefore, will be more readily used (Nigg, 1988; 

Yin and Moore, 1985; Yin and Gwaltney, 1981; Glaser 

and others, 1983). Researchers agree that knowledge is 

likely to be utilized where interpersonal communication 

networks have been established and maintained. The 

network of researchers and users must be supported 

during the life of the research, even as knowledge 

production is occurring and after it has been completed, 

to assist in utilization of that knowledge (Yin and Gwaltney, 1981; Yin and Moore, 1985; Yin and Andranovich, 

1987).

The focus of utilization is people, not maps and reports. 

When researchers interact with users, there is two-way 

communication. Preliminary information is transmitted 

to potential users, who in turn communicate their needs 

and explain how to modify the research to meet those 

needs. Individuals develop working relationships with 

each other. Not only do users become acquainted with 

the authors of reports, they also become acquainted with 

other research that may be useful. The researchers, in 

turn, benefit from refined problem identification and, by 

participation in a network of other scientists and users, 

help create an audience and a market for their information and products.

Knowledge utilization is enhanced through the networking process, which can sometimes be defined as 

collaboration. The numerous arenas where collaboration 

can take place include interactive workshops, advisory 

committees, interdisciplinary research projects, information centers, and professional societies. USGS chose 

interactive workshops as one of the arenas to foster 

collaboration between researchers and users of research 

because, during interactive workshops, individuals from 

many different disciplines meet, learn to appreciate each 

other's needs, learn about concurrent research and 

implementation of research, and finally, form ongoing 

networks to enhance the utilization of research.

Because of the importance of maximizing the resources 

allocated to research and because of society's need for 

new and better ways to solve problems, social science 

research has focused for the past 2Vz decades on how new 

information is incorporated into policy. During that time, 

researchers and practitioners have reached a similar 

conclusion: personal interaction between investigators 

doing the research and potential users of the research is 

essential to knowledge utilization.

Three of several theories (Glaser and others, 1983) 

that explain how research is utilized are as follows: 

1. Knowledge-driven theory: Utilization of research is

characterized by a sequence of activities where

research discovery moves through various phases. 

This theory is also called the "research development 

and diffusion theory."

2. Problem-solving theory: Utilization of research occurs 

when users identify a need or problem and research is 

initiated in response to that need.

3. Social interaction theory: Utilization of research 

occurs as a result of interaction between knowledge 

producers and knowledge users prior to, during, and 

following the research.

Yin and Moore (1985) scrutinized the natural hazards 

field to ascertain which of the above theories or combination of theories best explained why and how research 

gets used in the natural hazards field. They based their 

findings on case studies of natural hazards projects that 

experts had rated as exemplary.

In cases where knowledge from the research projects 

was utilized, the investigators found strong support for 

the social interaction theory, as evidenced by the following conditions:

1. Research producers and research users belonged to 

overlapping networks.

2. During early stages of research projects, communications and interactions resulted in modification of 

research design as a result of information obtained 

from users.

3. During the course of the project, communication 

occurred before, during, and after completion of the 

project.

4. Results were disseminated through some medium

catering to users, not to other researchers (Yin and

Moore, 1985).

Yin and Moore's work reinforces the importance of 

maintaining persistent interaction (two-way communication) between investigators doing the research and 

potential users of the research, so that their concept of a 

"marketplace of ideas" can develop in which the 

researchers and users of research exchange ideas, information, and experiences.

Yin and Moore's research is based in part on the 

theories and research findings presented by Glaser and 

others (1983). In the authors' encyclopedia of research on 

applications of knowledge for planned change, the role of 

personal interaction is explored, the importance of informal contact is documented, and the conclusion is reached 

that the most effective way to increase information is 

through personal interaction. A well-informed colleague 

serves to channel information to coworkers (Glaser and 

others, 1983, p. 302). For example, "as much as 85 

percent of useful scientific information is exchanged 

informally before the usual bibliographical sources are 

consulted to ascertain whether published information is 

available" (Glaser and others, 1983, p. 304). In fact, the 

studies showed that researchers depend heavily on informal networks and interaction with applied scientists who 

are in touch with colleagues from different disciplines. To 

increase information exchange, one researcher recom-
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM

mended that isolated scientists be brought into closer 

contact with scientists who are the foci of information 

networks (Glaser and others, 1983, p. 303).

Glaser and others (1983) document how workshops and 

seminars that include users as well as producers of 

research serve to effectively increase utilization of 

knowledge. Workshops and seminars contribute to utilization by providing an arena for practitioners to acknowledge the implications of research findings and researchers to obtain feedback from those who would use their 

findings. The authors also document the effectiveness of 

conferences and workshops to link research to practice 

through the personal bonds that are formed at these 

meetings.

Utilization of new information is further enhanced 

when the conference or workshop provides a publication 

of the conference proceedings and when the conference is 

one of a series of annual meetings on the same topic 

(Glaser and others, 1983, p. 306). In addition, when 

attendees participate in the formation of action plans to 

implement research results, utilization of research tends 

to occur at a quicker pace (Glaser and others, 1983, 

p. 306).

Participants at a workshop entitled "A Synthesis of 

Technology Transfer Methodologies" sponsored by the 

U.S. Department of Energy in 1984 documented similar 

experiences and prescribed similar actions to increase 

the use of scientific information. The participants at this 

workshop, who were interested in the transfer of technical information not related to natural hazards, found 

that the transfer process is a human activity conducted 

by "enthusiastic people!" (Traeger, 1984, p. 181).

Bobbins (1984) suggested five principles necessary for 

successful technology transfer:

1. Access to information is necessary but not sufficient.

2. Information must be translated.

3. Personal contact is the most important channel 

through which technical information is obtained.

4. Solutions must be adapted to user's problems.

5. Products must meet the needs of users, not producers 

(Robbins, 1984, p. 72-74).

Others at the workshop emphasized the interpersonal 

aspect of technology transfer. "Information dissemination is a human function. While it is essential to incorporate a large resource base, including printed reports, 

library services, data bases, technical experts, consultants, as well as private, public, and governmental agencies, our experience has demonstrated that the amount of 

technology actually transferred is directly proportionate 

to the amount of face-to-face activity" (Marlow, 1984, p. 

143). Participants recommended many different ways to 

increase face-to-face activities, including professional 

society meetings, conferences, and workshops. In fact, 

Traeger, a workshop participant, related that when

individuals at Sandia National Laboratories were asked 

to identify the catalyst that initiated transfer of technology from 1981 to 1983, they cited meetings and workshops as among the most important (Traeger, 1984, 

p. 176).

Greene and Gori (1982) also documented the fact that 

hazard information was obtained by Charleston decisionmakers through personal contacts and that workshops 

were effective catalysts for stimulating action (Greene 

and Gori, 1982, p. 27-28). In presentations at the conference on "A Review of Earthquake Research Applications 

in the National Earthquakes Hazards Reduction Program" (Hays, 1988), workshops were cited as important 

areas for the exchange of new information on need for 

and measures to reduce earthquake vulnerability. 

Whitehead (1988) from Kentucky, Molinelli-Freytes 

(1988) from Puerto Rico, Johnston-Fischer (1988) from 

the U.S. Virgin Islands, and Olson (1988), Bagwell 

(1988), and Lindbergh (1988) from South Carolina referenced one or more interactive workshops conducted by 

the USGS as important factors in increasing the concern 

and knowledge that they and others had about earthquake hazards reduction in their region.

INTERACTIVE WORKSHOPS IN UTAH

METHODOLOGY OF THE STUDY

To gage the effectiveness of workshops in Utah, the 

opinions and experiences of participants in the program 

were sought and analyzed in two ways. First, the 

opinions and experiences of the leaders of the program 

were recorded during two lengthy roundtable conversations in Salt Lake City during an annual workshop. 

Second, the author completed a systematic survey of 

researchers, public officials, and private individuals participating in the program. Responses from recorded 

conversations and written questionnaires form the basis 

of the findings.

THE WORKSHOP PROCESS

Each workshop followed essentially the same model. A 

steering committee was established to formulate the 

basic working concepts and procedures for the meeting. 

The steering committee, made up of representatives 

from the sponsoring groups, then formulated an agenda, 

a list of speakers, and a list of invitees, all chosen to 

represent many disciplines, as well as the local experience. The workshop was organized to exchange information and to develop recommendations or "action plans" 

that could be implemented once the workshop had 

adjourned. Proceedings from each workshop, made up of
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

the talks given at the workshop and the recommendations of the participants, were published as open-file 

reports by the USGS and disseminated to the participants of the workshop and the public.

Following this model, seven workshops were convened 

in Utah between 1984 and 1989. Four of the workshops 

were objects of this study:

 August 14-16, 1984: Workshop on "Evaluation of 

Earthquake Hazards and Risk in Utah."

 July 10-11, 1985: Workshop on "Earthquake and 

Landslide Hazards in the Wasatch Front Region 

of Utah" (hosted by Utah Geological Survey).

 July 30-September 1,1985: Workshop on "Earthquake 

and Landslide Hazards in the Wasatch Front Region 

of Utah" (hosted by Utah Division of Comprehensive 

Emergency Management).

 July 14-18, 1986: Workshop on "Earthquake Hazards

Along the Wasatch Front, Utah." 

(The 1985 workshops were organized by the State agencies and dealt with topics pertinent to the host agency. 

Individuals participating in the Utah program were 

invited to one meeting or the other.)

The workshops in Utah were designed as important 

yearly events milestones in the program. Participation 

was open and well publicized. Lists of invitees and 

speakers, as well as the workshop agenda, were formulated by the steering committee, which was made up of 

representatives from the participating organizations. 

Workshop agendas were intended to involve the diverse 

interests in Utah in a way that would allow the exchange 

of new information that had been gathered through 

research and experience during the year. The other 

general objectives of the workshops were to

1. Set goals for research and implementation through 

consensus.

2. Energize participants, both in research and implementation communities.

3. Recruit allies and formulate advocates for earthquake

hazard reduction.

Typically, workshops were a mix of formal presentations, small discussion groups, and informal gatherings. 

A quarterly newsletter, "The Wasatch Front," edited 

and published by UGS, communicated with participants 

in the program during the year and offered the participants an informal method of disseminating new findings 

and experiences. Proceedings of the workshops, which 

included a summary of the workshop, papers presented, 

small discussion group reports, and list of participants, 

were published 6 months to a year following each workshop.

RESULTS FROM RECORDED CONVERSATIONS

Leaders in the program were invited to share their 

thoughts regarding the role of the workshops at two

luncheons held during the annual workshop in the summer of 1986. The first group consisted of scientists and 

the second of public officials and other nonscientists. The 

leaders were divided into two groups to make the 

conversations manageable and to give each individual a 

chance to focus on the conversation and to respond.

The following individuals took part in the conversations, which lasted approximately IVz hours each:

GROUP I:

David Schwartz, USGS, Menlo Park, Calif, (formerly

Woodward Clyde Consultants) 

Robert Smith, University of Utah, Dean, Department of

Geology and Geophysics and formerly Director,

University of Utah Seismograph Stations 

Al Rogers, USGS, Branch Chief, Golden, Colo. 

Jeff Keaton, Dames and Moore, Salt Lake City, Utah 

Walter Hays, USGS, Office of Earthquakes, Volcanoes,

and Engineering, Reston, Va. 

Don Mabey, Deputy Director, UGS, Salt Lake City,

Utah 

Wendy Hassibe, USGS, Director, Public Information

Office and Editor of Wasatch Front Forum, Salt Lake

City, Utah

GROUP II:

Loren Anderson, College of Engineering, Utah State

University, Logan, Utah 

Ralph Finlay,2 CEM, Salt Lake City, Utah 

Lawrence Reaveley, Reaveley Engineers and

Associates, Inc., Salt Lake City, Utah 

Walter Hays, USGS, Office of Earthquakes, Volcanoes,

and Engineering, Reston, Va. 

Genevieve Atwood, State Geologist and Director,

UGS, Salt Lake City, Utah 

Jim Tingey, CEM, Salt Lake City, Utah 

Lorayne Tempest Frank, Director, CEM, Salt Lake

City, Utah

Gary Johnson, FEMA, Washington, D.C. 

Delbert Ward, Structural Facilities, Inc., Salt Lake

City, Utah

Each group of leaders was asked to reflect on what 

happened at the workshops, what people they met, what 

they learned, and what they did differently following the 

workshop that they could attribute to what they learned. 

The two groups had similar views of the workshops, and 

therefore, their opinions will be reported together.

People responded to general questions or topics that 

the author had outlined, centering on the workshop's role 

in introducing new sources of information, research 

findings, and methodologies. Individuals spoke without

Deceased.
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM

much prompting or interference from the author except 

when it was necessary to move on to the next topic.

The leaders all remarked that the workshops gave 

them an opportunity to meet and communicate with new 

people. Individuals were able to identify those with 

information that they needed. Researchers met others 

conducting similar research, and they also met individuals whose work they knew but with whom they had never 

had a chance to talk. Researchers met the public officials 

and design professionals who depended on their work. 

Everyone met individuals from different parts of the 

country whom they might otherwise never have had the 

opportunity to meet. One Federal official stated that he 

met individuals from Utah whom he would call on to 

teach courses in other regions; he also stated that he 

would use demonstrations that he saw in the workshops 

at future training courses.

Both the researchers and practitioners agreed that the 

workshops were excellent forums to communicate with 

individuals "inside" and "outside" their fields. For some 

researchers, it was the first opportunity in their careers 

to hear from the users of scientific information. This 

opportunity resulted, in some cases, in redirection of the 

research into new areas. A university scientist stated 

that, from the workshops, he learned about scientific 

areas that were not being addressed and problems that 

needed to be solved. He therefore embarked on a new 

area of research in order to do something "brand new."

The workshop was seen as a mechanism to place 

individuals and their work into the larger program. Each 

year attendance at the workshop increased, and the 

areas of expertise and interest expanded. Local participants could see their relationship to Federal and State 

representatives, and vice versa. The contacts made in 

the workshop increased the likelihood that individuals 

would be called on during the year for assistance. A 

university scientist stated that he could not overestimate 

the importance of making contacts with people with 

common objectives. Contacts formed at the workshops 

made it easier to approach those people later for information or to get problems solved.

For the participants, especially the local scientists and 

design professionals, the workshops brought them "upto-date" quickly. The Director of UGS stated that the 

workshops gave her and her staff an opportunity to be 

up-to-date on scientific research. A geotechnical engineer stated that the workshop gave him an opportunity 

to have one-on-one discussions with scientists he may 

never have met. The workshops allowed the local scientists at UGS to learn what USGS scientists were discovering and what university and individual researchers 

funded by USGS were learning.

The researchers valued the time constraint that the 

workshops placed on them, forcing them to put their

findings down on paper for everyone to review. At the 

same time, the workshops gave the scientists a regional 

forum in which to relate their findings and an immediate 

method of disseminating their results. A university 

scientist remarked that the workshops may have lowered the cost of the program by getting "more bang for 

the buck," in that the workshops inspired other research 

that the university undertook on its own. An architect 

stated that the workshop brought the participants new 

information in a meaningful way because it showed them 

how to use that information. A university scientist 

remarked that, as a result of the workshop, he changed 

the earthquake engineering course that he teaches. An 

emergency manager stated that not only did the workshops keep him "current," but they made his job easier, 

especially in his contacts with the news media.

The conversations reinforced the theories previously 

discussed. The leaders emphasized the importance of the 

workshops to introduce the participants and their 

research, experiences, and responsibilities to each other. 

A representative from UGS stated that the workshops 

were a bonding experience, and a university scientist 

stated that the workshops served as a forum to present 

work, get recognition, and interact with people who 

would use the information. A practicing architect identified the important aspect of the workshop as the "driving 

mechanism for coordination of random research." 

Finally, representatives from the State government 

stated that the intangible benefit of the workshops was 

the commitment they instilled in the participants to the 

goals of the program.

The scientists valued the sense of involvement in 

reducing hazards. They were cajoled into putting their 

results into a form that would be usable to planners. A 

scientist from the Federal government stated that scientists were forced to talk to planners in a hitherto 

unaccustomed lay language. A university professor 

related his experience of sitting down with an engineer 

and showing him how to use the data in his model.

The proceedings of the workshops were also seen as 

important topical references of what was being done in 

Utah and by whom. Conversations with the leaders in 

the program showed that they valued the workshops not 

only as arenas to meet new people and learn new ideas, 

but as an essential ingredient in the overall program, 

coordinating and focusing the research, expanding the 

uses of the research, focusing the participants on the 

goals of the program, and finally, tying the program and 

its diverse participants together.

RESULTS FROM QUESTIONNAIRE

Participants were asked to assist in evaluating the role 

of the workshops by completing a questionnaire mailed
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

late in 1986. (See Appendix A for a copy of the questionnaire.) The mailing list for the Wasatch Front Forum 

newsletter was used because it included all past workshop participants and others interested in earthquake 

hazards in the Wasatch Front. (Individuals who had 

attended the luncheons and recorded conversations were 

not mailed a questionnaire.) Of the 250 questionnaires 

mailed, 91 responses were received (79 from individuals 

who had attended one or more workshops and 13 from 

individuals who had not attended the workshops). Only 

the responses from those who attended the workshops 

were used for this study. Some respondents chose not to 

answer all questions, and respondents were not asked to 

identify themselves. The response rate was approximately 37 percent. Responses to the questionnaire were 

used to corroborate opinions that the leaders had 

expressed in the recorded conversations.

Respondents represented all sectors of the Utah 

earthquake hazards community in terms of affiliation and 

profession. Most respondents worked for a county, city, 

or State government agency; however, many worked for 

the Federal Government, a university, or the private 

sector. The following is a breakdown of how the respondents characterized their workplaces:

City or county 24

State 20

Federal Government 17

University 9

Private 9

Respondents represented many different disciplines

involved in the program. The majority were scientists

and engineers, but there was a good response from

land-use planners and emergency service professionals.

Respondents described their agency or office as follows:

Scientific 25

Planning 21

Emergency services 14

Geotechnical engineering 8

Structural engineering 3

Building department 1

Architectural 1

Other 6

Most of the respondents had attended two or three

workshops, although many had attended only one, and a

smaller number had attended all four. The responses

were as follows:

Attended 1 workshop 24 

Attended 2 workshops 27 

Attended 3 workshops 19 

Attended 4 workshops 9 

Participants in the workshops were asked questions 

concerning who they met at the workshops, what they 

learned at the workshops, and what use they made of

their new contacts and information. In addition, they 

were asked a series of questions to document what other 

needs and functions the workshops fulfilled.

Most respondents met new people within their field at 

the workshops. Of the respondents, 41 met between 1 

and 5 new individuals, 15 met between 6 and 10, and 9 

met more than 10. Only 14 individuals responded that 

they met no one new in their own field at the workshops. 

The new people the respondents met were from the 

following locations:

Salt Lake City 42 

Other parts of Utah 30 

Washington, B.C. 27 

Other parts of country 28 

Denver and California were mentioned frequently 

under "other parts of country." The concentration of 

responses in Utah and Salt Lake City (72) points out that 

attendees of the workshops (the majority of whom were 

from Utah and Salt Lake City) met other individuals in 

their field of interest who were from the Wasatch Front 

study area. In fact, when asked if they had called on 

these new contacts after the workshops, 48 individuals 

responded that they had contacted between 1 and 10 or 

more individuals for information. The responses were as 

follows:

Contacted none 

Contacted 1-5 

Contacted 5-10 

Contacted 10 or more

31

40

6

2

The respondents were also asked how many new 

people they met at the workshops from other fields. The 

majority of individuals met more new people outside than 

within their own fields. Only four individuals stated that 

they met no one new outside their own discipline. 

Twenty respondents met over 10 new individuals, 21 met 

between 6 and 10 new individuals, and 34 met between 1 

and 5 new individuals outside their own field. Respondents were asked to identify one or more of the following 

disciplines as the fields represented by the new individuals:

Scientific

Geotechnical engineering

Structural engineering

Architecture

Planning

Emergency services

Building department

Other

The respondents selected between zero and 8 areas 

from which they met new individuals. Of these, 34 met 

individuals in 2 or 3 other disciplines, 31 met individuals 

in 4 or 6 other disciplines, and 5 met individuals in 7 or 8 

new fields. The actual responses are as follows:
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM

No new disciplines

1 new discipline

2 new disciplines

3 new disciplines

4 new disciplines

5 new disciplines

6 new disciplines

7 new disciplines

8 new disciplines

4

5

16

18

15

11

5

3

2

A major conclusion of the questionnaire is that a large 

number of participants at the workshops met individuals 

outside their immediate profession or discipline.

Respondents were then asked to rank new sources of 

information they encountered at the workshop. The 

responses were grouped into very useful, useful, and not 

useful. To be counted as very useful, an answer would 

need to use an adjective such as extremely, very useful, 

or, in some cases, contain an explanation as to how the 

information was subsequently used. To be characterized 

as useful, the respondent would need to use adjectives 

such as helpful or useful. No response to the question or 

responses with "not" as the adjective were characterized 

as not useful. Of the respondents, 38 characterized their 

new sources of information as very useful, 17 as useful, 

arid 24 as not useful or not a source.

Explanations of how the new information sources were 

used were also given by respondents. A Utah State 

scientist stated that it was "extremely useful to meet and 

ask questions of authors of reports he had previously 

read." An official from a Utah State emergency services 

department stated, "Even though we receive the printed 

material in our office, the people making the presentations added to my understanding of the earthquake 

threat." A geotechnical engineer with the State wrote, 

"The contacts have been useful in exchanging information and acquiring technical assistance." Another individual with the State emergency services department commented, "I refer questions to contacts that I have made 

or back up my reply with a reference to such a contact. 

Also, I ask people whom I met at the workshops to speak 

at local workshops." A local land-use planner said that he 

has a "better idea of what agencies I can contact for 

assistance or technical expertise." And finally, a journalist answered that the workshops provided "new sources 

for news stories and personal contacts with people who 

had previously been only names."

Many of the Federal scientists at the workshop also 

found the new contacts useful. A Federal scientist 

stated, "The workshops were most helpful in knowing 

who's doing what in Utah. Being located out of Salt Lake 

City is a hindrance, so this aspect of workshops is very 

beneficial." Another Federal scientist found the workshops to be useful for "renewing contacts with colleagues

in order to remain current on the directions and results of 

their research."

Approximately two-thirds of the participants responding to the questionnaire characterized the new contacts 

they met at the workshop as useful, and many of these 

contacts were from different fields. Thus respondents 

agreed with the leaders' recorded conversation about 

meeting new people at the workshops.

Participants were also questioned about new information obtained at the workshop. In terms of earthquake 

hazards in Utah, respondents were specifically asked to 

identify new information they had acquired about segmentation of the Wasatch fault system, recurrence intervals, maximum size of the expected earthquakes, the 

characteristic earthquake, liquefaction, and landslides. 

Of those who responded, 63 were capable of describing, 

in their own words, much of the new information that 

they acquired. Of these, 45 were able to identify and 

describe one or more of the above topics, and 18 identified only one; 16 were either unable or did not attempt to 

answer the question. With 80 percent of those responding to the questionnaire capable of stating what they 

learned, the workshop participants, like the leaders in 

the program, clearly came away with new knowledge 

about the earthquake hazards of the Wasatch Front.

It is important for new information to be applied if it is 

to be of value. Therefore, participants were asked if they 

used the information in their research, job, or private 

life. Of the 62 individuals (approximately 80 percent) who 

stated that they had an opportunity to apply the new 

information, 50 used the information on the job, 30 in 

research, and 18 in private life.

Nearly two-thirds of the respondents found the information learned at the workshops to be useful. Of those 

who responded, 41 characterized the information as very 

useful, 12 as somewhat useful, and 26 as not useful or no 

response. The following comments exemplify how the 

new information was used. A building department official 

stated that he used the new information in "siting new 

State buildings and preparing environmental assessments." A State land-use planner said that the new 

information was used in "promoting a comprehensive 

earthquake hazard mitigation program." A State emergency services official used the information to "better 

inform the public and private industry of the possibility 

of damage to their particular facilities and how they 

might mitigate such damage." A Federal scientist used 

the information in a risk-based evaluation of dams. 

Another Federal scientist stated, "The awareness of 

other researchers' work has contributed to applying new 

ideas to my area of study." A university scientist bought 

earthquake insurance after attending one of the workshops, and a county land-use planner used the information to design a sensitive-land ordinance for geologic
10 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

hazards and to designate which areas would require 

regulation.

Finally, the respondents were asked what other needs 

and functions the workshops fulfilled. They were asked 

to respond to a list of statements by ranking their 

answers from 1-5, with 1 representing low agreement 

and 5 representing high agreement with the statement. 

By selecting 5, 4, or 3, more than 80 percent of the 

respondents registered their beliefs that the workshops:

 Enhanced appreciation of other disciplines.

 Provided focus for news media.

 Enhanced public awareness of earthquake hazards.

 Provided a forum for recognition of individual 

research.

 Set an agenda for research.

 Provided a timely document for research or implementation (the proceedings).

 Renewed commitment to solving problems or implementing policy.

The majority of respondents did not believe that the 

workshops "provided a deadline for adoption of mitigation" nor that they "provided a deadline for completion of 

research." However, most respondents (27 and 32, 

respectively) gave these questions a rank of 3. The actual 

responses to all the statements follow.

Workshops also may have fulfilled other needs and functions for 

you, your community, or State. Please rate how well the 

workshops may have contributed to the following:

Low High 

12345

1. Enhanced appreciation of other

disciplines....................... 0 6 20 7 15

2. Provided focus for news media .... 1 14 18 29 15

3. Enhanced public awareness of

earthquake hazards............... 3 9 23 27 17

4. Provided forum for recognition of

individual research............... 0 10 19 33 16

5. Set agenda for research........... 1 9 28 25 8

6. Set agenda for action............. 2 10 29 26 7

7. Provided deadline for completion of

research......................... 6 16 32 2 5

8. Provided deadline for adoption or

implementation of policy.......... 9 2 27 7 3

9. Provided a timely document for 

research and/or implementation (the 

proceedings)..................... 0 8 20 34 11

10. Renewed commitment to solving

problems or implementing policy... 2 4 20 33 15

The respondents were also asked to list other contributions, not previously addressed, that the workshops 

may have made. Most respondents chose not to answer 

the question; however, of the 11 who answered, nine 

identified contributions to understanding and two identified contributions to research. The following are some 

of the Federal scientists' comments.

 I gained appreciation of the need for clearer communication of 

scientific results in terms that users can understand and 

apply.

 I understand better than before the importance of subtleties 

of implementing scientific information.

 From a scientific point of view, the information was very 

useful to me. Focused scientific sessions which bring together 

people who are working on the same problem or related 

problems are much more effective means of communication 

than ordinary scientific meetings.

A university geotechnical engineer and a private structural engineer stated:

 The workshops provided opportunity to determine what was 

needed by nontechnical people regarding geotechnical issues.

 Without the workshops, the Utah community would be years 

behind in seismic awareness and planning issues.

Possibly one of the best explanations of the role of the 

workshops was expressed by a State planner:

Workshops provide one of the few forums where individuals 

from many disciplines can exchange information and ideas 

directed toward a specific goal. Through concerned experts, 

earthquake problems and solutions have been better defined. For myself, the contacts with these experts instill confidence and reassurance that I can influence earthquake 

hazard mitigation.

CONCLUSION

The survey of participants was conducted to gage 

whether leaders' opinions were shared by the participants. The respondents' answers to the questionnaire 

were indeed similar to those expressed by the leaders. 

According to the participants' responses, the workshops 

served as arenas where individuals met others working 

on earthquake hazard reduction in the Wasatch Front. 

The individuals expanded their circle of colleagues to 

include individuals from other disciplines, other agencies, and other regions of the country. The new sources 

of information were contacted for many reasons, and 

most of the respondents judged these contacts useful.

Like the leaders, the participants learned new information about earthquake hazards in the Wasatch Front 

and used the information in their research, their jobs, 

and their private lives. The respondents' explanations of 

how they used the information replicated many of the 

statements made by the leaders of the program. Like the 

leaders, the participants believed that the workshops 

fulfilled a role of broadening their appreciation and 

understanding of the many different disciplines and 

individuals involved in the program. The respondents 

agreed also that the workshops provided a forum for 

recognition of individual researchers, as well as a method 

for disseminating timely information in the form of 

workshop proceedings. Many individuals also saw the 

workshops as tools for influencing the research agenda. 

In terms of increasing awareness and commitment to
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM 11

solving problems and implementing policy, most participants gave high marks to the workshops, as did the 

program leaders.

The representatives of institutions involved in planning earthquake hazards research and reduction programs were correct to give the annual workshops a 

prominent role in the program. The interviews and 

questionnaires verified the effectiveness of interaction 

between researchers and users of research and the use of 

workshops to encourage implementation. The workshop 

process set up a "marketplace" of ideas that did not begin 

or end with the workshop itself, but was carried on 

throughout the 5-yr program. What individuals gained at 

the workshops and how contacts and information were 

later applied in research and implementation activities 

lead to the conclusion that the workshop process was an 

invaluable element in the 5-yr program. Any plans for 

future, complex, multidisciplinary programs would do 

well to follow the example of this program and incorporate the use of frequent interactive workshops.

The use of workshops was valuable to the earthquake 

hazards research and reduction program. The workshop 

process also may have facilitated the incorporation of 

hazards information into public and private practice. This 

assessment can only take place after sufficient time has 

elapsed to allow for implementation of public and private 

policy. The evaluation of the influence of the earthquake 

hazards research and reduction program focused in the 

Wasatch Front will be an important future research 

topic.

REFERENCES

Bagwell, J.B., 1988, Application of the National Earthquake Hazards 

Reduction Program through an earthquake education center at 

Charleston, South Carolina, in Hays, W.W., ed., A review of 

earthquake research applications in the National Earthquake 

Hazards Reduction Program, 1977-1987: U.S. Geological Survey 

Open-File Report 88-13A, p. 106-114.

Glaser, E.M., Abelson, H.H., and Garrison, K.N., 1983, Putting 

knowledge to use, Facilitating the diffusion of knowledge and 

implementation of planned change: San Francisco, Jossey-Bass, 

636 p.

Greene, M.R., and Gori, P.L., 1982, Earthquake hazards information 

dissemination, A study of Charleston, South Carolina: U.S. Geological Survey Open-File Report 82-233, 57 p.

Hays, W.W., ed., 1988, A review of earthquake research applications 

in the National Earthquake Hazards Reduction Program, 

1977-1987: U.S. Geological Survey Open-File Report 88-13A, 

583 p.

Hays, W.W., and Gori, P.L., 1984, Regional and urban earthquake 

hazards, evaluation, Wasatch Front, Utah, Draft work plan, FY 

84-85, in Hays, W.W., and Gori, P.L., eds., Proceedings of 

conference XXVI, A workshop on "Evaluation of regional and 

urban earthquake hazards and risk in Utah": U.S. Geological 

Survey Open-File Report 84-763, p. 17-22.

Johnston-Fischer, P., 1988, Earthquake vulnerability and risk assessment in the U.S. Virgin Islands, in Hays, W.W., ed., A revie\/ of 

earthquake research applications in the National Earthquake 

Hazards Reduction Program, 1977-1987: U.S. Geological Survey 

Open-File Report 88-13A, p. 309-314.

Lindbergh, C., 1988, Southeastern United States, in Hays, W.W., ed., 

A review of earthquake research applications in the National 

Earthquake Hazards Reduction Program, 1977-1987: U.S. Geological Survey Open-File Report 88-13A, p. 118-129.

Marlow, H.L., 1984, Another perspective on technology transfer The 

PENNTAP experience, in U.S. Department of Energy, Proceedings, A synthesis of technology transfer methodologies, U.S. 

Department of Energy Technology Transfer Workshop: Washington, D.C., U.S. Department of Energy, p. 135-160.

Molinelli-Freytes, J., 1988, The earthquake vulnerability study for the 

metropolitan area of San Juan, Research applications, in Hays, 

W.W., ed., A review of earthquake research applications in the 

National Earthquake Hazards Reduction Program, 1977-1987: 

U.S. Geological Survey Open-File Report 88-13A, p. 304-308.

Nigg, J.M., 1988, Framework for understanding knowledge dissemination and utilization, Applications for the National Earthquake 

Hazards Reduction Program, in Hays, W.W., ed., A review of 

earthquake research applications in the National Earthquake 

Hazards Reduction Program, 1977-1987: U.S. Geological Survey 

Open-File Report 88-13A, p. 13-33.

Office of Science and Technology Policy, 1978, Earthquake hazards 

reduction, Issues for an implementation plan: Washington, D.C., 

Executive Office of the President, 229 p.

Olson, N.K., 1988, Applications: Seismic safety organizations South 

Carolina seismic safety consortium, in Hays, W.W., ed., A review 

of earthquake research applications in the National Earthquake 

Hazards Reduction Program, 1977-1987: U.S. Geological Survey 

Open-File Report 88-13A, p. 259-271.

Robbins, M.D., 1984, Technology transfer an overview, in U.S. 

Department of Energy, Proceedings, A synthesis of technology 

transfer methodologies, U.S. Department of Energy Technology 

Transfer Workshop: Washington, D.C., U.S. Department of 

Energy, p. 65-76.

Trager, R.L., 1984, Technology transfer revisited, in U.S. Department of Energy, Proceedings, A synthesis of technology transfer 

methodologies, U.S. Department of Energy Technology Transfer 

Workshop: Washington, D.C., U.S. Department of Energy, 

p. 173-200.

U.S. Department of Energy, 1984, Proceedings, A synthesis of technology transfer methodologies, U.S. Department of Energy Technology Transfer Workshop: Washington, D.C., U.S. Department 

of Energy, 432 p.

Whitehead, C., 1988, Earthquake hazards research applications in 

Kentucky, in Hays, W.W., ed., A review of earthquake research 

applications in the National Earthquake Hazards Reduction Program, 1977-1987: U.S. Geological Survey Open-File Report 

88-13A, p. 315-319.

Yin, R.K., and Andranovich, G.O., 1987, Getting research used in the 

natural hazards field, The role of professional associations: Washington, D.C., Cosmos Corporation, p. 1-172.

Yin, R.K., and Gwaltney, M.K., 1981, Knowledge utilization as a 

networking process, in Knowledge, Creation, diffusion, utilization, vol. 2, no. 4: Beverly Hills, Calif., Sage Publications, Inc., 

p. 555-580.

Yin, R.K., and Moore, G.B., 1985, The utilization of research, Lessons 

from the natural hazards field: Washington, D.C., Cosmos Corporation, 101 p.
12 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

APPENDIX A

United States Department of the Interior

GEOLOGICAL SURVEY 

RESTON, VA. 22092

In Reply Refer To: 

Mail Stop 905 November 24, 1986

Dear Colleague:

For the past 3 years, the Wasatch front has been the focus of an integrated 

seismic hazard assessment study. The study has been conducted by the 

U.S. Geological Survey in cooperation with the Utah Geological and Mineral 

Survey. Many other government agencies, universities, and practicing 

architects and engineers have taken part in this study which has 3 principal 

goals:

1) Determination of recurrence rates and maximum size of earthquakes.

2) Estimation of the nature and severity of the expected ground shaking.

3) Identification and mapping of areas where earthquake ground shaking 

may induce landslides, liquefaction, settlement, and other ground 

failures.

In conjunction with the study, workshops were held annually since 1984 in Salt 

Lake City to review each year's accomplishments, identifying program needs, 

and stimulating research and implementation of research findings. Currently I 

am evaluating the role these workshops played in facilitating the progress of 

the integrated seismic hazards assessment study in the Wasatch front.

To understand what role the workshop process has played, I am requesting your 

help. Please take a few minutes to answer the questions on the following 

pages and return the entire form in the enclosed self-addressed stamped 

envelope by December 19, 1986.

This systematic survey of researchers, public officials, and private 

individuals active in the three-year effort in the Wasatch front will form the 

basis of a publication on the role of the workshops and also contribute to 

planning future integrated seismic hazard assessment studies in other regions 

of the country.

Thank you for responding to this survey and returning it promptly,

Sincerely,

Paula L. Gori 

Office of Earthquakes, Volcanoes, 

and Engineering

Enclosure
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM 13

Wasatch Front Questionnaire 

1) How would you best describe your agency or office:

(Select one) 

___ Private 

___ University 

___ City/county 

___ State 

Other

(Select one)

___ Scientific

___ Geotechnical Engineering

___ Structural Engineering

___ Architectural

___ Planning

___ Emergency Services

___ Building Department

___ Other________

2) Which of the following workshops or meetings did you attend?

(Select one or more)

___ August 14-16, 1984; Workshop on "Evaluation of Earthquake Hazards 

and Risk in Utah."

___ July 10-11, 1985; Workshop on "Earthquake and Landslide Hazards in 

the Wasatch Front Region of Utah," (hosted by Utah Geological and 

Mineral Survey).

___ July 30-September 1, 1985; Workshop on "Earthquake and Landslide 

Hazards in the Wasatch Front Region of Utah," (hosted by Utah 

Division of Comprehensive Emergency Management).

___ July 14-18, 1986; Workshop on "Earthquake Hazards Along the 

Wasatch Front, Utah."

3) At the workshop(s) did you meet people in your field whom you had never 

met previously?

___ yes ___ no about how many ___

4) Where were these people from?

(Select one or more)

___ Salt Lake City Area ___ Utah

___ Washington, B.C. Area ___ Other ____________

5) Have you had an opportunity to call on any of these people in your field 

for information?

___ yes ___ no about how many ___
14 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

6) At the workshop did you meet people in other fields whom you had never met 

previously?

_____ yes ___ no about how many ___

7) What fields did these people represent?

(Select one or more)

_____ scientific

___ geotechnical engineering

_____ structural engineering

___ architectural

___ planning

___ emergency services

___ building department

___ other _________

8) Please comment on the usefulness of any of the new sources of information 

(i.e., experts, colleagues, etc.) who you met at the workshop(s).

9) At the workshop(s) did you learn something new about earthquake hazards in 

Utah?

___ yes ___ no

10) Please state in a few words some of these new ideas.

11) Have you had an opportunity to apply any of the new information? 

___ yes ___ no

12) How?

___ In your research?

___ In your job?

___ In your private life?
WORKSHOPS: EARTHQUAKE RESEARCH AND REDUCTION PROGRAM 15

13) 

14)

1)

2)

3)

4)

5)

6)

7)

8)

9)

10)

11)

Please comment on the usefulness of this information,

Workshop(s) also may have fulfilled other needs and d 

your community, or state. Please rate how well the \ 

contributed to the following: 

(where 1 is the lowest and 5 is the highest ratii

Enhanced public awareness of earthquake

Vl J3 ?si ve\ o

Provided forum for recognition of individual

T* o co t>f r>Ti

Q<al~ acronrla fcii* fooostft^Tn

Qol" acronrla fnv stt*^1mn

Provided deadline for adoption or implementation

Provided a timely document for research

Renewed committment to solving problems

Please list other contributions workshop(s) may have

been addressed above.

>

functions for you, 

*orkshop(s) may have

ig«)

Low High

12345

12345

12345

12345

12345

12345

12345

12345

12345

12345

12345

had which have not
REDUCING EARTHQUAKE HAZARDS IN UTAH: 

THE CRUCIAL CONNECTION BETWEEN RESEARCHERS AND

PRACTITIONERS

By WILLIAM J. KOCKELMAN

ABSTRACT

Complex scientific and engineering studies must be translated for 

and transferred to nontechnical personnel for use in reducing earthquake hazards in Utah. The three elements needed for effective 

translation, likelihood of occurrence, location, and severity of potential 

hazards, and the three elements needed for effective transfer, delivery, 

assistance, and encouragement, are described and illustrated for Utah. 

The importance of evaluating and revising earthquake hazard reduction 

programs and their components is emphasized. More than 30 evaluations of various natural hazard reduction programs and techniques are 

introduced.

This report was prepared for research managers, funding sources, 

and evaluators of the Utah earthquake hazard reduction program who 

are concerned about effectiveness. An overview of the Utah program is 

provided for those researchers, engineers, planners, and decisionmakers, both public and private, who are committed to reducing human 

casualties, property damage, and interruptions of socioeconomic 

systems.

INTRODUCTION AND PURPOSE

Effective comprehensive programs having earthquake 

hazard reduction as a goal need five components, each a 

prerequisite for its successor:

1. Conducting scientific and engineering studies of the 

physical processes of earthquake phenomena, including source, location, size, likelihood of occurrence, 

severity, triggering mechanism, path, ground 

response, and the effects on man-made structures and 

equipment.

2. Translating the results of such studies into reports 

and onto maps at an appropriate scale so that the 

nature and extent of the hazards and their effects are 

understood by nontechnical users.

3. Transferring this translated information to those who 

will or are required to use it, and assisting and 

encouraging them in its use through educational, 

advisory, and review services.

4. Selecting and using appropriate hazard reduction 

techniques, such as legislation, regulations, design 

criteria, education, incentives, public plans, and corporate policies.

5. Evaluating the effectiveness of the hazard reduction 

techniques after a period of use and making revisions, 

if necessary. Evaluation and revision of the entire 

program as well as the basic studies and the translation and transfer components may also be undertaken.

These five components (fig. 1) encompass a broad 

range of activities that are often described or divided 

differently. Examples include the 48 resolutions by the 

United Nations Educational, Scientific, and Cultural 

Organization (1976), six general topics and 37 issues by 

the U.S. Office of Science and Technology Policy (1978), 

48 detailed initiatives recommended by the California 

Seismic Safety Commission (1986), and 171 action items 

at a state governor's conference on geologic hazards 

(Utah Geological and Mineral Survey, 1983).

The purpose of this report is to emphasize the crucial 

connection between scientific and engineering studies 

and their ultimate use for hazard reduction by Utahans. 

The connection consists of two of the five components 

shown in figure 1: translation and transfer. Emphasis on 

this crucial connection is provided by a discussion of the 

problem failure to translate and transfer and efforts 

toward making the connection in Utah. Translation and 

transfer are defined, described, and then illustrated, 

first by the use of general examples and then by the use 

of specific examples in Utah.

SCIENTIFIC AND ENGINEERING STUDIES

A prerequisite for a successful Utah earthquake hazard reduction program is adequate and reliable scientific and engineering information about potential earthquake hazards surface-fault rupture, ground shaking, 

liquefaction, landsliding, seiches, tsunamis, subsidence, 

and the effects of each. Actual hazards occur when land 

uses, structures, or equipment are located, constructed, 

or operated in such a way that people may be harmed,

16
REDUCING EARTHQUAKE HAZARDS IN UTAH 17

5. EVALUATION/REVISION

Studies

Translation

Transfer

Reduction

Program

4. REDUCTION TECHNIQUES

Mitigation

Preparedness

Response

Recovery

Reconstruction

3. TRANSFER TECHNIQUES

Education services 

Advisory services 

Review services 

Other

2. TRANSLATION ELEMENTS

Likelihood

Location

Severity

Format

Other

1. EARTHQUAKE STUDIES

Geologic

Geophysical

Seismologic

Engineering

Other

FIGURE 1. Five components needed for an effective comprehensive earthquake hazard reduction 

program. The components are depicted as steps or building blocks, each a prerequisite for its successor.

their property damaged, or their socioeconomic systems 

interrupted.

Numerous geologic, geophysical, seismologic, and 

engineering studies are necessary to assess potential 

earthquake hazards in Utah. These studies are concerned with the physical process of earthquakes, including source, location, size, likelihood of occurrence, triggering mechanism, path, and severity of effects on a site, 

man-made structure, or socioeconomic activity. These 

studies can be divided in several ways. To give the
18 ASSESSMENT OF EEGIONAL EAETHQUAKE HAZAEDS AND EISK ALONG THE WASATCH FEONT, UTAH

nontechnical reader an overview, some of the studies and 

the knowledge derived are shown in list 1.

A description of many of these studies can be obtained 

from perusing various scientific and technical reports and 

texts, such as Richter (1958), Wallace (1974), Borcherdt 

(1975), Applied Technology Council (1978), Hays (1980), 

Ziony (1985), Power and others (1986), Evernden and 

Thomson (1988), and Schwartz (1988). Most of these 

studies are complex and interconnected, have limitations 

because of lack of data, and require special technical 

skills.

Many of these studies were envisioned and are 

described in the "Regional Earthquake Hazards Assessments" draft work plan for the Wasatch Front. This plan 

was reproduced in a workshop proceedings edited by 

Hays and Gori (1984, p. 17-44). The results of those 

studies may be seen in a two-volume report edited by 

Gori and Hays (1987).

Such studies are vital because, in the words of former 

U.S. Geological Survey director Walter C. Mendenhall, 

"There can be no applied science unless there is science 

to apply." It has been my experience that it is not 

prudent for planners to develop land-use regulations, 

engineers to design structures, and lenders and public 

works directors to adopt policies reducing earthquake 

hazards without reliable scientific and engineering 

assessments. Hanks (1985, p. 3) observes that "implementation plans may not mean much if they are not based 

on the best scientific knowledge and data available."

HAZARD REDUCTION TECHNIQUES

Numerous earthquake hazard reduction techniques 

are available in Utah to engineers, planners, and decisionmakers, both public and private. These techniques 

are specifically aimed at awareness of, avoidance of, 

accommodation to, or response to the effect of earthquake phenomena on people, land use, structures, and 

socioeconomic systems. The general goal of these objectives is to reduce human casualties, property damages, 

and socioeconomic interruptions.

Many of the reduction techniques are also complex, are 

interconnected, and require special skills legal, financial, legislative, design, economic, communicative, educational, political, and engineering. To give the reader an 

overview, examples of specific reduction techniques are 

shown in list 2. These techniques can be divided in other 

ways, such as the following:

 Mitigation techniques before an event, which may take 

1 to 20 yr.

 Preparedness measures before an event, which may 

take 1 to 20 weeks.

 Response during and immediately after an event.

 Recovery operations after an event, which may take 1 

to 20 weeks.

 Reconstruction activities after an event, which may

take 1 to 20 yr.

These estimated time periods vary, depending on the 

postulated or actual size of the earthquake, the damage, 

the reduction techniques in place, and the resources 

available to the State of Utah, its communities, its 

corporations, and its families.

Many of the hazard reduction techniques identified in 

this report have been discussed and illustrated by Blair 

and Spangle (1979), Kockelman and Brabb (1979), Brown 

and Kockelman (1983), Kockelman (1985, 1986), Jochim 

and others (1988), Mader and Blair-Tyler (1988), BlairTyler and Gregory (1988), and the United Nations Office 

of the Disaster Relief Coordinator (Lohman and others, 

1988).

UTAH'S DRAFT WORK PLAN

A collective partnership of Utahans and others in 1983 

created a unique State earthquake hazard reduction 

program. The formulators of the draft work plan for the 

Wasatch Front not only envisioned the use of scientific 

and engineering studies to reduce the hazard but also 

provided for an "implementation" component having 

three priorities: (1) determining the needs of users, (2) 

producing translated information that meets the need, 

and (3) fostering an environment for use of research 

results by local government. For the purpose of this 

report, users are defined as those who are interested in 

or who have responsibility for reducing earthquake 

hazards.

Examples of specific techniques to reduce hazards (list 

2) and potential users of earthquake hazard information 

(list 3) were compiled. The reduction techniques most 

appropriate for Utah were to be selected by these users. 

These techniques and users were included in the draft 

work plan reproduced by Hays and Gori (1984, p. 37-44). 

The adopted work plan provides a bench mark for 

evaluating its accomplishments.

IMPLEMENTATION UNDER WAY

Descriptions and illustrations of the reduction techniques are beyond the scope of this report. However, 

many techniques were selected and successfully used or 

are pending in Utah. Descriptions of some of them may 

be seen in the volumes edited by Gori and Hays (1987, 

1988). A model natural hazards reduction ordinance 

drafted by the Salt Lake County planning staff (Barnes, 

1988a, b) has been adapted and adopted by the city of 

Washington Terrace.
REDUCING EARTHQUAKE HAZARDS IN UTAH 19

List 1. Examples of scientific and engineering studies necessary to assess earthquake hazards

Study Knowledge derived

Geologic

Detailed geologic mapping

Lithologic investigations

Stratigraphy

Borehole sampling

Trenching

Paleontology

Scarp analysis

Stream offsets

Geomorphologic studies

Structural geology

Fault slip rates, physical properties, fault length, fault age, fault 

geometry, bedrock strength, zones of deformation, amplification 

of ground motion, lateral and vertical offsets, earthquake recurrence intervals, earthquake sources, depth to ground water, fault 

location, bedrock types, deformation patterns, plate tectonics 

context, driving forces, and other knowledge concerning surface 

rupture, ground shaking, landsliding, liquefaction, seiches, tsunamis, and subsidence.

Geophysical/Geochemical

Geodetic leveling and trilateration 

Field monitoring

Stress and strain

Tilt and creep

Electrical changes

Radon/helium emissions

Water chemistry changes

Water-well levels 

Electromagnetic soundings 

Gravity, electrical, and magnetic studies 

Seismic refraction and reflection profiling 

Radiometric dating

Precursor detection, ongoing deformation, fault zone properties, 

recurrence intervals, shear wave velocity, stress accumulation, 

crustal anatomy, crustal properties, wave attenuation, crustal 

velocity model, ground-motion characteristics, deformation patterns, buried faults or structure locations, and three-dimensional 

crustal geometry.

Seismologic

Historical seismicity

Earthquake monitoring

Strong ground-motion monitoring

networks 

Ground response 

Seismic wave propagation 

Segmentation analyses 

Wave propagation 

Rupture process

Asperity locations, velocity, severity of shaking, acceleration, 

displacement, seismic gaps, source zones, fault mechanism, rupture direction, seismic direction, recurrence interval, epicenters, 

epicentral intensity, fault type, fault length, fault width, maximum probable magnitude, seismic hazard zones, rupture characteristics, seismic moment, stress drop, local amplification, duration of shaking, focal mechanism and depth, and response 

spectrum.

Engineering

Structural mechanics 

Engineering characteristics 

Risk analysis 

Monitoring of structures 

Damage inventories 

Soil-structure interaction 

Structural vulnerability 

Soil mechanics 

Rock mechanics 

Soil/rock acoustic impedance 

Standard penetration tests

Seismic risk maps, structural performance, hysteretic behavior, 

strength of materials, stiffness degradation, structural strength, 

structural reliability, design criteria, material properties, 

response spectra, seismic intensities, nonlinear behavior, inelasticity, ductility, damping, energy absorption, bearing capacity, 

soil properties, amplification levels, shear wave velocity, shear 

modulus, failure limits, load limits, ultimate load limits, and foundation design..

Notes

These are just some of the studies that are necessary to assess earthquake "hazards"; many other types of 

studies are necessary to evaluate "vulnerable" structures, "secondary" hazards (fires, floods, and toxin spills), 

people "exposed," and socioeconomic activities "at risk."

The term "studies" is loosely used here to include experiments, measurements, investigations, observations, 

models, techniques, analyses, mapping, monitoring, or testing. Many of the seismologic studies are a special 

type of geophysical research.

Robert Brown, geologist, Robert Simpson, geophysicist, Allan Lindh, seismologist, and Mehmet Celebi, 

structural engineer, U.S. Geological Survey, provided critical comments and valuable suggestions that have 

refined and improved this list. However, because of its abbreviated form, the author remains responsible for 

omissions and errors.
20 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

List 2. Examples of techniques for reducing earthquake hazards in Utah

Incorporating hazard information into plans and programs

Community-facilities inventories and plans

Economic development evaluations and plans

Land subdivision layouts

Land-use and transportation inventories and plans

Public-safety plans

Redevelopment plans (predisaster and postdisaster)

Utility inventories and plans 

Regulating development

Placing moratoriums on building

Reviewing annexation, project, and rezoning applications

Enacting building and grading ordinances

Adopting design and construction regulations

Requiring engineering, geologic, and seismologic reports

Requiring investigations in hazard zones

Enacting subdivision ordinances

Creating special hazard-reduction zones and regulations 

Siting, designing, and constructing safe structures

Reconstructing after a disaster

Reconstructing or relocating community facilities

Reconstructing or relocating utilities

Securing building contents and nonstructural components

Evaluating specific sites for hazards

Siting and designing critical facilities

Training design professionals 

Discouraging new development in hazardous areas

Disclosing potential hazards to real estate buyers

Adopting lending policies that reflect risk of loss

Adopting utility and public facility service-area policies

Requiring nonsubsidized insurance related to level of hazard

Posting public signs that warn of potential hazards

Making a public record of potential hazard locations

Clarifying the legal liability of builders and property owners 

Strengthening, converting, or removing unsafe structures

Condemning and demolishing unsafe structures

Creating nonconforming land uses

Repairing unsafe dams or lowering their water levels

Retrofitting bridges and overpasses

Strengthening or anchoring buildings

Acquiring or exchanging hazardous properties

Reducing land-use intensities or building occupancies 

Preparing for and responding to emergencies and disasters

Estimating damages and losses from an earthquake

Preparing damage scenarios for critical facilities

Providing for damage inspection, repair, and recovery

Conducting emergency or disaster training exercises

Operating monitoring, warning, and evacuation systems

Initiating public and corporate education programs

Preparing emergency response and recovery plans

Creating community recovery information clearinghouses

In addition, geologists, engineers, and planners, both 

public and private, are evaluating the location or design 

of developments in relation to earthquake hazards, as in 

these examples: rezonings and annexations by the Utah 

and Juab Counties geologist R.M. Robison (written 

commun., 1985, 1986); subdivision layouts, apartment 

project locations, fire station design, and aqueduct relocation by Salt Lake County geologist C.V. Nelson (1988;

written commun., 1985, 1986); and long-range environmental plans, subdivision layouts, and critical facilities, 

including water tanks, fire stations, jails, and waste 

disposal by the Weber and Davis Counties geologist Mike 

Lowe (written commun., 1989).

According to Utah Geological Survey geologist W.F. 

Case (written commun., 1988), a residential development 

in Ogden was scrutinized because its proposed location
REDUCING EARTHQUAKE HAZARDS IN UTAH 21

List 3. Examples of potential users of earthquake hazard information in Utah

City, county, and multicounty government users

City building, engineering, zoning, and safety departments

County building, engineering, zoning, and safety departments

Mayors and city council members

Multicounty planning, development, and preparedness agencies

Municipal engineers, planners, and administrators

City and county offices of emergency services

Planning and zoning officials, commissions, and departments

Police, fire, and sheriffs departments

Public works departments

County tax assessors

School districts 

State government users

Department of Community and Economic Development (Community Services Office, Economic 

and Industrial Development)

Department of Business Regulation (Contracts and Real Estate divisions)

Department of Financial Institutions

Department of Health (Environmental, Health Care Financing)

Department of Insurance

Department of Natural Resources

Department of Public Safety

Department of Social Services

Department of Transportation

Division of Comprehensive Emergency Management

Division of Risk Management

Division of Water Resources

Division of Water Rights

Facilities Construction and Management

Geological and Mineral Survey

Legislative Fiscal Analyst

Legislative Research and General Counsel

Legislature and legislators

National Guard

Office of the Governor

Planning and Budget Office

Public Service Commission

Science Advisor

State Board of Regents

State Fire Marshall

State Tax Commission

State Office of Education

State Planning Coordinator 

Private, corporate, and quasi-public users

Civic, religious, and voluntary groups

Concerned citizens

Construction companies

Consulting planners, geologists, architects, and engineers

Extractive, manufacturing, and processing industries

Financial and insuring institutions

Landowners, developers, and real estate salespersons

News media

Professional and scientific societies (including geological, engineering, architecture, and planning 

societies)

Utility companies

University departments (including geology, civil engineering, structural engineering, architecture, urban and regional planning, and environmental departments)

was in a rockfall hazard area. The developer then hired 

an engineering firm to determine the extent of the 

hazard and to reduce it.

Previously adopted techniques to reduce losses from 

natural hazards can be revised to include the latest

earthquake research information. Examples of regulations that can or have been revised include the site 

development regulations of the Salt Lake City Council 

(1981), Emigration Canyon master plan adopted by the 

Salt Lake County Commission (1985), multihazard miti-
22 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

gation plan for Ogden City and Weber County prepared 

by the Utah Multi Hazards Mitigation Project Administrative Review Committee (1985), and the critical environmental zone created by the Mapleton City Council 

(1985).

Others include seismic risk reduction recommendations for primary and secondary schools by Taylor and 

Ward (1979), hillside site development regulations by the 

Spanish Fork City Council (1980), regulations governing 

dam safety by Hansen and Morgan (1982), structural 

seismic resistance regulation by the Ogden City Council 

(1983), sensitive area overlay zone ordinance by the 

Ogden City Council (1985), hillside development standards and sensitive lands development ordinance by the 

Provo Municipal Council (1985), seismic hazard area 

regulations by the Orem City Council (1986), structural 

directives of the Headquarters Structural Engineering 

Staff (1987), development overlay zone by the Washington Terrace City Council (1988), emergency training 

exercises by the Utah Division of Comprehensive Emergency Management (Tingey and May, 1988), and the 

emergency recovery plans proposed by the Financial 

Institution Emergency Preparedness Committee (James 

Tingey, written commun., 1988).

ACKNOWLEDGMENTS

Walter Hays, Earl Brabb, Donald Nichols, and Robert 

Brown, U.S. Geological Survey; Genevieve Atwood, Don 

Mabey, Doug Sprinkel, and Gary Christenson, Utah 

Geological Survey; James Tingey, Utah Division of Comprehensive Emergency Management; county geologists 

Mike Lowe, Robert Robison, and Craig Nelson; and 

many others read all or part of this report and provided 

many critical comments and valuable suggestions. However, the author is responsible for all errors of fact or 

interpretation. Alice Olsen and Ray Eis, U.S. Geological 

Survey, are especially thanked for processing the words 

and drawing the figures.

TOWARD THE CONNECTION IN UTAH

Sometimes planners, engineers, and decisionmakers 

fail to fully use the research information available. The 

connection between research (list 1) and the use of 

research to reduce hazards (list 2) simply is not made. 

According to several experienced and perceptive observers (McKelvey, 1972; Jacknow, 1985, p. 18; Reilly, 1987; 

Szanton, 1981, table 3-1, p. 64; Yin and Moore, 1985, p. 

18-19; Petak, 1984, p. 456), the reasons vary. They may 

be simply stated as: not all of the research information is 

in a language or format understandable to or directly 

usable by nontechnical users, or it is not effectively 

transferred to them.

UTAH'S USER NEEDS

In Utah, nontechnical users such as government officials, corporate planners, land developers, and private 

citizens have different needs from those in the scientific, 

engineering, and other technical fields. The nontechnical 

users in list 3 do not constitute a homogeneous group; 

rather, they differ widely in the kinds of information 

needed and in the capability to use that information. 

Thus, detailed technical information prepared by scientists or engineers often is unsuitable for and unusable by 

nontechnical users. For example, most professional landuse planners and local officials do not have the training or 

experience to directly apply earthquake hazard research 

information (U.S. Office of Science and Technology Policy, 1978, p. 170). Few academic programs train students 

of planning or public administration to avoid, reduce, or 

design for natural hazards.

Although many land-use planners and local officials in 

Utah have some experience with natural hazards, such 

experience is usually with floods, landslides, or soil 

problems. Without translating and transferring the 

earthquake research information, the effective user community is limited to scientists and engineers. At the 

other extreme, if the users do not become familiar with 

and proficient in using research information, it is likely to 

not be used or, worse, misused!

PROBLEM RECOGNIZED

Both researchers and users of research have recognized the needs of nontechnical users such as decisionmakers (Alexander, 1983, p. 49), State and local governments (Council of State Governments, 1976), nonspecialists (Wenk, 1979), potential user groups (Yin and 

Moore, 1985), journalists (Peterson, 1986), nontechnical 

users (White and Haas, 1975), the general public (Petak, 

1984), and city, county, and multicounty planners (Kockelman, 1975, 1976b, 1979).

From the beginning of their 5-yr focused effort in 1983, 

both the Utah Geological Survey (UGS) and the Utah 

Division of Comprehensive Emergency Management 

(CEM) were aware of and concerned about the problems 

of research information being effectively used by nontechnical persons. For instance, during a Utah Governor's conference on geologic hazards held in 1983, most of 

the 36 working groups identified specific problems or 

needs of nontechnical users, as in these examples:

 Officials need risk maps.

 Officials lack knowledge concerning expertise available.

 Officials are not aware of the availability of hazards 

information.
REDUCING EARTHQUAKE HAZARDS IN UTAH 23

 Most local governments require technical assistance.

 State and local agencies need a central data bank.

 Some mechanism is needed to transfer information.

 There is a lack of hazard susceptibility maps. 

According to UGS deputy director D.A. Sprinkel (written commun., 1986), "most of the research scientists feel 

the amount of data collected can and should be translated 

into products for the public and disseminated as soon as 

possible."

Part of the solution has been widely recognized as 

simply one of adequate translation for, and effective 

transfer to, nontechnical users. International agencies 

(United Nations Educational, Scientific, and Cultural 

Organization, 1976), Federal agencies and committees 

(Wallace, 1974; NEHRP Expert Review Committee, 

1987), and State agencies (Utah Seismic Safety Advisory 

Council, 1981; California Seismic Safety Commission, 

1986) have all addressed the need for translation and 

transfer of research information.

Recommendations for translation and transfer have 

been included in hazard reduction programs for natural 

hazards other than earthquakes, such as coastal area 

hazards (White and others, 1976), flood hazards 

(National Science Foundation, 1980), landslide hazards 

(U.S. Geological Survey, 1982), and the major natural 

hazards considered by the Advisory Committee on the 

International Decade for Natural Hazard Reduction 

(1987).

UTAH'S WORK PLAN

Two of the five components (fig. 1) in the work plan 

adopted by Utahans directly relate to the connection 

between research and its use. The work plan clearly 

identifies the need for scientific information to be "translated" before it can be transferred to a user and subsequently used for earthquake hazard reduction. The work 

plan then specifically addresses those actions likely to 

improve effective use of scientific information by nonscientists, namely:

 Identify the hazard maps and reports needed for 

hazard reduction measures and ensure that new information is prepared in detail and at the scales needed 

by the users.

 Make special efforts to present the information in a 

format and language suitable for use by engineers, 

planners, and decisionmakers.

 Design the communications program after an assessment of potential users' needs and capabilities.

 Select the most effective educational, advisory, and 

review services appropriate to the targeted users.

 Design the communications program so that information can be effectively disseminated (including use of 

the scientists and investigators to help communicate).

According to Atwood and Mabey (1987, p. S30), 

achieving this plan "requires communication of translated scientific information to responsible officials and 

interested parties seeking to reduce losses from the 

hazards. This is a major challenge to the program 

because many of the products of scientific research are 

not directly usable by responsible officials and the public. 

To accomplish this goal, it is essential to involve the user 

of the information early in the program."

In their book, In Search of Excellence, management 

consultants Peters and Waterman (1982, p. 145) observe: 

"Finally, and most important, is the user connection . .. 

we will simply say that much of the excellent companies' 

experimentation occurs in conjunction with a lead user." 

A social scientist (Drabek, 1986, p. 416) remains "convinced that the quality of disaster research will be 

improved immeasurably if the interaction between practitioners and researchers is increased." A comprehensive 

review of the use of research (Yin and Moore, 1985, p. 70) 

includes a conclusion that "the most consistent pattern 

leading to utilization was the prevalence of rich and 

direct communication between knowledge producers and 

users throughout the design and conduct of the research 

project." Taylor (1979, p. 278) notes that "if users 

participate in the research process most especially at 

the beginning when the problem is defined then they 

are likely to identify with the research project and with 

its outcome."

One way to ascertain nontechnical users' needs is to 

arrange for a dialogue between researchers and users of 

hazard information (list 3). In the case of Utahans, this 

dialogue took place at conferences, workshops, and special sessions, each of which required careful preparation, 

good-faith effort, and skillful facilitating. Three examples are discussed in more detail in the following subsections.

GOVERNOR'S CONFERENCE

The Governor's Conference, held August 11 and 12, 

1983, on the campus of the University of Utah, was 

sponsored by the Utah League of Cities and Towns, 

Utah Association of Counties, Utah State Legislature, 

Federal Emergency Management Agency (FEMA), 

U.S. Geological Survey (USGS), and the University of 

Utah; it was coordinated by UGS and GEM. The purpose 

of the conference was to bring together scientists and 

engineers, elected and appointed officials, leaders of 

business and private organizations, and private citizens 

to discuss geologic hazards and to recommend appropriate actions to all levels of government. The first day of 

the conference was designed to provide information on 

the principal geologic hazards in Utah. During the second 

day, 36 working groups met in half-day sessions to
24 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

develop recommendations for actions by all levels of 

government to reduce the geologic hazards in Utah.

The working groups recommended 171 actions that 

would reduce the impact of geologic hazards on the lives 

of Utahans. They concluded that, although much of the 

information needed to make site-specific decisions has 

not yet been developed, sufficient information exists on 

which to base public policy. The working groups determined that the primary support for research on geologic 

hazards should come from the Federal Government and 

that the State should take a major role in identifying 

research priorities and applying research results. The 

working groups also concluded that information collection and dissemination is the role of State agencies and 

that local governments should take a more active role in 

identifying information needs and providing matching 

assistance. An excerpt from one of the working groups 

follows:

33. HAZARDS INFORMATION FOR PLANNERS

Chairperson: James P. McCalpin, Geologist, Utah State 

University

Topic c: Interpretation of information

Problem: Planners are often unable to interpret available 

geologic hazards information and therefore cannot use it effectively in land-use planning or 

regulation. This problem has two related 

aspects: the data are presented in too technical 

and specialized a format for planners, or planners have insufficient geologic background.

Action: (1) Offer natural hazard information in derivative or interpretive maps .... Such interpretive 

maps would assess hazards directly with some 

kind of rating system (e.g., serious, moderate, 

slight) .... (2) Educate planners via technical 

workshops ... to train them in hazard interpretation from existing geologic maps and forthcoming interpretive maps, or (3) Local governments in critical hazard areas should hire a 

full- or part-time geologist to identify local hazards and to help draft local government ... regulations.

The results of the conference, including suggestions for 

action, remarks of the Governor, action items of the 

working groups, and a summary of the questionnaire, 

were published by the Utah Geological and Mineral 

Survey (1983). The dialogue between researchers and 

the users of geologic hazard information had begun.

EARTHQUAKE HAZARDS WORKSHOPS

The first of five workshops was held on August 14-16, 

1984, in Salt Lake City. The workshop was sponsored by 

USGS, FEMA, UGS, GEM, and the University of Utah. 

The 115 participants, representing the fields of earth 

science, social science, planning, architecture, engineering, and emergency management, came from various 

industries, volunteer agencies, academic institutions, 

local and State governments, the private sector, and the 

Federal Government.

The two primary objectives of the workshop were to 

(1) strengthen the capability of the scientific and technical community to compile and synthesize geologic, geophysical, and engineering data needed for evaluating 

earthquake hazards, and (2) work with public officials in 

fostering an environment for implementation of research 

results, creating partnerships, and providing highquality scientific information that can be used by local 

government to reduce hazards.

Four discussion groups were created, each composed 

of both researchers and users of hazard information. Two 

of the groups recommended translation and transfer 

activities. An excerpt from the "information systems" 

group moderated by a USGS research geographer reads:

2) An extraordinary effort should be made to communicate. 

Possible actions include:

b) Devising outreach activities to involve a wide range of 

groups. These activities could use strategies such as workshops, small group meetings, exchange of technical information, demonstration of products and results of research, 

neighborhood meetings, and generation of special information packets and audiovisual materials to give them a stake 

in the process.

An excerpt from the "implementation options" group 

moderated by a FEMA emergency manager reads:

3) County geologists Local governments need to attain the 

capability to take the products (data, maps, reports, etc.) 

produced ... and apply them to solve problems in their 

jurisdictions. This application is the only way that the ultimate goal of reducing the loss of life and property from 

earthquakes will be attained. The Wasatch Front counties 

... are the places to start. The county geologists are the 

key resource. Such a process is needed now.

The results of this innovative workshop and the recommendations of the discussion groups were published in 

the proceedings edited by Hays and Gori (1984). The 

results of the 1986 workshop were published in the 

proceedings edited by Hays and Gori (1987). These 

workshops resulted in early release of research findings, 

continued dialogue between researchers and practitioners, and an increased awareness of earthquake hazards 

by the public.

USER NEEDS SESSION

A special session was held in the evening (convened 

and moderated by the Utah State geologist and the 

USGS earth sciences applications planner) to provide an 

opportunity for users of earth science information to
REDUCING EARTHQUAKE HAZARDS IN UTAH 25

communicate their needs to the UGS, USGS, universities, consultants, and others who produce such information. Invitations to participate in this session were 

sent to more than 70 city, county, and State officials, 

planners, engineers, and university researchers and educators. Representatives of the Utah League of Cities and 

Towns, League of Women Voters, American Planning 

Association (Utah Chapter), Wasatch Front Regional 

Council, The Western Planner, and the Southeastern 

Utah Association of Governments also attended.

Seven speakers experienced in determining or meeting user needs made presentations that were prepared 

specifically for this session. The speakers' collective 

experience included conducting studies of user needs, 

translating scientific information for nontechnical users, 

communicating information to nontechnical users, or 

using earth science information to reduce hazards. Briefing materials emphasizing the needs of users were provided to participants.

Six panelists representing important city, county, 

State, and private planning and decisionmaking agencies 

were selected on the basis of their experience in the use 

of earth science information and on their need to have 

research information translated, transferred, and used. 

The panelists began the "brainstorming" session by 

commenting on the usefulness to their organizations of 

the techniques presented by the speakers. The panelists 

were asked to list types of information that they felt 

rated the highest priorities.

The meeting then was thrown open to the nontechnical 

participants. A brainstorming" approach was scrupulously followed and resulted in a blackboard filled with 

items needed. The items listed were organized into five 

categories: (1) scientific research topics, (2) translation of 

science for use by nontechnical users, (3) transfer of the 

information to the users, (4) use of the translated information to reduce hazards, and (5) evaluation of the uses 

of the information to ensure effectiveness.

After the items were organized, the moderators asked 

for a weighting of the importance of each need by a 

simple showing of hands. The users were then asked 

whether they would actually use the information if it 

were available. Both information producers and users 

fully understood that a "no" vote did not mean that the 

information was not necessary or useful to someone else, 

but rather that this particular group of users did not 

think that they would use the information. The spontaneous voting by only the user attendees resulted in a 

rating on a scale of 1 to 10, the number 10 indicating that 

virtually all the users present felt that their organizations needed and would, or should, use a specific type of 

information. Some of the needs (and weights assigned) 

follow:

 Site-specific geologic reports that are legally and politically defensible (10).

 Early-warning "red flag" maps, scales 1:9,600 (10).

 Structure types susceptible to failure by shaking (8).

 Location of surface-fault rupture zones (7).

 Maps showing multihazards, scales of 1:2,400 or more 

detailed (10).

 Maps showing susceptibility to damage or hazard (10).

 Retention of five staff geologists to serve 10 counties

(9).

 "Red flag" hazard maps for counties at a scale of 

1:100,000 (6).

 Maps interpreting research for nontechnical persons

(10).

 Education of local planning commissioners (10).

 Increased awareness of hazards (10).

 Educational materials explaining earthquake processes and their effects, meant for adults but that can 

be understood by sixth graders (5).

 Advisory services (10).

 Training for local government, including planners (10).

 Prototypical community training exercises (9). 

The names of the session's speakers, panelists, and 

participants, along with the papers, briefing materials, 

and the complete results of the "brainstorming," are 

included in the workshop proceedings edited by Hays 

and Gori (1984, p. 606-674). This session provided the 

researchers with the specific translation and transfer 

needs of the nontechnical users.

RESEARCHERS AND TRANSLATORS

Various views have been expressed concerning who is 

responsible for translating and transferring research 

information to nontechnical users. The following examples concerning the responsibility of researchers and 

translators are paraphrased from the comments of experienced and perceptive observers:

 Identify user groups, meet their needs, and plan on 

producing a major product aimed directly at users (Yin 

and Moore, 1985, p. ix-x).

 Be prepared to make their analyses of earthquake 

danger comprehensible in common-sense terms by 

frequent and imaginative use of metaphors and examples from common experience (Turner and others, 

1981, pt. 10, p. 96).

 Be willing not only to face the adverse reactions but 

also to persist in finding truly effective ways of conveying information that is important to societal needs 

(Peterson, 1986, p. 245).

 See user problems as interesting and worthy of serious 

intellectual commitment beyond the theoretical implications for other scientists in the field (White and 

Haas, 1975, p. 152).
26 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

 Seek much greater direct participation by geologists 

and by planners with better training and understanding of the significance and application of earth science 

information (Nichols, 1982, p. 290). 

In identifying problems and opportunities as experienced by USGS, Bates (1979, p. 29), in his Transferring 

Earth Science Information to Decisionmakers, concluded that the entire earth science community must 

mobilize to provide specialized, technical information in a 

form and language understandable to the intelligent 

citizen, and to engage in the educational, advisory, and 

review services necessary to assist the public and its 

representatives in making effective use of that information. The remarkable efforts made in Utah to translate 

and transfer research information to nontechnical persons will be seen in subsequent sections of this report.

OTHER ASPECTS

Translation and transfer activities considered in this 

paper are only part of the solution to the problem of lack 

of effective earthquake hazard reduction. Some other 

aspects that must be considered are the following:

 Perhaps the most telling factor acting against adoption 

of earthquake-risk reduction measures is that Utah 

has not experienced a highly destructive earthquake in 

a heavily populated area (Atwood and Mabey, 1987, 

p. S19).

 Utah needs trained people to analyze the technical 

data bases, to extrapolate beyond the limits of the 

data, and to translate the basic data into maps and 

other products that can be applied in the community 

(Hays, 1987, p. R8).

 The research begins with approval of the effort by 

those top officials who have power to see that results 

are utilized (White and Haas, 1975, p. 152).

 Lack of leadership due to competing, day-to-day problems, lack of interest or commitment, potential citizen 

opposition, and inadequate educational programs 

(Perkins, 1986, p. 3).

 The public lacks knowledge of and underestimates 

the hazardous quality of the environment; these 

underestimations reflect busy people occupied with 

their own life priorities day-to-day issues of living 

(Drabek, 1986, p. 320).

Hays (1988b, p. 100-101) emphasizes that the risk 

management process in every nation depends on seven 

factors: a perceived need for risk reduction, informed 

internal advisors, strong external champions, credible 

products, user-friendly products, balanced political, 

legal, and economic considerations, and a window of 

opportunity. Sprinkel (1988), in his review of the earthquake assessment program in Utah, asks, "Will Utah

meet the challenge?" and then answers that question in 

the affirmative by noting the existence of the following 

key factors: champions, challenge, symbiotic relationship, true believers, strong partnership, key players, 

early planning, long-time advocates, mutual buy-in, 

enthusiasm, credibility of the program, excellent media 

coverage, commitment of funds, translation expedited, 

talented people, and potential devastating earthquake.

TRANSLATION FOR PRACTITIONERS

The objective of translating hazard information for 

practitioners is to: make them aware that a hazard exists 

which may affect them or their interests; provide them 

with information that can easily be presented to their 

superiors, clients, or constituents; and provide materials 

that can be directly used in a reduction technique (list 2). 

The Utah work plan is quite specific as to what is 

expected of translated information:

 Easy access to data in media, scales, and formats that 

will be most useful.

 Standard base maps and mapping scales.

 Interpreted information derived from basic scientific 

data.

 Easy for local government, engineers, architects, 

planners, and emergency responders to use the technical information.

 Information in a format and language suitable for use 

by engineers, planners, and decisionmakers.

DEFINITION

Much has been said about the need for and objectives 

of translation. No clear, concise definition or criterion 

has been offered, nor are any found in the literature 

except by inference or by an analysis of what is actually 

used by practitioners. However, various researchers, 

translators, and users of earthquake research information are specific about what is needed by nontechnical 

users: "Knowledge of the distribution of earthquakes in 

time, location, and size is essential for insurance ratings 

and underwriting purposes," (Steinbrugge, 1982, p. 13) 

and "Successful translation of science must (1) show 

hazard locations on maps at suitable scales, (2) provide 

some sense of the damage likely to result from occurrence of a hazardous event, and (3) provide some sense of 

when a hazardous event is likely to occur" (Keaton and 

others, 1987, p. 73).

My experience with reducing potential natural hazards 

(primarily atmospheric hazards, floods, unstable soils, 

landslides, and earthquakes) indicates that hazard information successfully used by nontechnical users has the 

following three elements in one form or another:
REDUCING EARTHQUAKE HAZARDS IN UTAH 27

1. Likelihood of the occurrence of an event that will 

cause human casualties, property damage, or socioeconomic disruption.

2. Location of the effects of the event on the ground.

3. Estimated severity of the effects on the ground, 

structure, or equipment.

Engineers, planners, and decisionmakers will usually 

not be concerned with a potential hazard if the likelihood 

of occurrence is rare, the location is unknown, or the 

severity is slight. However, concern varies widely with 

the individual user, the cost of hazard reduction, and who 

or what might be affected. For example, a pedestrian 

might prepare for a 50-percent probability of rainfall 

tomorrow by carrying an umbrella; a lender might 

require flood insurance if the mortgaged property is 

within a flood zone with a 100-yr recurrence interval; and 

a regulatory agency might curtail construction if a critical facility is being located near a fault that has moved in 

the last 10,000 yr. The reader will note that both location 

(areal, zonal, or specific) and likelihood of occurrence are 

conveyed in these three examples. Severity, however, is 

perceived in a much different way for example, from 

personal experience, documented damage, or fear of a 

disaster and possible liability.

Unfortunately, these three elements come in different 

forms and with different names, some quantitative and 

precise, others qualitative and general. In each of the 

several examples that follow, for a product to be defined 

as "translated" hazard information, the nontechnical user 

must be able to perceive likelihood, location, and severity 

of the hazard so that he or she becomes aware, can 

convey information to others, and can use the information directly in selecting and adopting a hazard reduction 

technique.

LIKELIHOOD OF OCCURRENCE

Likelihood of occurrence can be conveyed for a 

selected size and location of a damaging earthquake by 

the use of various concepts probability, return period, 

frequency of occurrence, or estimated, average, or composite recurrence interval. Sometimes a specific event is 

chosen: design earthquake, hypothetical earthquake, 

characteristic earthquake, or postulated earthquake. 

Each of these terms has a specific definition that is 

beyond the scope of this report. In all cases, each event 

chosen must be credible; that is, it must have some 

likelihood of occurring.

In some cases, an engineering parameter is used for a 

specific ground failure: "the probability that the critical 

acceleration would be exceeded in 100 years" for liquefaction by Anderson and others (1986, p. 39) or for 

landslides by Keaton and others (1987). Algermissen and 

others (1982) use a map showing probabilistic bedrock

peak horizontal ground acceleration that has a 90-percent 

probability or likelihood of not being exceeded in a 50-yr 

period. In another case, the term "opportunity for liquefaction" was used where "a return period of about 30-50 

yr is anticipated for ground motions sufficient to exceed 

the liquefaction threshold at a given susceptible site" 

(Tinsley and others, 1985, p. 315). The period of 30-50 yr 

is selected because it embraces the economic or functional life of most buildings.

No matter what term is used, it must convey a 

likelihood of occurrence that is important to the user. 

This likelihood varies widely, depending upon its use. 

For example, the National Research Council (1986, p. 5) 

notes that "various public agencies define an active fault 

as having had displacements (a) in 10,000 yr, (b) in 35,000 

yr, (c) in 150,000 yr, or (d) twice in 500,000 yr." The 

interest of an engineer, planner, or decisionmaker in 

likelihood of occurrence also varies widely. For example,

Insuring agent 

Elected official 

Lending officer 

Bridge designer 

Waste manager 

Pyramid builder

Premium period (1 yr) 

Term of office (2-6 yr) 

Amortization schedule (10-30 yr) 

Structure's life (50-100 yr) 

Hazard's life (1,000-10,000 yr) 

Next world (10,000-10,000,000 yr)

LOCATION AND EXTENT

Once users are convinced of the likelihood of a damaging event, they want to know if their interests might be 

affected. This information is conveyed by showing the 

location and extent of ground effects or geologic materials susceptible to failure. These are usually shown on a 

planimetric map having sufficient geographic reference 

information to orient the user to the location and extent 

of the hazard. Topographic maps showing geographic 

information, such as streams, highways, railroads, and 

place names, are very helpful. Some maps show streets; 

others show property boundaries. The scales of such 

maps vary widely; examples from Utah range from 

1:36,000 (1 in. equals 3,000 ft) to 1:1,200,000 (1 in. equals 

approximately 3 mi) (compare figs. 3 and 4).

The scale selected depends on the detail and amount of 

information to be shown, as well as the users' needs. For 

example, the seismic zone map of the United States 

adopted by the International Conference of Building 

Officials (1988, p. 178) and incorporated into the widely 

used Uniform Building Code is at a scale of 1:30,000,000; 

it is based on the national map by Algermissen and 

others (1982), which is at a scale of 1:7,500,000. Some 

building site hazards have been shown at scales of 1:1,200 

(1 in. equals 100 ft) or larger. Most hazard maps are a 

compromise between scale, detail, reliability, difficulty 

and cost of preparation, and the purpose for which they
28 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

were designed. There are no ''best" scales, only more 

convenient ones.

ESTIMATED SEVERITY

After the users recognize the likelihood of an event 

that may affect their interests, the next concern is how 

severe the effects will be. In other words, is the hazard 

something that should be avoided or designed for? 

Should preparations be made to respond during, and 

recover, repair, and reconstruct after a damaging event? 

Severity of anticipated effects is best expressed by use of 

measurable engineering parameters for the various hazards:

 Vertical and horizontal displacements for surface-fault 

ruptures.

 Peak acceleration, peak velocity, peak displacement, 

frequency, and duration for ground shaking.

 Velocity and volume for landslides.

 Extensional and vertical displacement for liquefaction.

 Vertical displacement for tectonic subsidence.

 Run-up height for tsunamis.

Modified Mercalli or Rossi-Forel intensity scales of 

observed or estimated damage also show severity. These 

scales are used primarily for ground shaking but can 

include the effects of surface-fault rupture, landsliding, 

and liquefaction, as well as some of the observed or 

anticipated effects on structures, occupants, and contents.

FORMAT

Likelihood, location, and severity have been combined 

into various formats, some easy for the nontechnical 

user, and others requiring additional information or an 

experienced user to appreciate, adapt, and use in a 

reduction technique. The format may be a single map 

containing all elements, or all information may be combined in a report or volume, or outside supplemental 

information must be obtained. Sometimes one of the 

elements (likelihood of occurrence) is derived from public 

knowledge or experience, or elements may only be 

available or combined for a demonstration area. When 

adequate research information is available for other 

areas, additional translation work can be done. Otherwise new research must be undertaken to cover the 

user's area of jurisdiction or interest.

At other times, the format is a "seismic hazards zone" 

(sometimes called "seismic zonation") showing the location and severity of all the effects from one postulated 

event. Qualitative terms are often used to show relative 

susceptibility (high, moderate, low, and very low) of 

geologic or other units to landslides or liquefaction, or to

show relative severity (very violent, very strong, strong, 

and weak) of shaking. Examples of some of these formats 

follow.

Wesson and others (1975) and Ziony and Yerkes (1985) 

show location of faults that have, or may generate, 

damaging earthquakes or surface-fault rupture on indexscale maps. Maps at much larger scales (1:24,000) for 

surface-fault traces are readily available. Likelihood of 

occurrence (estimate of recurrence intervals) and severity (maximum surface displacement) are conveyed by 

discussions, tables, and graphs in the text accompanying 

the index maps. Both reports are in a volume that 

illustrates surface faulting as part of the predicted effects 

of a postulated earthquake (magnitude 6.5) for a selected 

fault.

Algermissen and others (1982) show location and 

severity of ground shaking (in terms of peak velocity and 

acceleration) by areas on a map. In the map caption, 

likelihood of occurrence is conveyed by probability (percent) of not being exceeded for various exposure times 

(10, 50, and 250 yr).

Rogers and others (1985) show location of a demonstration site and severity (mean amplification factor 

compared with level of shaking at site on rock) by areas 

on maps for predicted relative ground response. Individual maps are used to show predicted relative ground 

response in three period bands having significance to 

buildings of specific heights (2-5, 5-30, and 30 or more 

stories). Likelihood of occurrence is conveyed by other 

papers in the same volume.

Wieczorek and others (1985) show location and extent 

(levels of susceptibility) and percentage of area likely to 

fail on a map for slope stability during earthquakes. 

Likelihood of occurrence is conveyed by a discussion of a 

lower bound hypothetical (or "design") earthquake large 

enough to trigger landslides (Richter magnitude 6 or 7, 

depending on location of the earthquake). Severity is 

conveyed by a discussion on the map by noting that 

"structures generally cannot withstand more than 10 to 

30 cm of movement without damage ...." and then by 

selecting 5 cm (2 in.) as a conservative design threshold.

Tinsley and others (1985) map location and extent 

(levels of relative susceptibility) of liquefaction. Likelihood of occurrence (return period of liquefaction opportunity) for magnitude 5 or larger earthquakes is shown 

by contours on a separate map. Severity is partially 

conveyed by photographs showing liquefaction damage 

to such critical facilities as a causeway, a juvenile hall, 

and an earth-filled dam. Their paper is in a volume that 

illustrates liquefaction-related ground failure as part of 

the predicted effects of a postulated earthquake for a 

selected fault; the text also conveys severity.

Agnew and others (1988) use a map to show conditional 

probability of large earthquakes for selected segments.
REDUCING EARTHQUAKE HAZARDS IN UTAH 29

Probabilities are based on expected recurrence times, 

and calculated for the likelihood of occurrence during the 

next 30 yr. Severity is generally conveyed by the 

expected magnitude of a major earthquake, which is 

provided for each segment.

In some cases, lists of damaging events, photographs 

of damage, or diagrams of effects on ground or buildings 

for similar events are used to convey severity. Examples 

include the works of Youd and Hoose (1978) for ground 

failure, Ziony (1985) and Borcherdt (1975) for earthquake 

hazards, and Hays (1981) for several geologic and hydrologic hazards.

This type of information is an important part of the 

researcher's observations, but when used in translated 

information becomes an effective transfer technique, 

namely, communicating possible effects casualties, 

damage, and socioeconomic interruptions. Sometimes 

this conveyance can be misleading because of differences 

in the user's environment and that depicted, in terms of 

earthquake location and size, ground conditions, structure vulnerability, people exposed, and reduction techniques already implemented.

SUCCESSFUL TRANSLATION

One of the best ways to confirm that likelihood, 

location, and severity are needed is to look at information 

that has been prepared for, and successfully used by, 

engineers, planners, and decisionmakers to reduce 

earthquake hazards. Many examples of the use of translated (and of course transferred) earthquake research 

information for specific reduction techniques can be 

cited. In other words, the connection between research 

and its use in hazard reduction techniques is being made. 

Selected examples follow:

 Shaking intensity maps for maj or fault systems (E vernden and others, 1981) used for anticipating damage and 

interruptions to critical facilities and preparing for 

emergencies by utilities and local, multicounty, and 

State government agencies (Davis and others, 1982; 

Steinbrugge and others, 1987).

 Fault-rupture zone maps by various Federal, State, 

university, and consultant researchers (Brown and 

Wolfe, 1972; Sarna-Wojcicki and others, 1976) used for 

statewide legislation, city and county regulations, and 

real-estate seller disclosures (Hart, 1988).

 Fault-rupture, tsunami, liquefaction, shaking, and 

landslide hazard information combined by computer 

and used for county seismic safety plans (Santa Barbara County Planning Department, 1979).

 Maximum credible ground acceleration on bedrock 

map (Greensfelder, 1972) used to assign priorities and 

to design for strengthening of highway overpasses by 

a State transportation agency (Mancarti, 1981).

 Maximum earthquake intensity map (Borcherdt and 

others, 1975) used for estimating cumulative damage 

potential for different building types by a multicounty 

agency (Perkins, 1987).

 Numerous studies of ground-shaking acceleration, 

losses, and predicted intensities used as a basis for 

inventorying unreinforced masonry buildings and 

requiring the strengthening or demolishing of unsafe 

ones (Los Angeles City Council, 1981).

 Probabilistic intensity (Algermissen and others, 1982) 

and local site amplification (Hays and others, 1978) 

maps used to estimate loss and replacement cost for 

various building types in Salt Lake City (Algermissen 

and Steinbrugge, 1984, p. 12-22).

 Continuous monitoring and analysis of earthquake 

precursor information for a specific fault segment used 

to warn local governments, the public, and the press 

via a governor's office of emergency services (Bakun 

and others, 1986).

Discussions and illustrations of some of these and other 

examples can be found in the works of Blair and Spangle 

(1979), Kockelman and Brabb (1979), Brown and Kockelman (1983), Kockelman (1985, 1986), Jochim and others 

(1988), Mader and Blair-Tyler (1988), and Blair-Tyler 

and Gregory (1988).

COMMENT

These examples of translation vary as to scale, area 

covered, format, postulated or probable occurrence, single or multiple hazards, limitations, and supplemental 

information required. What they all have in common is 

that they convey the likelihood of the occurrence of a 

damaging event, show location and extent of the hazard 

on a map, and provide some indication of severity of 

effects on the ground.

Some of these examples have gone, or can easily be 

taken, a step further to show potential response of 

structures, occupants, and equipment. This next step is 

actually using translated information in a reduction technique (list 2) such as development regulations, loss 

estimates, overpass retrofits, preparedness scenarios, 

and warning systems, as seen in the above examples. 

This step requires the collection, analysis, and use of new 

information concerning the type, age, and condition of 

vulnerable structures; characteristics of exposed populations; sensitivity of equipment; and importance of the 

socioeconomic systems at risk.

Numerous benefits are derived from translating earthquake hazard research for nontechnical users:

 Reports and maps designed for one common user 

group intelligent and interested citizens provide a 

common basis for discussion during public meetings.
30 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

[All values for age and time intervals (columns A-C) are rounded to the nearest 100 years. Ages based on calendar-corrected radiocarbon dates and 

thermoluminescence analyses. The average recurrence interval is determined by dividing the sum of time intervals (column C) by the sum of intervals between 

faulting events (column D). Time intervals (column C) for some segments include time between the oldest (undated) event at a site and the age of the datum; 

thus, some values in column C are maximum values. N/A indicates a value that is not applicable to the calculation]

B D

Fault segment Trench site Oldest event (t) 

or datum (d) 

(years ago)

Estimated time

since most recent

faulting (years)

Time interval 

(A-B) 

(years)

Number of faulting 

events (and intervals)

Events Intervals

Brigham City .........

Weber ................

Salt Lake City........

American Fork .......

Spanish Fork .........

Nephi.................

Levan ................

Totals* (based on

Totals (based on g

. . . . Brigham City ............

. . . . East Ogden ..............

. . . . Dry Creek ...............

. . . . AF-1, AF-2 .............

. . . . Mapleton. ................

. . . . North Creek .............

. . . . Deep Creek ..............

five segments: segments 1^4, 6) .

iix segments: segments 1-6). . . . . .

4,700t

4,000 t

5,500 t

5,300 1

3,000 t

5,300d

7,300d

3,600

500

1,500

500

600

400

1,000

1,100

3,500

4,000

4,800

2,400*

4,900

>6,300N/A

18,300

20,700

2

4

2

3

2*

3

1

14

16

1

3

1

2

1*

2

0

9

10

Calculated recurrence intervals (in years) for segments 

of the WFZ having repeated Holocene movement#

Minimum Maximum 

value value

Average recurrent interval (RI) on a single segment. 

Average composite recurrence interval (CRI)........

2,035

340

2,070

415

Notes: t Time of oldest well-dated faulting event.

d Age of datum from dating, stratigraphic, or tectonic considerations (rounded to nearest 100 years).

* For a five-segment model, we use only the number of events and intervals from American Fork for the Provo segment.

# Three significant figures are used to compute average values of recurrence from the totals in columns C and D. Values are rounded to nearest 5 years. 

Minimum values calculated from 20,700 years, 10 intervals, and 6 segments. Maximum values calculated from 18,300 years, 9 intervals, and 5 

segments. The latter model (maximum value) is based on our preferred model of segmentation.

FIGURE 2. Example of a table showing average recurrence interval on a single segment and average composite recurrence interval for several

segments (Machette and others, 1989, table 2).

Researchers are relieved from repetitive requests for

translation.

Numerous nontechnical transfer agents are available

to transfer nontechnical information.

Transfer and use occur more rapidly, and more correct

and appropriate use is made of the research.

Researchers become more sympathetic to users and

their needs, and users become more appreciative and

supportive of the researchers.

EXAMPLES OF SUCCESSFUL TRANSLATION 

IN UTAH

An unusual effort is being made in Utah to translate 

earthquake research information for nontechnical users. 

During 1986, the Utah State geologist convened several 

meetings to discuss and develop criteria for "translated" 

research and to identify potential translators. D.A. 

Sprinkel, UGS Deputy Director (written commun., 

December 24, 1986), reported that a common understanding was established, a logical progression from the 

research to its use was identified, and a tentative definition of translation was developed, namely, occurrence, 

location, and consequences.

Translators in Utah include university, State, and 

Federal researchers, geotechnical consultants, and

county geologists. Hazards being addressed include 

surface-fault rupture, ground shaking, and failures 

induced by shaking liquefaction, landslides, rockfalls, 

tectonic subsidence, and dam failure. An example and 

illustration of translated information from Utah for each 

of these hazards follow.

SURFACE-FAULT RUPTURE

Machette and others (1989) have prepared a report on 

surface-fault rupture for the segments in the Wasatch 

fault zone. The report includes a discussion of recurrence 

of large earthquakes and a table giving the number of 

faulting events on seven of the segments, and it introduces the idea of a composite-recurrence interval 

between 340 and 415 yr (see fig. 2). Personius (1988) 

shows the location of faults that offset the surficial 

material on a topographic map (scale 1:50,000). Similar 

maps are being prepared for the urbanized portion of the 

Wasatch Front.

In an earlier report, Machette and others (1987) conclude that "recurrence intervals vary widely" on some 

segments, that some "earthquakes tend to occur in 

clusters," and that "recurrence intervals within clusters 

may be as short as 100 years" (revised to 180 yr). They 

suggest that the lack of faulting events in the past
REDUCING EARTHQUAKE HAZARDS IN UTAH 31

400-500 yr, and the relatively imprecise dating (±100 yr) 

of the most recent events, may indicate that "a major 

surface-rupturing earthquake is overdue on one or more 

of the segments." They include displacement, slip rates 

for the segments, and length of surface rupture from 

recent large earthquakes in the northern Basin and 

Range province.

Machette and others (1987) begin their report by 

stating that the "heavily urbanized part of the Wasatch 

Front between Ogden and Provo coincides with the 

part of the fault zone that shows the highest slip rates, 

shortest recurrence intervals ..., and most recent fault 

activity" and conclude that major earthquakes have 

struck the central, heavily urbanized section of the 

Wasatch fault zone, on average, once every 310 yr 

(revised to 415 yr) during the past 4,000-8,000 yr; that a 

form of temporal clustering of earthquakes has been (and 

may still be) active; and that lack of movement along the 

Brigham City segment during the late Holocene (past 

3,600 yr) is somewhat ominous.

Their work on recurrence intervals is applicable to, 

and frequently provides the likelihood of occurrence 

element for, the Wasatch Front hazards that are discussed in the following subsections. In addition, 

McCalpin (1987) has analyzed the geometry of nearsurface ground breakage across some normal faults and 

defined reasonable setback distances.

The three county geologists serving Davis, Juab, 

Weber, Salt Lake, and Utah Counties are combining this 

and other information to show a surface-fault rupture 

study zone on county maps (see fig. 3). In addition, the 

geologists are transferring this map information to nontechnical users by use of texts that discuss and illustrate 

fault characteristics, segments, boundaries, recurrence 

intervals, and displacement, and they are suggesting use 

of the maps for hazard reduction. For example, Robison 

(Surface-fault rupture: A guide for land-use planning, 

Utah and Juab Counties, Utah, this volume; 1988a) 

summarizes displacement per event for each of the 

segments.

GROUND SHAKING

Youngs and others (1987, fig. 37, p. M88) map the 

location and severity of ground shaking (peak ground 

acceleration). Likelihood of occurrence is conveyed in the 

figure caption by probability (percent) of being exceeded 

for various exposure times (10, 50, and 250 yr).

Tinsley (1988) has prepared a map showing increased 

shaking due to ground conditions in the Salt Lake Valley. 

Figure 4 is a generalized version of this map at an 

original scale of 1:200,000. Location of increased ground 

shaking on unconsolidated deposits is shown by contour 

lines on the map. Severity is conveyed by use of Modified

Mercalli Intensity (MMI) units, representing an increase 

in damage intensities that would occur on the underlying 

bedrock.

The size and location of a credible earthquake can be 

obtained by referring to Machette and others (1987). A 

map of MMI on bedrock for such an earthquake is 

available, and Tinsley's increased intensities can be 

added to such a map to meet the needs of a nontechnical 

user.

LIQUEFACTION POTENTIAL

Anderson and others (1986) have prepared a liquefaction potential map and report for Utah County. The base 

map used is a USGS 7W quadrangle showing topography 

that has been reduced to a scale of 1:48,000 (1 in. equals 

4,000 ft) (see fig. 5). They have also prepared similar 

maps and reports for Davis, Salt Lake, Weber, Cache, 

Millard, Sanpete, Sevier, and Wasatch Counties and the 

eastern portions of Box Elder and Juab Counties.

The boundaries of the high, moderate, low, and very 

low liquefaction-potential areas in figure 5 are based on 

the probability that a critical acceleration will be 

exceeded in a 100-yr period. The critical acceleration for 

a given location is defined as "the lowest value of the 

maximum ground surface acceleration required to induce 

liquefaction." The categories of high, moderate, low, and 

very low correspond to probabilities of exceeding critical 

acceleration in the ranges of greater than 50, 10-50, 

5-10, and less than 5 percent, respectively. All of the 

information for a nontechnical user is shown on the map. 

The text includes discussions on methods, geotechnical 

conditions, existing ground failures, and techniques for 

reducing the susceptibility of site sediments to the 

liquefaction process.

In addition, Anderson and others (1986) have provided 

maps showing some information on soils, ground water, 

geology, and slope that can be used in combination with 

the liquefaction-potential map (fig. 5) to assess the type 

of ground failure likely to occur, either loss of bearing 

capacity, lateral spreading, landslides, flows, or translational landslides. These maps require further translation, which is being done by county geologists.

LANDSLIDE POTENTIAL

Keaton and others (1987) have prepared an 

earthquake-induced landslide-potential map and report 

for the urban corridor of Davis and Salt Lake Counties. 

The base map used is a USGS 7W quadrangle showing 

topography that has been reduced to a scale of 1:48,000 (1 

in. equals 4,000 ft) (see fig. 6).
32 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

0 3000 FEET 

I I I I

FIGURE 3. Part of a cadastral map (original scale 1:36,000) of 

Salt Lake County upon which Nelson (1987) shows a surfacefault rupture zone and the potential liquefaction areas. Fault 

traces are indicated by a solid line where location is known from 

scarps or trenching; dashed where approximately located or

inferred; dotted where concealed. Bar and ball symbol indicates 

downthrown side. Shaded area indicates where site-specific 

studies addressing surface rupture should be performed prior to 

construction. High, moderate, and very low refer to the areas' 

potential for liquefaction during an earthquake.

Boundaries of high, moderate, low, and very low 

landslide-potential zones in figure 6 were assigned on the 

basis of failure criteria, landslide susceptibilities, and 

acceleration exceedence probabilities. The text gives the

displacement related to these terms, for example, 10 cm 

or more in a "moderate" zone during a wet condition, 10 

cm or more in a "high" zone during a dry condition. 

Severity is then described as, "Such ... displacement
KEDUCING EAKTHQUAKE HAZAKDS IN UTAH

FIGURE 4. Three levels of ground shaking on alluvium relative to 

bedrock in the period band 0.2-0.7 sec in the Salt Lake Valley by 

Tinsley (1988, fig. 1). Contours were drawn on the basis of geology 

and show alluvium/rock spectral ratios recorded and computed by 

Kenneth King and Kobert Williams. Black dots indicate points of 

control for the contours and are sites where USGS recorded ground

motion. Map is preliminary, and contours may be modified owing to 

further analysis of the geologic data or after considering other effects 

including source characteristics, directivity, or geometry of basin 

margins. Letters indicate an increase in Modified Mercalli Intensity 

units: A (+1), B (+2), and C (greater than 2).
34 ASSESSMENT OF KEGIONAL EAETHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

FIGURE 5. Part of a topographic map (original scale 1:48,000) of Utah County upon which Anderson and others (1986, plate 

4B) show areas with high, moderate, low, and very low potential for liquefaction corresponding to the probability of 

exceeding a critical acceleration.

would certainly cause substantial damage to structures 

on ... or utilities buried within a sliding mass" (Keaton 

and others, 1987, p. 75).

These four zones depend on the probability that a 

critical acceleration will be exceeded in a 100-yr period. 

The period of 100 yr is arbitrary but useful for planning, 

and is the same as that used for liquefaction potential

discussed above. The terms high, moderate, low, and 

very low are functions of the critical acceleration exceedence probabilities and the ground-water conditions similar to those used for liquefaction potential.

All of the information needed by a nontechnical user is 

shown on the map. The text includes discussion of 

method, geology, ground water, and ground motion; a
REDUCING EARTHQUAKE HAZARDS IN UTAH 35

FIGURE 6. Part of a topographic map (original scale 1:48,000) 

of Davis County, Utah, upon which Keaton and others (1987, 

plate Ib) show potential for earthquake-induced landslides 

and liquefaction. Letters H, M, L, and VL indicate high,

moderate, low, and very low potential for landslides. The 

letter S indicates existing landslide. The labels, high, moderate, low, and very low, indicate potential for liquefaction.
36 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

list of historical earthquake-induced landslides; and maps 

showing the historical limit of landsliding due to magnitude 7.5 earthquakes for all segments of the Wasatch 

fault.

ROCKFALL SUSCEPTIBILITY

Case (1987, p. V1-V36) has prepared a report and map 

concerning rockfall hazards in the central Wasatch Front 

between Layton and Draper (including Magna and 

Tooele) with particular emphasis on earthquake-induced 

rockfalls. The base map used is a USGS 7W quadrangle 

map showing topography that has been reduced to a scale 

of 1:100,000 (see fig. 7). Field work was at a scale of 

1:24,000 and is available from Case. Rockfall source areas 

are shown, but the maximum downslope extent of the 

hazardous areas is not. According to C.V. Nelson (oral 

commun., 1988), three county geologists plan to identify 

such areas using a computer-simulated model program.

Although frequency of rockfall occurrence is not shown 

on the map, the text contains a table of historic rockfalls 

and a conclusion based on a report by Reefer (1984) that 

reads:

Widespread damage could occur in the Central Wasatch Front 

area if an earthquake of magnitude 7.0-7.5 should occur. Some of 

that damage would be due to thousands of rockfalls that would 

be the result of ground shaking during the event and aftershocks 

greater than magnitude 4. The Borah Peak and Hebgen Lake 

earthquakes are examples of such earthquakes that can be 

reasonably expected in the future somewhere along the Wasatch 

Front.

W.F. Case (written commun., 1988) makes the frequency of occurrence quite clear:

Ground shaking during an earthquake can produce hundreds to 

thousands of rockfalls over an area of several thousand square 

kilometers. They are initiated by nearby earthquakes of magnitudes as low as 4. Aftershocks of large earthquakes will continue 

to produce rockfalls after the main shock, particularly if outcrops 

were loosened by the main shock. A "characteristic" (magnitude 

7-7.5) earthquake anywhere in the Wasatch Front will trigger 

rockfalls throughout the entire Wasatch Front.

Case says the purpose of his mapping project is to 

"red-flag" hazardous rockfall areas that need site-specific 

studies. He points out that such studies would require 

additional translation before use by community planners.

TECTONIC SUBSIDENCE

Keaton (1987) has prepared a report and map on 

potential consequences of earthquake-induced regional 

tectonic subsidence. The area covered includes the Great 

Salt Lake and vicinity from Salt Lake City to Brigham 

City along the Wasatch Front, Provo and vicinity, and

Juab Valley north of Nephi. The base maps used are 

USGS maps (1:100,000 and 1:125,000 scales) showing 

topography (see fig. 8).

The locations of effects of two earthquake events are 

shown on the maps: (1) the predicted subsidence that 

would accompany a "characteristic" Wasatch earthquake 

of moment magnitude 7.1 and (2) the observed subsidence that accompanied the 1959 Hebgen Lake, Montana, 

surface wave magnitude 7.5 earthquake. In the report, 

Keaton (1987, p. 19) restates earthquake occurrence as 

the "Wasatch fault is ... considered to be capable of 

generating earthquakes in the range of local magnitude 

... 7.5" and "subsidence should be expected to accompany major earthquakes."

Severity is shown on the map by contour lines of 

subsidence in 5-ft increments, by areas of potential 

ponding, and by areas of potential lake-margin flooding. 

In addition, the locations of sewage-treatment plants are 

shown along with directions and amount of tilt. A relatively slight change in hydraulic gradients at plants, 

outfalls, or other major drain lines will interrupt gravity 

flows. Such interruptions may cause ponding of sewage 

and health hazards.

The text contains general discussions of the effects of 

subsidence on such critical facilities as transportation, oil 

refineries, and waste-water treatment plants. Similar 

critical facilities are likely to be interrupted by the same 

event, reducing system backup and redundancy.

DAM FAILURE

McCann and Boissonnade (1985) assessed the impact of 

shaking on the Pineview Dam and its failure on portions 

of the city of Ogden. The base map used is a USGS 7W 

quadrangle that has been reduced to a scale of 1:48,000. 

A design earthquake of Richter magnitude 7.5 with an 

epicenter in downtown Ogden is assumed. Several feet of 

vertical offset along the 31.5 mi (50 km) of fault rupture 

is estimated. Ground acceleration in the range of 50-80 

percent of gravity at the dam site is estimated. Since the 

Pineview Dam is only 6 mi (10 km) from the fault trace, 

McCann and Boissonnade (1985, p. 5-1) assume that the 

ground motion exceeds the design basis of the dam, and 

failure occurs.

In the event that Pineview Dam fails, the breach of the 

dam will release the reservoir. The boundaries of the 

inundated parts of Ogden for a filled reservoir are shown 

on a map (fig. 9) with peak flood depths. The flood wave 

is expected to travel with velocities as high as 20 mph (32 

km/hr). As part of the study, damage to commercial and 

residential buildings from the design earthquake and 

flooding that results from the dam failure is assessed. In 

addition, casualties from both the earthquake and the 

dam failure are also estimated.
REDUCING EARTHQUAKE HAZARDS IN UTAH 37

FIGURE 7. Part of a topographic map (original scale 1:100,000) of Salt Lake and Tooele Counties upon which Case (1987, p. V-11) 

shows mountain spur areas susceptible to rockfalls. Those areas with a rockfall hazard are stippled. Numbers within each USGS 

7V2' quadrangle are referred to in Case's text.
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

FIGURE 8. Part of a topographic map (original scale 

1:100,000) of northern Juab Valley, Utah, upon which Keaton 

(1987, pi. 6) shows potential consequences of tectonic deformation along the Nephi segment of the Wasatch fault. Fault 

trace is indicated by a heavy line, and contours of subsidence

(in feet) by a less heavy line. Cross-hatched area indicates 

potential ponding of shallow Qess than 3 ft, or 1 m) ground water 

due to subsidence. Solid square indicates the location of a sewage 

treatment plant with direction and amount of anticipated tilt 

(ft/mi) shown.
REDUCING EARTHQUAKE HAZARDS IN UTAH 39

FIGURE 9. Topographic map (original scale 1:48,000) of Ogden/Pineview, Utah, study area 

upon which McCann and Boissonnade (1985, fig. 3-4a, pp. 3-27) show inundation area from 

a failure of Pineview Dam. Numbers indicate peak flood depths in feet.

Even though likelihood, location, and severity are 

given for the inundation hazard, the example is one of a 

failure and damage scenario only for the purposes of 

emergency management planning. McCann and Boissonnade (1985, p. 3-2) are careful to point out that "no 

speculation is made concerning the likelihood that the 

consequences evaluated ... could occur."

This example is one of the uses of translated research 

for the purpose of assessing the impact of a secondary 

hazard (dam failure) as well as earthquake shaking. All 

dams impounding greater than 20 acre-ft (24,660 m3) of 

water, and all dams for which dam-failure inundation 

studies have been completed in Utah, have been compiled by Harty and Christenson (1988).
40 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

COMMENT

In all of these Utah examples, the elements of likelihood, location, and severity are found, although various 

scales, parameters, and formats are used. Some examples require further translation for the nontechnical user. 

If these examples are easy to understand and use, then 

the researchers/translators are meeting major goals of 

the Utah work plan.

In some cases, the translators have taken the opportunity to include discussions or illustrations of past 

casualties or damage, and recommendations for using the 

translated work for hazard reduction. In other cases, 

county geologists are providing guidelines for use of the 

translated information for debris flows and liquefaction 

(Lowe, "Debris-flow hazards: A guide for land-use planning, Davis County, Utah," and "Liquefaction hazards: A 

guide for land-use planning, Davis County, Utah," this 

volume), surface-fault rupture and tectonic subsidence 

(Robison, 1988a, b), landslides (Robison and Lowe, 

"Landslide hazards: A guide for land-use planning, Davis 

County, Utah," this volume), rockfalls (Nelson, "Rockfall hazards: A guide for land-use planning, Salt Lake 

County, Utah," this volume) and other geologic hazards 

(Lowe and Eagan, 1987).

Often the simplicity of format and ease of use mislead 

users to believe that the translated products are easy to 

produce. A familiarity with the references cited in each 

report will remind the reader that numerous geologic, 

geophysical, and engineering studies over many years 

along with many innovative and creative ideas were 

necessary to produce these examples.

According to C.V. Nelson (oral commun., 1988), the 

county geologists and others are performing additional 

studies or compilations that will result in translated 

information. For example, nonearthquake-induced 

landslide-potential information will be combined with the 

earthquake-induced landslide-potential map prepared by 

Keaton and others (1987) to produce a composite landslide hazards evaluation. A text has also been prepared 

discussing other hazards such as failure in sensitive 

clays, seiches, subsidence in granular materials, and 

hydrologic changes (Lowe, "Hazards from earthquakeinduced ground failure in sensitive clays, vibratory settlement, and flooding due to seiches, surface-drainage 

disruptions, and increased ground-water discharge, 

Davis County, Utah," this volume). Emmi ("A mapping 

of ground-shaking intensities for Salt Lake County, 

Utah," this volume) has created maps showing the 

ground-shaking hazard of Salt Lake County using MMI 

scales.

TRANSFER TO NONTECHNICAL USERS

The objective of transferring hazard information is to 

ensure its use in reducing losses from future earthquakes. Translated hazard information is a prerequisite 

for transfer to nontechnical users. Its objective has been 

previously described as making the users aware that a 

hazard exists; providing information that can easily be 

presented to superiors, clients, or constituents; and 

providing materials that can be directly used in a reduction technique (list 2). The Utah work plan is quite 

specific as to what is expected of transfer activities:

 Foster the creation and implementation of hazardreduction measures.

 Ensure that users will have easy access to data.

 Release information promptly.

 Provide the most effective educational, advisory, and 

review services appropriate to the targeted users.

 Encourage both the transfer of hazard information and 

its effective use for hazard reduction.

DEFINITION

Various terms are used to convey "transfer" of information to users, namely, disseminate, communicate, 

circulate, promulgate, and distribute. Often these terms 

are interpreted conservatively, for example, merely 

issuing a press release on hazards or distributing 

research information to potential users. This level of 

activity cannot be expected to result in effective hazard 

reduction techniques or even to make users aware of the 

hazard.

According to Slovic (1986), communicators must 

appreciate the limitations of public understanding, 

namely that perceptions are often inaccurate, risk information may frighten and frustrate the public, strong 

beliefs are hard to modify, and naive views are easily 

manipulated by the format used to present other perspectives. Slovic then suggests that research is needed in 

the areas of informed consent, information relevance, 

perceived risk, and the use of the media. Sorensen and 

Mileti (1987) provide an excellent discussion on the 

dilemmas of perception, the warning response process, 

the determinants of senders and receivers, the personalizing of warnings, and the nonbehavioral aspects of 

response.

No concise definition of, or criteria for, "transfer" has 

been offered or can be found in the literature except by 

inference or by analysis of what actually works for those 

who have developed and adopted reduction techniques. 

Therefore, I suggest that we use "transfer" to mean the 

delivery of a translated product in a usable format at a 

scale appropriate to its use by a specific person or group 

"interested" in, or responsible for, reducing hazards. To 

delivery of a product, I would add assistance and encouragement in its use; in other words, an active, ongoing 

learning experience.

This definition of "transfer" is somewhat analogous to 

the passing of a football or baton. Assume that the
REDUCING EARTHQUAKE HAZARDS IN UTAH 41

football or baton is understandable and in a usable 

format. Once the hand-off or passing has taken place, the 

receiver (for various reasons) may not run, win the race, 

or otherwise act appropriately.

It is the same with a receiver of earthquake hazard 

information. The information alone without action will 

not reduce casualties, damages, and interruptions. Obviously, something else is needed. My experience indicates 

that effective transfer must include not only delivery but 

assistance and encouragement in the selection and adoption of an appropriate reduction technique. Only then 

have the researchers, translators, and transfer agents 

fulfilled their professional obligations.

TRANSFER TECHNIQUES

Such delivery, assistance, and encouragement can be 

accomplished through specific transfer techniques, which 

may be categorized into educational, advisory, and 

review services (list 4). These services were identified 

and tested by me during the 1960's, successfully used by 

the Southeastern Wisconsin Regional Planning Commission (1968, 1987), incorporated into the overall program 

design for the New Mexico State Planning Office (Kockelman, 1970, p. 34^1), brought to the attention of the 

USGS (Kockelman, 1976a), and incorporated into the 

USGS national program of landslide hazard reduction 

(U.S. Geological Survey, 1982, p. 34, 37^7). In addition, 

these services are provided by some USGS scientists, 

engineers, planners, and others as a personal commitment or under various earth science application and 

public information programs. The remarkable effort in 

Utah to provide these services can be seen in the 

following section.

Educational services range from merely announcing 

the availability of earthquake hazard information, 

through the publishing and distributing of newsletters 

and brochures, to sponsoring, conducting, or participating in seminars and workshops for potential users.

Advisory services range from explaining or interpreting earthquake hazard reports and maps, through publishing guidebooks and assisting in the design of regulations based on the information, to giving expert 

testimony and depositions concerning the information.

Review services include review and comment on policies, procedures, studies, plans, statutes, ordinances, or 

other regulations that are based on, cite, interpret, or 

apply earthquake hazard information.

The educational and advisory services should not supplant existing programs or activities of educational institutions, or replace services of private consulting firms or 

State and local organizations, but should serve as supplements!

The importance of educational and advisory services to 

accomplish delivery, assistance, and encouragement is 

obvious. The importance of review services is less obvious. When used in a regulatory technique that affects 

land use and property values, hazard information is 

eventually challenged in a courtroom or other public 

forum. At that time the researcher is requested or 

subpoenaed to explain (or confirm the proper use of) the 

research information.

The researcher must have had the opportunity to 

review the use of the research and to correct any 

potential misuse, or the regulation will lose validity, the 

researcher will be embarrassed, and the user chagrined. 

It is foolish not to review when the effort to review is 

compared with the time and scarce resources needed to 

perform the required scientific and engineering studies 

(list 1), to translate and transfer them, and to prepare, 

adopt, and enforce a reduction technique (list 2).

Multiple ways of imparting information should be 

encouraged. A single exposure to new information, especially if the information is complex or differs from a user's 

previous knowledge, is often insufficient. Repeated 

exposure in different formats and through different 

conduits is needed. This strategy is particularly successful when new information is supplied by persons who 

customarily provide guidance, such as members of the 

same professional group. The most effective transfer 

techniques (list 4) should be selected jointly (if possible) 

by the translator, transfer agent, and user.

Most public hearings or presentations to decisionmakers allow little time, and the transfer agent is competing 

with numerous other issues. The simplest, most concise 

translation and transfer techniques are the most successful. A senior scientist at USGS (A.H. Lachenbruch, 

written commun., 1981), with experience in successfully 

transferring research information to Congress as well as 

to local decisionmakers, observed: "Simple maps with a 

few bright colors are needed ...." Obviously, such maps 

must be derived from larger scale and more detailed 

information that, if needed to meet a challenge, are 

readily available.

TRANSFER AGENTS

For the purposes of this report, the term "transfer 

agents" is defined as those who deliver translated 

research information to potential users and assist and 

encourage them in selecting and adopting appropriate 

hazard reduction techniques. In his final report on the 

County Hazards Geologist Program, Christenson (1988, 

p. 3) identifies several options for transferring geologic 

expertise to local governments: 

 Permanent, full-time city or county geologist.
42 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

List 4. Examples of techniques for transferring hazard information

Educational services

Providing serial and other types of publications reporting on hazard research under way, reduction techniques in process, and the adoption and enforcement of reduction techniques.

Assisting and cooperating with universities, university extension divisions, and other schools in 

the preparation of course outlines, detailed lectures, casebooks, and audio or visual materials.

Contacting speakers and participating as lecturers in State and community education programs related to the use of hazard information.

Sponsoring, conducting, and participating in topical and areal seminars, conferences, workshops, short courses, technology utilization sessions, cluster meetings, innovative transfer meetings, training symposia, and other discussions with user groups.

Releasing information needed to address critical hazards early through oral briefings, newsletters, seminars, map-type "interpretive inventories," open-file reports, reports of cooperative agencies, and "official use only" materials.

Sponsoring or cosponsoring conferences or workshops for planners, engineers, and decisionmakers at which the results of hazard studies are displayed and reported on to users.

Providing speakers to government, civic, corporate, church, and citizen groups, and participating in radio and television programs to explain or report on hazard reduction programs and 

techniques.

Assisting and cooperating with State and community groups whose intention is to incorporate 

hazard information into school curricula.

Preparing and exhibiting displays that present hazard information and illustrate their use for 

hazard reduction.

Guiding field trips to disaster areas, damaged structures, and potentially hazardous sites.

Preparing and distributing brochures, television spots, films, kits, and other visual materials 

to the news media and other users.

Operating public inquiries offices, sales offices, and clearinghouses.

________________________Advisory services________________________

Preparing annotated and indexed bibliographies of hazard information and providing lists of 

pertinent reference material to users.

Assisting local, State, and Federal agencies in designing policies, procedures, ordinances, statutes, and regulations that are based on, cite, or make other use of hazard information.

Providing explanations of hazard information and reduction techniques during public hearings.

Assisting local, State, and Federal agencies in the design of hazard information collection and 

interpretation programs and in work specifications.

Providing expert testimony and depositions concerning hazard research information and its 

use in reduction techniques.

Assisting in the presentation and adoption of plans and plan implementation devices that are 

based on hazard information.

Assisting in the incorporation of hazard information into local, State, and Federal studies and 

plans.

Preparing brief fact sheets or transmittal letters about hazard products to explain their impact 

on, value to, and most appropriate use by local, State, and Federal planning and development 

agencies.

Assisting users in the creation, organization, staffing, and formation of local, State, and Federal planning and plan implementation programs to ensure the proper and timely use of hazard 

information.

Preparing and distributing appropriate guidelines and guidebooks relating to processes, mapping, and reduction techniques for natural hazards.

Preparing models for State safety legislation, regulations, and development policies.

Preparing models for local safety policies, safety plan criteria, and hazard reduction techniques.

Advising on and providing examples of the methods or criteria for hazard identification, vulnerability assessments, hazard reduction, and emergency management.

_______________________Review services_______________________

Reviewing proposed programs designed for collecting and interpreting hazard information.

Reviewing local, State, and Federal policies, administrative procedures, and legislative analyses that relate to assessing and reducing hazards.

Reviewing studies and plans that are based on, cite, or otherwise use hazard information.

Reviewing proposed regulations, policies, and procedures that incorporate or cite hazard 

information.
REDUCING EARTHQUAKE HAZARDS IN UTAH 43

List 5. Potential transfer agents for earthquake hazard information in Utah

American Planning Association, Utah Chapter 

American Society of Civil Engineers, Utah Section 

American Society of Public Administrators, Utah Chapter 

Association of Engineering Geologists, Utah Section 

Bear River Association of Governments

Children's Museum

Church groups, church organizations, and church leaders

Civic and volunteer groups

Consultants (engineers, planners, geologists, and others)

County geologists and extension agents

Educators (university, college, secondary, and elementary) 

Governor's Advisory Council on Local Governments 

Hansen Planetarium

International Conference of Building Officials, Utah Chapter 

League of Women Voters

Local building, engineering, zoning, and safety departments

Local seismic safety advisory groups

Media (journalists, commentators, editors, and feature writers)

Mountainlands Association of Governments

Neighborhood associations

Public information offices

Relief Society, Church of Jesus Christ of Latter-day Saints 

Researchers, engineers, and planners (local, State, and Federal) 

Society of American Foresters, Wasatch Front Chapter 

Southeastern Utah Association of Governments

Speakers' bureaus (State, local, or project area)

Structural Engineering Board, Church of Jesus Christ of Latter-day Saints

University of Utah Seismograph Stations

Utah Association of Counties

Utah Division of Comprehensive Emergency Management

Utah Department of Social Services 

Utah Geological Association 

Utah Geological Survey 

Utah League of Cities and Towns 

Utah Museum of Natural History

U.S. Forest Service

U.S. Geological Survey

U.S. Soil Conservation Service

Wasatch Front Regional Council

Western Governors' Policy Office

 Circuit-rider geologist serving several governments 

contemporarily.

 Geologist employed by an umbrella agency (regional 

association of governments, State survey) but dedicated to serving local governments.

 Private consulting geologist on retainer or under contract with local government.

It should be noted that consultants under contract with a 

local government may have the appearance of a "conflict 

of interest" if they represent other parties within the 

local government's jurisdiction.

Potential transfer agents of earthquake hazard information in Utah are given in list 5. Many of the users in 

list 3 will also be transferring such information. Bates 

(1979, p. 11) notes that "although both the use of transfer

agents and the education of planners in the earth sciences 

... are increasingly important components of the 

information-transfer system, nothing replaces intensive 

producer-user interaction ...."

Of course, geologists, seismologists, and other earthquake researchers may be available to provide some of 

the educational, advisory, and review services, but it is 

unreasonable to rely solely or heavily on these skilled and 

scarce resources, as this would divert them from their 

work of understanding the process, assessing the hazard, 

and translating their research.

The role of the professional associations of planners, 

engineers, geographers, and geologists should be emphasized. For example, Petak (1984, p. 457) points out that 

"hazard and risk assessment must be ... fully supported
44 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

by the efforts of the geotechnical profession." The professions not only can contribute to identifying user 

needs, translating and transferring complex information, 

and fostering an environment for use, but they are 

principal users themselves. The Yin and Andranovich 

(1987) study on getting research used in the natural 

hazard field concluded that the role of professional associations "is a diffuse model, in which multiple sources of 

ideas are mixed with multiple types of users ...." Transfer agents should solicit and use the expertise of those 

members of the sociological community who are trained 

and experienced in reducing natural hazards.

Examples of successful transfer agents and their 

transfer programs follow:

 Circuit rider geologist in the State of Washington 

(Thorsen, 1981).

 Planning, reviewing, and enforcing by city and county 

geologists (McCalpin, 1985; Christenson, 1988).

 Advisory services unit of the California Division of 

Mines and Geology (Amimoto, 1980).

 Educational, advisory, and review services by the 

Southeastern Wisconsin Regional Planning Commission (1968, 1987).

 Earth science information dissemination activities of 

the U.S. Geological Survey (Information Systems 

Council's Task Force on Long-range Goals for USGS's 

Information Dissemination, 1987).

 Earthquake hazard reduction activities of the staff, 

members, and committees of the California Seismic 

Safety Commission (1986).

SUCCESSFUL TRANSFER

One of the best ways to determine which transfer 

techniques are effective is to look closely at techniques 

that have been used and that have resulted in the 

reduction of natural hazards. For more than 25 yr, a 

midwestern multicounty planning commission has transferred geologic, hydrologic, and pedologic hazard information to public and private users. The annual project 

completion report by the Southeastern Wisconsin 

Regional Planning Commission (1968) shows that almost 

every educational, advisory, and review service in list 4 

was repeatedly used. Many other examples of the transfer techniques shown in list 4, including their transfer 

agents, can be cited. Selected examples follow:

 Earthquake hazard reduction series by the Federal 

Emergency Management Agency (1985-1989).

 Home guide section on how a house withstands an 

earthquake in the Chicago Tribune by Kerch (1988).

 Guidebook on reducing earthquake risks for planners 

by Jaffe and others (1981).

 Isoseismal map users guide by the Central United 

States Earthquake Consortium (1987).

 Canoe trip to view evidence of probable magnitude 8 

or 9 earthquake in the Pacific Northwest by Atwater 

(1988).

 Introduction to geologic and hydrologic hazards in the 

United States by Hays (1981).

 Using earth science information for earthquake hazard 

reduction in the Los Angeles region by Kockelman 

(1985).

 Guidelines for preparing a safety element of the city 

and county general plan by a governor's office of 

planning and research (Mintier, 1987, p. 146-153).

 Case studies on strengthening hazardous buildings by 

the San Francisco Bay Area Regional Earthquake 

Preparedness Project (1988).

 Guidebook for disaster mitigation for planners, policymakers, and communities by Lohman and others 

(1988).

 Guidebook on identifying and mitigating seismic hazards in buildings, including a model ordinance for 

rehabilitating masonry buildings by the California 

Seismic Safety Commission (1987).

 Guidebook on seismic safety and land use planning by 

Blair and Spangle (1979).

 Handbook on land-use planning for earthquake hazard 

mitigation for planners by Bolton and others (1986).

 Analyzing and portraying geologic and cartographic 

information for land-use planning, emergency 

response, and decisionmaking in San Mateo County, 

California, by Brabb (1987).

 Getting ready for a big quake in Sunset Magazine by 

Lane Publishing Company (1982).

 Landslide hazard mitigation plan for Colorado by 

Jochim and others (1988).

 Trail signs describing the 1959 Hebgen Lake 

earthquake-triggered landslides and vertical displacement along the fault in the Gallatin National Forest, 

Montana, by the U.S. Forest Service.

 Workshop on the evaluation of regional and urban 

earthquake hazard and risk in Alaska convened by 

Hays and Gori (1986).

 Periodical on earthquakes and volcanoes (formerly 

Earthquake Information Bulletin) by the U.S. Geological Survey (Spall, 1975-present).

 Bibliography and index to seismic hazards of western 

Washington from 1855 to 1988 compiled by Manson 

(1988).

 Review of State landslide hazard maps by USGS 

physical scientist W.M. Brown, III (written commun., 

1985).

 Peace of mind in earthquake country How to save 

your home and life by Yanev (1974).

 Selected annotated bibliography of recent publications 

concerning natural hazards by Morton (1986).
REDUCING EARTHQUAKE HAZARDS IN UTAH 45

 Washington State earthquake hazards by Noson and 

others (1988).

 Pilot earthquake education projects in Arkansas, Tennessee, Mississippi, Washington, and South Carolina 

by Bolton and Olson (1987b, app. B).

 Steps to earthquake safety for local governments by 

Mader and Blair-Tyler (1988).

COMMENT

Many researchers provide educational, advisory, and 

review services on a limited and informal basis. Federal, 

State, and university scientists are frequently called on 

to assist users. Such services should be formally recognized and included as a work element in any earthquake 

hazard reduction program, as was done in the Utah work 

plan.

Many of these services are provided in Utah through 

cooperative agreements, serial publications, report and 

map sales offices, geologic inquiries staff, public inquiries 

offices, professional groups, local and State geologists, 

municipal planners and engineers, and ordinary day-today contacts with the public by the researchers and 

translators of earthquake hazard information. Specific 

examples from Utah are given in the following section.

The reader familiar with the successful transfer 

agents, programs, and techniques cited here will note 

that they accomplished the following:

 Delivered the information to those who are interested 

in using it or required to use it.

 Conveyed the hazard in such a way as to result in the 

user's awareness.

 Provided the user with a wide selection of reduction 

techniques.

 Suggested a strategy for using the hazard information

in a reduction technique through examples. 

It is my experience that educational, advisory, and 

review services must accompany any successful earthquake research, hazard assessment, translation, and 

transfer program designed for planners, engineers, and 

decisionmakers.

Several benefits accrue to the transfer agents and 

those researchers and translators involved in transfer 

activities:

 Satisfaction that professional obligations are complete 

and the "ball is now in another court."

 Sense of accomplishment when community safety is 

improved.

 Perception of how local, State, and corporate decisions 

are made.

 Awareness of where and how to make a civic contribution to encourage appropriate decisions.

EXAMPLES OF SUCCESSFUL TRANSFER 

IN UTAH

A remarkable effort is being made in Utah to transfer 

earthquake hazard information to nontechnical users, 

including real estate salespersons, financial institutions, 

and church groups. For example, in June 1985 three 

county geologists began providing educational, advisory, 

and review services to Weber-Davis, Salt Lake, and 

Utah-Juab Counties. The geologists were funded by 

USGS, and other support was provided by the UGS and 

the five counties. Financial support by local governments 

for 1989 is an indication of the success of this type of 

transfer program.

According to Christenson (1988, p. 2), the purpose of 

the Wasatch Front County Hazards Geologist Program 

is to

 Compile geologic hazards information and produce 

maps to delineate hazard areas.

 Review engineering geologic reports.

 Advise planners regarding hazards ordinances.

 Provide geologic expertise as required. 

These geologists are a part of the county planning 

departments under direct supervision of the planning 

director; the UGS provides technical supervision and 

other support as needed. The geologists are also available to perform the same services to the cities within 

their county. Some of the services provided over just a 

6-month period may be seen in the excerpt from the 

report shown in figure 10. A final report on data collection, hazards mapping, ordinance reviews, and many 

other accomplishments has been prepared by Christenson (1988, p. 5-9; 'Wasatch Front county hazards geologist program," this volume).

Much of this work is directed toward reduction techniques (list 2) and therefore is not discussed in this 

section on transfer techniques. According to county 

geologist Mike Lowe (unpubl. speech, 1986), examples of 

such work include site investigation and hazard evaluation for South Weber City, city of Washington Terrace, 

city of North Salt Lake, Emigration Canyon (Salt Lake 

County), and the Lake Mountain and Pine Flat areas 

(Utah County).

Several Federal, State, and county planners, geologists, and emergency managers identified the "provision 

of education, advisory, and review services" as one of 

their most significant accomplishments to date (Christenson and others, 1987, p. 84). Examples of some of the 

transfer techniques used in Utah follow. Each technique 

can be categorized as an educational, advisory, or review 

service, or a combination of two or all of the services. In 

most cases, the transfer agents not only are delivering 

translated information as defined and illustrated in previous sections of this paper, but also are assisting and 

encouraging its use for hazard reduction.
46 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

PHASE II (year 2) Wasatch Front County Hazards Geologist Program

Date: June 7, 1987 

Grant No. 14-08-0001-G991

Grantee: Utah Geological and Mineral Survey 

Don Mabey (principal investigator)

Title: Wasatch Front County Hazards Geologist Program 

Grant effective date: February 7, 1985 

Grant expiration date: June 7, 1988 

Period covered by report: December 7, 1986-June 7, 1987

This report covers the six-month period from December 7, 1986 to June 7, 

1987, completing the second year of this three-year program. Phase I (data 

collection and compilation) and Phase II (basic data map compilation) are 

complete or nearly complete, and Phase III (preparation of interpretive or 

translated maps and text) is about to begin. In February, the UGMS and 

county geologists met with planning directors and others from each county 

.... All planning directors indicated firm support for the program and will 

include the geologists in their budgets for 1988. The principal need now is 

to convey the importance of the program to the county commissions who must 

approve the budgets. To do this, special presentations and field trips for 

commissioners and others are planned for June 1987. Also, the UGMS is 

planning to devote an issue of its quarterly publication, Survey Notes, to 

the county geologist program, with copies going to commissioners, mayors, and 

others involved in the decisionmaking. Final budgets must be approved in 

December 1987, at which time we will know whether or not the counties have 

decided to maintain the geologists.

Services provided to cities and counties during this report period 

include: aid in developing ordinances, reviews of engineering geologic 

reports, and memos to planners and developers indicating potential hazards at 

proposed developments requiring geologic investigations. Major special 

projects have included preparation of: 1) a gravel resource assessment for 

county property in Davis County, 2) a surface fault rupture hazard study for 

a proposed Provo City landfill in Utah County, 3) site investigation reports 

for two water tank sites for the city of North Salt Lake in Davis County, 4) 

a geologic hazards evaluation of property owned by Payson City proposed for 

development in Utah County, 5) a review of a proposed county fire station 

site along the Wasatch fault in Salt Lake County, 6) the engineering geologic 

section for the Pineview Reservoir Clean Lakes study to control development 

near the lakeshore to avoid contamination, Weber County, 7) the geologic 

hazards portion of the master plan for the city of Washington Terrace in 

Weber County, and 8) an engineering geologic report regarding geologic 

hazards, slope stability, and potential for ground-water contamination at the 

North Davis Refuse Dump and new burn plant in Davis County. The county 

geologists and UGMS have also given talks to various civic groups and 

governmental organizations, participated in radio talk shows, and been 

involved in a variety of technical and policy publications ... related to the 

program.

FIGURE 10. Part of a final performance report on educational, advisory, and review services over a 6-month period prepared by G.E. 

Christenson (written commun., 1987). These types of services are identified in list 4.
REDUCING EARTHQUAKE HAZARDS IN UTAH 47

WORKSHOPS

During the period from 1984-1988, six workshops 

were held in Utah on assessing and reducing earthquake 

hazards. A field trip followed the 1986 workshop, and 

preliminary reports for this Professional Paper were 

released after the 1987 workshop. Each workshop fulfilled a commitment made in 1983 to bring key researchers and users of hazard information together each year 

for the purpose of providing current information on the 

earthquake hazard, distributing translated reports and 

maps, describing how they can be used, and fostering an 

environment for use of the information for hazard reduction.

Each workshop had various sponsors, including the 

University of Utah, UGS, CEM, FEMA, and USGS. 

Five were attended by as many as 130 earth scientists, 

engineers, planners, and emergency managers. One 

workshop, attended by more than 400 persons, 

addressed multihazards and comprehensive hazard 

reduction (May, 1988). An example of some of the topics 

addressed may be seen in figure 11. The proceedings of 

two of the workshops were edited by Hays and Gori 

(1984, 1987) and published as open-file reports to ensure 

early release and delivery. The UGS compiles examples 

of interim maps and reports available and uses the 

workshops as an opportunity to distribute them.

SERIAL PUBLICATIONS

Several serial reports designed to transfer earthquake 

hazard information in Utah to nontechnical persons were 

continued or begun during the past 5 yr. The attractive 

easy-to-read Survey Notes (fig. 12), published quarterly 

by the UGS (Stringfellow, 1983-present), features excellent articles such as the historic and scientific content of 

earthquake hazards in Utah by Mabey (1985), UGS 

information programs (Smith, 1985a), earthquake activity recorded by the University of Utah Seismograph 

Stations, hiring of county geologists, new publications, 

and such related activities as ongoing geologic projects, 

status of applied geology programs, personnel changes, 

and how UGS responds to disasters (Atwood, 1983).

The Wasatch Front Forum was specially created for 

the earthquake hazards program and is published and 

distributed quarterly by the UGS (Hassibe, 1983-1986; 

Jarva, 1987-present). It features timely articles on 

neighboring earthquakes (Crone, 1984), prediction in the 

Wasatch Front (Smith and others, 1985), earthquakeinduced soil liquefaction (Keaton, 1986), disruption of 

critical facilities (Frank, 1987), and earthquake preparedness projects (Tingey, 1986).

The newsletter also reports on the regional earthquake hazards assessment program (Hays, 1984), accomplishments of the ground-shaking hazards and loss estimation program (Rogers and others, 1986), Utah County 

Comprehensive Hazard Mitigation Project (Dewsnup, 

1987), progress of geologic, seismologic, and engineering 

research (Tarr, 1984), earthquake activities recorded by 

the University of Utah Seismograph Stations, and the 

results of surveys on the perceptions of risk by residents 

along the Wasatch Front. Notices of scheduled professional meetings, recent publications, out-of-state workshops of interest, new research programs, and reprints 

of timely articles such as that by Rogers (1986) are 

included on a regular basis (see fig. 13).

In addition, the Earthquake Information Bulletin 

(now Earthquakes and Volcanoes) (Spall, 1975-present), 

written for nontechnical readers, is published bimonthly 

by the USGS. It contains feature articles such as "Earthquake Potential of the Wasatch Front" (Spall, 1985), as 

well as reports on earthquake activity by states and 

countries. Notices of State, national, and international 

workshops and conferences on earthquakes and recent 

publications are also included on a regular basis.

OUTREACH PROGRAMS

The Utah Museum of Natural History contributes to 

the geologic education of the general public through 

exhibits, classes, lecture series, film series, field trips, 

teaching kits, and teacher workshops. Since the fall of 

1985, "Utah Geologic Hazards" has been a popular outreach program.

According to the museum's earthquake safety instructor, Deedee O'Brien (written commun., 1988), the program has reached 3,000 students and adults for each of 

two school years (1985-86 and 1986-87). During the 

following year (1987-88), the outreach program was 

phased down in favor of training teachers to use the 

materials (fig. 14) and teach the information to their own 

classes. Three workshops were held in 1988 with instructors from the Museum, CEM, UGS, and the University 

of Utah. Seventy-nine teachers from five Wasatch Front 

school districts completed the course. Teachers may 

check out a teaching kit, which includes a 2-ft square 

model, cardboard fault blocks, 150 slides with text, and a 

packet of follow-up earthquake safety activities.

In addition to the geologic hazards curriculum, O'Brien 

developed an earthquake safety curriculum appropriate 

for kindergarten through third grade. The program has 

been tested in approximately 30 classrooms and has been 

offered to teachers in two in-service workshops entitled 

"Earthquake Safety in the Elementary Classroom." 

Forty-eight teachers attended these workshops, cosponsored by CEM. The museum continues to offer earthquake safety in-service courses annually.
48 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

FOREWORD

Welcoming Remarks at the Workshop on "Earthquake Hazards Along the 

Wasatch Front": The Honorable Governor Norman H. Bangerter ...... i

BACKGROUND INFORMATION AND SUMMARY OF THE WORKSHOP

Background and Summary of the Workshop on "Earthquake Hazards 

Along the Wasatch Front, Utah"

Walter Hays and Paula Gori 

Introduction ..................................................... 1

1984 Workshop on "Evaluation of Regional and Urban Earthquake

Hazards and Risk" ............................................. 2

1985 Workshops on "Earthquake and Landslide Hazards" ............. 3

The Research-Applications Process ................................ 3

1986 Workshop Sessions ........................................... 7

Awards ........................................................... 11

Field Trip ....................................................... 12

EVALUATION

Observations on the 1986 Workshop

Peter May ................................................... 43

Statement Prepared for Presentation to the House Subcommittee on 

Science Research and Technology, March 10, 1987

Don Mabey ................................................... 46

REPORTS OF THE RESEARCH AND IMPLEMENTATION TRIADS

Tectonic Framework and Earthquake Potential of the Wasatch Front 

Area and other Parts of Utah

Michael Machette, Bill Lund, and Walter Arabasz ............. 49

The Ground Shaking Hazard and Various Aspects of Loss Estimation 

in the Wasatch Front Region of Utah

Delbert Ward, Albert Rogers, and Robert Smith ............... 60

Ground Failure, Rock Falls, and Tectonic Deformation in the 

Wasatch Front .Area

Loren Anderson, T. Leslie Youd, and Earl Brabb .............. 75

Collecting, Compiling, Translating, and Disseminating EarthquakeHazards Information for Urban and Regional Planning and Development in the Wasatch Front Area, Utah

Gary Christenson, Jerold Barnes, Joseph Moore, Craig Nelson,

Robert Robison, Mike Lowe, and William Kockelman ............ 80

Development and Implementation of Loss-Reduction Measures in Utah

Genevieve Atwood, Lorayne Tempest, Gary Johnson and Jerome

Olson ....................................................... 87

Integrating Scientific and Engineering Information into EarthquakeResistant Design in Utah

Lawrence Reaveley, Delbert Ward, and Walter Hays ............ 96

FIGURE 11. Part of a table of contents from a workshop proceedings edited by Hays and Gori (1987). This type of workshop

is a good example of a successful transfer technique.
EEDUCING EAETHQUAKE HAZAEDS IN UTAH 49

PUBLISHED QUARTERLY BY UTAH GEOLOGICAL AND MINERAL SURVEY

SURVEY NOTES

VOL.18 NO. 4 SERVICE TO THE STATE OF UTAH WINTER 1985

EARTHQUAKE 

HAZARDS 

IN UTAH

(See Page 3)

Wasatch fault at the mouth of Little Cottonwood Canyon, Southeast of Salt Lake City. Latest movement on the fault 

here pre-dates historic record but the fault has displaced young Quaternary alluvium and glacial moraine probably 

during the last 1000 years. Photograph courtesy of Lloyd Cluff and George Brogan.

FIGURE 12. Typical cover of a serial publication that addresses geologic hazard and resource issues. This type of publication is an 

excellent example of an information transfer technique identified as an educational service in list 4.
50 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

COLLECTING, COMPILING, TRANSLATING, AND

DISSEMINATING EARTHQUAKE-HAZARDS INFORMATION FOR

URBAN AND REGIONAL PLANNING AND DEVELOPMENT IN

THE 

WASATCH FRONT AREA, UTAH

By Gary Christenson, Jerold Barnes, Joseph Moore, Craig Nelson, 

Robert Robison, Mike Lowe, William Kockelman

MOST SIGNIFICANT ACCOMPLISHMENTS

Much of the work planned under existing programs is in progress but 

will not be completed for one or two more years. Under the UGMS 

Wasatch Front County Geologists Program, a series of translated 

(interpretive) maps (1:100,000) depicting hazards along the Wasatch 

Front are planned along with a report describing these hazards. 

Collecting and indexing hazards information and providing technical 

assistance to planners are being emphasized under this program. 

Under the UGMS Applied Geology Program, statewide hazard maps 

(1:750,000) are being completed. Other projects emphasize specific 

hazards mapping, evaluation of reduction techniques, education, and 

information dissemination.

Some of the most significant accomplishments to date are:

* Education of planners and decisionmakers in the Wasatch Front 

area regarding earthquake hazards through meetings, workshops, and placement of geologists on planning staffs in five 

Wasatch Front counties.

* Creation of county hazard information libraries with ready 

access to existing hazards information in five county planning 

department offices.

* Quality control over geotechnical investigations, particularly 

seismic hazards studies, by providing geological review of 

reports submitted to local planning agencies.

* Compilation of liquefaction potential maps and reports for three 

counties.

* Increased communication between earthquake hazards investigators.

* Incorporation of the School Outreach Program into the Museum's overall program, staffing, and budget.

* Provision of educational, advisory, and review services to State 

and local units of government.

RECOMMENDATIONS AND PRIORITIES FOR THE NEXT TWO 

YEARS

Because technical and scientific information is a prerequisite for 

effective implementation, it is recommended that information collected during the first three years be made available for translation 

and dissemination. It is further recommended that emphasis during 

the remaining two years of the program be placed on implementation 

projects. Many of the projects that have been funded will extend into 

this period, but priority should be assigned to projects which:

- Continue the building excavation inspection program (UGMS

staff)

- Continue the compiling of the statewide hazards bibliography 

(UGMS staff)

- Provide occurrence intervals and severity of various hazards to 

give planners and decisionmakers a basis for estimating risk 

(USGS staff and grantees)

- Provide State and local hazards susceptibility maps and reports 

(County geologists; UGMS staff)

- Develop guidelines for local governments to use in writing earthquake hazard ordinances (UGMS staff)

- Continue providing educational, advisory, and review services 

aimed at State and local planners and decisionmakers (UGMS 

staff; County geologists; CEM staff; Museum staff)

- Incorporate collecting, compiling, translating, and disseminating 

work into ongoing programs of State and local governments

During the past two years, some additional needs have been identified; 

the following specific needs should be assigned priority:

- Developing model ordinances, which address earthquake hazards, 

for local governments

- Collecting examples of reduction techniques for each hazard, and 

evaluating them for effectiveness

GROUND MOTION ELEMENTS

(from a presentation by Al Rogers at July 1986 Workshop)

SOURCE

SIGNIFICANT ACCOMPLISHMENTS

> Revised segmentation of the Wasatch Front

> New segmentation slip rates for some segments

> Suggestion that slip rates are related to paleo-lake level

> Discovery that some scarps in the Great Basin may be 

terminated by detachment faults at shallow depths

> Successful testing of experimental high-frequency reflection 

techniques for studying Quaternary fault geometry and 

exploration for Quaternary faults

> Discovery of strike-slip faulting in both the geologic and 

seismic records for a portion of the Colorado Plateau-Basin 

and Range Transition Zone

> Borah Peak

Reaffirmation of segmentation

KNOWLEDGE REQUIRED

> Continued segmentation studies and slip rate estimates

> Continued studies of active fault geometry

> Strong ground motion measurements in the vicinity of Great 

Basin earthquakes

TRANSMISSION PATH

SIGNIFICANT ACCOMPLISHMENTS

> Revised peak acceleration and velocity curves for western 

Utah based on regression models and a worldwide strong 

motion data set

> High and Low Q versions

FIGURE 13. Typical article reporting on the status of the Utah Earthquake Hazard Reduction Program in the Wasatch Front Forum (vol. 2, 

no. 4, p. 5). This type of newsletter is a unique example of a transfer technique in Utah identified as an educational service in list 4.
REDUCING EARTHQUAKE HAZARDS IN UTAH 51

EARTHQUAKE HAZARDS

A MAJOR EARTHQUAKE (UP TO M 7.5) COULD OCCUR 

ALONG THE WASATCH FAULT AT ANY TIME!

Such on earthquake could cause.

I. RUPTURE OF THE EARTH'S SURFACE-SCARP FORMATION

A. Distinction ol buildings on the scarp 

B. Breaking ol utility lines that cross scarp

(1) Disruption ol gas. water, & electric services

(2) Fire hazards 

C. Flooding shifting ol the Great Salt Lake and Utah Lake

GROUND SHAKING

A. Damage to rigid manmade structures such as buildings.

freeway overpasses, dams 

6. Liquefaction soil becomes quicksand,

so cannot support buildings 

C. Landslides, Rocktalls. Mudflows 

D. Falling objects that cause injuries

EARTHQUAKE SAFETY

I. BE PREPARED AHEAD OF TIME 

A. EARTHQUAKE PROOF YOUR HOME

1. Identity possible hazards; anchor or rearrange.

2. Reduce risk ol fire.

a. Learn how to turn oil utilities.

(gas. electricity, water) 

b. Anchor water heater.

B. DEVELOP FAMILY RESPONSE PLAN

1 . Determine "sale" areas in each room.

2. Hold earthquake drills.

3. Discuss actions each lamity member should take 

during and alter quake.

4. Identify out-ol-state contact person.

C. PUT TOGETHER POST-QUAKE SURVIVAL KIT

1. Water, & Canned Food 2. Flashlight

1

3 First-AidKit

4. Fire Extinguisher 5. Battery-operated Radio

a

net

II. KNOW WHAT TO DO DURING

*A. Stay Calm! . 

B. DUCK & COVER.

1. If Inside, Stay There. 

Duck under table, or 

stand in door frame, or 

brace yourself in inside corner 1 

away Irom windows.

2. II Outside, Stay There.

a. Move into open away from buildings & electric wires. 

b.Park car & stay inside until shaking stops.

III. RESPOND AFTERWARD

A. Administer lirst-aid

B. Check lor utility damage & turn oil il necessary 

C. Use telephone only lor medical emergency. 

D. Be prepared lor aftershocks.

FIGURE 14. Example of materials provided to students, teachers, and the general public under an outreach program by the Utah Museum of 

Natural History (1985). This innovative transfer technique is identified as an educational service in list 4.

Utah's GEM has developed various hazards outreach 

programs that include educational and advisory services. 

A good example is an inexpensive booklet by Tingey 

(1989) that provides both an awareness of the earthquake hazard and suggested preparations to reduce the 

hazard. According to Tingey and Findlay (1987, p. Til), 

CEM has made many presentations and, in one year 

alone, distributed more than 730,000 brochures on 

earthquakes and hazard reduction. One project completed in 1986 was the production of a television program (video format) that succinctly covered the earthquake hazard, risk, and safety concepts specific to the 

Wasatch Front. Near the end of the project, the local 

CBS affiliate, KSL Television, produced an excellent 

half-hour program ("Not If ... But When"), which 

was shown twice in response to public reaction, during

January 1987. The program won a regional Emmy 

Award out of 150 entrants from seven western states. 

Several copies of the video are being used to make 

presentations to school, church, business, and other 

interested groups.

Integrated into the video were results of the latest 

research on fault-surface expression, segmentation, rupture, and geometry, ground shaking and amplification, 

liquefaction, and loss estimates for postulated events. 

Translation of this research was performed by CEM, 

UGS, scientific and public safety oriented agencies, and 

the producer of the video program. According to Tingey 

(1988, p. 102), the producer "had a terrific feel for the 

material" and was able to distill and translate complex 

ideas into concepts understandable by the nontechnical 

audience.
52 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

The Utah State Office of Education (Burningham, 

1983) has produced an inexpensive, well-illustrated comprehensive booklet on natural hazards entitled "I can 

make the difference Emergency preparedness." One 

chapter (Burningham, 1983, p. 15-28) addresses earthquake hazards through three personalized scenarios, 

questions and solutions, a quiz, and a word-hunt game.

The UGS has provided one-page flyers for public use 

concerning, for example, earthquake hazard situation, 

safety, and faulting in Utah by Kaliser (1984a-c). These 

flyers address scientific evidence, historic events, population exposed, past damages, expected magnitude, critical facilities vulnerability, retrofitting, topographic 

expressions, and other aspects of earthquake hazards 

and their reduction. Cogent, one-sentence "bullets" are 

used (see fig. 15).

The county geologists are continually providing educational services. For example, as county employees, they 

are available to explain earthquake hazards and reduction techniques to various county officials, staffs, and 

citizens. They have increased community awareness 

through a slide-lecture program presented to university 

students, community councils, civic groups, and other 

local government organizations such as the Ogden City 

Seismic Committee, citizens groups in Nephi and Provo 

(Lowe, personal commun., 1986), Salt Lake Board of 

Realtors, and various community councils in Salt Lake 

County. The UGS and the Utah County geologist conducted a class and field trip on geologic hazards for the 

1988 annual education meeting of the Utah Chapter of 

the International Conference of Building Officials.

FIELD TRIPS

Field trips for both small and large groups have been 

conducted. A particularly comprehensive half-day trip to 

selected geologic features and buildings in southern 

Davis and northern Salt Lake Counties sponsored by 

UGS and USGS was arranged and conducted by Keaton 

and Reaveley (1986). Their well-illustrated text 

enhanced the opportunity for the nontechnical attendees 

to observe key geologic features and buildings in the 

metropolitan area.

Geologic features seen during the trip included surface 

evidence of movement along a fault plane, topographic 

scarps, and lateral spreads caused by earthquakeinduced liquefaction. Vulnerable buildings visited 

included gravity-frame structures with masonry infill 

walls, potable water tanks straddling the Wasatch fault, 

sewage treatment plants subject to subsidence by tectonic deformation, and communications centers with 

little lateral force resistance. Seismic-resistant structures viewed included Salt Lake County Government 

Center buildings with concrete shear walls, braced and

anchored brick-clad buildings, and the seismically 

strengthened Veterans Administration Hospital.

The three county geologists have conducted numerous 

field trips for county commissioners, mayors, and other 

public officials to see geologic hazards in their respective 

jurisdictions. The UGS also conducts trips to trench sites 

for State and local government officials to present 

research results and to see first-hand evidence.

NEWS MEDIA

Wide dissemination of information to television viewers, radio listeners, and newspaper readers is one of the 

most effective ways of delivering information about 

earthquake hazards to nontechnical users. A typical 

release by the USGS Public Affairs Office is shown in 

figure 16. Typical newspaper coverage is shown in figure 

17.

According to Sprinkel (1988), UGS, USGS, and CEM 

targeted the news media as an effective means to inform 

the public of the positive accomplishments of the earthquake program and to raise public awareness of the 

potential threat that earthquakes pose to Utahans. The 

news media are invited to all field trips, and nearly 

always attend. In addition, county geologists participate 

in local radio talk shows. The Utah Department of 

Natural Resources also works to ensure good press 

coverage. Sprinkel observes that there is an eagerness 

by the Utah press community to cover most of the 

earthquake-related stories. The result is an increased 

level of public understanding and awareness of Utah's 

susceptibility to earthquake hazards along the Wasatch 

Front.

INFORMATION SYSTEMS

At the inception of the Regional Earthquake Hazards 

Assessment Program in Utah, Tarr and Mabey (1984, p. 

148) specified the objectives of the information system as 

follows:

 To make quality data readily available to meet the 

needs of researchers and policymakers.

 To create an information system that assures that new 

data will be available in the form most useful to 

meeting program objectives.

 To devise a system whereby potential users will have 

easy access to data in media, scales, and formats that 

will be most useful.

The authors suggested creating a "clearinghouse" with 

directories to all information. Much of what they envisioned is now reality (Sprinkel, 1988, p. 94).

During 1985-1988, UGS compiled a comprehensive 

bibliography of geologic hazards in Utah. References
REDUCING EARTHQUAKE HAZARDS IN UTAH 53

UTAH GEOLOGICAL AND MINERAL SURVEY 

606 Black Hawk Way, Salt Lake City, Utah 84108

BUILDING OR BUYING A HOME IN UTAH

Prepared by BruceN. Kaliser, Chief Engineering Geologist

BEFORE YOU BUY:

 Most geologic hazards such as landslides, floods, ground settling and aggravated earthquake ground motion 

can be avoided by proper site selection. Careful examination of sites during initial househunting searches 

can avoid costly water, wastewater, foundation and terrain stability problems later.

 Whether buying a vacant lot or existing structure, observe the property carefully and thoroughly. Look for: 

ground cracks ground holes disturbed earth deposits of sediment or debris left by receding flood 

waters signs of erosion steep slopes, including on neighboring parcels salt efflorescence on ground 

surface surface depressions wet ground anomalous vegetation cracked or disturbed foundations, 

walls, driveways, sidewalks man-placed fill, engineered and non-engineered water bodies or conveyances 

(canals, ditches) on or above the property distribution of bedrock and/or boulders at ground surface.

Interpretation of the significance of each of the above items must be done with caution; if any are present, 

professional advice should be sought.

Be aware that operations such as landscaping and utility installation may alter the ground surface appearance to resemble or conceal a natural phenomenon.

Modification of terrain in the vicinity of your parcel, either before you buy or after you build, particularly 

up-slope, may prove critical for you. Examples might include cutting into a slope, filling over a slope, 

drilling of an uncontrolled flowing well, diverting a spring, or installation of a deeply buried utility line.

Ground surface observation normally is sufficient for the evaluation of a residential property; if there is 

doubt, one or more holes will need to be dug or drilled and soil samples taken to resolve difficult questions. 

All examinations for subsurface fluid waste disposal require percolation tests in the soil by Health Authorities.

Ask questions of the realtor, homeowner, neighbors, but MOST IMPORTANT, conduct your own investigation, preferably with competent professional assistance (engineering geologist, geotechnical engineer).

 Consult State and Federal real estate and environmental documents for a broad statement of terrain conditions, 

but do not confine your examination of a particular parcel to the literature search.

WHEN YOU BUILD:

 Avoid constructing a home in the vicinity of moving earth, flood paths, fault traces or rock fall zones; do not 

build over underground openings or in depressions.

 Cost of construction, particularly in rural areas, can be reduced by knowing foundation conditions, depth to 

bedrock, depth to shallow groundwater, suitability of soils for wastewater disposal leach fields and groundwater depth and quality for primary or secondary water supply purposes.

 Adjust construction to accommodate these potential problems: moisture sensitive soils, high water table (shallow 

groundwater), low density soils, shallow bedrock or hardpan, severe earthquake ground-shaking zone, poor 

surface drainage, erosion-susceptible soil, steep or irregular topographic slope, boulders buried at shallow 

depth, springs or seeps on the property, variability of permeability of soils for fluid waste disposal.

 Maintenance problems can be reduced by prevention of erosion and soil movement under pavement, retaining 

walls and landscaping. Earth retention structures should all be properly engineered.

 Risk from earthquake to a-single-family dwelling can be reduced by proper siting and construction.

Where you choose to build, even within a given parcel of land, can make a considerable difference.

4-8/81 BNK

FIGURE 15. Example of a general fact sheet widely distributed in Utah that illustrates a common type of transfer

technique identified as an educational service in list 4.
54 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

United States

Department of the Interior

Geological Survey, Western Region

Menlo Park, California 94025

Public Affairs Office Pat Jorgenson (415) 329-4000

For release: UPON RECEIPT (Mailed August 26, 1988)

EAST-CENTRAL UTAH AREA HAS UNEXPECTED EARTHQUAKES

A series of earthquakes that have been shaking east-central Utah and 

western Colorado for the past two weeks (since Aug. 14, 1988) occurred in a 

part of Utah where earthquakes have been rare in the past, according to a 

U.S. Geological Survey scientist.

"These quakes happened in a relatively inactive seismic area," said 

Ernest Anderson of the USGS Office of Engineering Geology and Tectonics in 

Golden, Colo. The tremors have been centered about 35 miles south of Price, 

Utah, in a sparsely populated area of Emery County.

Most of Utah's earthquakes have occurred along the Wasatch fault, a 

north-south fracture in the Earth's crust, generally paralleling the western 

base of the Wasatch Mountains Just east of the Great Salt Lake. But Dr. 

Anderson said the Wasatch fault zone, which runs about 220 miles from Malad 

City, Idaho, south to Gunnison, Utah, about 120 miles south of Salt Lake 

City, would not have been a factor in the current series of earthquakes.

Carl Stover, a USGS geophysicist in Golden, Colo., who has compiled a 

series of seismicity maps for individual states, confirmed that the area of 

the August earthquakes has "no record of historic seismicity." The 

seismicity map he prepared of Utah shows only one other recorded earthquake 

in that area since 1850. It occurred Sept. 7, 1962, and had a magnitude of 

only 3.3.

The largest of the current earthquakes occurred Aug. 14 and was recorded 

at a preliminary magnitude of 5.6 on the Richter scale. The tremor, which 

occurred at 2:03 p.m. MDT, was preceded by a 3.5 magnitude earthquake at 

12:59 p.m. and a 4.3 magnitude 4.3 magnitude tremor at 1:08 p.m. The area 

has continued to have aftershocks, with the largest (magnitude 3.5) 

occurring on the morning of Aug. 15.

Although the August earthquakes have caused no injuries and little 

damage, the 5.6 magnitude earthquake Aug. 14 was the fourth largest recorded 

earthquake in Utah's history. The only larger ones were a 6.1 magnitude 

earthquake in a remote area of the Utah-Idaho border in March 1975 and two 

earthquakes of magnitudes 6.0 and 6.6 in northwestern Utah in March 1934.

* * * USGS * * *

EARTH SCIENCE IN THE PUBLIC SERVICE

FIGURE 16. Typical press release by the USGS Public Affairs Office illustrating a common but effective transfer 

technique. It is identified as an educational service in list 4.
REDUCING EARTHQUAKE HAZARDS IN UTAH 55

Salt Lake Tribune 2/18/87

Tests Warn 

Of S.L. 

Earthquake

By Joan O'Brien 

Tribune Staff Writer

The trenches tell the story of the past, 

and sound the warning.

Trenching studies along the Salt Lake 

section of the Wasatch Fault show that a 

major earthquake occurs every 2,200 to 

2,500 years and the last one was 2,200 

to 2,400 years ago.

'We are right in the window of vulnerability for the next earthquake," said 

Salt Lake County Geologist Craig V. 

Nelson.

The Wasatch Front is replete with 

geologic hazards, but residents can take 

precautions and mitigate the damage 

that would occur in a "characteristic" 

earthquake measuring 7.2 on the Richter 

Scale, Mr. Nelson said.

For the last year and a half Mr. Nelson 

has been translating hard geologic data 

into a language city planners can understand. His maps detailing "red flag" 

zones will be available to developers and 

the public within a few months.

Mr. Nelson's federally funded position 

was created, in part, so the Salt Lake 

County Planning Commission could take 

geologic hazards into consideration in 

development proposals. The United 

States Geological Survey has also provided funding for similar positions in 

Weber and Davis counties and Utah and 

Juab counties.

The Wasatch Fault, stretching from 

Nephi to Brigham City, is actually a 

series of fault segments that could produce earthquakes independently of other 

segments, Mr. Nelson said.

Unlike California's San Andreas 

Fault, the Wasatch Fault does not creep. 

"Unfortunately, the Wasatch Fault does 

not creep and the strain is accumulating," Mr. Nelson said. "What we see in 

the trenches is that there are 6-foot 

breaks and then nothing, so it all builds 

up to a critical point."

When that critical point is reached, 

scientists expect a "characteristic" earthquake with a magnitude of over 7 on the 

Richter Scale.

Salt Lake Tribune 8/24/86

County Geologist 

Advocates LongRange Planning

Special to The Tribune

FARMINGTON-Mike Lowe, Davis 

County geologist, believes long-range 

planning is the key to protecting residents from geologic hazards.

Mr. Lowe, speaking to members of the 

Davis County Council of Governments, 

summarized his findings after one year as 

county geologist.

He said recent landslides, flooding, 

debris flows and the rising Great Salt 

Lake have created a high degree of public awareness concerning geologic hazards.

As a result of threats and damages by 

such hazards, Mr. Lowe was hired to 

collect and translate technical information for use by planners and local government officials in Davis and Weber counties.

Mr. Lowe said, during the Aug. 20 

meeting, the county and many cities have 

adopted ordinances requiring geologic 

reports in potentially hazardous areas.

"By requiring these reports, hazards 

and mitigative measures can be identified and assessed," said Mr. Lowe.

"If development is allowed to proceed 

based on the report's recommendations, 

with zoning enforcers and building 

inspectors ensuring that those recommendations are followed, problems 

related to geologic hazards are less likely 

to arise," he added.

The geologist said he also has performed recent site evaluations focusing 

on new water tanks in North Salt Lake 

and Layton, three sites for a proposed 

new county jail and several landslide 

locations in the county.

In addition, the geologist said he did a 

number of site investigations of Bountiful 

and Farmington homes experiencing 

foundation cracks.

Deseret News 9/9/86

Geologist 

gathering 

data for 

hazards 

ordinance

PROVO - Utah County doesn't have 

a geological hazards ordinance yet, but 

by the time Robert Robison finishes a 

three-year stint as a special consultant 

for the county, there will be more than 

enough information to write the ordinance.

Robison is one of three geologists 

assigned to the Wasatch Front by the 

federal government.

His work area includes Utah and Juab 

Counties and he is also available to work 

with cities in both those counties.

This week Robison told Utah County 

commissioners he is moving into his second year of work for the county. He said 

that during the past year he has established a library with 700 maps and articles pertaining to soils and geology in 

Utah County.

"The purpose of my assignment is to 

collect information, establish a library, 

index maps and act as a technical assistant to the county and cities," said Robison.

Jess Mendenhall, Utah County planner, said Robison has provided much 

valuable information to the county.

"By the time he has finished gathering 

all the information, the county will be 

able to design the hazards ordinance and 

that will be a big help to us," Mendenhall 

said. "Most of the cities have one, but we 

haven't had the expertise to draw one up 

until now."

FIGURE 17. Typical local newspaper coverage of earthquake hazard reduction activities. Permission to publish. These examples are valuable

information transfer techniques shown in list 4.
56 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Text Weber Davis Salt Lake Utah Juab

1. Surface fault rupture 

(1:24,000)

2. Ground shaking 

(1:250,000)

3. Liquefaction potential 

(1:48,000)

4. Seismic slope stability 

(1:48,000)

5. Tectonic subsidence 

(1:100,000)

6. Dam failure

(variable scales)

7. Landslide hazard 

(1:24,000)

8. Rock fall hazard 

(1:24,000)

9. Debris flow hazard 

(1:24,000)

10. Lake/stream flooding

11. Shallow ground water 

(1:48,000)

12. Problem soils 

(1:24,000)

13. Other (seiche, sensitive clay, 

hydrologic effects)

F D D

D

F

F

D

F

F

F

Anderson and others (1982, 1986a, 1986b)

Topham and others (1987)

Keaton (1987)

U.S. Bureau of Reclamation

D D D D D 

D D D D D 

F F D D D

NO MAP PLANNED

Anderson and others (1982, 1986a, 1986b)

NO MAP PLANNED

FIGURE 18. Status of geologic hazard maps and texts being produced by county geologists as of June 

1988 (rev. December 1988) from Christenson (1988, table 1, p. 7). Letter F indicates final completed, 

D indicates draft text or partial mapping completed, and indicates completion planned for 

subsequent years. References are given for maps completed by others (see Christenson, 1988, p. 14).

were collected statewide from conventional sources of 

published information and some unconventional sources. 

All of the references were keyworded and entered into a 

computerized data base system for easy manipulation 

and retrieval. These sources were supplemented by 

many of the geotechnical engineering firms and government agencies in Utah that permit a review of existing 

files for more site-specific information.

This compilation was initiated in Octobe r 1985 with the 

goal of not only compiling a computerized hazards bibliography, but also producing generalized hazards maps 

for the State at a scale of 1:750,000. The Hazards bibliography includes a comprehensive listing of all published 

and unpublished hazards information statewide. Information can be retrieved according to specific hazard, 

type of information, and geographic locality covered by 

each entry. When completed, the bibliography can be 

sorted geographically and printouts made available to 

various government entities (cities, counties, and multicounty agencies) so that there will be an awareness of 

what data are available for each jurisdiction.

In conjunction with the bibliography, UGS maintains a 

file for each USGS IVz' quadrangle in the State that will 

include site-specific hazards reports (where appropriate), inventory sheets of the contents of each

report, and an index map showing the location of each 

site in the report. Mapping and bibliography compilation 

proceeded concurrently and were completed in 1989.

The second phase of the UGS hazards compilation 

project is a cooperative effort with the USGS and five 

Wasatch Front counties. The three county geologists 

serving the five counties have collected all pertinent 

hazards information and developed a hazards library for 

each county. This information is supplemented with 

additional field studies, as necessary, to compile hazards 

maps for each county. Files of site-specific hazards 

information are being maintained, and index maps showing locations of hazards information are being compiled.

Texts are being prepared to accompany each map to 

explain the hazard in terms of likelihood, location, and 

severity. Discussions of possible engineering and site 

design techniques for mitigation are included, as well as 

guidelines for the types of information that should be 

included in site investigation reports. Figure 18 shows 

the status of these texts and maps as of December 1988.

PUBLIC INQUIRIES

In addition to compiling and maintaining directories, 

the UGS maintains a library, public inquiries section,
REDUCING EARTHQUAKE HAZARDS IN UTAH 57

and sales office. According to Smith (1985b, p. 4), the 

library has several thousand items, including materials 

on earthquake phenomena and hazards. The librarian has 

access to the computerized "Bibliography of Utah Geology," can make searches by author, location, or type of 

study, and is adding new titles to keep the list up to date.

The list of UGS publications and maps is now on 

computer (PUBLIST) indexed by county and kind of 

study for easy location of specific publications. The data 

processing section is preparing a new program to keep 

records of sales and inventories. All except the most 

recent UGS publications are now available on microfiche, 

so that no publication is ever out of print.

The sales office fills mail orders for UGS publications 

(more than 70 percent of its business) and handles 

over-the-counter sales. Receipts for 1983-84 were 

$42,000, and sales have been increasing annually. In 

addition, many materials are provided to the public at no 

charge. The UGS staffs an Applied Geology Program to 

assist State and local units of government in assessing 

and reducing geologic hazards. The USGS operates 10 

public inquiries offices in the United States, one of which 

is in Salt Lake City.

ADVISORIES

Specific advice on reducing earthquake hazards may 

be in oral or written form. Written information may 

consist of a general fact sheet that is widely distributed 

or a letter addressing a specific issue that is requested by 

a planner or decisionmaker. Figures 15 and 19 illustrate 

these two types.

The UGS and county geologists provide various advisory services, such as offering explanations and advice 

along with hazard maps and hazard reduction literature, 

to prospective real estate buyers, sellers, lenders, and 

developers. Building officials and planners, both city and 

county, frequently request advice on specific sites where 

geotechnical problems are encountered or suspected. 

The UGS also advises the Utah State Departments of 

Community and Economic Development and Facilities 

Construction and Management regarding use of earthquake hazards information in State-funded projects.

The county geologists' advice has been sought by the 

cities of Salt Lake, Ogden, South Weber, Mapleton, 

Centerville, Riverdale, and Washington Terrace and the 

counties of Salt Lake, Utah, and Weber on the content of 

ordinances regulating the use of hazardous lands.

GUIDELINES

The Utah Section of the Association of Engineering 

Geologists (1986, 1987) has been preparing guidelines

concerning the preparation of engineering geologic 

reports and the evaluation of various geologic hazards 

including surface-fault rupture, shaking, liquefaction 

potential, and landslide potential. Two reports have been 

published and distributed by the UGS; one is shown in 

figure 20.

Sometimes a scientist-author includes a transfer technique along with the translated material. A good example is a recommendation included in the earthquakeinduced landslide-potential report by Keaton and others 

(1987) that accompanies their seismic slope stability map. 

The recommendations in matrix format for critical facilities and other land uses are shown in figure 21.

GUIDEBOOKS

Several guidebooks were specially prepared for reducing earthquake hazards in Utah including

 Reducing losses from earthquakes through personal 

preparedness by Kockelman (1984).

 Suggested approach to geologic-hazard ordinances in 

Utah by Christenson (1987).

 Utah's geologic hazards a review for realtors by 

Christenson and Mabey (1987).

 Planning for natural hazards by the University of Utah 

Center for Public Affairs and Administration (1988). 

The first guidebook introduces the five phases of 

reduction, namely, pre-event mitigation techniques and 

preparedness measures, response during the earthquake, and post-event recovery operations and reconstruction activities. Several examples and citations are 

given for each. Because of the unique effort toward 

individual and community "self-reliance" in Utah, the 

guidebook emphasizes the relatively inexpensive actions 

that can be taken by responsible parents, neighborhoods, 

and employers, such as inspecting and strengthening the 

home, organizing the neighborhood, and securing contents and other nonstructural parts of buildings.

The second book encourages prudent land use in areas 

of geologic hazards, including earthquakes, for the protection of the citizens of those cities and counties enacting ordinances. A concise discussion of hazards and 

availability of information is followed by a comprehensive 

survey of city and county geologic hazard ordinances in 

Utah. An outline of the steps to be included in a hazard 

reduction ordinance in jurisdictions having geologic hazard maps and those without such maps is shown in figure 

22. In addition, the Salt Lake County planning staff 

drafted an ordinance for natural hazards reduction 

(Barnes, 1988b) that follows the guidebook recommendations. The ordinance contains a guide to natural hazards 

reports required for various types of facilities or developments and has been used as a model by other cities and 

counties (Barnes, 1988a).
58 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

United States Department of the Interior

GEOLOGICAL SURVEY

Office of Earthquakes, Volcanoes, and Engineering

345 Middlefield Road, MS 922

Menlo Park, CA 94025

415/323-8111, x 23J2

FTS 467-2312

AMERICA;

May 6, 1986

EXPRESS MAIL

Mr. Jerold H. Barnes, AICP

Salt Lake County Planning Commission

2033 South State Street

Salt Lake City, Utah 84115

Dear Jerry:

In accord with your request yesterday, please find selected materials for 

use in developing a geologic-hazard-overlay amendment to the county zoning 

ordinance. These materials include examples of ordinances, discussions of need 

or use, and the content of geotechnical reports, all of which are paperclipped 

and highlighted for your convenience:

Ordinances

Potentially hazardous geologic conditions (Sonoma County, 1974)

Safety geologic (S-G) overlay (San Bernardino County, 1980)

Liquefaction investigation (City of San Diego, 1984)

G-H geologic hazard overlay district (Jefferson County, Colorado, 1983)

Geologic hazard maps (Santa Clara County, 1978)

Model geologic hazard area control (Colorado Geological Survey, 1974)

Resource management zoning district (San Mateo County, 1973)

Discussions

Site investigations in hazardous areas (Brown and Kockelman, 1983)

Engineering geology at the local government level (McCalpin, 1985)

Landslide hazard zones (Weber, 1980)

Role of geotechnical consultants and reviewers (Leighton, 1975)

Geologic review process (Hart and Williams, 1978)

Hazard avoidance and mitigation (Unknown)

Geotechnical Report Guidelines

Guidelines to geologic/seismic reports (CDMG, 1973)

General guidelines for geological reports (Ventura County, 1974)

Minimum standards for geotechnical reports (San Mateo County, 1977)

I deliberately selected a wide range of materials to provide you with the 

greatest flexibility, for example:

FIGURE 19. This example of a letter addressing a specific issue in Utah illustrates a type of transfer technique

identified as an advisory service in list 4.

The third book was prepared to provide Utah's realtors with information that will enable them to place the 

State's geologic hazards in proper perspective and to 

communicate this risk to prospective home buyers and

business clients. The hazards considered include floods, 

slope failure, earthquakes, subsidence, and expanding 

soils. The authors emphasize the need for hazard assessment and then provide general information about the
REDUCING EARTHQUAKE HAZARDS IN UTAH 59

o The ordinances range from Sonoma County's one-page regulation requiring a 

site investigation and recommendations for preventive and corrective 

measures to San Mateo County's 24-page resource management zoning 

district that reduces dwelling unit density in soil- and scenic-resource 

areas as well as fault-rupture and landslide-hazard areas.

o The discussions include a case history on "challenging a geologic-hazard 

zone," use of a l:12,000-scale hazard-overlay cadastral map, and land 

development goals from the viewpoints of the developer, the geologic 

consultant, and the public agency involved.

o The guidelines range from very general notes to four types of geologic 

reports requiring detailed data and descriptions, including county 

certification forms.

According to 3eff Keaton, the Utah Section of the Association of Engineering 

Geologists is preparing guidelines for engineering geologic reports, including 

surface-rupture, seismic-shaking, liquefaction, and slope-stability hazards. 

Genevieve Atwood advised me today that the UGMS is considering publishing these 

guidelines as UGMS notes.

As we discussed, it would be desirable to keep the geologic-hazard-overlay 

regulations succinct (as you did with the "hillside protection zone") and to adopt by 

reference both the official hazards maps and the required geotechnical reports. 

My experience indicates that such an approach makes it much easier for the public 

to understand; reduces direct pressure on the local government when references 

can be made to outside experts (State, Federal, university, consultants, and 

professional societies); and makes it easier to update them without amending the 

ordinance.

Caveat

The enclosed materials are in a raw form directly from my files and, of 

course, can not be endorsed or recommended by the U.S. Geological Survey. 

Although many of them have been in effect for several years without successful 

legal assault, others may have been revised, repealed, or not properly enforced. 

If a particular example seems promising for your needs, I would be pleased to make 

one or two inquiries concerning its status and provide you with the administrator's 

name and number for direct contact.

I hope these materials will be of some help to you, the Commission, and Salt 

Lake County. Please call me if you have any questions or if I can be of any 

further assistance.

Sincerely,

Enclosures

W.3. Kockelman

cc: G. Atwood 

3. Keaton

FIGURE 19. Continued.

availability of hazard information, status of various 

hazard-mapping projects, ordinances dealing with hazard warnings or mitigation, and work accomplished by 

the UGS Applied Geology Program. The report concludes that realtors "have a unique opportunity to inform 

the property owners of Utah and thus contribute to 

making Utah safer and more prosperous."

The fourth book offers a guide to the initial steps that 

may be undertaken at the local level to understand and

plan for reduction of potential hazards. The book includes 

a discussion of local government responsibility and liability, an outline of the planning process, and State and 

county contacts for information and assistance.

GEOGRAPHIC INFORMATION SYSTEMS

For the purposes of this report, geographic 

information systems (GIS's) are defined as the spatial
60 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

UTAH GEOL OGICAL 

AND MINERAL SURVEY

GUIDELINES FOR EVALUATING SURFACE 

FAULT RUPTURE HAZARDS IN UTAH

by

The Utah Section of the 

Association of Engineering Geologists

These guidelines have been compiled to assist geologists in the investigation of possible hazards due to surface fault rupture and to enable reviewers 

to evaluate the thoroughness of such investigations. The guidelines were 

developed by the Guidelines Committee of the Utah Section of the Association of Engineering Geologists, for the purpose of protecting the health, 

safety, and property of the people of Utah. Previously published guidelines 

for the State of California (California Division of Mines and Geology, 1975; 

Slosson, 1984) were used as models. The guidelines do not include systematic descriptions of all available techniques or topics, nor is it suggested that 

all techniques or topics be utilized on every project. Variations in site 

conditions and purposes of investigations may require more or permit less 

effort than is outlined here. All elements of these guidelines should be considered during the preparation and review of engineering geologic reports.

Future faulting generally is expected to recur along pre-existing faults 

(Bonilla, 1970, p. 68); the development of a new fault or reactivation of a 

pre-Quaternary fault is relatively uncommon and generally need not be a 

concern in site development for typical facilities. Generally, the more recent 

the faulting, the greater the probability of future faulting (Alien, 1975; 

Ziony and others, 1973). Regional and urban earthquake hazards and risk 

in Utah are reviewed by Hays and Gori (1984).

The evaluation of future fault rupture hazards involves careful application of skills and techniques not commonly used in other engineering 

geologic investigations (trenching, absolute dating). Many active faults are 

complex, consisting of multiple breaks which may have originated during 

different surface-faulting events. To accurately evaluate the potential 

hazards due to future surface fault rupture, the geologist must determine:

I. Fault Locations

This involves locating and accurately mapping all tectonic features at the 

site, at a scale large enough to be used for site planning (1 inch = 200 feet).

II. Nature of Deformation

Surface deformation over active faults may involve single large displacements, multiple small displacements, monoclinal flexure, backtilting, or a combination of all of these (see Bonilla, 1982). The way in which the surface deforms 

influences the type and degree of risk posed to various types of structures.

III. History of Fault Ruptures

The absolute age of past displacements should be obtained over as long a 

period of geologic time as possible. Two key measurements are: 1) the age 

of latest faulting, and 2) the average recurrence interval between surfacerupturing events.

Few structures intended for human occupancy are designed to withstand 

surface rupture of their foundations without serious damage. If such a 

structure is sited astride an active fault, the subsequent fault rupture hazard 

cannot be mitigated unless the structure is relocated. Therefore, the scope of 

the investigation depends on not only the complexity and economics of the 

project, but also on the level of risk acceptable for the proposed development. Because of variability in the risk and in the complexity of site geology, 

not all investigative techniques described here need to be or can be 

employed in evaluating a single site. The guidelines provide a checklist for 

preparing complete and well-documented reports.

Regardless of the size of the project (single-family residence vs high-rise 

building) the conclusions drawn from geologic data must be consistent and 

unbiased, and must not tie to the design life or perceived economics of the 

project. Recommendations must be clearly separated from conclusions, 

since recommendations are not solely dependent on geologic factors.

Suggested Outline for Reports 

Evaluating Surface Fault Rupture Hazard

The following subjects should be addressed in any geologic report on 

faults. Some of the investigative methods listed below should be extended 

well beyond the site being investigated. Not all of the methods identified will 

be useful at every site. 

A. Purpose and Scope of Investigation 

B. Geologic and Seismotectonic Setting

1. Regional Geology

2. Tectonic Setting

a. Location and style of known active faults (see Anderson and Miller,

1979; Nakata and others, 1982).

b. Major earthquakes in historic time (see Arabasz and others, 1979). 

C. Site Description and Conditions-Include information on depth to 

ground water, geologic units, graded and filled areas, vegetation, existing 

structures, and other factors that may affect the choice of investigative 

methods and the interpretation of data. 

D. Office Methods of Investigation

1. Review of published and unpublished literature, maps, or records 

concerning geologic units, faults, ground-water barriers, and 

other factors.

2. Stereoscopic interpretation of aerial photographs or other remotely 

sensed images to detect fault-related topography, soil and vegetation 

contrasts, and other lineaments of possible fault origin. Low-sunangle photographs are particularly useful for fault scarp recognition 

(seeCluffand Slemmons, 1971).

3. Personal communication with those who have first-hand knowledge

about geologic conditions or pertinent land-use history of the site. 

E. Field Methods of Investigation

1. Surface

a. Geologic mapping distribution, depth, thickness and nature of 

geologic units, both surficial and bedrock.

b. Location and relative ages of tectonic surface features, including 

fault scarps, sag ponds, aligned springs, offset bedding, disrupted 

drainage systems, offset ridges, faceted spurs; locations of zones of 

crushed rock (fault breccia). Relationships with dated alluvial terraces or shorelines (Currey, 1982) may yield indication of age. 

Surface topographic profiling of fault scarps may permit an age 

estimate if scarps result from a single rupture event (Nash, 1980; 

Hanks and others, 1984) or may show evidence of multiple events 

(Wallace, 1977).

c. Locations and relative ages of other possibly earthquake-induced 

features caused by lateral spreading, liquefaction, or settlement. 

Locations of slope failures should be noted, although they may not 

be conclusively tied to earthquake causes.

2. Subsurface

a. Trenching or other excavations across features of suspected tectonic origin. A detailed trench log should be prepared at a scale of 

1:60 or larger showing geologic units, soil profiles, and all discontinuities (unconformities, fractures, shear zones, fault planes, sand or 

rubble-filled cracks, burrows). The position of all samples used for 

absolute dating must appear on the log. Systematic photographs 

should be taken to document the presence or absence of tectonic 

features. Because the location of trenches is critical in obtaining

MISCELLANEOUS PUBLICATION N

UTAH GEOLOGICAL AND MINERAL SURVEY 

Genevieve Atwood, Director

606 Blackhawk Way 

Salt Lake City, Utah 84108

FIGURE 20. This example of guidelines for evaluating a hazard and preparing reports in Utah is a type of transfer 

technique from list 4. When adopted by State or local governments as a requirement, it becomes a reduction technique 

identified in list 2.
REDUCING EARTHQUAKE HAZARDS IN UTAH 61

tectonic or stratigraphic data, investigators are encouraged to discuss trench location, orientation, depth, and length with reviewers 

in advance of excavation. Multiple trenches, if needed, should be 

excavated concurrently, not sequentially. All critical excavation 

should be left open for at least 48 hours after logging is completed to 

allow access by reviewers. Fencing, posting, and shoring of all the 

trenches is strongly recommended (see Woods, 1976).

b. Absolute dating to determine timing of past surface rupture events. 

Methods commonly used for Quaternary deposits are reviewed by 

Colman and Pierce (1977, 1979) and McCalpin (1986). Samples 

should be collected which most tightly bracket the time of faulting; 

e.g., from the youngest parts of faulted units and from the oldest 

parts of unfaulted units.

c. Borings and test pits to collect data on geologic units, fault-plane 

geometry, and ground-water elevations. Data points must be sufficient in number and adequately spaced to permit valid correlations 

and interpretation.

3. Geophysical investigations. These are indirect methods that require 

knowledge of specific geologic conditions for reliable interpretation. 

Geophysical methods alone never prove the existence or absence of a 

fault, nor can they assess the recency of activity. Types of equipment 

and techniques used should be described. Methods commonly include 

seismic refraction, seismic reflection, electrical resistivity, gravity, 

magnetic intensity, and ground penetrating radar.

4. Other investigations; where special conditions or requirements for 

critical structures demand more intensive investigation, 

a. Aerial reconnaissance overflights, 

b. Geodetic and strain measurements, 

c. Microseismicity monitoring. 

F. Conclusions

1. Locations of mapped faults; style of associated displacement and age 

of past surface rupturing events.

2. Anticipated amount and pattern of earth displacements in the next 

probable surface-faulting event; delineation of areas of high risk.

3. Probability or relative potential for future surface displacements. The 

likelihood of future faulting may be estimated from the recurrence 

intervals between past events, plus the age of latest faulting, or from 

slip rates and amount of anticipated earthquake slip1 determined for 

the specific site or from an identified fault segment which includes the 

site (for Wasatch Fault segments, see Anderson, in press).

4. Comparison of conclusions developed from site data with previous 

interpretations on the same fault trace or segment.

5. Degree of confidence in and limitations of data and conclusions. 

G. Recommendations

1. Recommended building restrictions or use limitations within any

designated high-risk areas.

a. Setback distances from hazardous faults. Most Utah local governments currently have no laws dictating minimum setback. Therefore, justification must be clearly provided for recommended 

setback distances (see McCalpin, 1987).

b. Restrictions arising from causes other than discrete surface rupture 

(e.g., ground tilting, induced mass movements).

2. Risk evaluations relative to the proposed development. Any probabilistic estimates of fault rupture within the design life of the development 

should be supported with assumptions used and probable error ranges.

3. Need for additional studies. 

H. References

1. Literature and records cited or reviewed.

2. Aerial photographs or images interpreted list type, date, scale, 

source, and index numbers.

3. Other sources of information, including well records, personal communications, and other data sources.

I. Illustrations-These are essential in understanding the report and reducing 

the length of the text.

1. Location map identify site locality, significant faults, geographic 

features; 1:24,000 scale recommended.

2. General geologic map shows geologic setting of site, geologic units, faults, 

other geologic structures, geomorphic features, lineaments, springs, 

epicenters of historic earthquakes of M>4,1:24,000 scale recommended.

3. Site map combines a detailed, large-scale geologic map of the site 

with pertinent development-related data (site boundaries, existing and 

proposed structures, graded areas, streets, exploratory trenches, boring locations, geophysical traverses, and other data). Site geology 

must correlate with the regional geologic map but should provide 

refined data on surficial deposits. Recommended scale of 1 inch equals 

200 feet or larger (1:2,400).

4. Geologic cross-sections, to extend to the depth of exploratory borings 

or foundation elements, whichever is greater; same horizontal scale as 

the site map.

5. Logs of exploratory trenches or borings. Trench logs in particular 

should show all relevant detail at a scale of 1:60 or larger within zones 

of suspected deformation; no vertical exaggeration.

6. Geophysical data and its geologic interpretation.

7. Photographs of scarps, trenches, samples, or other features which

enhance understanding of the pertinent site conditions. 

J. Appendix-Supporting data not included above (e.g., water well data). 

K. Signature of Investigating Geologist-The report must be signed by the 

engineering geologist who conducted the investigation. The State of Utah 

currently has no statutory definition of an engineering geologist; however, 

some local governments do define the minimum qualifications of geologists 

who can submit reports. Current registration as ageologist in another state 

may be used in support of demonstrating qualifications.

REFERENCES

Alien, C.R., 1975, Geologic criteria for evaluating seismicity: Geological Society of 

America Bulletin, v. 86, p. 1041-1057.

Anderson, L.W., and Miller, D.G., 1979, Quaternary fault map of Utah: Fugro Inc., 

Long Beach, CA, 35 p., scale 1:500,000.

Anderson, R.E., in press. Regional and local hazards mapping in the eastern Great 

Basin: National Earthquake Hazards Reduction Program, Summaries of Technical Reports, vol XXIII, U.S. Geological Survey Open-File Report.

Arabasz, W.J., Smith, R.B., and Richins, W.D. (eds.), 1979, Earthquake studies in 

Utah, 1850 to 1978: Special Publication, University of Utah Seismograph Stations, Salt Lake City, UT, 552 p.

Bonilla, M.G., 1970, Surface faulting and related effects, in Wiegel, R.L. (ed.). Earthquake Engineering: Prentice-Hall Inc., Englewood Cliffs, N.J., p. 47-74.

 1982, Evaluation of potential surface faulting and other tectonic deformation:

U.S. Geological Survey, Open-File Report 82-0732, 91 p. 

California Division of Mines and Geology, 1975, Guidelines for evaluating the hazard

of surface fault rupture: CDMG Note 49, 4 p. 

Cluff, L.S., and Slemmons, D.B., 1971, Wasatch Fault Zone features defined by

low-sun-angle photography, in Hilpert, L.S. (ed.), Environmental Geology of the

Wasatch Front: Utah Geological Association Publication I, p. H1-H29. 

Colman, S.M., and Pierce, K.L., 1977, Summary table of Quaternary dating methods:

U.S. Geological Survey Map MF-904.

 1979, Preliminary map showing Quaternary deposits and their dating potential 

in the conterminous United States: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1052, scale 1:7,500,000.

Currey, D.R., 1982, Lake Bonneville: selected features of relevance to neotectonic 

analysis: U.S. Geological Survey, Open-File Report 82-1070,30 p., map 1:500,000.

Hanks, T.C., Bucknam, R.C., Lajoie, K.R., and Wallace, R.E., 1984, Modification of 

wave-cut and faulting-controlled landforms: Journal of Geophysical Research, 

v. 89, no. B7, p. 5771-5790.

Hays, W.W., and Gori, P.L. (eds.), 1984, Proceedings of Conference XXVI, A Workshop on Evaluation of Regional and Urban Earthquake Hazards and Risk in 

Utah: U.S. Geological Survey, Open-File Report 84-763, 674 p.

McCalpin, James, 1986, Thermoluminescence dating in seismic hazard evaluations; an 

example from the Bonneville Basin, Utah in Wood, S.H. (ed.). Proceedings of the 

22nd Symposium on Engineering Geology and Soils Engineering: Boise State 

University, Feb. 1986, p. 156-176.

 , 1987, Recommended setbacks from active normal faults, in McCalpin, James 

(ed.). Proceedings of the 23rd Annual Symposium on Engineering Geology and 

Soils Engineering: Utah State University, April 6-8, 1987, p. 35-56.

Nakata, J.K., Wentworth, C.M., and Machette, M.N., 1982, Quaternary fault map of 

the Basin and Range and Rio Grande Rift Provinces, western United States: U.S. 

Geological Survey, Open-File Report 82-579, scale 1:2,500,000.

Nash, D.B., 1980, Morphologic dating of degraded normal fault scarps: Journal of 

Geology, v. 88, p. 353-360.

Schwartz, D.P. and Coppersmith, K.J., 1984, Fault behavior and characteristic earthquakes: examples from the Wasatch and San Andreas fault zones: Journal of 

Geophysical Research, v. 89, p. 5681-5698.

Slosson, J.E., 1984, Genesis and evolution of guidelines for geologic reports: Bulletin 

of the Association of Engineering Geologists, v. XXI, no. 3, p. 295-316.

Wallace, R.E., 1977, Profiles and ages of young fault scarps, north-central Nevada: 

Geological Society of America Bulletin, v. 88, p. 1267-1281.

Woods, M.C., 1976, Trench shoring: California Geology, v. 29, no. 8, p. 178-181.

Ziony, J.I., Wentworth, C.M., and Buchanan, J.M., 1973, Recency of faulting; a 

widely applicable criterion for assessing the activity of faults: Fifth World Conference on Earthquake Engineering, Rome, Italy, p. 1680-1683.

FIGURE 20. Continued.
62 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

FACILITY CLASS

CRITICAL 

Hospitals, Fire Stations 

Police Stations 

Other Emergency Facilities

LIFELINES 

Communications 

Transportation, Water Supply 

Electric Power, Natural Gas

HIGH OCCUPANCY PUBLIC-OWNED 

Schools, State Capitol 

City Hall, Airports 

County Courts, Convention Centers

HIGH OCCUPANCY PRIVATE-OWNED 

Office Buildings 

Apartments, Hotels 

Shopping Malls

INDUSTRIAL-SEVERE CONSEQUENCE 

Refineries, Sewage Plants 

Hazardous Waste, Explosives

INDUSTRIAL-MINOR CONSEQUENCE 

Trucking, Shipping 

Light Manufacturing

RESIDENTIAL SUBDIVISION

RESIDENTIAL SINGLE LOT

EARTHQUAKE-INDUCED LANDSLIDE 

POTENTIAL ZONE

HIGH MODERATE LOW VERY LOW

YES YES YES YES

YES YES YES MAYBE

YES YES YES MAYBE

YES YES MAYBE NO 

Appropriate Disclosure Required

YES YES MAYBE NO 

Appropriate Disclosure Required

MAYBE MAYBE NO NO 

Appropriate Disclosure Required

MAYBE MAYBE NO NO 

Appropriate Disclosure Required

NO NO NO NO 

Appropriate Disclosure Required

EXISTING T ^TT^ , , T ANmT TDF LIQUEFACTION 

LANDSLIDE POTENTIAL

YES YES

YES YES

YES YES

YES YES

YES YES

NO MAYBE 

Appropriate Disclosure Required

NO YES 

Appropriate Disclosure Required

MAYBE MAYBE 

Appropriate Disclosure Required

FIGURE 21. Example of a matrix with recommendations for site-specific stability analysis for critical facilities and other land uses in several 

hazard zones by Keaton and others (1987, table 4, p. 76). This matrix is a special type of transfer technique in list 4. It was designed by the 

scientist-authors for nontechnical users. When adopted by State or local governments as a requirement, it becomes a reduction technique 

identified in list 2.

representation of geologic, hydrologic, topographic, land 

use, land ownership, and other physical and socioeconomic information that can be readily combined, 

manipulated, analyzed, and displayed for various purposes by computer technology. The result is a quantifiable analysis of point, line, area, and volume data. The 

nature and capability of GIS's provide an excellent basis 

for presenting and combining not only the various earthquake hazards, but critical facilities that might be 

affected. In addition, an easy-to-use georeference map 

can be provided for the nontechnical user.

For example, Alexander and others (1987), in demonstrating the use of digital mapping technology, entered 

surface-fault rupture, liquefaction potential, and landslide potential into a GIS for the Sugar House quadrangle 

in east-central Salt Lake County. In addition to the 

hazards maps used in their atlas, other maps were used 

to illustrate the kinds of information needed to reduce 

earthquake hazards, namely, political jurisdictions, 

roads, selected lifelines, and land uses. They then combined hazards with specific land uses, such as lifelines in 

potential surface-fault rupture zones, schools and residential areas in high liquefaction-potential zones, and 

schools and residential areas on lands with the lowest 

stability during earthquakes.

University of Utah Department of Geography professor Phillip Emmi has entered Salt Lake County's lifelines, other critical facilities, and building inventories 

into a GIS to estimate earthquake loss probabilities. 

CEM planner Wes Dewsnup entered all information for 

the Utah County Comprehensive Hazard Mitigation 

Project into the GIS operated by the Utah State Office of 

Automated Geographic Referencing. Salt Lake County 

uses the AUTOCAD system, which, according to C.V. 

Nelson (written commun., 1989), will greatly increase 

the transfer of hazard information that has been referenced to land ownership records.

REVIEW SERVICES

The State and county geologists are sometimes asked 

to provide the type of review services in list 4. For 

example, the Salt Lake County geologist has assisted
REDUCING EARTHQUAKE HAZARDS IN UTAH 63

1) Define boundaries of geologic hazards areas by establishing Geologic Hazards Zones (or equivalent) or officially adopting maps referenced to an ordinance.

2) Require geotechnical reports by qualified engineering geologists 

and engineers addressing hazards and, if necessary, recommending 

mitigation measures prior to development in geologic hazard areas.

3) Require review of geotechnical reports by county geologists or 

other qualified engineering geologists acting on behalf of local 

government.

4) Submit report and review comments to planning commission for action,

5) Amend geologic hazard area boundaries (zones or adopted maps) if 

proven necessary by site report.

B

1) Provide for review of all development proposals by county geologists or other qualified engineering geologists acting on behalf of 

local government to determine need for geotechnical reports.

2) Require geotechnical reports by qualified engineering geologists

and engineers to address potential hazards indicated in review and, 

if necessary, to recommend mitigation measures. If initial reviews 

of development proposals are not performed, complete reports may be 

required for all sites.

3) Require review of geotechnical reports by county geologists or 

other qualified engineering geologists acting on behalf of local 

government.

4) Submit report and review comments to planning commission for action,

FIGURE 22. Suggested topical outline for geologic hazards ordinances in areas with geologic hazards maps (A) and without geologic 

hazards maps (B) by Christenson (1987, table 1, p. 9). This outline is another type of transfer technique identified as an advisory 

service in list 4.

West Valley City by providing geologic hazard information to be incorporated into a computerized data bank for 

land-use planning; the UGS and Utah County geologist 

provided hazard maps and interpretations for a CEM and 

county project in the Provo-Orem area to aid emergency 

response personnel; and the Weber County geologist 

assisted the city of Washington Terrace in including 

geologic hazards into its 1987 master plan.

COMMENT

In all of the examples, delivery of translated information was provided; in many others, assistance and encouragement in the use of information for hazard reduction were provided or offered. The users ranged from 

practitioners and professional societies to interested 

citizens, including children. Several of Utah's transfer 

techniques included suggested reduction techniques.
64 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Special mention should be made of the unique efforts of 

the UGS, USGS, university, and consulting researchers 

to release research findings early to practitioners and 

other users. This efficiency was accomplished through 

oral briefings, workshops, workshop proceedings (Hays 

and Gori, 1984, 1987; Gori and Hays, 1987, 1988), serial 

publications (Stringfellow, 1983-present), newsletters 

(Hassibe, 1983-1986; Jarva, 1987-present), and "official 

use only" materials.

The commitment of the USGS to the transfer of 

research in Utah and the evaluation of its effectiveness 

may be seen in a recent award for a proposal by William 

Spangle and Associates (1989). The summary of their 

approach follows.

This project is designed to assist local officials in cities and 

counties of the Wasatch Front region of Utah apply the information provided by the USGS regional assessment of earthquake hazards. The direct experience of the consultants in 

research, planning practice and information transfer will be 

shared with Utah officials, especially city planners, on a regular 

basis during the year. This will be done by participating in up to 

four meetings throughout the year and being available as needed 

for direct consultation with local (and State) officials about 

options for earthquake-hazard reduction. A final report evaluating the effectiveness of the process and opportunities for 

transfer to other regions will also be prepared.

EVALUATION AND REVISION

The last component in Utah's comprehensive earthquake hazard reduction program is evaluating the effectiveness of the reduction techniques and revising them if 

necessary (see fig. 1). Evaluating and revising the entire 

program, as well as such other components as studies, 

translation, and transfer, may also be undertaken.

The evaluation component was included as a task in the 

National Earthquake Hazard Reduction Program 

(NEHRP) by Wallace (1974) and as recommendations of 

the California Joint Committee on Seismic Safety (1974) 

advisory groups. Evaluation has been emphasized in a 

review of efforts by 10 cities to manage flood plains 

(Burby and others, 1988, p. 9), in the comprehensive 

tasks of a national program to reduce landslide hazards 

(U.S. Geological Survey, 1982, p. 44), and in the recommendations of the NEHRP Expert Review Committee 

(1987, p. 81-85).

In Utah, evaluation is included in the abbreviated 

recommendations for earthquake risk reduction by the 

Utah Seismic Safety Advisory Council (1981), as an 

active item from a governor's conference on geologic 

hazards (Utah Geological and Mineral Survey, 1983), and 

as a task in the Utah work plan.

IMPORTANCE

The effectiveness of each hazard reduction technique 

varies with the time, place, and persons involved. Therefore, it is prudent to include a continuing systematic 

evaluation as part of any program for earthquake hazard 

reduction. An inventory of uses made of the information, 

reports of interviews with the users, and an analysis of 

the results and responses will also result in identifying 

new users and innovative uses, as well as any problems 

concerning the research information and its translation, 

transfer, and use. The evaluation will be helpful, even 

necessary, to those involved in funding, producing, 

translating, transferring, and using the research information as well as managing a comprehensive program.

Performing the scientific and engineering studies and 

then translating and transferring the research information is expensive and difficult because of the limited 

number of scientists and geotechnicians from national, 

State, local, university, corporate, and consulting areas, 

particularly when aligned with the needs of communities 

throughout the United States. The adoption and enforcement of an appropriate hazard reduction technique is 

time consuming and requires planning, engineering, 

legal, and political skills, as well as strong and consistent 

public support.

Scarce financial and staff resources must be committed; necessarily persistent and difficult actions must be 

taken to enact a law, adopt a policy, or administer a 

reduction program over a long period of time. To discover later that the hazard reduction technique selected 

is ineffective, unenforced, or has greatly disproportionate costs in terms of benefits derived is not only disheartening but may subject those involved to criticism and 

withdrawal of financial support.

Few systematic evaluations have been made of natural 

hazards reduction techniques, including those for earthquakes. To my knowledge, no rigorous studies of the 

ratio of benefits to costs have been conducted. However, 

a few intensive evaluations have been made for flood, 

landslide, and other reduction techniques and programs 

that may be applicable to earthquakes.

The following examples of various evaluations are 

presented for introductory purposes. The findings and 

recommendations, although beyond the scope of this 

report, will be helpful to Utahans in their selection of the 

most appropriate transfer and reduction techniques.

EVALUATION OF REDUCTION TECHNIQUES

Several reduction techniques (list 2) have been evaluated, problems identified, and improvements suggested:

 Preparing and implementing local seismic safety elements by the California Seismic Safety Element 

Review Committee (1985).

 Lending, appraising, and insuring policies of the 12 

largest home mortgage lenders in California by Marston (1984).
REDUCING EARTHQUAKE HAZARDS IN UTAH 65

 Disclosing surface-fault rupture hazards to real estate 

buyers in Berkeley and Contra Costa County by Palm

(1981).

 School earthquake safety and education project in 

Seattle and community outreach education centers at 

Memphis State University and Baptist College in 

Charleston, South Carolina, by Bolton and Olson 

(1987b).

 Strengthening, redeveloping, abandoning, or demolishing unreinforced masonry-bearing-wall buildings in 

the cities of Long Beach, Santa Ana, and Los Angeles 

by Alesch and Petak (1986).

 Strengthening masonry-bearing-wall buildings in the 

city of Los Angeles after the 1987 Whittier Narrows 

earthquake by Deppe (1988).

 Retrofitted highway bridges after the 1986 earthquake in Palm Springs by Mellon (1986).

 Mapping, investigating, and regulating surface-fault 

rupture zones by Hart (1986).

TRANSLATION AND TRANSFER TECHNIQUES

Several translation and transfer techniques (list 4) 

have been evaluated, problems identified, and recommendations made:

 Announcing earthquake prediction and forecast information by Turner and others (1981).

 Disseminating earthquake education material to public 

and private schools by Bolton and Olson (1987a).

 Disseminating earthquake hazards information to public officials and private sector representatives in 

Charleston, South Carolina, by Greene and Gori

(1982).

 Using earth science information in cities, counties, and 

selected multicounty agencies in the San Francisco 

Bay region by Kockelman (1975, 1976b, 1979), Kockelman and Brabb (1979), and Perkins (1986).

 Translating and transferring information in the U.S. 

Geological Survey by Bates (1979) and O'Kelley and 

others (1982).

 Conducting a workshop on preparing for and responding to a damaging earthquake in the eastern United 

States by Tubbesing (1982, p. 57-59).

 Adopting ordinances based on guidelines and model 

ordinances developed and transferred by the Southeastern Wisconsin Regional Planning Commission 

(1987, p. 24).

EVALUATION OF PROGRAMS

Several earthquake hazard reduction programs have 

been evaluated, problems identified, and revisions suggested:

 Community seismic safety programs before, during, 

and after the 1983 Coalinga, Calif., earthquake by 

Tierney (1985).

 Planning and implementing seismic hazard mitigation 

in Alaska by Selkregg and others (1984).

 Use of earthquake hazard information for enlightenment, decisionmaking, and practice in California, 

Washington, Utah, South Carolina, Massachusetts, 

Idaho, Puerto Rico, Kentucky, Alaska, Missouri, U.S. 

Virgin Islands, and the eastern, western, and central 

United States by Hays (1988a).

 National Earthquake Hazards Reduction Program in 

the United States by the NEHRP Expert Review 

Committee (1987).

 Effectiveness of the geology and planning program in 

Portola Valley, Calif., by Mader and others (1988, p. 

55-61).

 San Francisco Bay Region Environmental and 

Resources Planning Study by Arthur D. Little, Inc. 

(1975) and Brown (1975).

 Land use and reconstruction planning after the 1971 

San Fernando, 1964 Alaska, and 1969 Santa Rosa 

earthquakes by Mader and others (1980).

 Seismic safety policies of local governments by Wyner 

and Mann (1983).

 Structure design and behavior investigation after 

more than 200 earthquakes by members of the Earthquake Engineering Research Institute (Scholl, 1986).

VARIOUS EVALUATIONS IN UTAH

Several reduction and transfer techniques and programs in Utah have been evaluated, problems identified, 

and revisions suggested:

 Awareness and reduction of earthquake hazards by 

Perkins and Moy (1988, p. 9-19).

 Multihazard mitigation project for Ogden and Weber 

County by Olson and Olson (1985).

 Hazardous building abatement and sensitive lands 

development ordinances for Provo by May and Bolton 

(1986).

 County Hazards Geologist Program by Christenson 

(1988).

 Earthquake knowledge, risk perception, and mitigation priorities in Salt Lake County by Madsen (1988).

 Adequacy of engineering geologic reports by Nelson 

and others (1987).

 Perception of earthquake risk and support for regulations by Emmi (1987).

REDUCTION TECHNIQUES FOR OTHER HAZARDS

Several reduction techniques for other natural hazards 

have been evaluated, the problems identified, and
66 ASSESSMENT OP REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

improvements suggested. Their evaluation methods, 

findings, and recommendations may be applicable to 

earthquake hazards:

 Disclosing hurricane-flood hazards information to prospective home buyers in Florida by Cross (1985).

 Providing State financial incentives for flood hazard 

reduction to local governments by Burby and Cigler 

(1983).

 Subsidizing flood insurance for property owners and 

their lenders by Miller (1977), Burby and French 

(1981, p. 294), and Kusler (1982, p. 36, footnote 55).

 Notice, watch, and warning system for a potential 

1978 Pillar Mountain landslide in Kodiak by Saarinen 

and McPherson (1981).

 Warnings for the 1980 Mount St. Helens volcano 

eruption by Saarinen and Sell (1985).

 Planning and engineering response and recovery to 

1982 debris flows at Love Creek (Santa Cruz County) 

and Inverness (Marin County) by Blair and others 

(1985).

EVALUATION METHODS

There are numerous methods for evaluating the effectiveness of an earthquake hazard reduction program and 

related studies, translation, transfer, and reduction components. The above examples of evaluation indicate that 

these methods vary widely because of the human and 

financial resources available, the region involved, and 

the evaluator's interest, experience, and commitment. A 

thorough discussion of these methods is beyond the scope 

of this report; however, the following four illustrations 

show different levels of rigor:

1. Soliciting comments and suggestions from the producers, translators, transfer agents, and users of the 

research information.

2. Inventorying the documents where research information is cited and conducting systematic interviews 

with the users as to the types of information needed 

and used, the problems identified, and the improvements desired.

3. Comparing losses experienced in several areas having 

similar hazards and operating under the same type of 

reduction technique but where different levels of 

requirements, administration, or enforcement are in 

effect.

4. Collecting and comparing the benefits and costs, both 

public and private, of several different reduction 

techniques before and after a damaging earthquake in 

a jurisdiction having a uniform geologic and tectonic 

environment.

The phrase "public and private costs" is used here to 

mean all direct and indirect costs and losses such as 

market value declines, road and utility repairs, emergency response activities, real property damages, personal property losses, deaths, injuries, tax revenue 

losses, industrial production losses, commerce interruption, and traffic delays. If it is demonstrated that the cost 

of a reduction technique is substantially less than the cost 

of anticipated damage, we may conclude a favorable 

benefit-cost ratio for the use of the reduction technique. 

Several methods that address various topics and have 

different levels of rigor are introduced here:

 Use of earth science products by city, county, and 

selected multicounty organizations by Kockelman 

(1975, p. 20-26; 1976b, p. 16-20; 1979, p. 27-31).

 Appraisal and cost-benefit analysis of plans to reduce 

natural hazards by Lohman and others (1988, p. 

183-201).

 Economics of landslide mitigation strategies by Bernknopf and others (1985).

 Methods of cost-benefit analysis for different building 

codes and for upgrading existing structures by Pate 

and Shah (1980).

 Testimony before a State agency on the costs and 

housing impacts of rehabilitation of unreinforced 

masonry buildings (Boswell, 1987).

 Benefit-cost ratios for reconstructing more than 1,350 

State-owned buildings by H.J. Degenkolb Associates 

(1981).

COMMENT

These examples of evaluation vary as to topic, area 

affected, type of technique, evaluator, and comprehensiveness. What they all have in common is a critical look 

at the success or failure of a program or of the translation, transfer, or reduction techniques used.

Even if adequate earthquake hazard research information is available, presented in a language understandable 

by nontechnical users, effectively transferred, and properly used, as is being done in Utah, the lasting effectiveness of each earthquake hazard reduction technique (list 

2) depends on many other factors, usually outside the 

control of the researcher, engineer, planner, or decisionmaker. For example:

 Continued awareness and interest by the public.

 Careful revision (if needed) of enabling legislation by 

the State legislature.

 Accurate site investigations by qualified geologists 

and geotechnical engineers.

 Conscientious administration of regulations by plan 

checkers, inspectors, and other building officials.

 Sustained support of inspection and enforcement officials by political leaders and their constituents.

 Consistent enforcement by government inspectors and 

attorneys.
REDUCING EARTHQUAKE HAZARDS IN UTAH 67

Problem Seriousness Scores in the Six Sites

INFLATION

POLLUTION

UNEMPLOYMENT

CRIME

WELFARE

EDUCATION

DRUGS

TRAFFIC

HOUSING

FIRES

TOO LITTLE GROWTH

RACE

QUAKES

PORNOGRAPHY

FLOODS

TOO MUCH GROWTH

HURRICANES

TORNADOES

x=

CA 

x RANK

7.6 1

7.2 2

7.0 3

6.9 4

6.9 5

6.2 6

6.0 7

5.7 8

5.5 9

5.3 10

5.0 11

4.7 12

4.6 13

4.1 14

3.3 15

2.5 16

1.3 17

1.1 18

5.05

LA 

x RANK

6.6 4

7.5 1

7.0 3

5.9 8

7.1 2

6.3 5

6.0 7

6.2 6

5.7 9

4.2 14

5.0 12

4.4 13

5.5 10

5.3 11

2.8 15

1.6 16

1.0 17

1.0 18

4.95

MA 

x RANK

7.5 4

6.0 8

8.6 1

7.3 5

8.2 2

5.4 11

6.1 7

5.1 12

6.4 6

6.0 9

7.8 3

5.4 10

1.2 18

4.0 14

4.5 13

1.3 17

3.1 15

1.5 16

5.30

BOSTON 

x RANK

7.1 5

4.4 13

7.6 2

7.3 4

7.4 3

7.0 6

6.6 8

6.5 9

6.4 10

5.9 11

7.7 1

6.9 7

1.3 18

5.4 12

2.2 15

1.3 16

2.3 14

1.3 17

5.26

UTAH 

x RANK

7.2 1

5.7 3

4.2 8

5.5 4

5.9 2

4.1 9

5.1 5

3.8 10

4.8 7

3.4 12

3.7 11

2.6 16

3.2 15

5.0 6

3.3 13

3.3 14

1.0 17

1.0 18

4.04

SLC 

x RANK

7.5 1

6.7 2

4.5 9

5.6 3

5.0 6

4.3 11

4.9 7

4.7 8

5.5 4

3.7 12

3.3 14

3.4 13

1.2 16

5.1 5

4.5 10

3.0 15

1.2 17

1.0 18

4.17

FIGURE 23. Rankings by key public and private decisionmakers as to the relative seriousness of 18 State and local issues for three States and

three cities (Atkisson and Petak, 1981, table 19, p. 140).

 Judicious adjustment of regulations by administrative 

appeal bodies.

 Skillful advocacy by public regulators and plaintiffs, 

and proper interpretation by the courts.

 Genuine concern for individual, family, and community 

safety by real estate buyers, developers, insurers, and 

lenders.

A consultant and expert witness who is a former State 

geologist and former president of a State board of 

registration for geologists and geophysicists reports in 

the work by Slosson and Havens (1985) on his experience 

during the past 25 yr:

... many of the problems and losses related to damage from 

earthquakes ... are directly or indirectly attributable to government's (local, State, and/or Federal) inability and/or failure to 

enforce existing policies, codes, or regulations.

The benefits of evaluation and revision cannot be 

restated often enough, namely, to avoid an unconscionable waste of taxpayers' money and a usually irreparable 

loss of program managers' credibility.

CONCLUSION

The reduction of casualties, damages, and interruptions in Utah requires that appropriate earthquake 

research be conducted and used by planners, engineers, 

and decisionmakers. A major part of any effective earthquake hazard reduction program must be dedicated to 

the translation and transfer of research information to 

nontechnical users, as is being done in Utah.

The selection of earthquake areas or processes for 

study and the performance of the necessary scientific and

engineering studies are only the first steps in any 

earthquake hazard reduction program. If the information 

prepared is inadequate, inappropriate, not translated, 

not transferred, or not used, earthquake losses will 

increase, public and private monies will be wasted, and 

demands will be made on Federal, State, and local 

government agencies for disaster relief and costly reconstruction.

Usually, public planners, engineers, and decisionmakers give most of their attention and resources to problems that are perceived to be serious or pressing. A 1977 

study of six sites of varying political environments and 

attitudes toward seismic safety was conducted by Atkisson and Petak (1981, p. 139). They found at that time that 

the "seriousness attributed to earthquakes ... was consistently low in all sites" (see fig. 23). With the exception 

of floods (tenth in Salt Lake City) and earthquakes (tenth 

in Los Angeles), natural hazards at all sites were considered least serious, ranking 13 to 18 on the list of serious 

problems.

Recently, Perkins and Moy (1988, rept. 3, table 4, p. 

15) asked 15 city managers and county administrators in 

Utah to indicate what earthquake hazard reduction techniques had been adopted in the past 5 yr. According to 

J.B. Perkins (verbal commun., 1989), of the 13 respondents, all had adopted at least one technique, 9 had 

adopted a technique primarily for reasons of earthquake 

safety, and 4 of the 9 had adopted 4 or more techniques. 

Obviously, Utahans are not only more aware of the 

earthquake hazard but are continuing to take appropriate actions.

The effective use of research information in Utah 

depends on (1) the users' interest, capabilities, and
68 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

experience in hazard-related activities, (2) legislation 

authorizing State and local hazard reduction activities, 

(3) adequate detailed information in a readily usable and 

understandable form, and (4) the use of effective transfer 

techniques. These four elements exist in Utah. All that 

remains is for Utahans to continue to adopt appropriate 

reduction techniques and enforce them over many years.

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REDUCING EARTHQUAKE HAZARDS IN UTAH 69

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70 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

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REDUCING EARTHQUAKE HAZARDS IN UTAH 71

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72 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

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PUBLIC PERCEPTIONS OF THE IMPLEMENTATION OF EARTHQUAKE 

MITIGATION POLICIES ALONG THE WASATCH FRONT IN UTAH

By GARY E. MADSEN,S LOREN R. ANDERSON,4 JEROLD H. BARNES,S and GENEVIEVE ATWOOD/

ABSTRACT

The earthquake hazard potential along the Wasatch Front in Utah 

has been well defined by a number of scientific and engineering studies. 

Translated earthquake hazard maps have also been developed to 

identify areas that are particularly vulnerable to various causes of 

damage such as ground shaking, surface rupturing, and liquefaction. 

The implementation of earthquake hazard reduction plans are now 

under way in various communities in Utah. The results of a survey 

presented in this paper indicate that technical public officials (planners 

and building officials) have an understanding of the earthquake hazards 

and how to mitigate the risks. Although the survey shows that the 

general public has a slightly lower concern about the potential for 

economic losses, they recognize the potential problems and can support 

a number of earthquake mitigation measures. The study suggests that 

many community groups along the Wasatch Front, including volunteer 

groups, business groups, and elected and appointed officials, are ready 

for action-oriented educational programs. These programs could lead to 

a significant reduction in the risks associated with earthquake hazards.

INTRODUCTION

Earthquakes can cause loss of life and costly property 

damage, and therefore, in areas of high seismic activity, 

earthquake hazard mitigation is an important consideration in intelligent land-use planning and in the establishment and implementation of local ordinances and 

building codes. Damage during earthquakes can result 

from surface faulting, ground shaking, ground failure, 

generation of large waves (tsunamis and seiches) in 

bodies of water, and tectonic deformation. All of these 

causes of damage need to be considered in reducing the 

potential for economic and human losses during earthquakes.

The occurrence of earthquakes along the Wasatch 

Front in Utah has been documented since the arrival of 

the early pioneers about 1850 (Arabasz and others, 1979), 

and recent scientific work has documented the seriousness of the earthquake hazard problem (see Gori and

' Department of Sociology, Utah State University, Logan, Utah.

; Department of Civil Engineering, Utah State University, Logan, Utah.

' Salt Lake County Planning Division, Salt Lake City, Utah.

1 Utah Geological Survey, Salt Lake City, Utah.

Hays, 1987). In addition to earthquakes, a number of 

other geologic hazards exist along the Wasatch Front 

that should be considered in land-use planning. For 

example, during approximately 3 months in the spring of 

1983, the State of Utah, with a population of some 1.6 

million people, sustained direct damages from landslides, 

debris and mud flows, and flooding in excess of $400 

million. These disastrous events were so extensive that 

22 of the 29 counties in the state were declared natural 

disaster areas (Anderson and others, 1984). U.S. Geological Survey (USGS)-sponsored workshops on earthquake hazards in Utah from 1985 to the present have 

broadened earthquake hazard awareness beyond the 

scientific community. These well-organized workshops 

have summarized the research efforts of seismologists, 

geologists, and engineers and have heightened the 

awareness of planners and the staffs of local government 

agencies. However, much work must be done to bring 

the urgency of the earthquake hazard problem to the 

general public so that they will understand the work of 

scientists, engineers, and planners and then embrace the 

implementation of ordinances, building codes, and other 

actions aimed at mitigating earthquakes and other natural hazards.

Kockelman (1990, p. AA-22) has identified five components that are needed in the development of any 

earthquake hazard reduction program:

1. Conducting scientific and engineering studies of the physical 

processes of earthquake phenomena that may be hazardous, 

e.g., source, location, size, likelihood of occurrence, severity, 

triggering mechanism, path, ground response, structure 

response, and equipment response.

2. Translating the results of such studies into reports and onto 

maps at an appropriate scale so that the nature and extent of 

the hazards and their effects are understood by nontechnical 

users.

3. Transferring this translated information to those who will or 

are required to use it, and assisting them in its use through 

educational, advisory, and review services.

4. Selecting and using appropriate hazard reduction techniques 

such as legislation, regulations, design criteria, education, 

incentives, public plans, and corporate policies.

75
76 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

5. Evaluating the effectiveness of the hazard reduction techniques after they have been in use for a period of time and 

revising them if necessary. Evaluation and revision of the 

entire program as well as the other components studies, 

translation, and transfer may also be undertaken.

Research activities sponsored by the USGS Earthquake Hazard Reduction Program during the past several years have produced a number of translated 

research findings that identify the seriousness of earthquake hazards along the Wasatch Front. Maps specifically for Salt Lake County have been completed that 

identify the potential for fault rupture, ground shaking, 

ground failure (by liquefaction and earthquake-induced 

landslides), and tectonic deformation. Thus components 

1 and 2 above have already received a great deal of 

attention. Much more effort needs to be directed toward 

meeting objectives 3 through 5.

Before implementation activities can be successful, the 

public must have an awareness and an understanding of 

the hazards, and, at the same time, engineers, planners, 

and public policy officials must be aware of the level of 

hazard reduction activities that the public will accept. 

Much can be done by the engineering community and the 

public to significantly reduce earthquake hazards at little 

additional cost, provided that the problems are identified 

and mitigated early.

Recent projects (Madsen and others, 1988, 1990) have 

been aimed at implementing an earthquake hazard 

reduction plan for Salt Lake County, the most populous 

county in the State of Utah. The overall goal was 

directed toward earthquake preparedness rather than 

toward programs dealing with emergency response and 

recovery during or after earthquakes. The major objective was to develop a program of preparedness in Salt 

Lake County involving public officials, community 

groups, and the general public. The program was 

designed to create heightened awareness of earthquake 

problems, create a public acceptance of earthquake hazard reduction programs, and to develop and implement 

an earthquake hazard reduction plan for the county. The 

first step was to assess the earthquake hazard awareness 

and understanding of both public officials (those working 

in a technical capacity) and the general public, and to 

determine types of mitigation measures that each will 

support.

This paper presents the results of a survey of technical 

public officials (planners and building officials) and the 

general public. It assesses concerns of these two groups 

regarding the potential for widespread and damaging 

earthquakes in the Salt Lake County area of Utah and 

assesses the support they give to various mitigation 

strategies.

ACKNOWLEDGMENTS

This project was supported by the U.S. Geological 

Survey under award 14-08-0001-G1531. However, the 

contents do not necessarily represent the policy of that 

agency, and endorsement by the Federal Government 

should not be assumed.

Jeffrey R. Keaton, Larry Reaveley, and Craig Nelsen 

have been part of the project team. The work of these 

individuals is much appreciated. We have also received 

significant input from Gary Christenson and William 

Case of the Utah Geological Survey and from James 

Tingey of the Division of Comprehensive Emergency 

Management.

METHODOLOGY

Salt Lake County contains 12 municipalities, 10 of 

which have at least one planning or building official. 

Unincorporated areas are served by personnel of Salt 

Lake County government. Two surveys were conducted 

to determine levels of awareness of earthquake problems 

and support for various mitigation strategies. The first 

consisted of 28 planners and building officials. In the 

largest government units, the highest level administrative personnel were identified. Each individual was 

interviewed in person during May and June of 1988. The 

completion rate was 100 percent. The second survey 

consisted of 409 male and female adults who resided in 

Salt Lake County. They were randomly drawn from Salt 

Lake County telephone listings and were interviewed by 

telephone during September of 1988. The response represents a 70 percent completion rate from the sampling 

frame. The interviews were conducted by the Survey 

Research Center at the University of Utah and pertained 

to the assessment of three factors: earthquake hazard 

knowledge, perceptions of earthquake risks, and priorities for earthquake risk reduction.

RESULTS OF THE SURVEYS

The planners and building officials were asked to rank 

seven causes of damage from potential earthquakes in 

Salt Lake County (Salt Lake Valley), assigning the 

number I to the item with the highest potential for 

damage and the number 7 to the item with the lowest 

potential, and individually ranking the items between the 

extremes. The results, presented in table 1, indicate a 

high correspondence between rankings by local officials 

and by the scientific community (see Christenson, 1987). 

For example, based on scientific investigations, the 

problem of ground shaking is considered to be the
PUBLIC PERCEPTIONS OF THE IMPLEMENTATION OF EARTHQUAKE MITIGATION POLICIES 77

TABLE I. Rankings by local government planners and building 

officials as to potential damage from earthquake hazards in Salt 

Lake Valley

L;ciUS6S 01 Q3>rn3>££6

Ground shaking .............................

Ground failure induced by liquefaction ......

Fault rupture ...............................

Landslides and rockfalls .....................

Tectonic deformation ........................

Dam failure .................................

Water waves ................................

Rai

X

.... 1.52

. . . . 2.26

. . . . 3.63

. . . . 4.04

. . . . 4.82

. . . . 5.22

.... 6.52

nk*

S.D.

075

1 13

1 55

1 29

1 39

94

1.37

* A rank of 1 indicates the highest potential for damage and number 7 the lowest; #=mean, 

S.D.=standard deviation.

greatest potential hazard. Those surveyed in the general 

public were not asked to make this ranking because of its 

highly technical content.

The next item surveyed was how local planners and 

building officials (technical officials) and the public perceive earthquake risks. Both sample groups were asked 

to indicate the likelihood of an earthquake that would 

cause widespread, severe damage in the Salt Lake 

Valley within the next 100, the next 50, and the next 10 

yrs. The possible responses included very high (point 

value of 5), high, moderate, low, and very low (point 

value of 1). The results, presented in table 2, indicate that 

there is a great deal of concern about the likelihood of a 

future earthquake damaging the Salt Lake Valley. In the 

100-yr period the technical officials' mean (x) of 4.64 

approaches the ranking of very high, whereas the public 

sample mean of 3.97 is associated with the ranking of 

high. For each time period, the mean of the technical 

officials is higher than that of the public. However, even 

the public's rating for the 10-yr time period (x=2.80) 

approaches the ranking of moderate. There is also

greater variability among the public than among the 

technical officials, as indicated by the standard deviations (S.D.). The technical officials constituted a population, but since the public sample was randomly drawn 

from a larger population, a standard error (S.E.) was 

calculated for each public sample mean. For example, the 

95 percent confidence interval for the 100-yr period is 

£=3.97+0.1, which is a small range of variability from 

sample to sample drawn from the same population. Data 

from the public sample comparing men and women are 

also presented in table 2. A i-test between means yields 

a statistically significant difference at the 0.05 level for 

the 10-yr period only. Thus, in general, men and women 

appear to have similar views about the likelihood of 

future damage from earthquakes in the Salt Lake Valley.

Respondents to the public survey were also asked 

about concerns for personal safety and damage to their 

residences if a serious earthquake were to occur in the 

Salt Lake Valley. The questions were taken from a 

survey by Rossi and others (1982, p. 318), and the 

wording was modified to refer to earthquakes rather 

than to natural disasters in general. Data pertaining to 

these questions are presented in table 3. Respondents 

were asked whether they were very concerned, somewhat concerned, or not at all concerned that (1) the 

building in which they live would suffer serious damage, 

(2) the contents of their residence would be seriously 

damaged, and (3) they or someone in their family would 

be seriously injured.

The results indicate that approximately 85 to 90 percent of the respondents were either somewhat or very 

concerned about their residence, its contents, and the 

likelihood of personal injury. The category most often 

identified for both building damage and contents damage 

was "somewhat concerned," with 49.8 and 54.6 percent,

TABLE 2. Perceptions of the likelihood of a future damaging earthquake in the Salt Lake Valley: Comparison of local technical officials

(planners and building officials) and public residents

Technical officials* Public residents*

Earthquake risk time period

Public residents by gender* 

Men Women f-ratio

N S.D. N S.D. S.E. N S.D. N S.D.

Likelihood of earthquake causing 

widespread and severe damage 

in the Salt Lake Valley within 

the next 100 years?

Likelihood of earthquake causing 

widespread and severe damage 

in the Salt Lake Valley within 

the next 50 years?

Likelihood of earthquake causing 

widespread and severe damage 

in the Salt Lake Valley within 

the next 10 years?

28 4.64 0.62 394 3.97 1.02 0.05 179 3.98 1.05 212 3.94 1.00 0.38

28 4.18 .77 385 3.56 1.08 .06 172 3.48 1.07 210 3.65 1.07 1.55

28 3.14 .71 385 2.80 1.10 .06 171 2.68 1.03 211 2.91 1.15 2.05

* The response alternative of very high was assigned a point value of 5, high 4, moderate 3, low 2, and very low 1. No probability statistics were calculated for the technical officials, since 

they were a population, not a sample drawn from a population, as was the case for the public respondents. Gender was not determined for three public residents. S.E.=standard error
78 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

TABLE 3. Concern of public residents about a future serious earthquake occurring in Salt Lake Valley

Concern levels of public residents

Area of concern

Concern levels of public residents by gender* 

Men Women

Not at all Somewhat Very _, Not at all Somewhat Very _, , Not at all Somewhat Very _, ,

N % N N % N N N % N % N N % N . N %

Chi-

,1 I

N p

The building in 42 10.3 202 49.8 162 39.9 406 27 14.6 92 49.7 66 35.7 185 15 6.9 108 49.5 95 43.6 218 0.026

which you live

would suffer

serious damage. 

The contents of 62 15.3 221 54.6 122 30.1 405 41 22.1 100 54.1 44 23.8 185 21 9.7 118 54.4 78 35.9 217 .0006

your residence

(furniture, carpets, appliances)

would be seriously

damaged. 

You or someone 44 10.8 134 33.0 228 56.2 406 27 14.5 66 35.5 93 50.0 186 17 7.8 66 30.4 134 61.8 217 .025

in your family

would be seriously

injured.

* Gender was not determined for three public residents.

respectively. The mode for the personal injury question 

was "very concerned," with 56.2 percent of the total. 

These findings are consistent with the findings of Rossi 

and others (1982, p. 114-115). In their survey of California residents, they found that, with respect to natural 

disasters, people were more concerned about personal 

injuries than about building or content damage.

Gender was also found to be an important variable 

with respect to feelings of concern. A chi-square test to 

compare the responses of men and women yielded statistically significant differences for all three questions, 

with women indicating higher overall levels of concern. 

The percentages of men and women identifying themselves as somewhat concerned are very similar for the 

three questions. However, the percentages of women in 

the not at all concerned category were consistently about 

half the percentages for the men, and the responses of 

women were about 8-12 percentage points above the 

men in the very concerned category.

Higher levels of earthquake concern among women 

than men are supported by other related studies. In a 

review of the literature concerning responses to public 

disaster warnings, Sorenson and Mileti (1987) documented that women are more likely than men to hear 

warnings, to believe such warnings, and to engage in 

protective warning responses. Turner and others (1986) 

also found gender differences in levels of fear and concern about an earth uplift in the Palmdale, Calif., area. 

This uplift was identified as a possible precursor to an 

earthquake. Women reported higher levels of fear and 

concern than men, and taking warnings seriously was 

also related to fear and concern.

It is important to know if local technical officials are 

knowledgeable about earthquake hazards and consider a

serious earthquake to be likely. It is also important to 

determine whether the public perceives similar risks and 

is concerned about them. However, are these attributes 

of knowledge and concern related to support for policies 

to decrease earthquake risks in the Salt Lake Valley? To 

identify mitigation policies, the technical officials were 

also asked open-ended questions followed by fixedalternative questions regarding actions they felt should 

be taken to reduce the risks from earthquakes in the Salt 

Lake Valley. Several fixed-alternative items were 

derived from Kockelman (1986), and those receiving the 

highest overall ranks using both methods were then 

presented to the public sample for their evaluations. The 

data comparing the two groups are presented in table 4. 

The response alternatives to the policy items were as 

follows: very high importance (point value of 5), high 

importance, moderate importance, low importance, and 

not at all important (value of 1).

The averages of the technical officials for 10 of the 11 

policy items were higher than those of the public sample. 

However, with the exception of "requiring disclosure of 

earthquake hazards to real estate buyers," which the 

public rated 3.61, no item fell below a mean of 4.0 

(corresponding to high importance) among the public 

resident sample. In general, the standard deviations 

indicated greater variability among the public respondents than among the technical officials. The standard 

errors for each public sample mean when multiplied by 

1.96 produce 95 percent confidence intervals of slightly 

less than one-tenth to slightly more than one-tenth of a 

point.

Gender comparisons are also identified in table 4. The 

data reveal that the averages on all 11 policy items are 

higher for women than for men. These mean differences
PUBLIC PERCEPTIONS OF THE IMPLEMENTATION OF EARTHQUAKE MITIGATION POLICIES 79

TABLE 4. Policies to reduce earthquake risks in the Salt Lake Valley: Comparison of local technical officials (planners and business officials)

and public residents

Technical officials3 Public residents3 Public residents by gender3

N x S.D. N X S.D. S.E. N X S.D. N X S.D. ratio

Controlling the location 28 4.68b 0.54b 407 4.45 0.82 0.04 186 4.35 .88 218 

and specific design 

requirement of new 

schools, police facilities, and fire stations

4.54 0.76 2.28

28 4.64 .56 405 4.22

.95

.86

.91

.05 185 3.92 1.02 218 4.34 .85 4.46

.04 186 4.12 .93 219 4.43 .77 3.67

.05 186 4.10

406 4.13 .94 .05 185 3.99

.93 216

.94 218

28 4.54

28 4.58

.74 402 4.11 .99 .05 185 4.03 1.03 214

4.32 .89

4.25 .94

4.20 .91

2.50

2.76

1.75

400 4.31 .87 .04 183 4.19 .92 214 4.43 .75 2.79

28 3.86d 1.08 395 4.06 .97 .05 180 3.89 1.01 212 4.22 .87 3.45

Strengthening existing 28 4.58b .67b 406 4.15 

hospitals, schools, 

police facilities, and 

fire stations

Informing and educat- 28 4.75 .44 408 4.29 

ing the public about 

earthquake hazards 

and earthquake preparedness

Providing public officials with earthquake 

hazard information

Providing public officials with professional 

technical assistance

Promoting land-use 

planning that considers earthquake hazard 

areas

Adhering to existing 

earthquake-related 

building codes, zoning 

ordinances, and building inspections

Establishing more 

stringent earthquakerelated building 

codes, zoning ordinances, and building 

inspections

Adopting uniform 

earthquake-related 

building codes, zoning 

ordinances, and building inspections

Requiring disclosure of 28 4.32 1.02 397 3.61 1.15 .06 179 3.37 1.21 215 

earthquake hazards to 

real estate buyers

Encouraging public 28 4.21 

agency programs that 

improve emergency 

responses__________________________________________________________________

a The response alternatives for the items (except the two indicated) were as follows: very high importance was assigned a point value of 5, high importance 4, moderate importance 3, low 

importance 2, and not at all important 1. No statistical tests were calculated for the technical officials, since they were a population, not a sample drawn from a population, as was the case for 

the public respondents. Gender was not determined for three public residents.

These first two policy items were originally presented to the technical officials as eight separate items. Each type of facility was presented separately. The means and standard deviations 

for the technical officials in the table are the averages of the mean and S.D. for each item. The actual figures for controlling the location of new hospitals were x=4.96, S.D. 0.19; schools 4.82 

and 0.39, police facilities 4.39 and 0.79, and fire stations 4.54 and 0.79. Corresponding figures for strengthening hospitals were x=4.82, S.D.=0.39; schools 4.75 and 0.52, police facilities 4.29 and 

0.90, and fire stations 4.46 and 0.88.

c Two items were identified by the technical officials in open-ended questions that solicited policy items without the prompting one gets from fixed alternative items. These two items were 

not ranked in the same way as the fixed alternatives but were included because they were identified more often than others as being important policies.

This item fell below all others ranked by the technical officials. It was in the public survey because the mean of the planners was 4.29, while that for the building officials was 3.18. This 

difference between the two subgroups was greater than for any of the original 49 policy items that were ranked.

401 4.02 1.03 .05 183 3.91 1.00 215 4.13 .98 2.14

.79 405 4.03 1.08 .05 185 3.94 1.15 217

3.84 1.04

4.14 .96

4.10

1.97
80 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

are statistically significant at the 0.05 level or greater 

(^-ratios of 1.96 or larger) for all policy items except 

"promoting land-use planning that considers earthquake 

hazard areas." Not only are women more concerned than 

men about future earthquakes, they are also more supportive of mitigation policies to reduce earthquake risks.

APPLICATION OF RESEARCH FINDINGS TO

IMPLEMENTATION OF EARTHQUAKE HAZARD

REDUCTION ON THE WASATCH FRONT

Kockelman (1990), in his analysis of the success of the 

Wasatch Front Earthquake Hazard Reduction Program, 

identifies the importance of targeting specific audiences 

with specific messages tailored to the needs of each. 

Sorenson and Mileti (1987) provide a stepwise model that 

puts this observation in context: individuals must hear, 

understand, believe, and personalize a message before 

they will take action.

How do these observations apply to the Wasatch 

Front? First, the Salt Lake County survey results 

indicate a high degree of opinion congruence between 

technical officials and the general public. It follows that 

the elected and appointed officials who enact public 

policy also need to know that there is broad-based 

support for hazard mitigation. The importance of public 

support in the mitigation process has been identified by 

Selkregg and others (1984, p. 167), who stated:

This relationship between public awareness, support, and implementation is an important one. It suggests that the political and 

technical leaders are less likely to achieve policy goals related to 

risk reduction in the absence of public support.

Concerning the importance of educational programs, 

Selkregg and others (1984, p. 166) have further 

suggested:

Scientists and planners need to build communication skills to 

inform the public and the policy makers of their findings. 

Consideration of seismic risk in land use planning, building 

structures, site planning, critical facilities, and other areas will 

gain greater prominence only if scientists and researchers 

promote understanding of their work, learn how to communicate 

and evaluate their needs and the needs of planners and policy 

makers, and design their products and recommendations to be of 

optimum use. This broadening scientific responsibility would 

enhance public understanding and support of research needed to 

assist policy makers in setting guidelines for public safety. 

Elected officials, planners, professionals, and scientists need to 

assume the role of public education.

The results of the Salt Lake County surveys suggest 

that educational programs concerning earthquake hazards and earthquake preparedness can be directed 

toward receptive audiences. These data indicate that

many community groups along the Wasatch Front, 

including volunteer groups, business groups, and elected 

and appointed officials, are ready for action-oriented 

educational programs. These programs could lead to a 

significant reduction in the risks associated with earthquake hazards.

The gender differences identified among the public 

sample suggest that women in the general public are 

likely to be a readily identifiable group of individuals who 

believe in the earthquake hazards and are likely to take 

action. This raises the possibility that the National 

Earthquake Hazards Reduction Program (NEHRP) 

could target this group and tailor information to be 

readily understood and personalized. To our knowledge, 

this "targeting" has not been done on the basis of gender.

One implication of this study is the need to better 

understand this gender difference among the general 

public. An application of this study might be to develop 

information specifically targeted for the perceived needs 

of some of the more visible women's groups or those in 

which women are highly active, such as local chapters of 

the League of Women Voters, Parent Teacher Associations (PTA), and the Church of Jesus Christ of Latterday Saints (LDS) Relief Society. Each of these group's 

differing missions contains elements that could be related 

to NEHRP. For instance, the League of Women Voters 

has supported land-use planning along the Wasatch 

Front that incorporates geologic hazards such as earthquakes. Local PTA organizations have advocated earthquake hazard preparedness in the schools. The LDS 

Relief Society plays a key role in the preparation of food 

supplies in case of emergency. Can earthquake information be "translated" in terms specifically designed for 

these groups as well as others? Can the information be 

personalized for various memberships so that it leads to 

a commitment to personal preparedness? Can an education program be developed that leads not only to personal 

preparedness but also to active support for changes in 

public policy? We feel these challenges are worth pursuing.

Utah needs to prepare for a major damaging earthquake along the Wasatch Front. The scientific evidence 

for the hazard is overwhelming, even though it has not 

been experienced in historic time. The challenge in Utah 

is to take policy actions before the devastating earthquake. The results of this research strongly suggest a 

window of opportunity that should not be missed.

REFERENCES

Anderson, L.R., Keaton, J.R., Saarinen, T.F., and Wells, W.G., 1984, 

The Utah landslides, debris flows, and flood of May and June 1983: 

Washington, D.C., National Academy Press.
PUBLIC PERCEPTIONS OF THE IMPLEMENTATION OF EARTHQUAKE MITIGATION POLICIES 81

Arabasz, W.J., Smith, R.B., and Richins, W.D., eds., 1979, Earthquake studies in Utah, 1850-1978: Salt Lake City, University of 

Utah Seismograph Station, Special Publication.

Christenson, G.E., 1987, Suggested approach to geologic hazards 

ordinances in Utah: Utah Geological and Mineral Survey, 

Circular 79.

Gori, P.L., and Hays, W.W., eds., 1987, Assessment of regional 

earthquake hazards and risk along the Wasatch Front, Utah: U.S. 

Geological Open-File Report 87-585, 2 vols.

Kockelman, W.J., 1986, Some techniques for reducing landslide hazards: Bulletin of the Association of Engineering Geologists, v. 23, 

no. 1, p. 29-52.

 1990, Reducing earthquake hazards in Utah, The crucial connection between researchers and practitioners: USGS Open-File 

Report 90-225, p. AA1-AA153.

Madsen, G., Barnes, J., and Anderson, L.R., 1988, The implementation of an earthquake hazard mitigation program in Salt Lake 

County, Utah: U.S. Geological Survey, Grant 14-08-0001-O1531.

 1990, The implementation of an earthquake hazard mitigation 

program in Salt Lake County, Utah: U.S. Geological Survey, 

Grant 14-08-001-G1797.

Rossi, P.H., Wright, J.D., and Weber-Burdin, E. 1982, Natural 

hazards and public choice: The state and local politics of hazards 

mitigation, New York, Academic Press.

Selkregg, L.L., Preuss, J., Ender, R.L., Johnson, S.F., Kirn, J.C.K., 

Gorski, S.E., and Kelso, D., 1984, Earthquake hazard mitigation, 

Planning and policy implementation, The Alaska case: Anchorage, 

University of Alaska, and Seattle, Urban Regional Research.

Sorenson, J.H., and Mileti, D., 1987, Public warning needs, in Gori, 

P.L., and Hays, W.W., eds., A workshop on "The U.S. Geological 

Survey's role in hazards warnings," Proceedings of conference XL: 

U.S. Geological Survey Open-File Report 87-269, p. 9-75.

Turner, R.H., Nigg, J.M., and Heller Paz, D., 1986, Waiting for 

disaster, Earthquake watch in California: Berkeley, University of 

California Press.
A DATA BASE DESIGNED FOR URBAN SEISMIC HAZARDS STUDIES

By ARTHUR C. TARR

ABSTRACT

A computerized data base has been designed for use in urban seismic 

hazards studies conducted by the U.S. Geological Survey. The design 

includes file structures for 16 linked data sets, which contain geological, 

geophysical, and seismological data used in preparing relative ground 

response maps of large urban areas. The data base is organized along 

relational data base principles. A prototype urban hazards data base 

has been created for evaluation in two urban areas currently under 

investigation: the Wasatch Front region of Utah and the Puget Sound 

area of Washington. The initial implementation of the urban hazards 

data base was accomplished on a microcomputer using dBASE III Plus 

software and transferred to minicomputers and a work station.

INTRODUCTION

For more than a decade, the U.S. Geological Survey 

(USGS) has been studying seismic hazards in 

earthquake-prone urban areas of the United States. Part 

of the process of seismic risk assessment is the evaluation 

of site response of soils and underlying geological units 

(relative to nearby bedrock) to earthquake motions. Site 

response (also called relative ground response) is a 

complex function of many geological and geophysical 

variables (Rogers and others, 1985). Spatial variations of 

intensity in a localized area are due principally to site 

response.

Determining which combination of geological and geophysical factors is most significant in affecting site 

response is the subject of ongoing research. Once those 

significant factors are determined, one exceedingly 

important task is organizing a (frequently) large body of 

data so that site response may be correlated with geotechnical variables and with Modified Mercalli (MM) 

intensities, when they are available. This report 

describes a computerized data base designed for use in 

urban seismic hazards assessment.

ACKNOWLEDGMENTS

The design and implementation of the urban hazards 

data base evolved as a result of many long discussions 

with Stanley Brockman, David Carver, Edward Cranswick, Kenneth King, John Tinsley, David Trumm, and 

Robert Williams; their assistance is gratefully acknowledged.

SUMMARY OF METHODS

Previous theoretical and empirical studies have indicated that seismic site response may be influenced by the 

thickness and degree of consolidation of sediments at the 

site, by the seismic shear velocity and mean void ratio of 

the sediment layers, and by degree of saturation and 

depth to water table. Figure 24 schematically illustrates 

these general characteristics. In general, greater thicknesses of soft, low-velocity sediments beneath a site yield 

higher overall levels of relative ground response (fig. 24, 

site 1) relative to a bedrock reference site (Borcherdt, 

1975; Ohta and others, 1978; Kagami and others, 1982, 

1986; Rogers and others, 1985). In addition, narrowbandwidth amplification is frequently observed at sites 

where thin layers of low-velocity sediments overlay hard 

rock (fig. 24, site 2); the amplification is due to resonance 

in the thin low-velocity layers (Rogers and others, 1985).

Site effects, due to whatever causes, are commonly 

invoked to explain substantial variations, within rather 

localized areas, of observed earthquake intensity patterns and instrumentally recorded ground motions. For 

example, severe but localized damage to medium-rise 

structures in Mexico City has been explained by resonance amplification (due to deposits of young, soft, 

lakebed sediments) of seismic ground vibrations from the 

September 19, 1985, Mexico earthquake (Cluff, 1985).

Relative ground response can be determined without 

relying on strong earthquake ground motions. Studies 

conducted in the San Francisco Bay region of California 

(Borcherdt and others, 1975), in the Los Angeles, Calif., 

area (Rogers and others, 1985), and in the Wasatch 

Front region of Utah (Hays and King, 1982) have relied 

on nuclear explosions as seismic sources. Similar studies 

using microtremors (small-amplitude vibrations) as seismic sources have been conducted in Japan and the San 

Fernando Valley of southern California (Ohta and others, 1978; Kagami and others, 1982, 1986). Relative

82
A DATA BASE DESIGNED FOR URBAN SEISMIC HAZARDS STUDIES

ground response values determined from small ground 

motions have been shown to be comparable to response 

values determined from recordings of strong ground 

motions (Rogers and others, 1985).

The results of the Los Angeles study are illustrative. 

Fourier spectra of seismograms recorded at sites in the 

Los Angeles urban area were compared with spectra 

recorded at a single reference site (Rogers and others, 

1985). The recordings were of nuclear explosions at the 

Nevada Test Site (NTS). Seismic stations were widely 

distributed across the Los Angeles area and installed on 

diverse geologic materials; the reference site was located 

on hard rock.

Spectral ratios were computed for each seismic event 

by dividing smoothed Fourier spectra of the various site 

records by the smoothed Fourier spectrum of the reference site record. Mean spectral ratios for each recording 

site and seismic event were computed for three period 

bands: short period (0.2-0.5 s; 5-2 Hz), intermediate 

period (0.5-3.3 s; 2-0.3 Hz), and long period (3.3-10 s; 

0.3-0.1 Hz). Geological and geotechnical data were gathered from logs of nearby water wells and from boreholes 

drilled for soil-engineering studies. The geographical 

variation in relative ground response was evaluated in 

terms of the underlying geotechnical conditions at each 

recording site by means of cluster and discriminant 

analyses.

In the Los Angeles area, Rogers and others (1985) 

found that ground motions were enhanced at sites underlain by Holocene and Pleistocene sediments, with the 

overall response generally increasing with the thickness 

of Quaternary deposits and depth to bedrock. The chief 

factors controlling short-period relative ground response 

in the Los Angeles study were mean void ratio in 

near-surface layers, thickness of unconsolidated (principally Holocene) sediment, and depth to bedrock. 

Intermediate- and long-period responses were controlled 

principally by depth to bedrock and by thickness of 

Quaternary alluvium.

Similar studies have been completed by the USGS in 

Utah along the Wasatch Front urban corridor (Hays and 

King, 1982) and the Puget Sound area of Washington 

(King and others, 1990). Preliminary results in Utah 

indicate correlations of relative ground response with 

geotechnical parameters similar to the Los Angeles 

study. More than 50 boreholes were drilled and logged 

for the Wasatch Front study (J. Tinsley, written commun., 1989).

Once the critical geotechnical factors affecting site 

response have been identified, a theoretical ground 

response model is constructed, and maps displaying the 

model are produced. The theoretical ground response 

model is employed in the construction of probabilistic

EXPLANATION

Unconsolidated sediments of Holocene age 

Semiconsolidated sediments of Quaternary age 

Sedimentary rock 

Crystalline rock

FIGURE 24. Cross section of hypothetical seismic ground response 

study area. Three representative response sites are designated 

Reference, 1, and 2; the small rectangle at each site designates a 

seismic station. The small rectangular diagram above each site 

represents a Fourier amplitude spectrum (Fourier amplitude versus 

frequency) of a typical seismogram recorded at each site. Spectrum 

examples show that overall spectral level is elevated slightly at site 

2 and more so at site 1; high frequency resonance peak is shown in the 

spectrum at site 2.

acceleration maps, which are necessary for a variety of 

applications, such as loss estimation.

DATA BASE MANAGEMENT SYSTEM

Producing a site response map of a large urban area at 

risk from strong ground shaking requires many relative 

ground response values to establish response zones on 

the map. These values are derived from a clustering 

analysis of measured ground response utilizing variables 

that have been demonstrated to be significant factors in 

affecting ground response. Measured values of these 

significant factors can be quite numerous. Therefore, it 

should be clear that a large urban seismic hazards study 

involves an extensive data collection, data organization, 

and data analysis effort; this effort is facilitated by a 

utilitarian data base design and computerized data base 

management system (DBMS).
84 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

BENEFITS AND COSTS OF A DATA BASE 

MANAGEMENT SYSTEM

The benefits derived from organization of a voluminous amount of data with a good DBMS are

 Orderliness. A good data base design assures that 

logically associated data will be related by the DBMS.

 Efficiency. Data entry, editing, and retrieval operations are fast in comparison with manual recordkeeping systems.

 Flexibility. A good DBMS allows restructuring of data 

file design as necessary (without additional or redundant data entry) and permits establishing complex 

relationships among data contained within several 

files.

 Security. Once data have been entered into a data 

base, edited, and proofed, they are part of a permanent record and are less susceptible to accidental loss 

or alteration.

 Transportability. Data that are organized with a good 

DBMS on one computer system can be easily moved to 

another computer system.

The costs associated with the organization of large 

data sets in a DBMS are

 Software cost. DBMS software is sometimes expensive to purchase, depending on the host computer used 

and the application.

 Hardware cost. Hardware cost is minimal if an existing computer is used, more expensive (sometimes 

prohibitively so) if a new computer system is to be 

dedicated to the DBMS software.

 Labor cost. Manual data entry is labor intensive (and 

hence costly) for large data sets. Data base maintenance (updating, verification, backup, archiving) is 

usually less labor intensive after initial data entry. 

In-house programming costs are largely up-front and 

may be high (one of the trade-offs if DBMS software is 

written in-house).

A manual records system is entirely adequate for small 

numbers of observations of only a few geotechnical 

factors; one can keep the data close at hand and in mind, 

and the cost of organizing the data is insignificant. 

However, a manual records system becomes more 

unwieldy as the number of response observations and 

geotechnical factors increases. Further, as the geotechnical analysis becomes more complex, relating data items 

from numerous sources (data sheets, tables, notebooks, 

etc.) and graphing data become tedious, and the opportunities for error increase. Computerization of the data is 

inevitable if applications software is used to analyze the 

data. If several data formats are required for different 

applications software packages, incompatibilities may 

arise, and duplicate keyboarding may be required.

In summary, a good DBMS and standard data structures can minimize problems when data sets are large, 

when several applications software packages are used to 

analyze the data, and when analytical techniques become 

complex.

DESIGN OBJECTIVES

The preceding discussion has indicated the complex 

relationship of geological, physical, and geotechnical 

factors in determining a theoretical relative ground 

response model. Relative ground response maps derived 

from the model are the principal end products of seismic 

hazards research. The maps traditionally have been 

constructed by overlaying transparent sheets on which 

the various data sets have been plotted and by manually 

drafting the final map. Recently, Geographic Information System (GIS) technology has been employed to 

construct the maps by extracting the ground response 

data and associated geotechnical data from a data base 

and then electronically combining these data layers. 

Thus, three major considerations influence data base 

design: how the data are acquired, how the data are 

analyzed, and how the data are to be used.

DATA BASE DESIGN CONSIDERATIONS

Three sets of data base terminology are often used 

interchangeably, to describe similar entities and similar 

characteristics of the data base (Martin, 1977). The sets 

of terms differ because of differences in viewpoint of the 

data user, the data manager, and the applications programmer toward the form of the data and toward the 

organization of data:

1. The form of the data is tangible and physical for the 

user. The data user (and frequently the data gatherer) 

probably has a manual system for recording and 

organizing the data: notebook pages or sheets of paper 

upon which are written specific data values, often in 

tabular form; graphs upon which data values are 

plotted; and index cards, such as bibliographic citations, which can be sorted.

2. The form of the data is symbolic for the data manager. 

The data manager views the data as organized into 

generalized lists or tables of data items and seldom 

thinks in terms of the actual values the data items 

may assume.

3. The applications programmer visualizes the data both 

symbolically and physically. To the programmer, the 

symbolic lists and tables of the data manager become 

arrays of variables (containing data values) that will 

be manipulated within a program and that will be 

physically stored in computer memory or in a disk file.
A DATA BASE DESIGNED FOR URBAN SEISMIC HAZARDS STUDIES 85

TABLE

Column

Row

RELATION

Attribute

Tuple

Record

FIGURE 25. Relationships of terms used in three different representations of data in a data base.

Figure 25 compares the three sets of terms as they 

apply to a data table, a relation, and a data file. In the 

following discussion, square brackets enclose alternate 

terms to help the reader as the perspective shifts among 

the three viewpoints.

The provisional design for the urban hazards data base 

is relational in organization, consisting of several large

* SOI Station 

+ B13 Borehole *S04

B15+* S03

SOI * + B13

*S02

*S05

*S06

FIGURE 26. Seismic stations (asterisks) and boreholes (crosses) in a 

hypothetical area where seismic response studies are conducted.

tables [relations, arrays, files] of data. The data are 

arranged in the table in rows and columns, each row 

representing a unique entity, such as a seismic station, a 

borehole site, or a rock unit. Each column [attribute] 

represents one property or characteristic of the entities 

listed in the table; latitude and borehole depth are 

examples of attributes. Each row of attribute values is 

called a tuple or record, and the part of a record 

containing an attribute value is called afield. The entire 

collection of records is called a data set, data file, or flat 

file. A group of related data sets or data files is called a 

data base in all three terminologies.

EXAMPLE OF RELATIONAL ORGANIZATION

Suppose that we have completed an experiment at six 

locations where seismic instruments have recorded seismograms of seismic events; seismic response ratios will 

be computed from the seismograms. Further, suppose 

that at two of the sites (fig. 26) boreholes were drilled for 

determination of vertical profiles of seismic velocity and 

geological properties. Say that we desire a list that will 

comprehensively and completely summarize in one place 

the properties of the six response sites. In a manual 

records system, we would probably construct a table and 

list each of the site locations on a separate line, identifying each site by a number, a code, an address, or a 

comment. Each line would contain other information 

such as coordinates, elevation, site geology, and, if a 

borehole had been drilled at that site, the borehole 

depth. The information in the table constitutes a compact 

and usable data set.

If we computerize these data using a relational organization scheme, we conceptually transform the physical 

table into a relation or a flat file. The data describing 

seismic stations and associated boreholes would be 

stored in a file; in this example, the file is called STATION (fig. 27). Each record in the file contains data
86 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

STATION 

Ident. Latitude Longitude

Borehole ID Depth

S01

S02

SOS

S04

505

S06

37.068

37.113

37.990

38.012

38.245

37.112

-117.987

-118.007

-117.803

-118.122

-118.098

-117.889

B13

B15

87.9

72.0

STATION 

Ident. Latitude Longitude

S01

 n

S02

SOS

S04

S05

S06

37.068

'fr&ismm-mmmTHP

37.113

37.990

38.012

38.245

37.112

-117.987

-118.007

-117.803

-118.122

-118.098

-117.889

BORE

BoreIdent. hole ID Depth

~S01

-SOS

B13

B15

87.9

72.0

EXPLANATION

POINTER

FIGURE 27. Station and borehole data collected in a table [relation, 

file] called STATION (top) and two tables [relations, files] called 

STATION and BORE. Arrows designate pointers that link related 

borehole data to a station. Note that the combined physical size of the 

two lower tables [relations, files] is smaller than the upper table 

[relation, file] because of elimination of null data despite the need to 

duplicate the station identifiers in BORE.

describing a specific (and unique) seismic station and 

(optional) borehole. 7

The fields in each record contain data values such as 

the station's latitude, longitude, and elevation, a brief 

description of the site geology, the borehole identifier, 

and the borehole depth. One field, the station's unique 

identifier, is also called the primary key field', other 

fields (such as the borehole identifier), which may or may 

not be unique, are called secondary key fields. (Key 

fields are used for data retrieval operations in the data 

base; however, it is not necessary that a file have keys.)

This example is somewhat contrived to illustrate the point about null data 

elements. Because boreholes are seldom located precisely at a station location, 

borehole data (including latitude, longitude, and elevation) should be kept in a 

separate file.

Some attributes (such as borehole depth) may not contain 

data values in all records, perhaps because the data do 

not exist (in the example, boreholes were not drilled at 

all sites) or the data are not known; such empty data 

elements are called null data elements.

One principle employed in relational data base design 

is to eliminate duplication of identical attributes [columns] in different files wherever possible. Strict application of this principle eliminates the possibility of inconsistent data values for the same attribute in different 

files and reduces the amount of computer storage 

required for each record. Another design principle is to 

minimize the number of null data elements in the file. 

This is accomplished by eliminating attributes that have 

few occurrences of data compared with the number of 

null data elements. These data (which, although sparse, 

are often important) may be stored in a smaller, auxiliary 

file. This auxiliary file contains a field value that links the 

data in a record in the smaller file to an associated record 

in the larger file (fig. 27). The field that permits the 

linking of records in different files is called a pointer 

field.

In the STATION example, say that the borehole data 

are removed from STATION and stored in a small file 

named BORE. The link between the two files is established in the BORE file by the pointer field containing a 

value that is identical to a value in a field in STATION. 

The station identifier, since it is unique, would be a good 

choice for a pointer to associate records in STATION and 

BORE. A record may contain multiple pointers; the 

principal data base design requirement for pointers is 

that they must not cause confusion during retrieval 

operations. For example, a pointer in one file should not 

point to multiple records in another file because retrievals attempted at various times might retrieve a different 

record each time. However, the same pointer value in 

several records pointing to just one record in another file 

is permissible because no ambiguity exists. Thus, for 

unique retrievals, one-to-one and many-to-one pointers 

are permissible, but one-to-many pointers are not (fig. 

28).

The many-to-one case is illustrated by the 

RESPONSE data file. There are two fields in 

RESPONSE (station_id and event_id) whose values are 

pointers to unique records in the STATION and EVENT 

files, respectively. In the RESPONSE file, each measurement of the average spectral ratio across the band is 

entered as a separate record; consequently, the values 

for station_id and the values for event_id are identical 

for each of the RESPONSE records of that station and 

event combination. Thus, the station_id pointers in 

many RESPONSE records point to one STATION 

record, and the event_id pointers in the same records 

point to one EVENT record.
A DATA BASE DESIGNED FOR URBAN SEISMIC HAZARDS STUDIES 87

RESPONSE

Stn Event 

ID ID

EVENT 

Event 

ID

RESPONSE

Stn Event 

ID ID

STATION 

Stn 

ID

S01

S02

FIGURE 28. Examples of many-to-one (upper diagram) and one-tomany (lower diagram) pointer relationships among records in hypothetical STATION, RESPONSE, and EVENT relations. One-tomany pointers cause confusion in data retrieval operations of 

response records from station and event data because of the lack of 

uniqueness in the relationships; one-to-many pointers should be 

avoided in data base management.

Why could not the station identification, event identification, and a fixed number of mean spectral ratio fields 

be stored in a single RESPONSE record? There are two 

reasons that this suggestion is not feasible in the 

RESPONSE example: the need for flexibility and the 

need to eliminate null data elements. Establishing a fixed 

number of spectral ratio fields, one each for a predetermined frequency band, would preclude any band that did 

not fit the format. Further, the number of spectral ratio 

fields would have to be the largest number of fields to be 

expected, not just the number needed to describe the 

ratio spectrum; the larger the number of fields, the 

greater the likelihood of null data elements. In the 

preferred structure of RESPONSE, any bandwidth may 

be specified, and there are only as many records as 

needed to describe the ratio spectrum.

(MODEL_PAR)

EXPLANATION

BORE ) DATA BASE FILE 

POINTER

FIGURE 29. Relationships of data files (boxes) in the geotechnical data 

base. Names of files within boxes are described in the text. Arrows 

designate pointers that link records within data files.

DATA FILES IN THE DATA BASE

The data files and data structures that are used in the 

data base design are listed in Appendix A; figure 29 

shows how the data are linked by pointers.

Data files STATION and BORE are similar: they 

contain data characteristic of the site, such as the location and general geological description. Each record in 

the RESPONSE file contains a response measurement 

at one station from one event over one frequency band. 

Each record in EVENT contains location and origin time 

and other data regarding seismic sources such as explosions and earthquakes. BORE_GEO contains geological 

data from a specific depth interval in the borehole, and 

BORE_SEI contains seismic data (such as velocity and 

density) from a specific depth interval in the borehole. 

In the same way that a station identification field 

and an event identification field in each RESPONSE 

record point to associated records in STATION and 

EVENT, respectively, borehole identification fields in 

BORE_GEO and BORE_SEI point to associated records 

in BORE. A field in BORE containing the identifier of 

the nearest seismic station points to a record in STATION. A pointer expt_id in REFLECT and REFRACT 

links seismic reflection and seismic refraction experiment data to GEO_EXP, in which records describe the 

location and geology of the experiment site.
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

The design of the RESPONSE, BORE_GEO, and 

BORE_SEI data files is flexible enough to allow documentation of single, multiple, and reduced measurements at a specific seismic response site or borehole site. 

For example, the response in a given frequency band for 

a particular station and event is usually a single measurement, but in some instances it may be a simple mean, 

weighted mean, or smoothed value of several measurements. Similarly, the design of INTENSIT allows for 

multiple observations of MM intensity to be documented 

for a specific site.

IMPLEMENTATION OF THE DATA BASE

A prototype urban hazards data base (UHDB) utilizing 

the relational data base principles described in this 

report has been implemented to manage the seismic 

hazards data for two urban areas currently under investigation: the Wasatch Front in Utah and Puget Sound in 

Washington. The Wasatch Front hazards assessment has 

entered the final stages, and thus most of the seismic 

hazards data have been acquired. Entry of these data 

into the files of the UHDB has permitted evaluation of 

the degree of soundness and appropriateness of the 

initial data structures. In addition, a user interface called 

GEOTEK was programmed using the dBASE III Plus 

language.

The UHDB is currently implemented on a number of 

computer systems: a USGS PRIME 9955 minicomputer 

located in Lakewood, Colo.; five systems located in 

Golden, Colo. (a USGS VAX 11/750 minicomputer, a 

SUN Microsystems 3/60 work station, and three microcomputers); and microcomputers in California and 

Nevada.

There are significant advantages to implementation on 

multiple computer systems. The microcomputers are 

used principally in the data acquisition and data analysis 

phases of projects, both in the field an 1 in the office. 

After newly acquired data are edited and proofed, the 

data sets are transferred to one microcomputer, where 

the master data base is maintained. Copies of the master 

data base are installed on the two minicomputers and the 

work station in Golden and distributed to other users as 

needed. Thus, the data are available for use by GIS and 

other applications software installed on those systems. 

In addition, the data files are accessible to many additional USGS personnel and to a large number of analysis 

programs not available on a microcomputer.

Since the dBASE III Plus software is installed on 

several field microcomputers, data entry, data editing, 

and data retrieval are possible in the field as data are

being acquired. Program and data design development 

are much easier using a software package such as 

dBASE III Plus; once the data base design has been 

settled on, implementation on the VAX 11/750 (which 

requires FORTRAN programming because data base 

management software is unavailable in the present VAX 

installation) should be simplified.

Multiple site implementation is feasible because it is 

possible to transfer data files easily between the various 

user sites, electronically by using either a modem or one 

of several existing computer networks or physically by 

transporting a diskette or magnetic tape containing the 

data. No data file conversion is required between similar 

systems (microcomputer-to-microcomputer). Between 

dissimilar systems, a dBASE III Plus conversion utility, 

a communications software package, and hardware connection (or modem) are required.

REFERENCES

Borcherdt, R.D., Joyner, W.B., Warrick, R.E., and Gibbs, J.F., 1975, 

Response of local geologic units to ground shaking, in Studies for 

seismic zonation of the San Francisco Bay region: U.S. Geological 

Survey Professional Paper 941-A, p. A52-A67.

Cluff, L.S., 1985, Firsthand experience of the Ms 8.1 earthquake that 

struck Mexico City on 19 September 1985: Bulletin of the Seismological Society of America, v. 75, p. 1843-1846.

Hays, W.W. and King, K.W., 1982, Zoning of the earthquake groundshaking hazard, in Proceedings, Third international earthquake 

microzonation conference: Seattle, Wash., p. 145-156.

Kagami, H., Duke, C.M., Liang, G.C., and Ohta, Y., 1982, Observation of 1- to 5-second microtremors and their application to 

earthquake engineering Part II, Evaluation of site effect upon 

seismic wave amplification due to extremely deep soil deposits: 

Bulletin of the Seismological Society of America, v. 72, no. 3, 

p. 987-998.

Kagami, H., Okada, S., Shiono, K., Oner, M., Dravinski, M., and Mal, 

A.K., 1986, Observation of 1- to 5-second microtremors and their 

application to earthquake engineering Part III, A twodimensional study of site effects in the San Fernando Valley: 

Bulletin of the Seismological Society of America, v. 76, no. 6, 

p. 1801-1812.

King, K.W., Tarr, A.C., Carver, D.L., Williams, R.A., and Worley, 

D.M., 1990, Seismic ground-response studies in Olympia, Washington, and vicinity: Bulletin of the Seismological Society of 

America, v. 80, no. 5, p. 1057-1078.

Martin, James, 1977, Computer database organization (2nd ed.): Englewood Cliffs, N.J., Prentice-Hall, 713 p.

Ohta, Y., Kagami, H., Goto, N., and Kudo, K., 1978, Observation of 1- 

to 5-second microtremors and their application to earthquake 

engineering Part I, Comparison with long-period accelerations at 

the Tokachi-Oki earthquake of 1968: Bulletin of the Seismological 

Society of America, v. 68, no. 3, pp. 767-779.

Rogers, A.M., Tinsley, J.C., and Borcherdt, R.D., 1985, Predicting 

relative ground response in earthquake hazards in the Los Angeles 

region: U.S. Geological Survey Professional Paper 1360, 

p. 221-248.
A DATA BASE DESIGNED FOR URBAN SEISMIC HAZARDS STUDIES 89

APPENDIX A. URBAN HAZARDS DATA BASE 

FILE STRUCTURES

There are currently 16 data files in the urban hazards 

data base:

BORE [Borehole data]

BORE_GEO [Borehole geology data]

BORE_LOG [Borehole log data]

BORE_SEI [Borehole seismology data]

BUILDING [Building data]

EVENT [Seismic event data]

GEO.EXPT [Geophysical experiment data]

INTENSIT [Seismic intensity data]

MODEL [Model structure]

MODL_PAR [Model parameters]

RECORD [Seismic record]

REFLECT [Seismic reflection data]

REFRACT [Seismic refraction data]

RESPONSE [Seismic response data]

STATION [Seismic station data]

VEL_MODL [Velocity model]

The files and fields in the data base are:

BORE [Borehole data]

Borehole identification

Alternate borehole identification

Owner

Borehole location description

Borehole latitude

Borehole longitude

Borehole elevation

Quadrangle name

Section/township/range description

Logged by whom

Casing

Date(s) drilled

Date closed

Borehole (well) depth

Depth to cementation

Depth to water table

Depth to bedrock (basement)

Thickness Holocene sediments

Thickness Quaternary sediments

Total thickness sediments

Preferred station (pointer to STATION)

Distance to preferred station

Preferred geophysical experiment (pointer to GEO_EXPT)

Remarks

Reference 

BORE_GEO [Borehole geology data]

Borehole identification (pointer to BORE)

Minimum interval depth

Maximum interval depth

Percent silt and clay

Percent sand

Percent gravel

Description of interval

Texture

Soil classification

Age

Grain size

Liquid limit

Plastic limit

Plastic index

Moisture content

Density solids

Dry density

Void ratio

Remarks

Reference 

BORE_LOG [Borehole log data]

Borehole identification (pointer to BORE)

Minimum interval depth

Maximum interval depth

Color

Field description

Unit name

Remarks 

BORE_SEI [Borehole seismology data]

Borehole identification (pointer to BORE)

Minimum interval depth

Maximum interval depth

P-velocity

S-velocity

Remarks

Reference 

BUILDING [Building data]

Building identification

Building location (name, address)

Building latitude

Building longitude

Building elevation

Building description

Number of stories

Remarks

Reference 

EVENT [Seismic event data]

Event identification

Event type (earthquake, nuclear shot, HE shot)

Event date

Event time

Event latitude

Event longitude

Event elevation (focal depth, burial depth)

Event size (magnitude, pounds or tons TNT)

Remarks

Reference 

GEO.EXPT [Geophysical experiment data]

Experiment identification

Alternate experiment identification

Experiment type (reflection, refraction)

Experiment date

Experiment location description

Experiment latitude

Experiment longitude

Experiment elevation

Experiment description

Preferred station (pointer to STATION)

Preferred borehole (pointer to BORE)

Remarks 

INTENSIT [Seismic intensity data]

Event identification (pointer to EVENT)

Building identification (pointer to BUILDING)

MM intensity value

Number of observations

Remarks

Reference
90 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

MODEL [Model structure]

Model identifier

Model latitude

Model longitude

Model elevation

Remarks 

MODL_PAR [Model parameters]

Model identifier [pointer to MODEL]

Minimum interval depth

Maximum interval depth

P-velocity

S-velocity

Dip

Density

Shear modulus

Bulk modulus

Poisson's ratio

Remarks 

RECORD [Seismic record]

Record identification

Event identification (pointer to EVENT)

Station identification (pointer to STATION)

Event type

Event extension

VAX directory 

REFLECT [Seismic reflection data]

Reflection experiment identification (pointer to GEO_EXPT)

Geometry description

Length

Azimuth

CDPfold

Source type

Source spacing

Source offset

Source arrays

Shots per shotpoint

Geophone type

Geophone frequency

Geophone spacing

Geophone arrays

Recorder type

Recording medium

Recording format

Sampling interval

Record length

Filters

Number of files

Remarks 

REFRACT [Seismic refraction data]

Refraction experiment identification (pointer to GEO_EXPT)

Geometry description

Length

Azimuth

Source type

Shots per shotpoint

Geophone type

Geophone frequency

Geophone spacing

Recorder type

Recording medium

Recording format

Sampling interval

Record length

Filters

Number of files

Remarks 

RESPONSE [Seismic response data]

Station identification (pointer to STATION)

Event identification (pointer to EVENT)

Minimum frequency of band

Maximum frequency of band

Relative response

Number of measurements

Standard deviation (for multiple measurements)

Remarks

Reference 

STATION [Seismic station data]

Station identification

Alternate station identification

Station location description

Station latitude

Station longitude

Station elevation

Quadrangle abbreviation

Section/township/range description

Surface geology of station (generalized)

Preferred borehole (pointer to BORE)

Distance to preferred borehole

Nearest geophysical experiment (pointer to GEO_EXPT)

Preferred model (pointer to MODEL)

Remarks 

VEL.MODL [Velocity model]

Velocity model identification

Depth to top of layer

Depth to bottom of layer

P-wave velocity

S-wave velocity

Vp/Vs ratio

Two-way travel time P-wave

Two-way travel time S-wave
A MAPPING OF GROUND-SHAKING INTENSITIES FOR 

SALT LAKE COUNTY, UTAH

By PHILIP C. EMMI*

ABSTRACT

This paper documents the development of maps showing a probabilistic assessment of the earthquake of ground-shaking hazard for zones 

within an area of Salt Lake County, Utah, suitable for contiguous 

urban development. Measures of ground shaking are considered, and a 

preference for the Modified Mercalli Intensity (MMI) scale is established. Data and relationships relevant to a microzonation of MMI are 

reviewed. Alternative methods for estimating spatial variation in MMI 

are described and compared. The findings include the following: MMI 

with a 10 percent chance of being exceeded in a 10-yr period range from 

V on bedrock above benches of Pleistocene Lake Bonneville to VIII + 

on fine clays and silts of the Quaternary flood plain and delta complex 

south of the Great Salt Lake and along the margins of the Jordan River 

at the valley's center. MMI with a 10 percent chance of being exceeded 

in a 50-yr period range from VII at the valley's edge to X at the valley's 

center. MMI with a 10 percent chance of being exceeded in a 250-yr 

period range from VIII at the valley's edge to XI at the valley's center. 

These results are specific to the ground-shaking hazard and do not 

consider related hazards such as liquefaction, near-field directivity 

effects, rock fall, debris flow, fault rupture, seiches, and tectonic 

subsidence. These results are summarized in a set of maps developed 

with the use of a geographic information system.

INTRODUCTION

The purpose of this paper is to explain the development and use of ground-shaking intensity maps for an 

area of Salt Lake County, Utah, suitable for contiguous 

urban development. These maps show the degree of 

ground shaking to which this area is considered subject 

over a 10-, a 50-, and a 250-yr period of exposure. The 

maps are developed on a geographic information system 

(GIS) and are photographic reductions of computergenerated maps otherwise available at the 1:100,000 

scale. Use of a GIS facilitates an integration of data on 

bedrock motion, relative site amplification, and surficial 

geologic units. The integration of combined data permits 

a mapping of the ground-shaking hazard at a degree of 

spatial resolution that begins to approach the detail 

needed for seismically attentive land-use planning.

1 Department of Geography, University of Utah, Salt Lake City.

Ground-shaking intensity maps use the Modified Mercalli Intensity (MMI) scale to represent different degrees 

of shaking (Wood and Neumann, 1931). At each MMI 

level, a description of associated perceptions of ground 

motion and degrees of damage to common elements of 

the built environment are noted. (See Appendix A for an 

abbreviated description of the MMI scale.) Maps of 

ground-shaking intensity have many potential uses, such 

as estimating seismically related losses for insurance 

planning, designing seismic retrofit programs for vulnerable structures, siting and designing critical facilities and 

lifelines, and planning for earthquake emergencies.

This paper has four functions: enumerate viable 

approaches to assess ground-shaking hazards, develop 

alternative estimates of the local ground-shaking hazard, 

evaluate the alternative estimates, and present the preferred methodology together with the associated groundshaking hazard maps. The paper is divided into five 

additional sections that serve to review measures of 

ground shaking, describe a model for the assessment of 

ground shaking, review prior studies and detail available 

data, describe and compare alternative computational 

methods, and present research findings.

ACKNOWLEDGMENTS

The author wishes to acknowledge the help of Drs. 

Maurice Powers, Jeffrey Keaton, John Tinsley, and 

Kenneth King for assistance with issues of method and 

technique.

MEASUREMENT OF GROUND SHAKING

In general, ground shaking increases with the magnitude of a seismic event and decreases with distance from 

its epicenter. However, significant variations from this 

generality are caused by sensitive soil conditions, topological conditions, and stratigraphic geometry. The 

study of ground shaking and its spatial variation requires 

measurement of ground-shaking intensity. Measures of

91
92 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

ground shaking are divided into two classes: instrumental measures and observational measures.

INSTRUMENTAL MEASURES OF GROUND SHAKING

Instrumental measures are most commonly taken from 

seismograph readings called accelerograms. An accelerogram measures lower frequency horizontal and vertical 

components of site acceleration during an earthquake. 

Velocity and displacement seismograms are developed 

from the data recorded on an accelerogram (Trifunac, 

1970). Thus, the measures available from a seismograph 

reading include ground-motion duration, displacement, 

velocity, and acceleration at low frequencies (fig. 30). 

Other measures available from seismograph readings, 

including earthquake magnitude, are discussed by Hays 

(1980, p. 25-28).

The duration of shaking above some standard threshold of perceptibility is an earthquake's measured duration. Up to a point, duration increases with epicentral 

distance. Duration is longer on soft soils than on nearby 

rock sites. When allowance is made for other parameters 

of ground motion, longer duration implies greater damage. Greater durations also trigger liquefaction. Duration on soft soil of a Richter magnitude 7.0 earthquake 

has a mean and standard variation of from 13 s±8 s at 25 

km epicentral distance (Krinitzsky and others, 1987).

The maximal movement of soil particles from rest is a 

measure of displacement. Because of its relative insensitivity to geologic variations, ground displacement propagates more coherently than either velocity or acceleration. Displacement at the fault of a great earthquake 

probably does not exceed 200-400 cm, while displacement at a 3- to 5-km distance probably does not exceed 

20-40 cm (Trifunac and Brady, 1975).

The maximum speed attained by a seismically oscillating soil particle is its peak velocity. Peak velocity is 

measured in both horizontal and vertical directions. 

Oscillation causes a stretching and compressing of the 

soil and is noted as shear strain. The degree of shear 

strain to which the site is subject is proportional to the 

velocity of ground motion and inversely proportional to 

the shear wave velocity of its composite materials. Soft 

soils have a lower shear wave velocity than rock and are, 

therefore, subject to greater shear strain than are 

nearby rock sites. Richter magnitude 7.0 earthquakes 

induce a peak horizontal velocity (PHV) measured on soft 

soil at 25 km epicentral distance of 22-74 cm/s (Krinitzsky and others, 1987).

An oscillating soil particle has a measurable acceleration. Peak acceleration occurs midway between oscillations. The peak horizontal accelerations (PHA) for Richter magnitude 7.0 earthquakes range from 110-510 

cm/s/s at 25 km epicentral distance, i.e., from 0.11-0.52 

units of gravity (g) (Krinitzsky and others, 1987). Peak

vertical acceleration is usually about two-thirds peak 

horizontal acceleration (Werner and Ts'ao, 1975). Peak 

horizontal acceleration is widely used by structural 

engineers as a measure of the lateral forces on taller 

buildings.

PHA is also used to define earthquake magnitude on 

the Richter scale (Richter, 1935). Richter magnitude 

(ML) is defined as the logarithm of the maximum trace 

amplitude recorded on an accelerogram of a WoodAnderson seismograph at an epicentral distance of 100 

km. Adjustments are made for observations at distances 

other than 100 km (Hays, 1980).

Instrumental measures of ground-shaking intensity 

are important to assessing the risk of damage to structures. Each structure responds to ground shaking like an 

oscillating system with its own fundamental natural 

frequency. Buildings in excess of seven stories usually 

have a natural frequency less than 0.6 Hz. Buildings from 

three to seven stories resonate at 0.6-2.5 Hz. One- to 

two-story buildings resonate at 2.5 Hz or more 

(Borcherdt, 1985, fig. 3.2). Larger earthquakes are 

known to have a greater proportion of their energy 

concentrated in lower frequency ranges and are, thus, 

relatively more hazardous to taller buildings. Also, since 

lower frequency seismic energy is known to attenuate 

less rapidly with distance, taller buildings are subject to 

relatively more risk over a larger area than are shorter 

buildings. Yet the frequency-dependent effects of magnitude and distance are often secondary to the frequencydependent effects of local site conditions. This is particularly the case when considering buildings located on 

deep lake sediments as are found in the Salt Lake Valley. 

To better assess the risk of damage to structures, it helps 

to know at which frequencies a ground-motion parameter 

will peak when given certain assumptions about magnitude, distance, and local site conditions. It is also useful 

to know which classes of buildings resonate with the 

frequency ranges containing parameter peaks.

A transformation of ground-motion time histories can 

be used to generate a series of harmonic functions in the 

frequency domain. These define the maximum amplitude 

of harmonic oscillator response to a given ground-motion 

history. The many response maxima defined across a 

wide frequency range are called an earthquake response 

spectrum.

For ground-shaking studies, pseudo-relative velocity 

(PSRV) response spectra are perhaps the most important of the several different kinds of response spectra 

used in seismology. At a given frequency, the PSRV 

response spectra measure the velocity of the center of 

mass of a simple resonant structure relative to the 

velocity of its base. PSRV is often used to assess the 

amplification of bedrock motion by a resonant column of 

unconsolidated soil deposits. Thus, like other response
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY

1000-

. cj

Z LLJ

co

LU

_J 

LU 

CJ 

CJ

<

LJJ co

1000

Ground-Motion Acceleration

100-

co

u o-

> Z

100-

Ground-Motion Velocity

50

Q_ LU

CO CJ

Q Z

50

Ground-Motion Displacement

TIME, IN SECONDS

FIGURE 30. The S16°E component horizontal accelerogram recorded at Pacoima Dam and the velocity and displacement seismograms 

derived from it; 1971 San Fernando, Calif., earthquake (adopted from Hays, 1980, p. 28).

spectra, the PSRV response spectrum often shows a 

maximal value at a specific frequency that is several 

times larger than the maximal value shown by a corresponding low-frequency seismogram (fig. 31).

Pseudo-absolute acceleration, pseudo-relative velocity, and relative displacement are often graphed together 

against the frequency of vibration as pseudo-response 

spectra. Pseudo-absolute acceleration is graphed over a
94 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

VELOCITY SEISMOGRAM

(Slept)

HARMONIC OSCILLATOR RESPONSE 

FOR Hz=0.33

(Step 2.a)

TIME, IN SECONDS

4 8 

TIME, IN SECONDS

O

LU

CO

o

o 

g

LU

HARMONIC OSCILLATOR RESPONSE

FOR Hz=2.0

(Step 2.b)

PSEUDO-RELATIVE VELOCITY 

5 PERCENT DAMPED

(Step 3)

10'

o

LU 

CO

o

o 

g

LU

1tV 10"

TIME, IN SECONDS

10 U 10 1 

FREQUENCY, IN HERTZ

10'

FIGURE 31. Derivation of the harmonic oscillator response at 0.33-Hz and 2.0-Hz frequency from a velocity seismogram and the role in the 

construction of a pseudo-relative velocity response spectrum (adopted from Hays, 1980, p. 38).

high-frequency range (from 2.5-33 Hz) and is used when 

considering the response of shorter buildings (roughly 

one to five stories high). PSRV is graphed over an 

intermediate-frequency range (of 0.25-2.5 Hz) and is 

used when considering the response of buildings of 

intermediate height (roughly 5-16 stories high). Relative 

displacement is graphed over a low-frequency range 

(from 0-0.25 Hz) and is used when considering the 

response of taller buildings. Thus response spectra are 

used in conjunction with data on local site conditions to 

estimate the frequency-specific effects of earthquakes of

hypothesized magnitude and distance. Effects within 

given frequency ranges can then be related to the design 

of structures with known resonant frequencies.

OBSERVATIONAL MEASURES OF GROUND SHAKING

Observational measures of ground-shaking intensity 

rely on human perception and observation. At each 

intensity level on an observational scale, there is a 

description of associated human perceptions of ground 

motion (felt by a few persons, felt by nearly everyone), a
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 95

description of associated physical events (suspended 

objects may swing, unstable objects overturn, great 

damage to poorly built structures), and, at the higher 

intensity levels, descriptions of associated geophysical 

events (sand boils, surface faulting, liquefaction, rock 

falls, seiches, and tsunamis).

There are several observational scales of groundshaking intensity in use around the world today. They 

provide useful judgments about ground-shaking intensity in areas without permanently installed seismographs. They are useful in providing information about 

historic events for which there were no instrumental 

readings. Finally, most studies of the relationship 

between ground shaking and damage, loss, or injury use 

observational measures of ground shaking rather than 

instrumental measures. Researchers wishing to assess 

seismic loss potentials are bound by this fact to work 

with observational intensity measures. In this study, we 

use the MMI scale.

In spite of the distinction between instrumental and 

observational measures of ground-shaking intensity, it is 

necessary to work with both classes of measures. However, since there are real differences between instrumental and observational measures, caution must be 

used when converting from one class of measure to the 

other. First, since MMI, PHA, PHV, and displacement 

all have different rates of attenuation from epicentral 

distance, it is difficult to transform estimates of PHA to 

PHV and then to MMI without compounding errors. 

Second, observational measures will sometimes fail to 

perceive the differences in dominant frequencies among 

seismic events and their effects on observable damage or 

geophysical disturbance. This situation contributes to a 

partial tautology in the definition of seismic intensity 

based on subjective observations. Often intensity is 

deemed to be high (or low) because damage is great (or 

slight) and not because the dominant frequencies happened to resonate (or not resonate) with a large proportion of local structures. Third, the response spectra 

corresponding to two site intensities thought to be 

identical on the MMI scale can vary considerably in shape 

and in peak frequencies. Thus, two sites might be 

thought to be equally hazardous on the basis of past 

observations when, in fact, their seismic responses are 

quite different: the sites could be used safely if the 

structures to be located there were designed with instrumental data about their different response spectra in 

mind.

GENERAL MODEL FOR THE ASSESSMENT OF 

GROUND-SHAKING HAZARDS

A general model for the probabilistic assessment of 

regional ground-shaking hazard involves four steps. The 

first is to identify and characterize likely seismic sources.

The source region needs to be larger than the subject 

region because earthquakes outside the subject region 

can do considerable damage within the subject region. 

Along the Wasatch Front, any source capable of a large 

earthquake that is within at least 120 km of the subject 

area should be included in the source region. Seismic 

sources need to be characterized by the range of event 

magnitudes of which they are capable and the frequencies with which events of each magnitude are likely.

The second step is to construct a multiple-source-tomultiple-site geometry. This step requires measuring 

the distances from each source to various locations within 

the subject region. Typically, the subject region is 

divided into a grid, and the distance from each source to 

the center of each grid cell is measured and recorded. 

This procedure is repeated for all likely sources.

The third step is to attenuate ground motion from 

source to site. Each source is characterized by a distribution of event magnitudes (typically Ms or Mj). Each 

magnitude is characterized by a distribution of event 

frequencies. At each source, each event magnitude 

(weighted by its probability of occurrence during a 

specified exposure period) is converted to a measure of 

ground motion (typically PHA), and that measure is 

attenuated by distance from source to subject site.

Since there are several measures of ground-shaking 

intensity, there are several approaches to the problem of 

source-to-site attenuation. Again, the most important 

division among approaches is between the direct attenuation of MMI and the attenuation of either PHA or PHV 

with conversion to MMI at site. The attenuation problem 

is exacerbated in the present case by the limited availability of regional data with which to construct regionally 

specific attenuation curves for either MMI, PHA, or 

PHV. Recent studies by Hooper (1988) and by Algermissen and others (1988) correct this situation in part with 

their study and deployment of a regional MMI attenuation function.

The final step is to estimate the effects of site characteristics on ground motion (see Hays, 1983). Here the 

problem is principally one of adjusting for the possibility 

of ground-motion amplification because of seismically 

sensitive soils and soil stratigraphies (fig. 32). Again, 

there are several approaches used to address groundmotion amplification. One option is to use attenuation 

functions specific to soil types. These typically distinguish between "hard" and "soft" soils but make no 

further distinction among soil conditions. Another option 

is to attenuate MMI directly from source to site and then 

use intensity increments to adjust for the presence of 

amplifying soil conditions. (This method typically distinguishes between three or four different soil types.) A 

third option is to use site-response functions empirically 

calibrated within the study area. With this option, por-
96 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

O

o

LU

o

N 

DC 

O

I

LU

Z

o

CL

^

O

o

LU

< 

LU

SITE ON THE WESTERN SLOPE OF THE WASATCH (Crystalline Rock)

TEMPLE SQUARE (Quaternary Alluvial Deposits)

LIBERTY PARK (Quaternary Lake Bonneville Deposits)

0 16 32 48 64 80 96

TIME, IN SECONDS

12 28 44 60

FIGURE 32. Velocity seismogratns for three Salt Lake City locations exemplifying site amplification during low-amplitude ground motions 

initiated by a low-strain event that induced linearly elastic relative site responses (adopted from Hays, 1987, p. K-8).

table seismometers are deployed at numerous sites, and 

measurements are taken during seismic aftershocks or 

during nuclear or mining explosions. Ground-motion 

parameters are measured on different soils, and ratios of 

ground-motion parameters, usually the ratios of PSRV, 

are found relative to a reference rock site. These ratios 

are then used as site-specific ground-motion amplification factors. A variation on this third option is to 

correlate site-response functions to geological and geotechnical variables, so findings can be generalized 

beyond areas where seismographic readings were originally taken.

There is yet another site characteristic of potential 

importance. It has to do with subbasin geometry and the 

possibility of directivity (or focusing) effects (Benz and 

Smith, 1989). Directivity effects would be important to 

Salt Lake County in the event of a fault-rupturing 

earthquake on the Salt Lake segment of the Wasatch 

fault. Directivity refers to the effect that the great 

impedance contrast between high-density rocks to the

east of the Wasatch fault plane and the low-density 

sediments to the west of the fault plane is likely to have 

on directing seismic energy originating on that plane up 

the surface of the plane and on concentrating strong 

ground motion along the surface expression of the fault. 

Thus, in addition to the ground-motion amplification 

effects concentrated in the center of the Jordan River 

Valley, one could also have near-field directivity effects 

focused on areas adjacent to the surface expression of the 

Salt Lake segment of the Wasatch fault. The implications 

of the directivity effect for levels of risk in Salt Lake 

County are interpreted in a related paper (Emmi, 1989).

POINTS OF DEPARTURE-DATA AND 

RELATIONSHIPS

Data and relationships relevant to a mapping of MMI 

for Salt Lake County are reviewed in terms of source 

characteristics, ground-shaking, and ground-motion 

intensities at site.
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 97

SOURCE CHARACTERISTICS AND RECURRENCE 

INTERVALS

Studies of source characteristics for the Wasatch fault 

zone are numerous and ongoing. Early compilations were 

done by Williams and Tapper (1953) and again by Rogers 

and others (1976). Recent studies of recurrence relationships based on observational data and covering the 

complete range of seismic magnitudes are reviewed by 

Arabasz and others (1987). Paleoseismologic investigations documented by Machette and others (1987) add to 

the instrumental record. Estimates of the composite 

return interval for fault-rupturing events located along 

the entire length of the Wasatch fault zone appear to be 

converging upon a consensus. Summarizing paleoseismic 

studies, Schwartz and Coppersmith (1984) report a 

return interval of 400-600 yr, with a preferred estimate 

of 444 yr. Updating Schwartz and Coppersmith with a 

review of subsequent paleoseismic studies, Lund (1987) 

reports a preferred interval of 310-350 yr. Using the 

University of Utah earthquake catalog of instrumental 

recordings (July 1962-December 1985), Arabasz and 

others (1987) report a recurrence interval for ML 7.0 

events of 120-630 years, with a preferred estimate of 270 

yr. Young and others (1987) report a similar interval of 

330 ±90 years.

GROUND-SHAKING HAZARD

The Wasatch Front ground-shaking hazard study by 

Rogers and others (1976) identified sources, estimated 

recurrence intervals, and estimated the attenuation of 

intensities from sources to sites using three soil-specific 

attenuation curves based on a preliminary study of soil 

response factors. These curves accommodate soil amplification by the addition of intensity increments of 1.9 and 

2.6 MM I units over bedrock. Hypothetical earthquakes 

of magnitude 7.5 at selected epicentral locations are 

posited. In all cases, MMI in Salt Lake County ranges 

from level VI to level IX a range of three intensity 

units.

The study by Rogers and others (1976) illustrates the 

impact that site response has on spatial variation in 

ground-shaking intensities. Hays and others (1978) used 

a more extensive array of seismographs and measured 

site responses on soil and rock during nuclear explosions 

at the Nevada Test Site. They computed transfer functions (also called spectral ratios, site-response factors, 

and spectral amplification factors) in both the 0.1-0.2-s 

and the 0.2-0.7-s period bands. They found site amplification factors ranging from 1.5 to more than 10.0. (These 

correspond to MMI increments of up to three intensity 

units.) They presented their findings as point observations and generalized these observations to create isopleth maps showing contours within which they would 

expect to find similar spectral ratios.

Algermissen and others (1982) contributed a study of 

map contours showing probabilistic estimates of PHA 

and PHV in rock for the contiguous United States. The 

maps show values that have a 10 percent chance of being 

exceeded over 10-, 50-, and 250-yr periods. (These values 

correspond to expected return periods of 95, 475, and 

2373 yr, respectively.) The area along the Wasatch Front 

containing Salt Lake County has a 10-yr, 10 percent 

exceedence value for peak horizontal acceleration of 98 

cm/s2 or 10 percent of gravity (0.10 g). The 50-yr, 10 

percent exceedence value is 274 cm/s2 , or 0.28 g. The 

250-yr, 10 percent exceedence value is 686 cm/s2 , or 0.70 

g. (See Appendix B for an explanation of such risk 

statements.)

Algermissen and Steinbrugge (1984) used these estimates together with spectral ratios for the 0.2-0.7-s band 

from Hays and others (1978) to generate a map for Salt 

Lake City of expected MMI levels for a hypothesized 

Ms=1.5 earthquake. The areas of the city where spectral 

ratios are less than 1.5 have an estimated MMI level of 

VII, while areas where spectral ratios are greater than 

10.0 have an estimated MMI level of X. Intensities are 

larger by one unit over those shown by Rogers and 

others (1976). The low- to high-intensity range is the 

same: three intensity units. The low- to high-intensity 

range of two to three intensity units is confirmed by Oaks 

(1987) in a study of intensities from historic damaging 

earthquakes in Salt Lake City and across the Jordan 

River Valley.

Soil properties such as soil void ratios, densities, and 

shear wave velocities correlate well with spectral amplification ratios (Rogers and others, 1983). These properties can be captured reasonably well by surficial geologic 

units. Rogers and others (1984) offered correlations 

between three broadly defined surficial geologic units 

and the spectral amplification ratios published by Hays 

and others (1978). Silts and clays have a mean amplification factor of 6.2, sands and gravel a factor of 3.7, and 

rubble a factor of 2.7. With these correlations, one can 

more readily estimate site effects in areas on the 

Wasatch Front where specific site response studies have 

not been conducted but where soil types are known. Use 

of correlations with surficial geologic units permits a 

generalization and extension of analytical results. However, because of the limited number of soil classifications 

and the different and sometimes weak correlations, the 

findings reported by Rogers and others (1984) must be 

used with particular caution.

The study of seismic risk to State Government property, fuel lines, and water lines by Taylor and others 

(1986) begins with a reassessment of the ground-shaking 

hazard. They identify and characterize likely seismo-
ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

genie sources and then attenuate PHV in rock from each 

of several sources to sites in four Wasatch Front counties 

using a velocity attenuation curve published by Campbell 

(1984). They compute PHV in soil using the three 

surficial geologic units identified by Rogers and others 

(1984) and convert to MMI using a function developed by 

Wiggins and Taylor (1981). They find that MMI in Salt 

Lake County for a hypothetical ML=7.3 earthquake on 

the Salt Lake segment of the Wasatch fault ranges from 

below VII at the valley edge to X or more in the valley 

center, again a range of three intensity units.

Advances in paleoseismic investigations, plus innovations in probabilistic assessments of seismic hazards, 

prompted further investigation by Young and others 

(1987), whose study is regarded as among the most 

complete and sophisticated assessments of groundshaking hazard yet done for any region. It includes an 

inventory of seismic sources with ten segments of the 

Wasatch fault, five segments of the Oquirrh Mountains 

fault, two segments each of the East Cache Valley fault, 

the Hansel Valley fault, and the East Bear Lake fault, 

the West Valley fault, and a generalized background 

source. The study focuses on PHA in soil and on pseudoabsolute acceleration as preferred measures of groundshaking intensity. Local site effects are addressed by 

using attenuation functions and spectral amplification 

functions for rock and soil conditions calibrated on California data. The authors note (Young and others, 1987, p. 

M-57-58), "The applicability of these relationships to 

areas of [Bonneville] lake clays and silts is questionable, 

but alternative relationships are not available at present. 

The relationships used in the analysis may underestimate 

response spectra of longer-period motions in areas of soft 

lake deposits." Despite this conservative bias, estimates 

of PHA by Young and others (1987) for Salt Lake County 

are generally greater than earlier estimates by Algermissen and others (1982). Their estimate of PHA on rock 

with a 10 percent chance of being exceeded over a 10-yr 

period is 86 cm/s2 , or 0.09 g, for a 50-yr period is 353 

cm/s2 , or 0.36 g, and for a 250-yr period is 823 cm/s2 , or 

0.84 g.

CONVERTING ACCELERATION TO INTENSITY AT SITE

Lacking a functional relationship with which to compute the direct attenuation of seismic intensities from 

source to site while simultaneously addressing site characteristics, we face the alternative problem of converting 

smaller scale estimates of PHA on rock to larger scale 

estimates of MMI on soil sites with varying seismic 

sensitivities. Young and others (1987) provide the most 

accurate and spatially detailed estimates of PHA exceedence values. However, their findings introduce a further 

complication the need to account more accurately for 

site characteristics than was possible with hard and soft

soil attenuation functions. This need is met by converting 

PHA on hypothetical rock sites to MMI on hypothetical 

rock sites and then accounting for the alteration of MMI 

on rock by various site characteristics. There are several 

ways to convert from PHA to MMI values, and there are 

several ways to account for site characteristics. These 

problems are discussed next, along with combinations of 

approaches that promise reasonable results.

The two methods used to link PHA to MMI are (1) a 

continuing effort to define a direct and reliable relationship between acceleration and MMI (see the references 

cited in fig. 33) and (2) linking acceleration indirectly to 

MMI by way of ground-motion velocity as an intermediate variable. The second path must be considered for two 

reasons: velocity is thought to be more sensitive to site 

characteristics than acceleration, and site-specific spectral amplifications of PSRV should be applied to regional 

estimates of PHV (not PHA) when using spectral amplification factors to estimate spatial variation in MMI 

(C.E. Taylor, private commun., 1988).

A search of the literature yields ten functional relationships between PHA and MMI (figs. 33A and 335) and 

seven relationships between PHV and MMI (fig. 34). The 

parameters in some of these relationships are adjustable, 

depending on hypotheses concerning magnitude and distance. Other relationships are, in fact, suites of relationships controlled for variation in distance or soil-versusrock conditions. The relationships are converted to an 

identical functional form, so their slope and intercept 

coefficients can be readily compared. Outlying relationships are discarded. A suite of relationships by Krinitzsky and Chang (1987) was chosen for use in converting 

acceleration to intensity. A function by Wiggins and 

Taylor (1981) was retained for use in converting velocity 

to intensity. When needed, a relationship provided by 

Donovan (1983) was used to convert PHA to PHV given 

appropriate values for soil-versus-rock conditions, 

expected magnitude, and epicentral distance.

Given data and relationships currently available for 

this region, three general methodologies can be discerned with which to address local variation in site 

conditions. One way is to start with PHA on rock, 

convert either directly or indirectly to MMI on rock, and 

then, following Borcherdt and others (1979), add intensity increments associated with the relative siteresponse contours provided by Tinsley (1988). This procedure yields a localized estimate of MMI. This option 

will be referred to as the intensity increment option.

Borcherdt and others (1979) define a relationship 

between shear wave velocity and intensity increments 

measured on the San Francisco intensity scale. They also 

define a relationship between shear wave velocity and 

ground-motion amplification. Implied, with proper conversion among intensity scales, is a relationship between
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 99

B

12

10

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5 4 

o

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EXPLANATION

G&R

N(25)|M&0

E&T

T&B

B|m

-2-101 

LOG (PHA, IN UNITS OF GRAVITY)

Sources:

G&R: log (PHA)= -3.49+0.33 MMI, from Gutenberg and Richter (1956).

N(25)|M&O: log (PHA)= -3.55+0.38 MMI, for R=25 km from Neumann

(1954) as modified by Murphy and O'Brien (1977).

E&T: log (PHA)= -3.74+0.48 MMI, from Evernden and Thompson (1985). 

T&B: log (PHA)= -3.01+0.30 MMI, from Trifunac and Brady (1975). 

Blm: log (PHA)= -2.93+0.27 MMI, for M=6.5 from Bernreuter (1981).

12

10

Q 4 

O

K87|nh

K87|ns

K87|fb

M&O

M&Olmr

0 1

LOG (PHA, IN UNITS OF GRAVITY) 

Sources: 

From Krinitzsky and Chang (1987):

K87|nh: log (PHA)= -1.86+0.19 MMI, for near field, hard soil conditions.

K87|ns: log (PHA)= -1.63+0.13 MMI, for near field, soft soil conditions.

K87|fb: log (PHA)= -2.15+0.18 MMI, for far field, both soil conditions. 

From Murphy and O'Brien (1977):

M&O: log (PHA)= -2.74+0.24 MMI.

M&O: log (PHA)= -1.83+0.14 MMI, for R=24 km and M=6.25.

FIGURES 33A and B. Functional relationships suggested by various authors between MMI and the logarithm of peak horizontal acceleration

measured in units of gravity.

12

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2 -0.5

T&B

K87|nh

K87|ns

W81

E&TlVmax

0.5 1.5 

LOG (PHV, in cm/s)

2.5 3.5

Sources:

T&B: log (PHV)= -0.63+0.25 MMI, from Trifunic and Brady (1975).

From Krinitzsky and Chang (1987):

K87|nh: log (PHV)= -0.49+0.26 MMI, for near field, hard soils.

K87|ns: log (PHV)= -0.01+0.20 MMI, for near field, soft soils. 

W'81: log (PHV)= -1.48+0.37 MMI, from Wiggins and Taylor (1981). 

E&T|Vmax: log (MaxHV)=-1.24+0.40 MMI, from Evernden and

Thompson (1985).

FIGURE 34. Functional relationships suggested by various authors 

between MMI and the logarithm of peak horizontal velocity measured in centimeters per second.

ground-motion amplification and MMI increments (fig. 

35). This relationship is more consistent with historical 

observations and instrumental measurements than the 

comparable equation given earlier by Borcherdt and 

others (1975) (fig. 36).

Evernden and others (1981) invert this procedure. 

They start with PHA on alluvial soil, convert to MMI on 

soil, and apply MMI decrements for stiffer geologic units. 

This approach will not serve the present situation, since 

alluvial deposits are not the most seismically sensitive 

soils in Salt Lake Valley.

A second option is to convert from PHA on rock to 

PHV on rock, apply amplification factors (Rogers and 

others, 1984; Tinsley, 1988), and then compute MMI 

values using Wiggins and Taylor's (1981) equation. Since 

this is a variation of the method used by Taylor and 

others (1986), this option will be referred to as the Taylor 

variation.

A third option is a variation on a method employed by 

Krinitzsky (1988). It uses two starting points, two soilspecific conversion equations, and interpolates values in 

between. First, PHA on soil for the valley center is 

converted to MMI on soil using an equation specific to 

soft soils. Next, PHA on rock for the valley edge is 

converted to MMI on rock using an equation specific to 

hard soils. The next step is to interpolate between these
100 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

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-0.6

y = - 0.523 + 1.276x - 0.466xA 2

0.0 0.2 0.4 0.6 0.8 1.0 1.2 

LOG (Ground-Motion Amplification Ratio (PSRV))

FIGURE 35. A functional relationship between ground-motion amplification ratios (relative to a reference rock site) and intensity 

increments for nearby soil sites that can be added to estimates of 

MMI at the reference rock site to obtain MMI estimates for soil sites 

(based on relationships by Borcherdt and others, 1979).

extreme values for site-specific MMI values. This 

method is referred to as the Krinitzsky option.

These options are explored below. In addition to the 

issues raised here, challenges remain to clarify the 

relationship between soil properties and site amplification (see Tinsley, 1988), to apply response spectral 

attenuation relationships that control for detailed geotechnical properties (Joyner and Fumal, 1985), to 

develop and apply regionally specific MMI attenuation 

equations (see Algermissen and others, 1988), to specify 

basin geometric and directivity effects on relative ground 

motion (Benz and Smith, 1989), and to merge results to 

further refine localized estimations of MMI.

COMPARISON OF ALTERNATIVE METHODS

ALTERNATIVE METHODS

Different methods for converting acceleration to intensity are detailed below, and results are discussed and 

compared (table 5 and fig. 37). Different methods are 

explored to better understand the range of likely results 

and to better control for spurious results. The comparison also helps clarify the logic of each approach.

The intensity increment option is used to develop 

methods 1 and 2. For method 1, we begin with estimates 

of PHA on rock that have a 10 percent chance of being 

exceeded over 10-, 50-, and 250-yr periods (Young and 

others, 1987). We then use appropriate equations from 

Krinitzsky and Chang (1987) to convert to MMI on rock. 

We note the relative ground-shaking factors in the

31(79) is derived from Borcherdt and others (1979) 

31(75) is from Borcherdt and others (1975)

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EXPLANATION

 n 31(79)

 31(75)

2 4 6 8 10 

GROUND-MOTION AMPLIFICATION RATIOS

12

FIGURE 36. A comparison of curves defining the relationship between 

ground-motion amplification ratios and rock-site intensity increments (measured on the MMI scale) from material presented by 

Borcherdt and others (1975, 1979).

0.2-0.7-s period band (Tinsley, 1988), truncate at factors 

above eight (because of a possible nonlinear response 

above a factor of eight), and then apply the corresponding intensity increments given in figure 35. This procedure yields, for the intermediate (50-yr) time horizon, 

MMI values of VII for rock at the valley edge and MMI 

values of X for soft clays at the valley center.

For method 2, we begin with estimates of PHA on rock 

(Young and others, 1987), convert to PHV on rock 

(Donovan, 1983), estimate MMI on rock (Krinitzsky and 

Chang, 1987), note appropriate relative ground-shaking 

factors, and apply the corresponding intensity increments given in figure 35. This procedure yields MMI 

values for rock at the valley edge and for soft clays at the 

valley center of VI+ and IX+, respectively, for the 

intermediate (50-yr) time horizon.

The Taylor variation is used to develop methods 3 and 

4. For method 3, we begin with estimates of PHA on rock 

(Young and others, 1987) and convert to PHV on rock 

(Donovan, 1983). We then apply Tinsley's (1988) relative 

ground-shaking factors to find velocities at site and 

convert to MMI estimates using an equation provided by 

Wiggins and Taylor (1981). This procedure yields MMI
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 101

TABLE 5. Estimates of Modified Mercalli Intensity for the edge and 

center of the Jordan River Valley, Utah, using the six different 

methods of estimation discussed in this study

[The valley edge location assumes a crystalline rock site, while the valley center 

location assumes a site with silt and clay Quaternary flood plain and deltaic 

deposits.]

Time 

horizon,

10.....

50 .....

250.....

Location

Ede-e

Center 

. . Edge

Center 

. . Edge

Center

Method number

1

6.1 

8.9 

7.0 

10.1 

8.6 

11.7

2

5.6 

8.3 

6.7 

9.6 

8.0 

10.8

3

6.0

8.7 

7.4 

10.2 

8.3 

11.1

4

6.0 

8.4 

7.4 

10.0 

8.3 

10.8

5

5.4 

5.9 

7.3 

8.7 

9.0 

11.4

6

5.1 

6.4 

6.9 

7.8 

8.3 

9.5

values for rock at the valley edge and for soft clays at the 

valley center of VII + and X, for the 50-yr time horizon.

For method 4, we proceed as above except we replace 

Tinsley's relative ground-shaking factors with those provided by Rogers and others (1984) for surficial geologic 

units. Results derived by this method are about the same 

as in method 3.

The Krinitzsky option is used to develop methods 5 and 

6. For method 5, we begin with estimates of PHA on rock 

and PHA on soil and convert to MMI on rock and to MMI 

on soil using functions from Krinitzsky and Chang (1987). 

Intensities on sites with surficial deposits having densities somewhere between hard rock and soft soil can be 

estimated by interpolation between these two points. 

Rock and soft soil MMI values derived by this method 

are VII + and VIII+, respectively, over the 50-yr time 

horizon.

For method 6, we begin with PHA on rock and PHA on 

soil, convert to velocities, and then convert from PHV to 

MMI on rock and soil using Krinitzsky and Chang (1987). 

Rock and soft soil values derived by this method are VII 

and VIII, respectively over the 50-yr time horizon.

Results for the 10-, 50-, and 250-yr time horizons by 

generalized Salt Lake Valley location are given in figure 

37. Note that the valley edge location refers to bedrock 

sites with a site amplification ratio of 1.0, while valley 

center locations refer to sensitive soil sites with the 

highest site amplification ratio possible under each 

method.

EVALUATION OF ALTERNATIVE METHODS

Results from methods 1 through 4 have similar ranges. 

The range of results from methods 5 and 6 is notably 

narrower. In view of historical observations (Oaks, 1987) 

and instrumental measurements on various soils in the 

Jordan River Valley, methods 5 and 6 must be regarded 

as offering an unacceptably narrow range of results by 

location. Apparently, the use of simple PHA-to-MMI and 

PHV-to-MMI functions for rock and soft soils fails to

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VALLEY 

EDGE

VALLEY 

CENTER

SALT LAKE VALLEY LOCATION

VALLEY 

EDGE

VALLEY 

CENTER

SALT LAKE VALLEY LOCATION

VALLEY 

EDGE

VALLEY 

CENTER

EXPLANATION

-n- Method #1110

-»- Method #2110

-B- Method #3110

-o- Method #4110

-*- Method #5110

-G- Method #6110

EXPLANATION

-n- Method #1150

-»- Method #2150

-B- Method #3150

-o- Method #4150

-*- Method #5150

-G- Method #6150

EXPLANATION

-a- Method #11250

-»- Method #21250

-B- Method #31250

-o- Method #41250

-*- Method #51250

-G- Method #61250

SALT LAKE VALLEY LOCATION

FIGURE 37. A comparison of estimates of MMI with a 10 percent

chance of being exceeded over a 10-, a 50-, and a 250-yr exposure period

by valley location within Salt Lake County, Utah.

fully account for the range of site characteristics found 

locally. By averaging a broad range of ground-motion 

responses to two points on a broad spectrum of response 

and referring to each point respectively as "a rock 

response" and "a soil response," one destroys information and ignores differences that are notable at the 

geographic scale of this analysis. For these reasons, 

methods 5 and 6 are excluded from further consideration.
102 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Method 1 employs a direct conversion of acceleration 

to intensity. It has the simplest logic and, thus, appears 

least likely to propagate errors through extended chain 

models. However, method 1 relies on an estimate of the 

relationship between ground-motion amplification and 

MMI increments from Borcherdt and others (1979). 

Because of numerous intensity scale conversions (San 

Francisco to Rossi-Forell to MMI), this relationship is of 

questionable reliability.

Methods 2, 3, and 4 convert from velocity to MMI, and 

this procedure is preferred on theoretical grounds. However, method 2 yields uniformly lower estimates of 

intensities, while method 4 yields a somewhat smaller 

range of intensities by location. The choice is narrowed to 

methods 1 and 3. Results from method 1 tend to be 

higher, the method relies on a theoretically less preferred conversion from acceleration on rock directly to 

MMI on rock, and it uses a relationship between spectral 

amplification ratios and MMI increments that is of uncertain reliability. For these reasons, method 3 is preferred 

over method 1.

A VARIATION ON THE PREFERRED METHOD

Method 3 uses Tinsley's (1988) map of relative groundshaking factors. One difficulty in using the map is the 

manner in which the isopleth contours ignore differences 

in surficial geologic units known to influence site 

response. (Work in progress by Tinsley will correct this 

feature.) Rogers and others (1984) sought to address this 

issue by correlating three different surficial geologic 

units with site-response factors, although there is a loss 

both in range and in spatial resolution due to the small 

number of geologic units considered.

To resolve this problem, a schedule of six surficial 

geologic units is collapsed from a larger number of units 

represented on Davis's (1983) map compilation. Each of 

the six geologic units is assigned a spectral amplification 

factor (table 6). The reasonableness of the assigned 

amplification factors is confirmed through review of the 

literature, correlation with standard cone penetrometer 

test scores, and corroboration with geologists familiar 

with the problem (G. Christensen, D.R. Currey, and 

K.W. King, personal communs., 1988).

We then digitize these six units, digitize Tinsley's 

relative ground-shaking factors map, and use a geographic information system to create a composite map 

from the two underlying digital map planes, so that the 

polygons in the composite map have site-response scores 

that equal the square root of the product of the polygon 

scores from the two underlying map layers. This procedure results in a modified site-response surface that 

combines with equal weight the amplification factors 

associated with both Tinsley's isopleth contours and

Davis's surficial geologic units. The resulting map, which 

constructively combines information in the underlying 

map planes and offers a finer grained representation of 

site characteristics is used in method 3 in place of 

Tinsley's isopleth contours. The range and magnitude of 

results are the same, but the degree of spatial resolution 

is improved. (Methodological details are discussed in 

Appendix C.)

A MAPPING OF GROUND-SHAKING INTENSITIES

The central objective of this study is to create maps 

showing spatial variation in the ground-shaking intensities that have a 10 percent chance of being exceeded over 

a 10-, a 50-, and a 250-yr exposure period. The two digital 

map planes and the set of relationships used as inputs are 

maps of PHA by Young and others (1987), the composite 

site-response surface described above, and the relationships among PHA, PHV, site amplification, and MMI 

used in method 3. For each exposure period, we define a 

digital map plane in which MMI is a logarithmic function 

of the product of two input digital map planes, one 

defining spatial variation in PHA and the other defining 

spatial variation in relative site response. The result is a 

set of maps depicting spatial variation in MMI exceedence values for each of three time horizons (figs. 38.A-C).

Figure 38A shows MMI's that have a 10 percent 

chance of being exceeded in a 10-yr period. Refer to this 

map when addressing concerns about the internal contents of structures. Figure 385 shows the same informaTABLE &. A cross classification of surficial geologic units used by 

Davis (1983) and in this study with site amplification factors 

assigned by the author to each unit

Surficial geologic units

Davis (1983) This study

Amplification

factor

assigned to

each unit

Quaternary flood-plain and

delta complex ............ Fine clays and silts 8.0

Quaternary Lake Bonneville

plus Jordan River floodplain deposits............. Coarse clays and silts 5.6

Quaternary alluvium plus

active and abandoned

flood-plain deposits on

Jordan River tributaries... Fine sand and gravel 4.2 

Quaternary Bonneville and

Provo shore facies plus

Quaternary Bonneville

and Alpine complex ....... Coarse sand and gravel 3.2

Quaternary morraines and

tails..................... Rubble 2.0

Quaternary Hawkers

fanglomerate plus older

rocks ................... Rock 1.0
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 103

111° 45'00" 

 T 

Cartography by University of Utah. Geography Department, DIGIT Lab.

FIGURE 38A. A microzonation of MMI with a 10 percent chance of being exceeded over a 10-yr exposure period for the urbanizable area 

of Salt Lake County, Utah. These maps (figs. 38A-C) do not account for the effects of ground failure (liquefaction, slumps, slides, falls, 

flows, and fault rupture) or the focusing effects expected of a near-field event on the Salt Lake segment of the Wasatch fault.
104 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

B

Cartography by University of Utah, Geography Department, DIGIT Lab.

FIGURE S8B. A microzonation of MMI with a 10 percent chance of being exceeded over a 50-yr exposure period for the urbanizable area

of Salt Lake County, Utah.
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 105

MILES 0

Cartography by University of Utah. Geography Department, DIGIT Lab

FIGURE 38C. -A microzonation of MMI with a 10 percent chance of being exceeded over a 250-yr exposure period for the urbanizable area

of Salt Lake County, Utah.
106 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

tion for a 50-yr period. Refer to this map when addressing concerns about the structural integrity of ordinary 

buildings. Figure 38C shows the same information for a 

250-yr period. This is the reference map for addressing 

concerns about the structural integrity of lifelines, critical facilities, and structures containing hazardous materials.

Specific reservations must be noted about the use and 

interpretation of these maps. They refer only to the 

ground-shaking hazard as understood through an analysis of ground-motion amplification. They do not consider 

the near-field directivity effects recently noted by Benz 

and Smith (1989). They do not consider the induced 

effects of ground failures such as liquefaction, slumps, 

slides, flows, falls, and subsidence (Anderson and others, 

1986; Keaton, 1986; Case, 1987). They do not include the 

effects of fault rupture and surface displacement 

(McCalpin, 1987). The polygon boundaries drawn on 

these maps should be regarded as having a range of 

uncertainty extending over a few hundred meters.

In spite of these reservations, the maps do have useful 

applications. They can be used for regional loss estimations, regional calculation of insurance premiums, and in 

the overall design of earthquake emergency response 

systems. They can be used to help frame discussion of 

seismic retrofit policies and generalized land-use policies. 

They can be used to guide the general siting and design 

of lifelines, critical facilities, and large-capacity structures. They serve as a basis for the study of related 

geologic hazards activated by various intensities of 

ground shaking.

To improve this line of inquiry, further research needs 

to be done on several topics. Results need to be compared with those produced through the direct attenuation of intensity from source to site. Correlations of 

PSRV with the physical characteristics of surface and 

subsurface geology need to be detailed. Further study of 

directivity effects in the near field are needed to clarify 

the nature of this hazard. Critical intensities triggering 

liquefaction and other ground failure hazards in differentially sensitive soils need to be mapped. Also needed are 

loss estimations specific to building use and frame type 

based on a large-scale mapping of ground-shaking intensities and related ground-failure hazards (Emmi and 

Horton, 1991). The current study can serve, in part, as a 

basis from which to address these research and application needs.

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Evernden, J.F., Kohler, W.M., and Clow, G.D., 1981, Seismic intensities of earthquakes of conterminous United States Their 

prediction and interpretation: U.S. Geological Survey Professional 

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Hays, W.W., Algermissen, S.T., Miller, R.D., and King, K.W., 1978, 

Preliminary ground response maps for the Salt Lake City area: 

Proceedings of the 2nd International Conference on Microzonation, 

San Francisco, v. 2. p. 487-508.

Hooper, M.G., 1988, Isoseismals of some historical earthquakes affecting the Wasatch Front area, Utah, in Gori, P.L., and Hays, W.W., 

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the Wasatch Front, Utah: U.S. Geological Survey Open-File 

Report 88-680, v. 3, p. Y-l-28.

Joyner, W.B., and Fumal, T.E., 1985, Predictive mapping of earthquake ground motion, in Ziony, J.I., ed., Evaluating earthquake 

hazards in the Los Angeles region: U.S. Geological Survey Professional Paper 1360, p. 203-220.

Keaton, J.R., 1986, Evaluation of potential consequences of earthquake 

induced tectonic subsidence along the Wasatch Front, northcentral, Utah: Salt Lake City, Utah, Dames and Moore, p. 52.

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response in Salt Lake City and areas of Springville-Spanish Fork, 

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A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 109

APPENDIX A. ABBREVIATED DESCRIPTION OF 

THE MODIFIED MERCALLI INTENSITY SCALE

I. Not felt but by a very few under especially 

favorable conditions.

II. Only felt by a few persons at rest, especially on 

upper floors of buildings.

III. Felt noticeably by persons indoors, especially on 

upper floors of buildings. Many people do not 

recognize it as an earthquake. Standing cars may 

rock slightly. Vibration similar to the passing of a 

truck. Duration can be estimated.

IV. Felt indoors by many and outdoors by a few. At 

night, some are awakened. Dishes, windows, and 

doors are disturbed. Walls make cracking sound. 

Standings cars rock noticeably.

V. Felt indoors by practically all. Many are awakened. A few run outdoors. Some dishes are broken. Small or unstable objects overturn.

VI. Felt by all, indoors and out. Many are frightened, 

many run outdoors. Persons made to move 

unsteadily. Dishes and glassware are broken in 

considerable quantity. Some heavy furniture is 

moved. Some plaster may fall.

VII. All are frightened and run outdoors. Many find it 

difficult to stand. Sand and gravel stream beds 

cave in. Damage negligible in buildings of good 

design and construction; slight to moderate in 

well-built ordinary structures; considerable in 

poorly built or badly designed structures. Some 

chimneys are broken. Fall of plaster is considerable to large amounts. Loose brickwork and tiles 

are shaken down. Weak chimneys are broken at 

the roof line. Cornices fall. Heavy furniture is 

overturned and damaged.

VIII. General fright. Alarm approaches panic. Sand and 

mud are ejected in small amounts. Damage slight 

in specially designed structures; considerable 

damage in ordinary substantial buildings, with

partial collapse. Panel walls are thrown out in 

frame structures. Damage is great in poorly built 

structures. Chimneys, factory stacks, columns, 

monuments, and walls twist and fall. Very heavy 

furniture is moved and overturned.

IX. General panic. Ground cracks conspicuously. 

Damage considerable in masonry structures; welldesigned frame structures are thrown out of 

plumb. Damage is great in substantial buildings, 

which may partially collapse. Frame buildings are 

shifted off their foundations. Underground pipes 

are broken. Reservoirs are compromised.

X. Cracked ground, especially when loose and wet: 

yard-wide fissures run parallel to canal and 

stream banks. Landslides are considerable. Sands 

and mud shift horizontally on flat land. Some 

well-built wooden structures are destroyed. Most 

masonry and frame structures are destroyed as 

well as their foundations. Buried pipelines are 

torn apart or crushed end-wise. Open cracks and 

wavy folds in cement pavement and asphalt roads.

XI. Ground disturbances are many and widespread, 

including fissures, slumps, and slides. Water 

charged with sand and mud is ejected in large 

amounts. Seiches and tsunamis of significant magnitude occur. Damage is great to dams, dikes, and 

embankments, and to wood frame structures. 

Few if any masonry structures remain standing. 

Bridges are destroyed by the wrecking of supporting piers and pillars. Rails are bent greatly. 

Buried pipelines are put completely out of service.

XII. Damage is practically total. Moving waves are 

actually seen on the ground surface. Objects are 

thrown into the air.

Figures 39 and 40 depict expected damage to common 

structures as a function of MMI. These figures are based 

on data from the Applied Technology Council (Rojahn, 

1985).
110

80

C/)60 

O

40

O

IO 

oc

LU on Q_ 20

ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

80

EXPLANATION 

Wood

-4 Unreinforced masonry

- Reinforced masonry 

H Steel high-rise

-D Precast concrete

VII VIII IX X

MODIFIED MERCALLI INTENSITY

XI

FIGURE 39. Estimated loss to selected structures as a function of 

MMI based on relationships given by Rojahn (1985).

C/)60 

O

D _i

>

_40 

O

H-z.

LU 

O 

OC

£20

EXPLANATION

A

 0 

 Elect towers

VII VIII IX X XI 

MODIFIED MERCALLI INTENSITY

FIGURE 40. Estimated loss to selected lifelines as a function of MMI 

based on relationships given by Rojahn (1985).
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 111

APPENDIX B. THE INTERPRETATION OF 

TECHNICAL STATEMENTS OF RISK

Risk is defined as the chance of injury, damage, or 

loss. Technical statements of risk try to specify the 

degree of risk per unit of time. Risky events that are 

dichotomous (either happen or not) are easy to quantify 

by simply stating the probability of their occurrence 

during some relevant time period. However, most risky 

events vary in severity or intensity and, therefore, 

efforts to quantify such risk must deal simultaneously 

with three aspects of risk probability, exposure time, 

and intensity.

First is a measure of the intensity with which a 

hazardous event can occur. In the present context, a 

measure of ground-shaking intensity, the MMI is used. 

Second is a time horizon over which exposure is considered. Here, three time horizons, a 10-yr, a 50-yr, and a 

250-yr time period, are used. Third is a critical probability at which one wants to know, for each exposure 

period, the intensity of hazardous events to expect. Here 

the 10 percent probability level is used as the critical 

level. In this way, a specific degree of danger can be 

taken into account for certain kinds of design and siting 

decisions. For example, knowing that there is a 10 

percent chance of MMI>VIII+ over a 250-yr period 

would have important design implications were the University of Utah to propose installing a class IV biological 

laboratory capable of producing pathological organisms 

for which no cure is known.

For purposes of exposition, we try to reduce statements of risk to simple numbers. Clearly, hazardous 

events that vary in intensity are not adequately 

described by a single number. A curve or a functional 

equation needs to be used to specify the degree of risk. In 

fact, representing the risk of hazardous events requires 

a family of curves or functional equations.

Figure 41 presents this concept graphically. Earthquake ground shaking is classified into ranges of low, 

medium, and high intensity. The risk of low-intensity 

ground shaking is described by a curve that shows high 

probabilities of this low-intensity level being exceeded 

over various exposure periods. The curve intersects a 

horizontal line marking the 10 percent exceedence probability at the 10-yr time horizon and indicates, thereby, a 

10 percent chance of a low-intensity of ground shaking 

being exceeded over any 10-yr exposure period. But the 

curve for low-intensity ground shaking arcs upward 

rapidly to define higher exceedence probabilities over 

longer exposure periods. For example, it shows a very 

high (92 percent) chance of a low level of ground-shaking 

intensity being exceeded over a 250-yr exposure time.

The curve for medium-intensity ground shaking intersects the 10 percent exceedence probability line at the 

50-yr exposure period. It, too, arcs upward, though less

o 10 50 100 150 200 250 300

TIME, IN YEARS

EXPLANATION

-d Low-Probability, High-Intensity Events

- Medium-Probability, Medium-Intensity Events

-O- High-Probability, Low-Intensity Events

FIGURE 41. Functions describing the probabilities with which events 

of different intensity might occur over various exposure periods.

rapidly, to define higher exceedence probabilities over 

longer exposure periods. Someone concerned with the 

design of a structure expected to last 100 yr could 

determine from this curve that the structure has about a 

1 in 5 chance of being subject to at least an intermediate 

level of ground shaking. If, with standard design, the 

structure could not withstand such an event, then earthquake insurance over the useful life of the structure 

should cost at least one-fifth the structure's value. If, 

with proper design and limited expense, the structure 

can be made to withstand such an event, one would then 

be advised to adopt such designs in lieu of bearing the 

risk or carrying earthquake insurance.

The curve for high-intensity ground shaking intersects 

the 10 percent probability line at the 250-yr time horizon. 

The probability of high-intensity ground shaking over a 

100-yr time horizon is about 4 percent. Thus, only one out 

of every twenty-five 100-yr time periods is likely to have 

high-intensity ground shaking. The possibility should be 

kept in mind only when considering a limited class of 

important or hazardous structures.

Making comprehensible statements about seismic risk 

in the Salt Lake County, Utah, is made even more 

difficult because of the wide range of ground-shaking 

intensities to which the county is exposed during each of 

the three exposure periods. Figures 38A-C indicate that 

the ground-shaking intensities included in the three 

intensity classes broadly overlap. Structures on seismically sensitive soils can be subject to high intensities of 

ground shaking with intermediate levels of probability 

and subject to intermediate levels of ground shaking with 

high probability. In addition to severity, time horizon, 

and exceedence probability, the further aspect of site 

conditions, which vary considerably by location, must 

also be considered.
112 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

APPENDIX C. USE OF COMPUTER MAPPING 

AND CIS METHODOLOGIES

All GIS operations are done on a PC/AT compatible 

with a raster-based software package by Earth Resources Data Analysis System (ERDAS). Tabular data input 

is through tape and floppy disk drives, while mapped 

data input is through an E-size digitizing table. Mapped 

output is through a color dot-matrix printer or through 

photographs of a VGA standard color monitor.

A base map is digitized from a USGS intermediatescale (1:100,000) topographic map of Salt Lake County, 

Utah, with both Universal Transverse Mercador zone 12 

and Utah State plane coordinate ticks. The study area 

includes the central valley of Salt Lake County suitable 

for contiguous urbanization. This area is bounded on the 

north by the Davis County boundary, on the east by the 

Wasatch National Forest boundary, on the south by the 

Utah County boundary, and on the west by the boundaries of census tracts that intersect the increasingly 

steep slopes approximately marked by the 6,000-ft topographic contour. Freeways, highways, and major surface roads are added to provide informal locational 

reference. In digital form, the base map contains more 

than 260,000 picture elements (pixels). Each pixel represents approximately 80 by 100 m, or about half of an acre.

Maps published by Young and others (1987) with PHA 

values having a 10 percent chance of being exceeded over 

a 10-yr, a 50-yr, and a 250-yr period are photographically 

enlarged, transferred to the base map using a reflecting 

projector, and digitized. Full 1:100,000 scale spectral 

amplification maps from Tinsley (1988) are digitized at 

scale, as are the relevant geologic units interpreted from 

Davis's (1983) map compilation.

In digital form, Tinsley's spectral amplification ratios 

are used as our first digital map plane. Amplification

ratios assigned to selected surficial geologic units from 

Davis's compilation are used as our second digital map 

plane. These two map planes are combined to create a 

composite site-response surface. A program written in 

Pascal language reads the first pixel from the first digital 

map plane and the first pixel from the second digital map 

plane and computes a value for the first pixel of a third 

digital map plane as the square root of the product of the 

prior two pixel values. The program writes the new 

value as the first pixel of a composite site-response map 

and then repeats the cycle for all successive pixels. In 

this manner, a composite site-response surface is built up 

as an algebraic function of the two underlying map planes 

(fig. 42).

The composite site-response surface is then used in 

conjunction with each of three digital maps on PHA on 

rock. PHA on rock with a 10 percent chance of being 

exceeded in a 10-yr period is used as the first map plane. 

The composite site-response surface is used as the second 

map plane. Functional relationships between PHA on 

rock, site amplification, and MMI as specified in the 

previous description of method 3 are collapsed into a 

single functional equation. This equation has PHA on 

rock and composite amplification ratios as independent 

variables and MMI as the dependent variable. A second 

Pascal language program uses this equation to compute 

MMI values with a 10 percent chance of being exceeded 

over a 10-yr period for each pixel on a third map plane. 

The process is repeated to create maps showing MMI 

values with a 10 percent chance of being exceeded over a 

50-yr and a 250-yr period.

Maps of MMI exceedence values are put out to a color 

dot-matrix printer at 1:100,000 scale. Maps shown in 

figures 38A-C are reductions prepared from these larger 

scale maps by cartographer Steven Thomas of the University of Utah, Department of Geography, DIGIT Lab.
A MAPPING OF GROUND-SHAKING INTENSITIES, SALT LAKE COUNTY 113

Layer A

Spectral

Amplification

Ratios

Layer B

Amplification 

Factors for 

Surface 

Geologic 

Units

Composite

Site-Response

Surface

FIGURE 42. An illustration of a graphic overlay technique using a geographic information system to combine Tinsley's 

(1988) spectral amplification ratios (layer A) with the spectral amplification ratios assigned by the author to surficial 

geologic units from Davis's (1983) map compilation (layer B) to create a composite site-response surface Gayer C) as the 

square root of the product of the scores from layers A and B.
WASATCH FRONT COUNTY HAZARDS GEOLOGIST PROGRAM

By GARY E. CnRiSTENSON9

ABSTRACT

The Wasatch Front County Hazards Geologist Program was initiated 

and conducted by the Utah Geological Survey (UGS) with funding from 

the U.S. Geological Survey under the National Earthquake Hazards 

Reduction Program (NEHRP). The purpose of the program was to 

reduce hazards by aiding in the use of geologic information, particularly 

earthquake hazards information produced under the NEHRP. The 

rationale behind the program was that local governments have the 

responsibility to regulate land use and that geologic information and 

expertise would be most effective in reducing hazards if provided at the 

city and county level. Three geologists were placed in five Wasatch 

Front counties (Weber-Davis, Salt Lake, and Utah-Juab Counties) for 

a term of 3 years beginning in June 1985. The geologists were a part 

of the county's planning department staff but were available to other 

departments and to cities for educational, advisory, and review 

services.

The principal duties of the geologists were to (1) produce geologic 

hazards maps, (2) assist in writing geologic hazards ordinances, (3) 

review engineering geologic reports, and (4) provide other technical 

services as needed. Hazards maps were produced for inclusion in 

ordinances that require site investigations prior to development in 

hazard areas. Site investigation reports are reviewed and approved by 

the county geologist prior to issuance of building permits. The work of 

the geologists was coordinated by the UGS, which also provided 

support and technical supervision. At the end of the program in June 

1988, counties were in various stages of completing mapping and 

adopting ordinances; all three of the county geologists were retained 

and funded by the counties. The program has demonstrated the value 

of a staff geologist in populated, highly developed counties in highhazard areas such as the Wasatch Front.

INTRODUCTION

Geologic hazards play a significant role in life along the 

Wasatch Front and have caused hundreds of millions of 

dollars in property damage and at least one fatality since 

1982. The Wasatch Front is particularly vulnerable 

because of the variety of hazards and the concentration of 

population in the area. Although a number of techniques 

are available to reduce geologic hazards, one of the most 

effective is proper long-range land-use planning based on 

an assessment of the hazards and their potential impacts. 

However, planning with respect to geologic hazards

Utah Geological Survey, Salt Lake City, Utah.

along the Wasatch Front has been difficult because of a 

lack of hazards information, particularly in the form of 

translated hazards maps at suitable scales, and lack of an 

effective way to aid planners in incorporating this information into the planning process.

Because of the general lack of necessary hazards 

information and maps on which to base planning decisions, land use has progressed in may areas without 

proper consideration of hazards and the risks they 

present. Some of the damage incurred in wet years in the 

early 1980's, for example, could have been avoided 

through proper land use with respect to the rise of Great 

Salt Lake, stream flooding, debris flows, and landslides. 

Although damage was extensive, that which will result 

from a large earthquake along the Wasatch Front is 

much greater and can be significantly reduced by wise 

land-use practices.

The Utah Geological Survey (UGS) has long advocated 

the consideration of geologic hazards in planning. It has 

been available to local governments to provide hazards 

information and review engineering geologic reports, but 

these services have not been fully used. The UGS has no 

regulatory authority to implement recommendations 

made in report reviews. Therefore, effective influence on 

land use can best be accomplished by geologists in local 

governments, where decisions are made and enforced.

Geologists at the local level can become involved in 

projects early on and can follow the process further. The 

purpose of the Wasatch Front County Hazards Geologist 

Program was to provide geologic expertise at the local 

government level in order to better use geologic hazards 

information to reduce casualties and damage. The scope 

of work of the county geologists was to (1) compile 

geologic hazards information and produce maps to delineate hazards areas, (2) advise planners regarding hazards ordinances, (3) review engineering geologic reports, 

and (4) provide geologic expertise as required, including 

performing site investigations for critical public facilities 

and investigating hazardous geologic events. Emphasis 

of the program was on geologic hazards, and the geologists did not perform other services typically provided by

114
WASATCH FRONT COUNTY HAZARDS GEOLOGIST PROGRAM 115

a county geologist, such as resource evaluations or waste 

disposal siting, except when specifically requested.

ACKNOWLEDGMENTS

The idea that county geologists would be one of the 

most effective ways to implement geologic hazards information and loss reduction along the Wasatch Front was 

first proposed by William R. Lund (UGS). Genevieve 

Atwood (former Director, UGS) and Don R. Mabey 

(former Deputy Director, UGS) solicited support from 

the counties and provided for the administration of the 

program. Planning department directors Graham Shirra 

(Weber County), Rick Mayfield (Davis County), Jerold 

Barnes (Salt Lake County), and Jeff Mendenhall (Utah 

County) and Juab County Commissioner Thomas 

Fowkes ensured that the program worked and convinced 

their planning commissions and county commissions to 

support it. Particular thanks go to Graham Shirra and 

Jeff Mendenhall for taking key responsibility for payroll 

and administration for geologists serving Davis and Juab 

Counties, respectively. Principal credit for the success of 

the program goes to the county geologists Mike Lowe, 

Craig V. Nelson, and Robert M. Robison whose diligence and dedication demonstrated to the counties the 

value of a staff geologist and the need to consider 

geologic hazards in development.

Walter W. Hays and William J. Kockelman of the U.S. 

Geological Survey (USGS) provided information and 

reviewed work products. Michael Machette, Alan Nelson, and Steve Personius (USGS) provided advance 

copies of fault maps and, along with David P. Schwartz 

(USGS), have lent support in report reviews and trench 

investigations. During data collection phases of the 

project, information was obtained from State and Federal agencies and private consultants too numerous to 

list. Don Mabey, Mike Lowe, Craig Nelson, Robert 

Robison, and Bill Kockelman all reviewed this paper.

DESCRIPTION OF THE PROGRAM

To provide geologic expertise to local governments, 

several options are available (1) a permanent, full-time 

city or county geologist, (2) a circuit-rider geologist 

serving several governments simultaneously (Thorsen, 

1981), (3) a geologist employed by an umbrella agency 

(regional association of governments, State survey) but 

dedicated to serve local governments, or (4) a private 

consulting geologist on retainer or otherwise under contract with local government. Any one option may be 

appropriate, depending on population served, development pressure, extent of hazards, and other needs for 

geologic expertise. Option 1 is most appropriate where a

need exists for a full-time geologist, as is the case for 

some counties in the Wasatch Front area.

The UGS received USGS funding under the National 

Earthquake Hazards Reduction Program (NEHRP) to 

place three geologists in Wasatch Front counties for a 

3-yr pilot program. To set up the program, UGS met 

with the county commissioners and planning department 

directors of the most populous counties and solicited 

support and advice from regional associations of governments (Wasatch Front Regional Council) and county 

councils of governments (composed of all mayors of cities 

in the county and representatives of the county commission). Based on these discussions, it was decided that the 

three geologists should cover five Wasatch Front counties (Weber, Davis, Salt Lake, Utah, and Juab) (fig. 43).

These geologists were to be placed in one of the county 

planning departments under the direct supervision of the 

planning director; the UGS would provide technical 

supervision and other support, as needed. One geologist 

(Mike Lowe) covered both Weber and Davis Counties, 

maintaining an office in each county and dividing his time 

evenly. Another geologist (Robert M. Robison) covered 

both Utah and eastern Juab Counties, maintaining a 

permanent office in Utah County and making periodic 

visits to Juab County, as needed. The third geologist 

(Craig V. Nelson) covered Salt Lake County. The geologists were hired through the county personnel departments. The UGS assisted in evaluating resumes and 

participated in interviewing and selecting candidates. 

The three geologists selected had similar backgrounds, 

consisting of bachelor's degrees in geology and master's 

degrees or work experience in engineering geology. 

Because the positions were temporary, geologists were 

hired as contractors rather than merit employees, 

although they received the county fringe benefits.

The program was broken into three 1-yr phases. The 

first year consisted chiefly of data collection and literature research, as in-house geologic libraries were established in each county. During the second year, this 

information was compiled to produce basic data maps 

needed to derive hazard maps. During the third year, 

hazard map compilation was begun, and explanatory 

"translated" texts were developed that clearly explained 

the hazards and gave recommendations on how to 

address each of them in planning.

Technical supervision by the UGS included monthly or 

semimonthly meetings to discuss issues, encourage cooperative efforts, and provide a uniform approach. All 

reports, report reviews, and other products prepared by 

the county geologists were reviewed by the UGS. The 

county geologists were included in UGS activities, and 

information was freely exchanged. Quarterly meetings 

were also held between Davis and Weber Counties 

regarding the work of the geologist that they shared.
116 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

42'

EXPLANATION

Areas included in program 

Areas covered by hazards maps

41

WASATCH i \DUCHESNE

si Ql

j ^___

h 

37°LL____________1J_________

25 50 75 KILOMETERS 

FIGURE 43. Location map.
WASATCH FRONT COUNTY HAZARDS GEOLOGIST PROGRAM 117

The UGS provided a geologist for technical supervision 

on the program; many other staff members also contributed.

ACCOMPLISHMENTS

DATA COLLECTION

A principal goal during initial work was to identify 

and, if possible, collect library copies of all existing 

engineering geologic information. Published literature 

was relatively easily identified and collected, but unpublished literature in the files of government agencies and 

private consultants was not. All agencies and companies 

likely to possess information were contacted; information 

was collected to the extent possible, and, where not 

possible, its existence was noted for future reference. All 

references were indexed into a subject card catalog and 

organized into an easily accessible library in each county 

planning department.

A series of index maps showing locations of studies 

was compiled. For site investigations, locations were 

plotted on 1:24,000 scale topographic quadrangles. More 

regional studies were plotted on four smaller scale countywide maps at scales of 1:100,000 or larger, showing 

general geology, soil, landslide, and earthquake references. This information will be incorporated into the UGS 

statewide computerized hazards bibliography.

HAZARDS MAPPING

The principal goal of the final two phases of the 

program was to produce countywide hazards maps for 

use in planning. These maps, at 1:24,000 scale, covered 

the urbanizing parts of the counties in valley floors and 

extended up to the crest of the Wasatch Range (fig. 43). 

Thus, eastern Weber County (Ogden Valley), Cedar 

Valley, eastern Utah County, and western Juab County 

were not included in the mapping.

The county geologists prepared surface-fault-rupture, 

landslide, debris-flow, and rock-fall hazards maps. Some 

of the needed maps had already been prepared under the 

NEHRP, and these were evaluated and recommended 

for adoption as official county maps where appropriate. 

These maps include liquefaction potential, seismic slope 

stability (Salt Lake and Davis Counties), shallow ground 

water, tectonic subsidence, and dam failure inundation 

maps.

The purpose of the maps is to show hazard areas where 

detailed site investigations need to be performed prior to 

development. Texts were prepared to accompany each 

map to explain the hazard, including its location, approximate recurrence time (where appropriate), and consequences. A discussion of possible engineering and site

design techniques for mitigation was included, as well as 

guidelines for the types of information that should be 

included in site investigation reports. Copies of maps and 

explanatory texts were distributed to each municipality 

for use in urban planning and are also available for 

consultants, developers, and the general public. Both 

maps and texts will be updated continuously as new 

information becomes available. Examples of these products are included in this volume.

ORDINANCES AND REPORT REVIEWS

Another goal of the program was to assist local government planners in using hazards maps and information 

to reduce casualties and damage. Emphasis was on 

developing and improving hazard reduction ordinances. 

The general approach recommended in such ordinances 

is outlined in UGS Circular 79 (Christenson, 1987). Essentially, engineering-geologic site-investigation reports are 

required in hazard areas (delineated on generalized hazards maps) prior to development, with approval of the 

permit dependent on a favorable review of the report by 

a geologist acting on behalf of the local government. The 

Salt Lake and Utah County Planning Departments have 

adopted geologic hazards ordinances that follow this 

approach closely and are being used by various Wasatch 

Front cities and counties as models. The City of Washington Terrace in Weber County has also adopted a 

sensitive-areas ordinance addressing geologic hazards 

using this approach.

Many of the larger cities in all counties have already 

adopted ordinances addressing geologic hazards, and the 

county geologists aided their administration by providing needed geologic expertise in identifying hazard areas 

and reviewing engineering-geologic reports. Completion 

of an engineering-geologic report for a site does not 

necessarily mean that hazards affecting the site will be 

avoided or mitigated. Engineering-geologic reports 

reviewed by the county geologists are commonly inadequate when initially submitted and must be revised and 

amended before they are acceptable (Nelson and others, 

1987). Prior to the county hazards geologist program, 

engineering-geologic reports were occasionally reviewed 

by UGS when requested. The reviews were not done on 

a regular basis and had little effect on the overall quality 

of reports. Now that reports are reviewed regularly and 

returned for additional work when inadequate, a noticeable improvement in report quality has occurred.

SITE INVESTIGATIONS

The siting and construction of public waste-disposal 

facilities (landfills, incinerators) and critical facilities (fire
118 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

stations, municipal buildings, water tanks and waterstorage reservoirs) is another important function of local 

governments. Waste-disposal facilities must be sited to 

avoid contamination of the environment. Critical facilities must continue to operate or be quickly returned to 

service after an event such as a damaging earthquake. 

Therefore, it is important to consider geologic hazards in 

siting. The county geologists performed detailed site 

investigations for both types of facilities, as well as field 

investigations after damaging geologic events. These 

studies generally include a field reconnaissance, literature review, air photo interpretation, and in some cases, 

subsurface investigation. A report addressing the geologic hazards at the site is used by local governments in 

planning and making decisions. The UGS has compiled a 

volume containing all of the site investigation reports 

written during the contract period (see Black and Christenson, 1988).

Many types of site investigations have been performed 

for a variety of agencies. County flood-control and emergency management agencies have requested aid in 

responding to hazardous geologic events and in assessing 

hazards potential, particularly flooding and landsliding. 

Health departments have requested on-site investigations to evaluate potential soil and ground-water problems as they relate to septic-tank systems. The county 

engineer's office has asked for reviews of sites for 

bridges and help in reducing hazards that may affect 

county roads and other public facilities. Building officials 

have requested assistance in inspecting excavations for 

evidence of faulting or ground failure, evaluating unstable slopes, and recommending hazard-reduction techniques. Workshops and field trips highlighting geologic 

hazards for building officials have also been conducted. 

Building inspectors have become principal users of geologic services. Various cities and counties have used the 

county geologist to evaluate geologic hazards affecting 

proposed or existing public facilities such as waterstorage tanks. The county geologist aided Davis County 

in evaluating the gravel resource potential and the best 

use of its property on the Salt Lake Salient and in 

evaluating geologic hazards affecting the North Davis 

Refuse Disposal and new burn-plant sites.

OTHER SERVICES

An important service is also provided to the public by 

the county geologist. Prospective real estate buyers 

seeking hazards information often visit the planning 

office, where hazards maps, geologic and emergency 

preparedness literature, and geologic advice are available. Community awareness about geologic hazards has 

also been increased through a slide-lecture program the

geologists presented to community councils, civic 

groups, and local government organizations.

The county geologists also assist in other hazards 

projects. In Salt Lake County, West Valley City is 

completing a study involving a computerized compilation 

of seismic hazards data for use in municipal planning. 

Researchers from the University of Utah Geography 

Department are integrating seismic hazards data into a 

computer-based geographical information system for use 

in seismic risk assessment and loss estimation throughout Salt Lake County. Also in Salt Lake County, the 

geologist is advising Utah State University researchers 

in a project to poll public officials and private citizens 

regarding their perceptions of earthquake hazards and 

government responsibilities.

The Utah State Division of Comprehensive Emergency Management and Utah County initiated a comprehensive hazards mitigation project in the Provo-Orem 

area to aid emergency response personnel and planners. 

This project included geologic hazards map compilation 

and interpretation by the county geologist, UGS, and 

other agencies (Robison and others, 1987). Copies of the 

project maps are housed with the county geologist for 

dissemination and updating.

TIME AND TASK BREAKDOWN

The relative percentage of time spent on various tasks 

by each geologist (from June 1985 to March 1988) is 

shown in table 7. These percentages are calculated after 

removing time spent for leave and professional activities. 

The category "UGS coordination" includes biweekly 

meetings, preparation of time records, and writing of 

articles for UGS publications such as Survey Notes and 

the Wasatch Front Forum. "Aid to cities" and "aid to 

counties" include activities that were specifically 

requested, such as aid in writing ordinances, review of 

engineering geologic reports, and site investigations. 

Nearly all such requests were honored in an attempt to 

demonstrate the need for a county geologist and the 

varied applications of geology to government functions.

TABLE 7. Percentage of time spent on various tasks by the county 

geologists

Task Weber/Davis Salt Lake Utah/Juab

UGS coordination .........

County administration .... 

Data collection ............

Aid to cities ..............

Aid to counties ...........

Hazards mapping .........

Public education ..........

(inquiries, lectures)

7

7 

28

12

31

13

2

7

11 

29

7

20

21

5

9

9 

35

3

23

20

1
WASATCH FRONT COUNTY HAZARDS GEOLOGIST PROGRAM 119

Time spent in each activity varied from county to 

county, as did the types of jobs. This variation was due, 

in part, to the different relationships between each 

county planning department and the cities in the county 

and, in part, to the county's approach to development in 

unincorporated areas. For example, in Davis and Utah 

Counties, no services are provided to unincorporated 

areas, so development is in large part restricted to 

incorporated cities, which provide water, sewer, and 

other services. In general, an area must be annexed by a 

city before development can occur, so geologic hazards 

information is used both by the cities and county to 

evaluate incorporation plans. In contrast, considerable 

development occurs in unincorporated Salt Lake and 

Weber Counties because public services are provided; 

therefore geologic services are of particular interest to 

the county as well as cities in planning for development. 

Most of the larger cities in the five counties maintain 

their own planning departments, while the smaller cities 

generally contract with the county for planning services. 

Under the county geologist program, the geologists 

provided services to larger cities as well. Ogden, Layton, 

and Salt Lake City in particular used the geologist to 

review reports. As is apparent from table 7, Weber and 

Davis Counties made considerably more use of the 

county geologist's services for special projects than did 

Salt Lake, Utah, or Juab Counties.

EVALUATION AND SUGGESTIONS

The need for geologic services at the local government 

level has now been demonstrated in many areas, but 

initiation of a program to provide these services still 

requires that local government officials be made aware 

that they exist and be convinced that they are needed. 

Thus the need and usefulness must be demonstrated. In 

attempting to establish a county geologist position, initial 

funding from outside sources is a very effective and 

perhaps necessary first step. It is unlikely that counties 

could have been convinced to fund a geologist without 

such a demonstration program. The program also helped 

to determine the need for and best way to provide the 

services.

One aspect that contributed to the success of the 

program was the placement of the geologist in the 

planning department. Because the program was directed 

at geologic hazards and the protection of life and property through planning, it was most effective to make the 

geologists part of the review and permit process for all 

new development, which is principally a planning function. In the initial plan review, the geologist (or administrator using maps prepared by the geologist) needs to 

identify the geologic hazards that exist and must be 

addressed in site-investigation reports. In final review,

the geologist must approve these reports prior to granting permits (Nelson and others, 1987). Other departments in which the geologist may be placed include 

engineering, health, flood control, building inspection, or 

a separate and independent office of the county geologist. 

These departments are perhaps a logical place for a 

county geologist in areas where waste disposal is a major 

problem, large public works projects are under way, or 

geologic services other than hazards are emphasized. 

Planning departments are preferred because of their 

more active role in long-range planning as opposed to 

short-term problem solving. A separate office of the 

county geologist may be the most effective means of 

getting geologic services to all departments, but the 

geologist is then left without an affiliation and requires 

development of a network of contacts and considerable 

effort in making services known and seeing that they are 

used. With an introductory program such as this, an 

unaffiliated geologist may be more vulnerable to budget 

cuts than one who is a part of an existing department.

The close association between the county geologists 

and the UGS was important to the success of the 

program both in maintaining consistency of approach 

from county to county and in providing technical support. 

One concern of planning directors and the regional 

association of government personnel was that ordinances 

and approaches to geologic hazards be consistent among 

jurisdictions along the Wasatch Front; the UGS facilitated this uniformity of approach. Local governments 

employ few scientists, and maintaining state-of-the-art 

expertise is difficult. Contact with other geologists is 

necessary, and the UGS staff worked with the county 

geologists on may occasions to foster the exchange of 

new ideas, information, and technology. On occasion, 

county geologists make recommendations that may 

be unpopular with local government officials; strong 

technical support from a State agency enhances their 

credibility.

One difficulty in administering the program was in the 

counties where geologists were shared. Under outside 

funding, one county took responsibility for handling the 

salary pass-through, and a memorandum of agreement 

and contract were written and signed by both counties 

outlining how the time was to be divided. This worked 

well during the period of outside funding, but when the 

counties took over funding, it became difficult to arrange 

for the geologist to be a merit employee of two different 

counties. Such a shared arrangement is better handled 

through a contract, circuit-rider program, or umbrella 

agency.

CONCLUSIONS

The principal goal of the project was to demonstrate 

the usefulness of geologic expertise at the local govern-
120 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

ment level such that the counties would retain the 

geologists with county funding when the outside funding 

expired. This goal was achieved in three of the five 

counties. Salt Lake, Utah, and Davis Counties all hired 

the geologists as permanent merit employees on their 

planning department staffs. Weber County worked out a 

funding plan to continue the project for another year 

under the same shared program with Davis County, but 

Weber County's contribution was entirely from outside 

sources, i.e., there was no contribution from the county, 

and all indications were that Weber County would not 

continue the funding after 1989. The Weber County plan 

also required continuation of contract rather than merit 

employment. Davis County offered a full-time staff position, so it was decided that the geologist should stay with 

Davis County. Juab County is sparsely populated, has no 

permanent planning department, and was not able to 

justify having a geologist on its staff.

Little has changed in terms of the goals and administration now that counties are funding the county geologists. Most counties still provide services to cities, 

although Salt Lake County has worked out a fee schedule 

to charge cities for time spent reviewing reports. UGS 

continues to provide technical supervision but plays a 

less active role. Maps by the county geologists will be 

used by UGS in compiling statewide hazards maps, and 

data collected by the geologists is being incorporated in 

the UGS computerized hazards bibliography.

The program has done much to advance local government awareness and concern with regard to geologic 

hazards, particularly earthquake hazards, along the 

Wasatch Front. Planning departments now routinely 

require site-specific reports in hazard areas, and the 

systematic review of those reports by county geologists

has improved their quality. The program is a very 

important part of both the UGS and the USGS efforts to 

translate and transfer geologic hazards information to 

users. The program, originally conceived as an experiment to demonstrate that a geologist at the local government level could be effective in carrying out these goals, 

has been a success. Much progress has been made in the 

production of "translated" hazards information usable by 

planners and others and in transferring this information 

to users. The development and adoption of effective 

geologic hazards ordinances to protect people and reduce 

property damage are just one example of this success.

REFERENCES

Black, B.D., and Christenson, G.E., compilers, 1988, Technical reports 

of the Wasatch Front county geologists, June 1985^June 1988: 

Utah Geological and Mineral Survey Report of Investigation 218, 

154 p.

Christenson, G.E., 1987, Suggested approach to geologic hazards 

ordinances in Utah: Utah Geological and Mineral Survey Circular 

79, 16 p.

Nelson, C.V., Christenson, G.E., Lowe, Mike, and Robison, R.M., 

1987, The review process and adequacy of engineering geologic 

reports, Wasatch Front, Utah, in McCalpin, James, ed., Proceedings of the 23rd annual symposium on engineering geology and 

soils engineering: Utah State University, Logan, Utah, p. 83-85.

Robison, R.M., Christenson, G.E., Knight, R.V., Dewsnup, Wes, and 

Johnson, Mike, 1987, Earthquake and slope failure hazards, Utah 

County Comprehensive Hazard Mitigation Project, Utah, in 

McCalpin, James, ed., Proceedings of the 23rd annual symposium 

on engineering geology and soils engineering: Utah State University, Logan, Utah, p. 499-521.

Thorsen, G.W., 1981, The circuit rider geologist: Final Report for U.S. 

Geological Survey Project 9-7020-26001, 29 p.
SURFACE-FAULT RUPTURE: A GUIDE FOR LAND-USE PLANNING,

UTAH AND JUAB COUNTIES, UTAH

By ROBERT M. ROBISON 10

ABSTRACT

Surface-fault rupture may be one of the most damaging effects of 

large-magnitude earthquakes in Utah and Juab Counties, Utah. Much 

research has been conducted to identify and evaluate the location and 

effects of surface faulting, and this paper is a compilation of the most 

current information available. This work is presented as an example of 

translated information from various sources, primarily the U.S. Geological Survey's National Earthquake Hazards Reduction Program. 

The principal purpose is to help identify and suggest mitigation 

measures for lowering the risks associated with surface-faulting earthquakes.

Large-magnitude earthquakes (ML=6.5+) with accompanying surface faulting have occurred repeatedly in Holocene time (past 10,000 

yr) along the 213-mi (343-km) trace of the Wasatch fault zone. Evidence 

from past earthquakes suggests a potential for surface offset of 6-9 ft 

(2-3 m) and scarp heights of 9-15 ft (3-5 m). The Wasatch fault zone is 

a dip-slip (normal) fault, which commonly has a graben (downdropped 

block) or zone of deformation along the downthrown side. This disturbed zone may extend hundreds of feet (meters) from the main fault 

trace. Recent mapping by the U.S. Geological Survey indicates that 

there may be 10 or 11 segments along the Wasatch fault zone, each with 

its own recurrence interval and rupture characteristics, which give a 

combined recurrence rate for a surface-faulting earthquake somewhere 

along the Wasatch fault zone every 340-415 yr. Recurrence on any 

particular segment varies from hundreds to several thousands of years. 

Because of uncertainties in the timing of the most recent events and 

apparent irregularity in recurrence intervals, a surface-faulting earthquake could occur at any time on any of the segments in Utah and Juab 

Counties.

In Utah County, special study zones have been delineated along 

mapped traces of the Wasatch fault zone to identify areas where more 

detailed study is recommended prior to development. These study 

zones are 250 ft (76 m) wide on the upthrown side of the fault and 500 

ft (153 m) on the downthrown side. Because surface ruptures generally 

occur along existing fault traces, we use minimum setback distances 

from traces identified in special studies to help avoid loss of life and 

property damage and to reduce the cost of geotechnical investigations. 

The recommended setbacks are 50 ft (15 m) from the 30 percent slope 

break on the top of the scarp and 50 ft (15 m) from the 30 percent slope 

break at the bottom of the scarp. If the scarp does not attain a slope of 

30 percent, then the 50-ft (15-m) setback on both the top and the bottom 

of the scarp is measured from the midpoint of the scarp. If antithetic 

scarps or backtilting are present, then the setback is measured from 

the antithetic scarp farthest from the main fault or backtilt inflection 

point, and the entire zone of deformation should be avoided. If

Utah County Planning Department, Provo, Utah.

construction is proposed within the setbacks or zone of deformation, 

then a site-specific investigation is needed to accurately locate the 

faults and deformed strata before placement of buildings is recommended. If a building site is within the special study zone on sediments 

younger than 10,000 yr, then site-specific investigations would be 

required to prove that no faults are below the proposed structure in 

sediments younger than 10,000 yr.

INTRODUCTION

Surface faulting has been identified as a potential 

hazard in Utah and Juab Counties, Utah. This paper is an 

effort to address the problems associated with surface 

faulting, to suggest investigation methods, and to propose certain mitigation procedures. Much of the specific 

information on faults is from various studies by the U.S. 

Geological Survey and the Utah Geological Survey. 

Machette (1989) has prepared maps to show the known 

areas in Utah County where hazards exist from surfacefault ruptures. The purpose of this report is to discuss 

the nature of the hazard and its potential consequences 

and to give recommendations regarding the use of the 

maps and how the hazard should be addressed in land-use 

planning, development, and regulation. This work is one 

of several documents addressing natural hazards that 

has been translated for planners and other decisionmakers who have a limited geology background.

Utah and eastern Juab Counties are in north-central 

Utah (fig. 44) and along the base of the central portion of 

the Wasatch range. The range and the adjoining basin, of 

which Utah Valley is a part, are the result of millions of 

years of faulting, which caused the mountains to be 

uplifted and the basins to be downdropped along the 

Wasatch fault zone (WFZ). Although no surface ruptures 

have occurred along this fault zone in historic time, 

evidence gathered from detailed geologic studies of existing scarps indicates that large-magnitude earthquakes 

and accompanying surface ruptures have occurred 

repeatedly within the past 10,000 yr and earlier.

Earthquakes are generated by movement along faults 

at depth. During large-magnitude earthquakes (Richter

121
122 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

FIGURE 44. Map showing the location of Utah and eastern Juab 

Counties, Utah. The Wasatch fault zone is located at the western 

base of the Wasatch Mountains.

magnitude 6.5 + ), ruptures generally propagate to the 

surface as one side of the fault is uplifted and the other 

side is downdropped (fig. 45); the resulting (normal) fault 

scarp has a near-vertical slope. Broad subsidence of the 

valleys accompanying surface faulting may affect areas 

several miles (kilometers) away from the fault. These 

effects are not considered here but are covered in a 

separate report (Robison, "Tectonic subsidence hazard: 

A guide for land-use planning, Utah and Juab Counties, 

Utah," this volume).

ACKNOWLEDGMENTS

This paper was reviewed by Gary E. Christenson of 

the Utah Geological Survey (UGS), Michael N. Machette 

and William J. Kockelman (U.S. Geological Survey), 

Craig Nelson (Salt Lake County geologist), and Mike V. 

Lowe (Davis County geologist). William Lund (UGS) 

provided pertinent information as well as technical data 

in his review. Michael N. Machette also graciously 

furnished preliminary mapping from the Wasatch Front 

portion of the National Earthquake Hazards Reduction 

Program in addition to technical information. William D. 

Black (UGS) prepared the figures.

Wasafch Fault Zone

FIGURE 45. Schematic diagram of the Wasatch fault zone showing the 

relation of the epicenter to the focus and the trace of the surface-fault 

rupture (fault scarp). The plane of the fault probably dips at 50°-60° 

toward the valley. The epicenter of the earthquake is located in the 

valley (downthrown block), not on the trace of the surface rupture 

(adapted from a special poster by the Utah Museum of Natural 

History).

CHARACTERISTICS OF THE 

WASATCH FAULT ZONE

The WFZ extends from near Malad City in southern 

Idaho to Fayette in central Utah, a distance of about 213 

mi (343 km) (Machette and others, 1989). The fault zone 

trends roughly north-south and dips steeply to the west 

at the surface, as shown in figure 46. The WFZ is not a 

single fault plane but a zone of deformation containing 

many individual subparallel faults. Where the zone intersects the surface, it commonly consists of one main 

down-to-the-west fault with a disturbed area, generally 

to the west on the downthrown side, as much as several 

hundred ft (m) wide, or possibly a series of down-to-thewest faults. This disturbed area, commonly termed the 

zone of deformation, contains small cracks and tilted or 

displaced blocks and may include a graben that is 

bounded on the west by a scarp formed by a down-tothe-east (antithetic) fault (fig. 46).

The entire length of the WFZ is not expected to 

rupture in any one earthquake. Instead, discrete segments of varying lengths rupture independently. Originally, 6 segments were proposed, but more recent studies indicate there may be as many as 10 or 11 (fig. 47) 

(Schwartz and Coppersmith, 1984; Machette and others, 

1987, 1989). The most important aspect of the concept of 

segmentation is that segments control the length of the
SURFACE-FAULT RUPTURE: A GUIDE FOR LAND-USE PLANNING 123

West East

Wasatch Mountains

Extensional Features

Utah 

Valley

Zone of Deformation

Surface Offset Scarp 

 'Height

Alluvium and Lake Bonneville Sediments

y

Main Fault

FIGURE 46. Schematic diagram of a normal fault showing features typical of the Wasatch fault zone near the ground surface. Sketch is not 

to scale, but surface offset is usually about 6-9 ft (2-3 m). Note that the scarp height is commonly greater than the surface offset.

expected surface rupture, control the starting or stopping points of ruptures, and place physical constraints on 

the maximum magnitudes of potential earthquakes.

Several different analyses of the history of the WFZ 

suggest an event every 200-415 yr. From a study that 

considered the number of surface-faulting earthquakes 

on the original 6 segments over the past 8,000 yr, 

Schwartz (1988) suggests that such earthquakes occur on 

the average every 200-400 yr, and studies that assessed 

10 or 11 segments arrived at a similar recurrence of 

340-415 yr (Machette and others, 1989; W.R. Lund, oral 

commun., 1988). The most recent rupture along the WFZ 

may have occurred on the Nephi fault segment in Juab 

County, between 300 and 500 yr ago (Schwartz and 

Coppersmith, 1984), although Jackson and Ruzicka 

(1988) suggest a time of 500 or slightly more years ago.

Utah County and northeastern Juab County contain 

two (or more) of the segments defined by Machette and 

others (1989) (fig. 47). From north to south, these 

segments are the Provo segment (tentatively subdivided 

into the American Fork, Provo (restricted), and Spanish 

Fork subsegments) in Utah County and the Nephi segment in southern Utah and northeastern Juab Counties.

Details of segment length, average recurrence, and age 

of last movement are given in table 8. The average 

recurrence of surface faulting along each segment varies 

but is generally between 1,300 and 2,700 yr (Machette 

and others, 1987).

Schwartz and Coppersmith (1984) did not differentiate 

subsegments for the Provo segment. The most recent 

studies (Machette and others, 1989; Machette, 1989), 

which should be consulted for a more complete discussion 

of segments and faulting, indicate that the Provo segment may consist of subsegments (table 8) that have 

nonpersistent boundaries. The Provo segment extends 

about 43.4 mi (70 km) from the boundary of Utah and Salt 

Lake Counties south to Payson Canyon (Machette and 

others, 1989) and includes the American Fork, Provo 

(restricted), and Spanish Fork subsegments.

The American Fork subsegment is 14.0 mi (23 km) long 

and extends from the middle of the Traverse Mountains 

to the mouth of Provo Canyon (Machette and others, 

1987). Lake Bonneville deposits south of American Fork 

Canyon are offset 50-65 ft (15-20 m). Trenching investigations about 0.5 mi (0.8 km) south of the canyon 

revealed evidence for three surface-faulting events in the
124 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Malad Dty °\ ^ MALAD CITY

"MDUNTAiN ' "1

CDLLINSTDN CDLLINSTDN

SALT LAKE CITY

PRDVD UTAH 

LAKE

o'j ' Salt Lake City

SALT LAKE CITY

American Fork 

. Provo

,O\ Provo <-i

o) Spanish Fork Spanish Fork

NEPHI

LEVAN

> >' *

°< Nephi

0 10 ZO 30 40 50 I 

0 1020304050607010.

 phi

°/

/ Levan

\

O I Fayette

NEPHI

LEVAN

FAYETTE

PROVO

FIGURE 47. Map showing boundaries and names for the Wasatch fault 

zone segments. Segment boundaries are noted by solid arrows. The 

left column is from Schwartz and Coppersmith (1984) and the right is 

from Machette and others (1989). The total number of identified 

segments has increased from 6 to 10, possibly 11, depending on the 

persistence of the segment boundaries (represented by open arrows). 

The total number of segments determines the amount of potential 

generative earthquake zones (adapted from Machette and others, 

1989).

past 5,300 yr, the most recent being about 550 yr ago 

(Machette, 1988).

The Provo (restricted) subsegment extends from the 

Provo River south to Springville, where it overlaps the 

Spanish Fork subsegment, a total distance of about 11.5 

mi (18.5 km) (Machette and others, 1987). A trenching 

study at the mouth of Rock Creek Canyon indicated that 

the most recent surface rupture occurred between 500 

and 1,000 yr ago. Surface offset in the trench was about 

7 ft (2 m) and had an additional 8 ft (2.5 m) of tilt and 

deformation, which produced a scarp 15 ft (4.5 m) high.

The Spanish Fork subsegment extends from the north 

side of Springville City about 19.6 mi (31.6 km) south to 

the mountains behind Woodland Hills City. This segment 

was trenched about 1 mi (1.2 km) northwest of Hobble 

Creek (Swan and others, 1981; Schwartz and others, 

1984), where evidence for six or possibly seven surfacefaulting events within the past 13,500 yr was found. A 

multiple-trench investigation on the Spanish Fork segment near Mapleton revealed dates for the most recent 

event of 550-700 yr ago (W.R. Lund, oral commun., 

1988). However, the U.S. Bureau of Reclamation found 

evidence for two events within the past 1,000 yr, which 

could suggest that the Spanish Fork subsegment had 

moved during earthquakes on both the Provo and Nephi 

segments.

The Nephi segment of the WFZ extends about 26.4 mi 

(42.5 km) from near Payson in southern Utah County to 

Nephi in Juab County. This segment was first trenched 

at the mouth of North Creek and exhibits what is 

probably the most recent (about 300-500 yr old) rupture 

along the entire WFZ (Schwartz and Coppersmith, 

1984). Jackson and Ruzicka (1988) trenched at Rock 

Creek near Nephi and reported three faulting events, 

the most recent being 500 yr or older, which roughly 

agrees with previously published age estimates for the 

segment.

TABLE 8. Data for the Wasatch fault zone in Utah and northeastern Juab Counties

[Segment names, lengths, recurrence intervals, displacement, and age information are taken from the references given and should be consulted for detailed 

explanations of the derivation of each parameter. Specific segment data are given in the text. See figure 47 for relation of listed segments to the entire Wasatch 

fault zone.]

Length

Segment or subsequent Surface trace End to end

Recurrence Displacement Age of 

. , , npr pvpnt most recent interval Per eveni surface References

Miles Kilometers Miles Kilometers V6r S&' Feet Meters faulting (yr)

Provo (segment)

American Fork

(subsegment).

Provo (restricted,

subsegment).

Spanish Fork

(subsegment).

Nephi (segment)

43.

14.

11.

19.

26.

,1

,0

,5

,5

,4

69.5

22.5

18.5

31.5

42.5

36.

13.

10.

14.

,9

,0

,5

,9

23.3

59.5

21.0

17.0

24.0

23.3

2,425 7.6-8.6 2.3-2.6

 

- 5.3-7.6 1.2-2.3

1,700-2,700 6.6-8.3 2.0-2.5

about 550

>660-1000

550-700

about 400

Machette (1988)

Machette and others

(1989).

W.R. Lund (personal

commun., 1987).

Jackson and Ruzicka

(1988); Schwartz and

Coppersmith (1984)
SURFACE-FAULT RUPTURE: A GUIDE FOR LAND-USE PLANNING 125

On individual segments of the WFZ, ruptures may 

occur every few hundred to a few thousand years. 

Detailed studies on the central segments of the fault zone 

indicated periods between surface faulting events that 

range from less than 1000 yr to more than 3,000 yr, an 

individual segment average being 2035-2070 yr 

(Machette and others, 1989). However, it must be understood that the data are incomplete and imprecise and that 

events do not necessarily occur at regular intervals; 

recurrence on individual segments is quite variable 

(Schwartz, 1988). Thus, considering the previously mentioned recurrence interval of 200-666 yr for all segments 

and the time since the most recent event (300-600 yr), 

earthquakes may be expected somewhere along the fault 

at any time.

There is some evidence that earthquakes on different 

segments may cluster in time and occur so closely 

together that they appear as one event in the geologic 

record. If clustering occurs, groups of earthquakes with 

very short time intervals (possibly weeks, months, or 

years) between events could occur sequentially along the 

WFZ. Then the average recurrence calculated for the 

entire fault (200-666 yr) could be misleading, and events 

may have occurred in more closely spaced clusters with 

larger periods between clusters. The recurrence estimates for earthquakes on individual segments would not 

change, however.

Other faults, perhaps capable of surface rupturing, 

have been located in Utah County. Dustin and Merritt 

(1980) reported faults beneath Utah Lake in an investigation of the hydrogeology of the lake (see Machette, 

1989, map). These faults may be 18 mi (29 km) long, are 

roughly parallel to the Wasatch fault, and exhibit evidence of movement within the past 15,000 yr. The faults 

do not pose a surface-fault rupture hazard to urbanized 

areas, but further work is needed to define recurrence 

intervals because ground shaking from an earthquake 

generated by these faults would significantly affect Utah 

Valley. Fault scarps also were noted in western Juab 

Valley (R.M. Robison, unpublished data, 1987), but little 

is known about these features.

CONSEQUENCES OF SURFACE-FAULT 

RUPTURES AND REDUCTION OF HAZARDS

Studies along the Wasatch fault have indicated that 

during a "characteristic" earthquake that produces surface faulting, offsets of 6 ft (1.8 m) or more (average 6.6 

ft, or 2 m) may occur on the main trace of the fault zone 

(Schwartz and Coppersmith, 1984). This offset will result 

in formation of a near-vertical scarp, generally in unconsolidated surficial deposits, that begins to ravel and 

erode back to the material's angle of repose (33°-35°)

soon after formation. Antithetic faults west of the main 

trace may also form, generally exhibiting a lesser amount 

of offset, but sometimes as much as several feet (meters) 

(fig. 46). The zone between these two faults may be 

complexly faulted and tilted, with offset along minor 

faults of several inches or more. In some cases, a broad 

zone of flexure may form west of the main fault in which 

the surface is tilted downward toward the fault zone. An 

example of this warping is preserved south of the mouth 

of Hobble Creek, where backtilting extends more than 

650 ft (200 m) from the fault, with a maximum dip of 3° to 

the east.

It is difficult, both technically and economically, to 

design a structure to withstand 6 ft (2 m) or more of 

offset through its foundation. Youd (1980) indicates that 

displacements through a foundation of 2.5 ft (0.76 m) or 

more could cause collapses. Thus, avoidance of the main 

trace of the fault and preparedness to respond and 

rebuild are the principal reduction techniques that can be 

reasonably undertaken.

In some areas, adjacent to the main trace but still 

within the zone of deformation, avoidance may not be 

necessary. Less damaging (smaller) offsets and tilting 

may occur, and structural measures may be taken to 

reduce casualties and damage. However, structural damage may still be great, and buildings in the zone of 

deformation may not be safe for occupants following a 

large earthquake.

USE OF SPECIAL STUDY ZONE MAPS

Machette (1989) has prepared a map that shows the 

main traces of the WFZ in Utah County. This map is at 

a scale of 1:50,000 and clearly indicates the areas where 

surface-fault rupture hazards need to be considered. I 

have used this map as the basis to prepare the special 

study zone maps (fig. 48). The special study zone follows 

the mapped trace of the WFZ surface ruptures and is 

about 250 ft (76 m) wide on the upthrown side of the fault 

zone and 500 ft (153 m) wide on the downthrown side. 

The purpose of this zone is to delineate areas where 

site-specific investigations addressing surface-fault rupture hazards are recommended. Because the fault maps 

used to delineate these zones were prepared at a scale of 

1:50,000 (1 in.=0.79 mi), they are not detailed enough to 

delineate all fault traces and zones of deformation at a 

particular location; thus site-specific investigations are 

recommended in the study zone.

SCOPE OF SITE INVESTIGATIONS

The scope of site investigations will vary, depending 

on the proposed land use, nature of faulting, and amount
126 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

0 .5 1 km 

EXPLANATION

Wasatch Fault, bar and ball on downthrown side 

Surface fault rupture hazard special study area

FIGURE 48. Map showing the Wasatch fault zone at the mouth of Rock Canyon, Utah. Study zone 

surrounds the mapped trace of the fault and is 250 feet wide on the upthrown side and 500 feet wide 

on the downthrown side. Setback recommendations are discussed in the text.
SURFACE-FAULT RUPTURE: A GUIDE FOR LAND-USE PLANNING 127

of preexisting disturbance of the surface. Prior to construction, a geotechnical report delineating the location 

of the faults and a suggested setback distance will be 

required. At undisturbed sites, the initial phase of the 

surface-faulting investigation should include mapping 

and topographic profiling of all suspected faults and 

scarps. Mapping consists chiefly of identifying fault 

scarps or other fault-related geomorphic features based 

on interpretation of aerial photographs and detailed field 

investigations. Topographic profiles (two-dimensional 

cross sections) of fault scarps should be made to define 

the features that are usually apparent from these profiles. Profiles should extend several hundred feet above 

and below the main fault scarp in order to provide the 

basic information needed to define standard fault setbacks.

In disturbed or geologically young areas, such as an 

active stream flood plain or farmed areas, the surficial 

material may be regraded or less than 10,000 yr old and 

of sufficient thickness to conceal older faulted deposits 

and faults. These areas would require that site-specific 

studies contain recommendations for setback distances 

derived from projections of faults on adjacent property 

through the study area. If setback distances cannot be 

determined from projections, then trenching may be 

done to a depth that encounters undisturbed material 

older than 10,000 yr, to determine if faulting had 

occurred.

Studies by McCalpin (1987) indicate that a fault is 

commonly located at the midpoint of its scarp. It is 

recommended that structures be set back a minimum of 

50 ft (15 m) from the midpoint of the scarp (fig. 49A) if 

the scarp angle does not reach 30 percent. If the scarp 

slope is 30 percent or greater, then the setback should be 

taken from the 30 percent slope break at the top and 

bottom of the scarp (fig. 495). Following these recommendations should help keep structures from straddling 

the main, and potentially most dangerous trace of the 

fault but will not remove structures from the entire zone 

of deformation. If profiles indicate that backtilting, secondary faulting, or graben-bounding antithetic faults are 

present and a wide zone of deformation exists, a 50-ft 

(15-m) setback should be taken from the outermost 

antithetic fault (fig. 49C) or, in areas of flexure and 

backtilting, from the area where the original prefault 

surface slope is regained. It is recommended that construction in the zone of deformation not be allowed unless 

detailed studies involving trenching are performed to 

define the hazard. Fault-trench investigations are used 

to accurately locate, characterize, and, in some cases, 

date past events at a specific location and to delineate the 

zone of deformation. Based on data from trenches, 

further recommendations can be made for variances from 

these minimum setback guidelines.

Fault Scarp (> 30%)

\

! 50 ft Setback 

 50 ft Setback

30% Slope break (toe)'

Fault

30% Slope break (crest)

Zone of deformation

Slope break of farthest 

antithetic fault scarp

Farthest antithetic fault 

(location inferred) Main Fault

FIGURE 49. Schematic diagram of recommended minimum setback 

distances relative to fault scarps in areas where trenching studies are 

not performed. Recommended setback distances are (A) 50 ft (15.25 

m) from the midpoint of a scarp that does not have a 30° slope; (B) 50 

ft (15.25 m) from the top and bottom slope break on a scarp that has 

30° or more slope; and (O for scarps where a graben is present, 50 ft 

(15.25 m) from the 30 percent slope break at the top and 50 ft (15.25 

m) from the farthest antithetic fault scarp.

At sites where the surface is disturbed but the causative faults cannot be located on the basis of surface 

evidence, trenching of proposed locations of structures is 

recommended. In some cases, it would be advisable to 

offset trenches (along the strike of the fault) from actual 

building foundations to avoid adversely affecting soil 

foundation conditions with trench backfill. A publication 

from the Utah Section of the Association of Engineering 

Geologists (1987) lists guidelines for performing surfacefault rupture investigations and preparing reports, and it 

should be consulted prior to performing such studies. 

Recommendations include consulting the county geologist to further clarify the scope of investigation and types 

of information that should be obtained from such a study.
128 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Once site-specific reports have been completed, they 

should be reviewed by the county geologist; then problems should be discussed and resolved prior to submittal 

to the planning commission for approval.

The information in this paper is the most accurate 

available as of August 1989. Much research is being 

conducted along the Wasatch Front, and the text that 

accompanies the surface-fault rupture hazard zone maps 

will be updated periodically as necessary. As they 

become available, new and more accurate fault locations 

will also be added to the accompanying maps. The text 

and maps are kept on file at the Utah County Planning 

Office and Utah County recorder's office.

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area Association with geologic structure, space-time occurrence, 

and stress state, in Hays, W.W., and Gori, P.L., eds., Workshop 

on "Evaluation of regional and urban earthquake hazards and risk 

in Utah": U.S. Geological Survey Open-File Report 84-763, 

p. 310-339.

Bucknam, R.C., and Anderson, R.E., 1979, Estimation of fault scarp 

ages from a scarp-height-slope-angle relationship: Geology, v. 7, 

p. 11-14.

Colman, S.M., and Watson, Ken, 1983, Ages estimated from a diffusion 

equation model for scarp degradation: Science, v. 221, p. 263-265.

Dustin, J.D., and Merritt, L.B., 1980, Hydrology of Utah Lake with 

emphasis on Goshen Bay: Utah Geological and Mineral Survey 

Water Resources Bulletin 23, 50 p.

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Hazards Reduction Program Fiscal year 1984 activities: Report 

to the United States Congress, 192 p.

Hays, W.W., and Gori, P.L., eds., 1987, A workshop on "Earthquake 

hazards along the Wasatch Front, Utah": U.S. Geological Survey 

Open-File Report 87-154, 146 p.

Jackson, M.E., and Ruzicka, J., 1988, Holocene paleoseismic history of 

the Levan and Nephi segments, Wasatch fault zone, Utah, Application of the thermoluminescence (TL) method: Geological Society 

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G.K. Gilbert Lake Bonneville and neotectonics of the eastern 

Basin and Range province, guidebook for field trip twelve: Utah 

Geological and Mineral Survey Miscellaneous Publication 88-1, 

120 p.

Machette, M.N., 1989, Preliminary surficial geologic map along the 

Wasatch fault zone in the eastern Utah Valley, Utah County, and 

parts of Salt Lake and Juab Counties, Utah: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-2109, scale 1:50,000.

Machette, M.N., and Lund, W.R., 1987, Late Quaternary history of 

the American Fork segment of the Wasatch fault zone, Utah:

Geological Society of America Abstracts With Programs, v. 19, no. 

5, p. 317.

Machette, M.N., Personius, S.F., Scott, W.E., and Nelson, A.R., 

1987, Quaternary geology along the Wasatch Front: Evidence for 

ten fault segments and large-scale changes in slip rate along the 

Wasatch fault zone, in Gori, P.L., and Hays, W.W., eds., Assessment of regional earthquake hazards and risk along the Wasatch 

Front, Utah: U.S. Geological Survey Open-File Report 87-585, 

p. A1-A72.

Machette, M.N., Personius, S.F., Nelson, A.R., Schwartz, D.P., and 

Lund, W.R., 1989, Segmentation models and Holocene movement 

history of the Wasatch fault zone, Utah, in Schwartz, D.P., and 

Sibson, R., eds., Proceedings of conference XLV Fault segmentation and controls on rupture initiation and termination: U.S. 

Geological Survey Open-File Report 89-315, p. 229-242.

McCalpin, James, 1987, Recommended setbacks from active normal 

faults, in McCalpin, James, ed., Proceedings of the 23rd symposium on engineering geology and soils engineering: Utah State 

University Press, Logan, Utah, p. 35-56.

Nelson, A.R., and Personius, S.F., 1987, A nonconservative barrier to 

Holocene rupture propagation in the northern Wasatch fault zone, 

Utah [abs.]: Proceedings of XII INQUA congress, July 31 to 

August 9, Ottawa, Canada.

Robison, R.M., 1988, Surface fault rupture hazard and tectonic subsidence maps for the Wasatch Front, Utah: Geological Society of 

America Abstracts With Programs, v. 20, no. 6, p. 465.

Schwartz, D.P., 1988, Geologic characterization of seismic sources 

 Moving into the 1990s, in Von Thun, J.L., ed., Recent advances 

in ground-motion evaluation: American Civil Engineers Geotechnical Special Publication 20, p. 1-42.

Schwartz, D.P., and Coppersmith, K.J., 1984, Fault behavior and 

characteristic earthquakes Examples from the Wasatch and San 

Andreas fault zones: Journal of Geophysical Research, v. 89, no. 

B7, p. 5681-5698.

Schwartz, D.P., Swan, F.H., and Cluff, L.S., 1984, Fault behavior and 

earthquake recurrence along the Wasatch fault zone, in Hayes, 

W.W., and Gori, P.L., A workshop on "Evaluation of regional and 

urban earthquake hazards and risk in Utah": U.S. Geological 

Survey Open-File Report 84-763, p. 113-125.

Smith, R.B., and Richins, W.D., 1984, Seismicity and earthquake 

hazards of Utah and the Wasatch Front Paradigm and paradox, 

in Hays, W.W., and Gori, P.L., eds., A workshop on "Evaluation 

of regional and urban earthquake hazards and risk in Utah": U.S. 

Geological Survey Open-File Report 84-763, p. 73-112.

Swan, F.H., II, Hanson, K.L., Schwartz, D.P., and Kneupfer, P.L., 

1981, Study of earthquake recurrence intervals on the Wasatch 

fault at the Little Cottonwood Canyon site, Utah: U.S. Geological 

Survey Open-File Report 81-450, 30 p.

Utah Section of the Association of Engineering Geologists, 1987, 

Guidelines for evaluating surface fault rupture hazards in Utah: 

Utah Geological and Mineral Survey Miscellaneous Publication N, 

2 p.

Youd, T.L., 1980, Ground failure displacement and earthquake damage 

to buildings: American Society of Civil Engineers 2d conference on 

civil engineering and nuclear power, Knoxville, Tenn., v. 2, 

p. 7-6-2-7-6-26.
LANDSLIDE HAZARDS: A GUIDE FOR LAND-USE PLANNING, DA VIS

COUNTY, UTAH

By ROBERT M. RoBisoN11 and MIKE LOWE 12

ABSTRACT

Landslides pose one of the most common geologic hazards in Davis 

County, Utah, where more than 700 slides have been identified and 

mapped. Landslides are downslope, mass movements of earth materials under the influence of gravity. Many types of landslides occur in 

Davis County. This report addresses only translational and rotational 

landslides and associated earth flows. Potential for damage to structures, rupture of underground water lines and sewers, and damming of 

streams with resultant catastrophic flooding exists in areas susceptible 

to landsliding in Davis County.

Two sets of landslide-hazard maps showing where landslides exist or 

are considered likely to occur in the future have been produced for 

Davis County. The first set of landslide-hazard maps shows where 

landslides are likely to occur in the absence of earthquakes. This set of 

maps was constructed by overlaying geologic maps, slope maps, and 

landslide-inventory maps and combining areas of known landslides, 

landslide-prone geologic units, and areas having slope greater than 30 

percent into a landslide-hazard special study zone. The second set of 

landslide-hazard maps delineates areas where landslides are likely to 

occur in the event of an earthquake. This set of maps was produced by 

combining data on the strength of earth materials, slope geometry, 

ground-water conditions, and magnitude of ground shaking to determine where earthquake-induced landslides may occur throughout 

Davis County. Zones or areas having probabilities of earthquakeinduced landslides ranging from high to very low are shown on these 

earthquake-induced landslide-potential maps.

Static (nonearthquake) slope-stability studies of specific sites are 

recommended prior to planning commission approval of new development within the special study zone for landslide hazards. It is recommended that dynamic (earthquake-induced) landslide potential be evaluated for specific sites prior to planning commission approval of critical 

facilities, lifelines, and high-occupancy industrial and commercial buildings in areas of high or moderate earthquake-induced landslidepotential ratings.

INTRODUCTION

Landsliding historically has been one of the most 

damaging geologic processes occurring in Davis County, 

both in the unincorporated county and in many cities. All 

active landslides and most older slides have been mapped 

at a scale of 1:24,000 to produce landslide-inventory

Utah County Planning Department, Provo, Utah. 

Davis County Planning Department, Farmington, Utah.

maps. These maps serve as an indication of unstable 

ground. The landslide inventories, along with slope maps 

and other geologic data, have been used to evaluate slope 

stability on a broad scale and to prepare landslide-hazard 

maps. These hazard maps show areas of landslides and 

slopes that are potentially unstable under static (nonearthquake) conditions. Separate dynamic (earthquakeinduced) landslide-hazard maps have been prepared for 

Davis County by Keaton and others (1987). This report 

describes landslide hazards and recommends guidelines 

for use of both landslide-hazard maps and earthquakeinduced landslide-potential maps in land-use planning. A 

major goal is to translate technical information so that 

government officials and the general public can appreciate the need to reduce landslide hazards.

ACKNOWLEDGMENTS

Gary E. Christenson, Utah Geological Survey; William 

J. Kockelman and Rex Baum, U.S. Geological Survey; 

Craig Barker, Weber County Planning Department; and 

Wilf Sommerkorn and Barry Burton, Davis County 

Planning Department, kindly reviewed this paper and 

provided valuable suggestions. Bill Black, Utah Geological Survey, drafted the figures.

LANDSLIDE CHARACTERISTICS

Landslides are generally defined as "mass movements 

of rock or soil downslope under the direct influence of 

gravitational forces without an aiding transporting 

medium such as water, air, or ice" (Costa and Baker, 

1981, p. 243). Landslides considered in the landslidehazard maps include rotational and translational slides 

and associated earth flows (Varnes, 1978). Rotational 

slides generally have a curved failure plane. The head of 

the rotational slide is backtilted in comparison with the 

slope of the original surface. Most rotational slides are 

termed slumps and may include an earth flow at the toe,

129
130 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

ORIGINAL GROUND 

SURFACE

FIGURE 50. Block diagram of a rotational landslide. Note the backtilt below the main 

scarp and material at the zone of accumulation at the toe. If this landslide was 

translational, then the surface of rupture (failure plane) would be planar like the surface 

of separation beneath the foot (adapted from Varnes, 1978).

where material moves onto the land surface below the 

slump (fig. 50). Translational slides generally have a 

more planar failure surface and may be broken into 

several discrete blocks. If rock is involved, the term rock 

slide may be used. The speed of landslides may vary. 

Both slide types may occur slowly and progressively over 

periods of years, or may be extremely rapid and occur 

within a few seconds. The landslide-hazard maps do not 

address rockfalls or debris flows, which are other types 

of failures commonly grouped under the term landslides.

Landslides may be caused by any of several conditions. 

Oversteepening of slopes, loss of lateral support, weighting of the head, increased pore pressure, and earthquake 

ground shaking are among the major causes of landslides. Older landslides are particularly susceptible to 

reactivation due to conditions that exist in a displaced 

soil mass such as increased permeability and established 

failure planes.

Landslides are likely to occur in Davis County if a 

moderate to strong earthquake occurs in northern Utah. 

Ground failures, including landslides, commonly accompany earthquakes with Richter magnitudes greater than 

4.5 (Keefer, 1984). Some form of landslide or ground 

failure (predominantly rockfall or rockslide) has been 

noted in the descriptions of 12 earthquakes that occurred 

in or immediately adjacent to Utah from 1850-1986 with 

magnitudes 4.3-6.6 (Keaton and others, 1987). Geologic 

evidence from trench excavations across Wasatch fault 

zone scarps indicates that past earthquakes on the 

Wasatch fault had magnitudes ranging from 7.0-7.5 

(Schwartz and Coppersmith, 1984). It is expected that 

future Wasatch fault earthquakes will have similar magnitudes. Earthquakes of magnitude 7.5 could cause slope

failures as far as 185 mi (300 km) from the epicenter 

(Keaton and others, 1987).

Landslides are also likely to occur in years of abnormally high precipitation. Many landslides occurred in 

Davis County during the recent wet cycle (1982-1985), 

causing significant damage to homes and property. The 

Memorial Day 1983 Rudd Canyon debris flow damaged 

35 houses, 15 severely, and resulted in deposition of more 

than 100,000 yd3 (80,000 m3) of earth material at the 

canyon mouth. The debris flow was initiated by landsliding of less than 20,000 yd3 (15,000 m3) in the Wasatch 

Mountains (Wieczorek and others, 1983).

CONSEQUENCES

Damage from a landslide can occur at any point on the 

slide mass and above or below the landslide. The tops of 

most landslides are characterized by an arcuate downhillfacing scarp (main scarp) created by the downward 

displacement of the ground surface (fig. 50). A building 

straddling the main scarp would lose partial foundation 

support and would potentially collapse. Structures 

upslope from the head of a landslide are endangered 

because the newly formed main scarp is commonly 

unstable and may fail, causing new scarps to form 

upslope. Buildings constructed within the central mass of 

the landslide may be subjected to differential displacement on minor scarps and movement in both vertical and 

horizontal directions. Table 9 shows the relationship 

between ground displacement and expected levels of 

damage to structures. The toe of a landslide will normally 

move horizontally and upward and may proceed downslope, causing extensive damage to structures. Cracks at
LANDSLIDE HAZARDS: A GUIDE FOR LAND-USE PLANNING 131

TABLE 9. Relationship between ground displacement and damage to 

structures (from Youd, 1980)

Ground displacement Level of expected damage

Less than 4 in. 

4 in. to 1 ft 

1 to 2 ft 

More than 2 ft

Little damage, reparable 

Severe damage, reparable 

Severe damage, nonreparable 

Collapse, nonreparable____

the head and a bulge at the toe may precede the principal 

landslide movement. Landslides can damage roads, railroads, and power lines. Furthermore, landslides may 

rupture canals, aqueducts, sewers, and water mains and 

thereby add water to the slide plane and promote further 

movement. In addition to ground movement, flooding 

may be caused by landslides. Flooding may occur due to 

discharge from springs along the basal slide plane (example, landslide located on 1500 East Street, Provo, Utah), 

usually in the toe area, or damming of streams that 

causes upstream flooding as water is ponded and possible 

downstream flooding if the impounded water overtops or 

breaches the landslide dam. Spring discharge from landslides is a minor problem and can generally be mitigated 

by diverting drainage. Damming of streams is a major 

problem (Schuster, 1987) and was a principal hazard 

associated with the Thistle landslide in 1983 in Utah 

County. Lake Thistle, which had a maximum depth of 

about 225 ft (69 m), formed behind the landslide mass and 

flooded the town of Thistle. A much larger and more 

populated area downstream was at risk from flooding had 

the landslide failed or been overtopped and washed out 

prior to draining of the lake. Another landslide that 

caused similar problems was the Gros Ventre landslide in 

Wyoming, where 6 or 7 people were killed in the flood 

that ensued 2 yr after the landslide event (Costa and 

Baker, 1981).

LANDSLIDE SUSCEPTIBILITY

Several geologic units in Davis County are susceptible 

to landslides. Landslide-prone geologic units were identified by overlaying landslide-inventory and geologic 

maps and tabulating the number of landslides occurring 

in each geologic unit. The Precambrian Farmington 

Canyon Complex in the mountains in eastern Davis 

County weathers in a manner that provides much unstable hillside debris (colluvium), and debris slides are 

common. Debris slides in colluvium derived from the 

Farmington Canyon Complex were responsible for initiating many of the debris flows that occurred in 1983 and 

1984. Landslides are also common in areas underlain by 

the sediments of Pleistocene Lake Bonneville. Rotational 

landslides (slumps) are particularly common in northern 

Davis County, where stream incision into the Weber 

River Delta has created high bluffs and exposed silts and

clays deposited during the high stand of Lake Bonneville. 

The many springs that occur along these bluffs increase 

landslide susceptibility.

Existing landslides pose a particular problem for 

development because of their tendency to reactivate. 

Many landslides in the mountains and along the bluff 

above the city of South Weber are reactivated landslides 

or have developed on portions of larger older landslides.

Slope steepness is another important factor in determining slope stability. Almost any material will fail if the 

slope is steep enough.

Landslides may also be triggered by earthquake activity. Although the same slopes that are considered unstable under static conditions will be even less stable during 

an earthquake, some slopes that are stable under static 

conditions may fail as a result of earthquake ground 

shaking, particularly if the earthquake occurs when 

slopes are wet. Most landslides caused by earthquakes 

are new slope failures, not reactivated older landslides.

REDUCING LANDSLIDE HAZARDS

Many methods have been developed for reducing landslide hazards. Proper planning and avoidance are the 

least expensive measures, if landslide-prone areas are 

identified early in the planning and development process. 

Care in site grading with proper compaction of fills and 

engineering of cut slopes is a necessary followup to good 

land-use planning. Where avoidance is not feasible, various engineering techniques are available to stabilize 

slopes. Dewatering (draining) can have a major impact 

on stabilizing both slopes and existing landslides. Retaining structures built at the toe of a landslide may help 

stabilize the slide and reduce the possibility of smaller 

landslides. In some cases, piles may be driven through 

the landslide mass into stable material beneath the slide. 

If the dimensions of the landslide are known and the 

landslide is not excessively large, removing the landslide 

may be effective. Landslide hazards may also be reduced 

by bridging, weighting or buttressing slopes with compacted earth fills, and drainage diversion. A more complete list of landslide-hazard reduction techniques may be 

found in the works of Costa and Baker (1981) and 

Kockelman (1986) and other engineering geology publications. Every landslide and potentially unstable slope 

will probably have differing characteristics and will need 

to be evaluated for an appropriate hazard reduction 

technique.

SUMMARY OF METHODS USED IN MAP 

PREPARATION

Landslide-inventory maps (figs. 51 and 52) showing 

existing landslides in Davis County have been compiled
132 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

DAVIS COUNTY

Salt Lake City

UTAH

10 Kilometers

EXPLANATION

Location of 

Figures 52 and 53

Location of 

Figure 54

FIGURE 51. Location map for figures 52, 53, and 54.

at 1:24,000 scale using U.S. Geological Survey topographic quadrangles as base maps. The following parameters were evaluated while preparing the landslideinventory maps: (1) landslide type, compiled from 

existing data and air photo interpretation using a classification scheme developed by Varnes (1978); (2) age class 

of landslides, using a classification scheme developed by 

McCalpin (1984); (3) elevation of the toe and crown of the 

landslide; (4) average prelandslide slope; (5) failed geologic unit, as determined from existing geologic mapping; 

(6) other geologic units involved; (7) slope aspect; (8) 

landslide complexity (multiple landslides); and (9) the 

role of humans in causing the failure. If the same 

landslide was mapped by more than one investigator and 

discrepancies were found in the mapping of the perimeter of the landslide, the two maps were overlaid and the 

outermost margin of the landslide on the combined maps 

was used.

The landslide-inventory maps and slope maps were 

then used to assess the susceptibility for slope failure on 

natural slopes under static conditions and to help construct l:24,000-scale landslide-hazard maps (figs. 51 and 

53). Slopes steeper than 30 percent have a relatively high 

potential for failure and are generally already subject to 

land-use restrictions for reasons other than slope stability. These slopes are therefore included in the recommended study area on the landslide-hazard maps. In 

certain failure-prone materials such as fine-grained Lake 

Bonneville deposits, failures have occurred at slopes less 

than 30 percent. These flatter areas with existing landslides have also been included in the recommended study 

area on the landslide-hazard maps.

In those areas where unstable slopes are surrounded 

by flatter, more stable slopes, it is necessary to extend 

the boundaries of the landslide-hazard study beyond the 

base and top of the unstable slope. This situation occurs 

along the bluff above South Weber and along incised 

drainages in Layton and Kaysville, where the potential 

instability in the steeper slope (bluff face) may affect 

areas both above and below. The width of the landslidehazard study area in this situation depends on the height, 

steepness, ground-water conditions, and strength of the 

material making up the slope. In these areas of flat land 

above and below landslide-prone slopes, a conservative 

stable slope angle was taken through the center of the 

steep slope to determine where slope-stability studies 

were needed for the flatter land. Rollins, Brown, and 

Gunnel, Inc. (1977) determined that this conservative 

slope angle should be two horizontal to one vertical (2:1, 

or 50 percent) for dry granular soils and 2.5:1 (40 

percent) for moist fine-grained material. In general, 

these zones extend less than 100-150 ft from the base or 

top of slopes and are too narrow to be shown at the map 

scale.

Earthquake-induced landslide-potential maps (1:48,000 

scale) for Davis County (figs. 51 and 54) have been 

prepared by Keaton and others (1987) using 50 percent 

reductions of U.S. Geological Survey topographic quadrangles as base maps. In evaluating seismic slope stability, Keaton and others (1987) considered the strength of 

slope materials, slope geometry, ground-water conditions, and the strength or intensity of earthquake ground 

shaking. These parameters were evaluated to determine 

the level (magnitude) of ground shaking necessary to 

cause slope instability in each type of earth material 

found in Davis County, for various slopes and slope 

geometries, and for dry and saturated ground-water 

conditions (Keaton and others, 1987). The probability 

that this level of ground shaking would occur during a 

100-yr time period was then determined and used to 

define geographic areas of high, moderate, low, and very 

low potential for seismic slope failure (Keaton and others, 1987). Table 10 summarizes each category of 

earthquake-induced landslide potential with respect to 

the probabilities that the critical accelerations needed to 

induce failure in each category would be exceeded in a 

100-yr time period and the possible levels of displacement associated with that failure.
LANDSLIDE HAZARDS: A GUIDE FOR LAND-USE PLANNING 133

FIGURE 52. Landslide-inventory map for the Centerville and 

northern Bountiful area of southern Davis County, Utah. DS, 

shallow failure, chiefly debris slides; DF, debris flow; LS, deep 

failure, chiefly slumps and earth flows; a, active (historic) slope 

failure; 123, inventory number for slope failure. Reproduced

RECOMMENDED USE OF MAPS FOR LAND-USE 

PLANNING AND DEVELOPMENT

The landslide-hazard maps that accompany this report 

show areas of existing landslides and potential landslide

from a portion of the slope-failure inventory map, Bountiful Peak 

Quadrangle. Original mapping by Keaton (1986), Nelson and 

Personius (1988), Olson (1981), and Lowe (unpublished Davis 

County Planning Commission maps).

hazard at 1:24,000 scale using U.S. Geological Survey 

1W (topographic) quadrangles as base maps. These maps 

are chiefly intended for use by planners to identify areas 

where site-specific investigations addressing slope stability should be performed prior to development. It is
134 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

FIGURE 53. Landslide-hazard map for the Centerville and northern Bountiful area of southern Davis County, Utah. Cross hatching 

indicates areas where slope-stability studies are recommended prior to planning commission approval of proposed development. 

This figure was reproduced from a portion of the landslide-hazard map, Bountiful Peak Quadrangle, Davis County, Utah, by Lowe 

(unpublished Davis County Planning Commission maps).

recommended (table 11) that slope-failure potential be 

evaluated and, if necessary, mitigative measures be 

recommended by an engineering geologist in site-specific 

reports. The developer then submits these reports to the

planning commission prior to approval of the development.

The results of the earthquake-induced landslidepotential study are presented on a l:48,000-scale map
LANDSLIDE HAZARDS: A GUIDE FOR LAND-USE PLANNING 135

3000 4000 6000 TOM FEET

FIGURE 54. Earthquake-induced landslide-potential map for the Centerville and northern Bountiful area of southern Davis County, 

Utah. Landslide potential is rated by S, landslide; VL, very low; L, low; M, moderate; and H, high. This figure was reproduced from 

a portion of the earthquake-induced landslide-potential map (south half) for Davis County, Utah, by Keaton and others (1987).

that separates Davis County into a south half and a north 

half. The earthquake-induced landslide-potential rating 

for a given location can be determined by locating the site 

on the map. The approximate probability that ground

shaking sufficient to induce slope failure, for both dry 

and wet soil conditions, would occur during a 100-yr 

period for the landslide-potential rating given on the map 

may then be determined by referring to the proper
136 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

TABLE 10. Earthquake-induced landslide potential categories, soil 

moisture levels considered, probability of exceedence of critical 

acceleration needed to cause failure during 100-yr period, and 

possible magnitudes of displacement (from Keaton and others, 

1987)

Seismic 

slope-failure 

potential

High

Moderate

Low

Very low

Soil moisture 

conditions

Dry and wet

Dry

Wet

Dry

Wet

Dry and wet

Probability of critical

acceleration necessary

to cause 

slope failure 

being exceeded

in a 100-yr

time period (percent)

50 or greater

10 to 50

50 or greater

Less than 10

10 to 50

10 or less

Possible

levels of 

displacement

(in.)

4 or more

Ito4

4 or more

Less than

1

Up to 4

Less than

1

category in table 10. It is recommended (table 12) that 

earthquake-induced landslide potential be evaluated and, 

if necessary, mitigative measures be recommended by an 

engineering geologist in site-specific reports. The developer then submits these reports to the planning commission prior to approval of the development.

Both the landslide-hazard and the earthquake-induced 

landslide-potential maps provide a general indication of 

where slope-failure hazards may exist and serve as a 

means for evaluating the need for site-specific studies. 

These maps are at a regional scale and, although they can 

be used to gain an understanding of the potential that 

landslides will occur in a given area, are not designed to 

replace site-specific evaluations. Mapped areas rated as 

having landslide hazards or a high potential for 

earthquake-induced landsliding may contain isolated

TABLE 11. Recommended requirement for site-specific investigations of slope stability for various classes of facilities proposed within 

Davis County, Utah

Facility class

Critical facilities, includ

Areas within 

landslidehazard area

ing Yes

Areas outside 

landslide-hazard 

area

Yes

lifelines and highoccupancy buildings.

Industrial and commercial Yes 

buildings (other than high 

occupancy).

Residential subdivisions Yes 

Residential single lots_______Yes

No

No 

No

TABLE 12. Recommended requirement for site-specific investigations of seismic slope stability for various classes of facilities in 

different earthquake-induced landslide-potential zones

Facility class

Zones of high to Zones of low to

moderate potential very low potential

for earthquake- for earthquakeinduced landslides induced landslides

Critical facilities, includ- Yes 

ing lifelines and highoccupancy buildings

Industrial and commer- Yes 

cial buildings (other 

than high occupancy)

Residential subdivisions No1 

Residential single lots __ No1

Yes

No

No 

No

Appropriate disclosure should be required.

areas that are not prone to landsliding, even during 

earthquake ground shaking. Also, areas outside the 

landslide-hazard study boundary, or rated as having a 

low earthquake-induced landslide potential, may contain 

isolated areas that are highly susceptible to landsliding.

SCOPE OF SITE INVESTIGATIONS

Site evaluations for landslides and potentially unstable 

slopes, including earthquake-induced landslides, should 

be performed prior to construction of any structures for 

human occupancy, as outlined in tables 11 and 12. The 

investigation should include accurate maps of the area 

showing the proposed development, existing landslides 

and steep slopes, and the site geology. An assessment of 

present slope stability and the effects of development on 

slope stability should be included. Where necessary, a 

factor of safety should be computed by a competent 

geotechnical engineer or engineering geologist to determine the stability of natural or proposed cut slopes. 

Slope-stability analyses should include potential for 

movement under static, development-induced, and 

earthquake-induced conditions as well as all likely 

ground-water conditions. Site grading, including design 

of cuts and fills, should comply with chapter 70 of the 

1988 Uniform Building Code. A useful guide for preparing site-investigation reports is found in the publication 

by the Utah Section of the Association of Engineering 

Geologists (1986). Site-investigation reports should be 

reviewed by the county geologist and other appropriate 

officials. This review will determine if the submitted 

report is adequate and complete. As more accurate 

information becomes available, the landslide-hazard 

maps will be amended.
LANDSLIDE HAZARDS: A GUIDE FOR LAND-USE PLANNING 137

REFERENCES

Costa, J.E., and Baker, V.R., 1981, Surficial geology, Building with 

the earth: New York, John Wiley and Sons, 498 p.

Keaton, J.R., 1986, Landslide inventory and preliminary hazards 

assessment, southeast Davis County, Utah: Association of Engineering Geologists 29th Annual Meeting Program With Abstracts, 

San Francisco, Calif., p. 53.

Keaton, J.R., Anderson, L.R., Topham, D.E., and Rathbun, D.J., 

1987, Earthquake-induced landslide potential in and development 

of a seismic slope stability map of the urban corridor of Davis and 

Salt Lake Counties, Utah: Salt Lake City, Utah, Dames and 

Moore Consulting Engineers, and Logan, Utah, Department of 

Civil and Environmental Engineering, Utah State University, 

47 p.

Keefer, D.K., 1984, Landslides caused by earthquakes: Geological 

Society of America Bulletin, v. 95, p. 406-421.

Kockelman, W.J., 1986, Some techniques for reducing landslide hazards: Association of Engineering Geologists Bulletin, v. 23, no. 1, 

p. 29-52.

McCalpin, J.P., 1984, Preliminary age classification of landslides for 

inventory mapping: Twenty-first annual symposium on engineering geology and soils engineering, April 5-6, 1984.

Nelson, A.R., and Personius, S.F., 1988, Preliminary surficial geologic 

map of the Weber segment, Wasatch fault zone, Weber and Davis 

Counties, Utah: U.S. Geological Survey Miscellaneous Field Studies Map MF-2132, scale 1:50,000.

Olson, E.P., 1981, Geologic hazards of the Wasatch Range, Part 1, 

Ward Canyon to south side Ogden Canyon: U.S. Department of

Agriculture, Forest Service, R-4 Intermountain Region, unpublished maps of selected quadrangles within U.S. Forest Service 

boundaries, scale 1:24,000.

Rollins, Brown, and Gunnel, Inc., 1977, Provo City hazards study: 

Unpublished consultant's report, 28 p.

Schuster, R.L., 1987, Landslide damming of mountain streams: Geological Society of America Abstracts With Programs, v. 19, no. 5, 

p. 332.

Schwartz, D.P., and Coppersmith, K.J., 1984, Fault behavior and 

characteristic earthquakes Examples from the Wasatch and San 

Andreas fault zones: Journal of Geophysical Research, v. 89, no. 

B7, p. 5681-5698.

Utah Section of the Association of Engineering Geologists, 1986, 

Guidelines for preparing engineering geologic reports in Utah: 

Utah Geological and Mineral Survey Miscellaneous Publication M, 

2 p.

Varnes, D.J., 1978, Slope movement and types and processes, Landslides Analysis and control: Washington, D.C., Transportation 

Research Board, National Academy of Sciences, Special Report 

176, chap. 2, p. 11-33.

Wieczorek, G.F., Ellen, Stephen, Lips, E.W., Cannon, S.H., and 

Short, D.N., 1983, Potential for debris flow and debris flood along 

the Wasatch Front between Salt Lake City and Willard, Utah, and 

measures for their mitigation: U.S. Geological Survey Open-File 

Report 83-635, 45 p.

Youd, T.L., 1980, Ground failure displacement and earthquake damage 

to buildings: American Society of Civil Engineers conference on 

civil engineering and nuclear power, 2d, Knoxville, Tenn., v. 2, 

p. 7-6-2-7-6-26.
ROCKFALL HAZARDS: A GUIDE FOR LAND-USE PLANNING,

SALT LAKE COUNTY, UTAH

By CRAIG V. NELSON13

ABSTRACT

Rockfalls along the Wasatch Front are common natural events that 

pose a threat to development. Rockfall hazard maps for special study 

areas have been prepared for Salt Lake County by identifying source 

areas and by computer simulating rockfall runout distances along the 

Wasatch Front. An existing Salt Lake County ordinance prohibits 

building on slopes greater than 30 percent, and computer models 

indicate that rocks typically do not run out onto slopes less than 30 

percent. Where models suggest runout onto slopes that are less than 30 

percent, the longest computed runout distance is used to define a 

conservative boundary to the special study area. Because of the general 

nature and small scale of the hazard map, new developments proposing 

to place structures in a rockfall hazard special study area must conduct 

site-specific rockfall hazard investigations to define hazard areas and 

either avoid or reduce the hazard.

INTRODUCTION

Rockfalls are a naturally occurring erosional process in 

mountain areas along the Wasatch Front. For the purposes of land-use planning, the definition of rockfall used 

in this study has been broadened to include both rockfalls 

(newly detached rocks from a bedrock source) and debris 

falls (rock clasts originating from coarse-grained unconsolidated deposits such as glacial till and colluvium). As 

urban development advances further onto the bench 

areas and into the canyons, the risk from falling rocks 

becomes greater. The purpose of this report is to explain 

how the rockfall hazards special study area maps were 

made and how they should be used. This information can 

benefit land-use planners, developers, real estate 

agents, and the general public by imparting information 

on potential hazards and ultimately helping to avoid 

casualties and damage.

ACKNOWLEDGMENTS

F.T. Lee and W.J. Kockelman (U.S. Geological Survey), Gary Christenson and Bill Case (Utah Geological

13 Delta Geotechnical Consultants, Inc., Salt Lake City, Utah.

Survey), and Jerry Barnes (Salt Lake County Planning) 

all reviewed drafts of this paper and offered helpful 

suggestions. R.P. Sharon (Barrick Goldstrike Mines) 

provided the ROCKFALL program.

CHARACTERISTICS OF ROCKFALLS

Rockfalls originate when erosional processes and the 

pull from gravity dislodge rocks from slopes. The most 

susceptible slopes are those with outcrops broken by 

bedding surfaces, joints, or other discontinuities into 

abundant, loose individual fragments called clasts. Boulders in alluvium and glacial till on hillsides also contain 

clasts that may dislodge and fall. When the clast falls or 

rolls from the slope, it may travel great distances by 

rolling, bouncing, and sliding.

A primary mechanism responsible for triggering rockfalls is water freezing in outcrop discontinuities. When 

this confined water freezes and exerts pressure that 

exceeds the force that is keeping the discontinuity 

closed, frost shattering may occur. In Norway, for 

example, 60 percent of all rockfalls occur in April and 

May during maximum snowmelt and in October and 

November during periods of heavy rainfall (Costa and 

Baker, 1981). In both cases there is water seeping into 

the rocks when the temperature is fluctuating around the 

freezing point.

In mountainous areas, rockfalls are probably the most 

common form of slope instability initiated by the ground 

shaking from earthquakes (Keefer, 1984). Case (1987a) 

estimates that a major Wasatch Front earthquake (magnitude 7-7.5) could produce thousands of rockfalls along 

the Wasatch Front. Keefer (1984) indicates that rockfalls 

may occur in earthquakes as small as magnitude 4.0. In 

the August 1988 San Rafael Swell local magnitude (AfL) 

5.3 earthquake in central Utah (fig. 55), hundreds of 

rockfalls occurred, temporarily obscuring the surrounding cliffs in clouds of dust.

EFFECTS OF ROCKFALLS

Rockfalls present a hazard because of the potential 

damage that a large rock impact could cause to struc138
ROCKFALL HAZARDS: A GUIDE FOR LAND-USE PLANNING 139

50km

 r 

30 miles

FIGURE 55.-Location map of the August 14, 1988, San Rafael Swell, 

Utah, earthquake, ML 5.3, which triggered rockfalls up to 30 mi (48 

km) from the epicenter. The star represents the location of the main 

shock; the solid dots represent individual rockfall locations (modified 

from Case (1988) and Nava and others (1988)).

tures and persons. Rockfalls that occur in remote or 

uninhabited regions go largely unnoticed. It is only when 

falling rocks pose a threat to human life that rockfalls 

must be considered in land-use planning and development regulations.

A 1987 rockfall event near Dead Horse Point, Utah, 

was large enough to register on seismographs more than 

60 mi (96 km) away (fig. 56). Locally, rockfalls have 

historically caused problems along canyon roads by 

blocking traffic or occasionally striking vehicles. The 

structures most often affected by rockfalls in canyons are 

exposed aqueducts. Water service from Wasatch Front 

canyons has been periodically suspended due to damage 

to aqueducts from falling rocks. Homes built along the 

mountain front are also subject to rockfalls. Development in some high-foothill subdivisions in northeastern 

Salt Lake City has exposed boulders that become unstable through weathering of the supporting sediments and 

eventually roll downslope (fig. 57).

EVALUATING ROCKFALL SUSCEPTIBILITY

The primary factor in determining if an area is susceptible to rockfalls is the presence of a source for rockfall 

clasts. If there are no rocks on a slope, the rockfall 

hazard below becomes negligible. Case (1987c, 1989) 

identified all the range-front slopes, called spurs, along 

the Wasatch Front on which a rockfall source was found. 

The other major factor in identifying rockfall hazards is

the distance a dislodged rock will travel downslope. 

These two factors source and distance can be combined to provide reasonable estimates of areas susceptible to rockfalls, which are then classified as special study 

areas (Nelson, 1988).

The runout limit for each susceptible spur was determined using ROCKFALL, a computer simulation model 

program (Hoek, 1987). The program uses representative 

slope profile information for each spur and is based on 

two assumptions: that the slope surfaces are clean, hard 

bedrock, and that the rockfall is initiated from a 20-fthigh (6.1 m) outcrop. Rockfall events were simulated 

originating both at the top of each spur and at the 

steepest point on the spur. Rocks were started both with 

no initial velocity (simple gravity fall), and with an initial 

velocity (throw) (fig. 58). The combination of these 

factors (origination point and initial velocity) that yielded 

the longest runout distance was used as the lower limit of 

the special study area. It is believed that this represents 

a worst case rockfall event and provides some margin of 

safety.

The Salt Lake County Hillside Protection Zone ordinance prohibits building on slopes greater than 30 percent; therefore, all such slopes automatically fall into the 

special study area. The rockfall analyses suggest that, in 

general, most rocks would stop above the 30 percent 

slope break, making this slope the lower boundary of the 

study area. The runout continued below the 30 percent 

slope break onto gentler slopes on only 19 percent of the 

spurs. The special study area boundary between spurs 

follows the 30 percent slope break and includes all canyon 

areas. No studies have been performed in canyons, 

where all slopes are considered susceptible.

REDUCING ROCKFALL HAZARDS

When faced with any geologic hazard, the best alternative, where feasible, is avoidance. Therefore, it is best 

for developers to first try to locate buildings so that 

structures are not positioned in an area susceptible to 

rockfalls. Often, however, new developments cannot be 

designed around a rockfall path, or the rockfall paths 

cannot be accurately predicted, so hazard-reduction 

measures must be considered. When faced with land-use 

decisions, the costs of hazard reduction should be carefully compared with the costs of avoidance.

Techniques for reducing rockfall hazards may include 

mitigation of the actual hazard or modifying the exposed 

structure or facility. Rock stabilization techniques such 

as bolting, cable lashing, burying, and grouting discontinuities, as well as the removal or breakup of potential 

rockfall clasts, are all physical methods of mitigating the 

hazard. Deflection berms, slope benches, and rock-catch
140 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

109°

39°

110°

50 i i r i i100km

i r i r

0 50 miles

FIGURE 56. Location map of the July 3, 1984, Dead Horse Point rockfall, which registered on seismographs more than 60 mi (96 km) away

(modified from Case, 1987b).

fences may all stop or at least slow the falling rocks. 

Strengthening a structure to withstand impact is an 

example of modifying what is at risk. Twenty-seven 

techniques for reducing landslide hazards including rockfalls are described by Kockelman (1986). Mitigation 

problems can arise when the source area of the rocks is 

located on land not owned by the developer.

In areas where the rockfall hazard is very low, disclosure of potential hazards to land owners and residents 

with an acknowledgment of risk and willingness to accept 

liability may be an acceptable alternative to avoidance or 

mitigation, at least for single-family residences. In the 

past, Salt Lake County has used disclosure for airport 

noise zones and for surface-fault rupture hazards.

USE OF ROCKFALL HAZARD SPECIAL STUDY 

AREA MAPS

The rockfall hazards special study area map shows 

areas potentially susceptible to falling rocks (fig. 59) at a 

countywide scale (1:24,000). During the building permit 

approval process, the proposed site plan will be 

reviewed, and if any proposed structure falls within the 

special study area, a site investigation will be required to 

assess the hazard. If the site-specific data indicate that a 

hazard does not exist at the site, then development 

would proceed and the hazard map would be amended. 

Should the site-specific data indicate that a rockfall 

hazard exists, the consultant should give recommenda-
ROCKFALL HAZARDS: A GUIDE FOR LAND-USE PLANNING 141

CRASS CLAST CRASHES CLAMBAKE!

A barbeque party was rudely interrupted when a boulder 

two feet in diameter made a social comment by landing on 

the grill. The incident occurred the evening of 5 July, 1987, 

in the backyard of a house in the high avenues of Salt Lake 

City on North Cliff Drive.The rockfall clast originated from a 

back yard on North View Drive which is perched on a sand 

and gravel slope deposited by Ice-Age Lake Bonneville 

when it was at the Bonneville Level (5090 feet).

Craig V. Nelson, Salt Lake County Geologist, reported that 

the county was first notified when the owner of the barbeque grill asked about possible legal retribution. Craig, 

and Salt Lake City Environmental Planner Robert H. Buchanan, visited the scene of the crime on the 10th of July but 

missed seeing the culprit rock, presumably because it was 

retrieved by its previous owner.

Other boulders, partially hidden in weeds, appeared to 

be ready to follow their sibling and crash a party of their 

own. Slopes in the area were oversteepened when toes 

were removed during home construction. Erosion of the 

slope is gradually exposing large boulders which eventually 

must live down to their potential energy. Craig recommended a taller railroad tie retaining wall to prevent other 

social interruptions.

Interesting legal precedents, albeit small scale, may be set 

by the incident. Should the upslope owner be responsible 

for "acts of God" and replace the barbeque grill? Who 

owned the recalcitrant intruder, the source person or the 

receivership plaintiff?

There are copious boulders on retreating, oversteepened, slopes in the neighborhood to cause a recurrence of the problem. 

FIGURE 57. Article from the Utah Geological and Mineral Survey Survey Notes, spring 1987.

Gravity Fall

A. PURE GRAVITY FALL MODEL

B. INITIAL VELOCITY MODEL

FIGURE 58. Example of the output model generated by the computer 

program ROCKFALL (Hoek, 1987) for a rockfall event on a generalized slope. The total rock runout distance is estimated (A) given no 

initial velocity (pure gravity fall) and (B) given an initial velocity 

(throw).

tions for avoiding or reducing the hazard and include 

these considerations in the site plan. Regardless of the 

conclusions, results of the site-specific study should be 

submitted to the county geologist for review. A report 

discussing this review process has been prepared (Nelson and others, 1987) and is available from the county 

geologist. The Salt Lake County Planning Commission

considers the recommendations of planning staff and 

consultants and makes the final decision for approval of 

developments.

It is important that geological input be used early in 

the development process. In the past, developers have 

faced considerable expense in redesigning subdivisions 

around geologic problems. The astute real estate purchaser often seeks geological counsel prior to making an 

offer or makes a favorable geologic report a contingency 

of purchase. The hazard maps may also prove useful to 

private citizens and real estate agents by providing 

information needed to make an informed decision in the 

purchase of property.

SCOPE OF SITE INVESTIGATIONS

When development is proposed within the rockfall 

hazard special study area, a qualified engineering geologist or licensed geotechnical engineer must be employed 

to assess the site-specific rockfall hazard. Site investigations must define rockfall sources and estimate runout 

paths and runout distances from each source. Rockfall 

sources may be outcrops or individual clasts on a slope. 

Size, shape, depth of burial, and slope geometry are all 

factors to be considered in defining sources as well as 

runout path and distance. Computer models are available 

to simulate runout (Hoek, 1987; Pfeiffer and Bowen, 

1989), but physical evidence such as extent of clast 

accumulations below sources, topographic configuration, damaged vegetation, and natural barriers are also 

important.
142 ASSESSMENT OP REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

1200

FIGURE 59. Portion of the rockfall hazards special study area map in 

the Draper Quadrangle, southeast of Salt Lake City, Utah. Areas 

requiring site-specific investigations are stippled. Range-front 

source areas (spurs) are the more darkly shaded regions.

SUMMARY

The objective of special study area hazard maps, and 

regulation during permit approval, is not to restrict 

development but to help ensure that, when development 

does occur in geologically sensitive areas, the safety and 

property of citizens and their community are protected.

It must be realized that rockfalls are a natural phenomena and not every rockfall event can be accurately

modeled. Therefore, the rockfall special study areas are 

a best estimate of the probable hazard area. The hazard 

map is a regional, small-scale map suitable for indicating 

potential hazard areas. The map is not intended to 

substitute for site-specific data. As improved analytical 

tools become available, and the results of site-specific 

studies are completed, the hazard map will be updated.

REFERENCES

Case, W.F., 1987a, Rock fall hazards in Utah's urban corridor: Geological Society of America Abstracts With Programs, v. 19, no. 7, 

p. 614.

Case, W.P., 1987b, Dead Horse Point rockfall recorded on seismograph: Utah Geological and Mineral Survey, Survey Notes, v. 21, 

no. 4, p. 5.

Case, W.F., 1987c, Rock fall hazard susceptibility due to earthquakes, 

central Wasatch Front, Utah: U S. Geological Survey Open-File 

Report 87-585, p. V1-V36.

Case, W.P., 1988, Geology effects of the 14 and 18 August, 1988 

earthquakes in Emery County, Utah: Utah Geological and Mineral 

Survey, Survey Notes, v. 22. no. 1-2, p. 8-15.

Case, W.F., 1989, Rock-fall hazards in Cache, Salt Lake, and Tooele 

valleys, Wasatch Front, Utah: Utah Geological and Mineral Survey, unpublished map, scale 1:24,000.

Costa, J.E., and Baker, V.R., 1981, Surficial geology-Building with 

the Earth: New York, John Wiley and Sons, 498 p.

Hoek, E., 1987, ROCKFALL-A program in BASIC for the analysis of 

rockfalls from slopes: Unpublished NSERC Industrial Research 

Professor report, July 1, 1987, Toronto, Ontario, 10 p.

Keefer, O.K., 1984, Landslides caused by earthquakes: Geological 

Society of America Bulletin, v. 95, p. 402-421.

Kockelman, W.J., 1986, Some techniques for reducing landslide hazards: Bulletin of the Association of Engineering Geologists, v. 23, 

no. 1, p. 29-52.

Nava, S.J., Pechman, J.C., and Arabasz, W.J., 1988, The magnitude 

5.3 San Rafael Swell, Utah, earthquake of August 14, 1988: Utah 

Geological and Mineral Survey, Survey Notes, v. 22, no. 1-2, 

p. 16-19.

Nelson, C.V., 1988, Preparation and use of earthquake groundshaking 

and rock-fall hazard maps, Wasatch Front, Utah: Geological Society of America Abstracts With Programs, v. 20, no. 6, p. 459.

Nelson, C.V., Christenson, G.E., Lowe, Mike, and Robison, R.M., 

1987, The review process and adequacy of engineering geologic 

reports, Wasatch Front, Utah, in McCalpin, James, ed., Proceedings of the 23rd annual symposium on engineering geology and 

soils engineering: Utah State University, April 6-8, 1987, 

p. 83-85.

Pfeiffer, T.J., and Bowen, T.D., 1989, Computer simulation of rockfalls: Bulletin of the Association of Engineering Geologists, v. 26, 

no 1, p. 135-146.
DEBRIS-FLOW HAZARDS: A GUIDE FOR LAND-USE PLANNING,

DAVIS COUNTY, UTAH

By MIKE LOWE14

ABSTRACT

Debris flows, debris floods (hyperconcentrated streamflows), and 

clear-water flooding form a continuum of sediment and water mixtures 

that may be hazardous to development on alluvial fans. Debris flows 

can be generated either by scouring soil materials from the ground 

surface and stream channels during rainstorms, or by adding water to 

debris slides until they are fluid enough to reach a flowing stream. In 

Davis County, debris flows and debris floods have occurred often 

historically and have caused loss of life and significant damage to 

property.

Debris-flow hazards (including hyperconcentrated-streamflow hazards) in Davis County are mapped at a scale of 1:24,000 using U.S. 

Geological Survey 7V2' (topographic) quadrangles as base maps. It is 

recommended that debris-flow hazards be evaluated, and if necessary, 

hazard reduction measures be required, prior to planning commission 

approval of new development proposed within the debris-flow hazard 

area depicted on these maps.

INTRODUCTION

Debris flows are mixtures of water, rock, soil, and 

organic material, 70-90 percent solids by weight (Costa, 

1984), that form a muddy slurry, much like wet concrete, 

and flow downslope, commonly in surges or pulses, due 

to gravity. The flows generally remain confined to 

stream channels in mountainous areas but may reach and 

deposit debris over large areas on alluvial fans at and 

beyond canyon mouths. The eastern portion of Davis 

County is particularly susceptible to debris-flow hazards 

because of the steep mountains and the weathering 

characteristics of the bedrock (the Precambrian Farmington Canyon Complex), which provide much unstable 

hillside debris (Wieczorek and others, 1983; Pack, 1985). 

Debris flows have occurred often in Davis County during 

historical time and have caused damage to property and 

loss of life (table 13). It is the purpose of this report to 

discuss the nature of debris-flow hazards in Davis 

County, the potential consequences, the Davis County 

maps showing debris-flow hazards in a special study 

zone, and recommendations regarding use of the maps

Davis County Planning Department, Framington, Utah.

for land-use planning. A major goal is to translate 

technical information so that government officials and 

the general public can appreciate the need to reduce 

debris-flow hazards. The special study zone maps, which 

were constructed from the boundaries of active alluvial 

fans and areas with slopes steeper than 30 percent, 

identify areas where debris-flow hazards should be evaluated prior to approval of proposed development.

TABLE 13. Historical Davis County debris flows (from Marsell, 

1972; Wieczorek and others, 1983; U.S. Army Corps of Engineers, 

1984)

Drainage Years Reported damage or 

loss of life

Dry Fork, Kays Creek 

Middle Fork, Kays

Creek. 

South Fork, Kays

Creek.

North Fork, Holmes

Creek. 

South Fork, Holmes

Creek. 

Baer Creek 

Shepard Creek

Farmington Creek

Rudd Creek

Steed Creek 

Davis Creek

Ricks Creek

Parrish Creek

Stone Creek 

Mill Creek

1984

1947, 1953

1912, 1923,

1927, 1945,

1947.

1983

1917

1983

1923, 1930,

1983.

1878, 1923,

1926, 1930,

1947, 1983.

1983, 1984

1923

1878, 1901,

1923.

1923, 1929,

1930.

1930 (several

events).

1983

1983

House damaged

Seven deaths and 

several houses 

damaged (1923).

35 houses damaged, 

15 severely 

(1983).

One house damaged

in 1923 and one in

1930. 

Several houses

destroyed, school

damaged. 

Houses damaged

143
144 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

ACKNOWLEDGMENTS

Gary E. Christenson (Utah Geological Survey), Barry 

Burton, Tim Stephens, and Wilf Sommerkorn (Davis 

County Planning Department), Sidney W. Smith (Davis 

County Public Works), Scott R. Williams (Davis County 

Flood Control), Craig Barker (Weber County Planning 

Department), and Al Chleborad, William J. Kockelman, 

and Gerald F. Wieczorek (U.S. Geological Survey) 

kindly reviewed this paper and provided valuable suggestions. Bill Black (Utah Geological Survey) drafted the 

figures.

NATURE AND CAUSES OF DEBRIS FLOWS

Although this report chiefly addresses debris flows, 

other forms of flow are also considered because debris 

flow, debris flood (hyperconcentrated streamflow), and 

normal streamflow form a continuum of sediment-water 

mixtures that grade into each other as the relative 

proportion of sediment to water changes and as stream 

gradient changes (Pierson and Costa, 1987). Deposition 

of sediment transported by these types of flows ultimately takes place on alluvial fans at and beyond canyon 

mouths. Deposition on alluvial fans is caused by the 

decrease in channel gradient and increase in channel 

area, resulting in a decrease in depth and velocity of flow 

and an increase in internal friction of the flowing debris 

as the stream leaves its constricted channel and enters 

the main valley floor (Jochim, 1986).

Debris flows can form in at least two ways. In mountainous eastern Davis County, where cloudburst rainstorms are common, overland flow and floodwaters can 

scour materials from the ground surface and stream 

channels, thereby increasing the proportion of soil materials to water until the mixture becomes a debris flow 

(Wieczorek and others, 1983). The size and frequency of 

debris-flow events generated by rainfall are dependent 

on several factors, including the amount of loose material 

available for transport, the magnitude and frequency of 

the storms, the density and type of vegetative cover, and 

the moisture content of the soil (Campbell, 1975; Pack, 

1985; Wieczorek, 1987). Debris flows during the 1920's 

and 1930's in Davis County were generated by overland 

erosion during summer cloudburst storms that fell on 

watersheds that had been depleted of vegetative cover 

by overgrazing and burning (Copeland, 1960).

Debris flows can also mobilize directly from debris 

slides. A debris slide is a type of landslide in which the 

material involved is predominantly coarse-grained 

debris, chiefly colluvium, and the form of movement is 

mainly translational (Varnes, 1978). A debris flow may 

be generated when the debris slide reaches a stream, or 

when the water content is increased in the debris slide by

some other means until sufficient to permit flow. Debris 

flows during the springs of 1983 and 1984 in Davis 

County were mobilized from debris slides caused by 

rapid melting of an unusually thick snowpack (Wieczorek 

and others, 1983).

As the relative proportion of water to sediment 

increases with either the addition of more water or 

removal of sediment by deposition, debris flows become 

hyperconcentrated streamflows. Hyperconcentrated 

streamflows are often referred to as debris floods or mud 

floods because soil materials are transported by fastmoving floodwaters (Wieczorek and others, 1983). Solids 

account for 40 to 70 percent of the material by weight 

(Costa, 1984). These flows can originate either through 

progressive incorporation of materials into floodwaters 

or through dilution of debris flows (Waitt and others, 

1983; Wieczorek and others, 1983). Because of difficulties 

in distinguishing hyperconcentrated streamflow from 

flood stages of normal streamflow, there is no adequate 

record of historical hyperconcentrated-streamflow 

events in Davis County.

In normal streamflow, solids account for less than 40 

percent of the water-sediment mixture by weight (Costa, 

1984). Snowmelt flooding in Davis County is a nearly 

annual event, and abnormally high snowmelt floods 

occurred in Davis County in 1922, 1952 (Marsell, 1972), 

1983, and 1984. Snowmelt-induced flood magnitudes are 

somewhat predictable and depend on the volume of snow 

in the mountains and the rate of temperature increase in 

the spring. Summer cloudburst floods account for more 

localized but often very destructive flooding and can 

occur with little warning. Davis County experienced 39 

cloudburst floods between 1850 and 1969 (Butler and 

Marsell, 1972). The clear-water flooding hazard has been 

significantly reduced in recent years by the construction 

of flood detention structures and improvements in stormsewer systems and stream channels.

EFFECTS OF DEBRIS FLOWS

Loss of life during debris-flow, hyperconcentratedstreamflow, and normal-streamflow events may result 

from drowning, high-velocity impact, or burial. The 

following discussion of damages associated with debris 

flows is taken chiefly from Campbell (1975). The effects 

on residential structures range from simple inundation to 

complete destruction by high-velocity impact.

The velocity of a debris flow is an important consideration in determining the level of damage to structures. 

Many debris flows move with speeds on the order of 27 

mi/h (40 ft/s, 12 m/s), but others move as slowly as 1 ft/s 

(0.3 m/s) down relatively gentle slopes. Debris flows of 

sufficient volume and momentum have destroyed residential structures and moved the remains off their
DEBRIS-FLOW HAZARDS: A GUIDE FOR LAND-USE PLANNING 145

foundations. Debris flows of relatively small volume but 

high momentum have broken through outside walls and 

even completely through structures. Low-velocity debris 

flows may enter dwellings through open doors or push 

laterally through windows and doorways to flood interiors. All three types of flows may fill basements with 

mud, water, and debris or pile debris around structures. 

Debris may also bury yards, streets, parks, driveways, 

parking lots, and any ground-level structure. In the 

distal portions of the alluvial fans, damage is usually 

comparatively minor, consisting primarily of mud and 

water damage to outer walls of buildings, basements, 

and yards. Keaton and others (1988) have devised an 

intensity scale, generally related to thickness of deposition, for damages associated with debris-flow events 

(table 14). Table 14 gives a good indication of the types 

and severity of potential damage.

DEBRIS-FLOW HAZARD REDUCTION

Methods for reducing debris-flow hazards include 

avoidance, source-area stabilization, transportation-zone 

(debris-flow track between the source area and the 

depositional zone) modification, and defense measures in 

the depositional zone (Hungr and others, 1987). Different 

methods or combinations of methods may be appropriate 

for different drainages or types of development.

Debris-flow hazards may be reduced by avoiding, 

either permanently or at the time of imminent danger, 

areas at risk from debris flows (source areas, transportation zones, and depositional zones). Permanent avoidance is not possible in some areas because many Davis 

County cities have large numbers of existing structures 

on active alluvial fans (potential depositional zones), 

where damage due to debris flows may occur. Permanent 

avoidance of debris-flow hazards could be required for 

proposed new development in most Davis County cities 

through enforcement of existing ordinances concerning 

foothill development (zoning), but this is generally not 

politically acceptable unless other mitigation techniques 

are not feasible.

Warning systems may be used to avoid life threats 

from debris flows at the time of imminent danger, 

generally through evacuation of threatened areas. 

Hungr and others (1987) identify three categories of 

debris-flow warning systems: pre-event, event, and 

post-event. Pre-event warning systems are designed to 

identify periods of time when climatic conditions have 

increased the potential for debris-flow occurrence. Davis 

County has established a computer-linked remote 

weather station ALERT system that allows real-time 

evaluation of rainfall, wind, soil moisture, streamflow, 

and landslide-movement data. Although this ALERT 

system has not yet been used to predict debris-flow

TABLE 14. Alluvial-fan sedimentation intensity scale proposed by 

Keaton and others (1988)

Intensity Damage Description

0 None No damage.

1 Negligible Damage to landscape and access; no 

damage to structures; minor scour 

and (or) sediment deposition.

2 Slight Sediment generally less than 3.3 ft

(1 m) thick deposited against buildings without structural damage; sediment flooded around parked vehicles.

3 Moderate Sediment generally greater than 3.3 ft 

(1 m) thick deposited against buildings with easily reparable structural 

damage; basements partially filled 

with sediment; reparable damage to 

parked vehicles shoved by sediment.

4 Severe Sediment greater than 3.3 ft (1 m)

thick deposited against buildings with 

reparable structural damage; basements completely filled with sediment; wood structures detached from 

foundations; nonreparable damage to 

parked vehicles shoved by sediment 

(e.g., distorted frames).

5 Extreme Sediment greater than 3.3 ft (1 m)

thick deposited against buildings with 

nonreparable damage; structures collapsed by force (drag or impact) of 

flow; wood structures shoved from 

foundations; parked vehicles so badly 

damaged that they have small sal-

_____________vage value._______________

events, this use of the system may be possible in the 

future as the relationship between climatic conditions 

and the initiation of debris flows in Davis County 

becomes better understood.

Event warning systems are designed to provide an 

alarm when a debris-flow event is occurring (Hungr and 

others, 1987). Two types of event warning systems are 

being implemented in Davis County. Computer-linked 

remote extensometers have been used to monitor realtime movement of detached landslides in Rudd and Baer 

Canyons. Computer-linked remote streamflow gages, 

which have been placed on most Davis County streams, 

can sound alarms if streamflow drops below or rises 

above preset levels. In both cases, the event warnings 

are designed to alert Davis County Flood Control and 

Davis County Sheriff Department personnel of potential 

debris-flow events.

Post-event warning systems, such as slide-warning 

fences, are usually designed to warn of disruption of 

transportation routes (Hungr and others, 1987). This 

type of warning system has not been used in Davis 

County, where most transportation routes are in urban 

areas and where mass-media warnings, barricades, and 

detours have been sufficient in the past.
146 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Source-area stabilization consists of reducing the 

amount of hillside material available for incorporation 

into debris-flow or hyperconcentrated-streamflow 

events. Improving drainage-basin vegetation is one 

method of source-area stabilization. The prevention of 

wildfires and forest fires combined with restrictions 

against overloggmg and overgrazing will protect existing 

vegetation. Terracing of mountain slopes, such as was 

done in the 1930's in Davis County by the Civilian 

Conservation Corps under the supervision of the U.S. 

Forest Service (Bailey and Croft, 1937), is useful in 

preventing debris flows caused by erosion during cloudburst storms. Oversteepened slopes comprising the 

source-area scars of former debris flows may be the 

source of additional hillside material during future 

landslide-initiated debris-flow events (Baldwin and others, 1987). Landslide-mitigation techniques that have 

been used in California to reduce debris-flow hazards 

include control of subsurface drainage, diversion of surface drainage, grading of source-area scars to a uniform 

slope, riprap repair of the source-area scar, and use of 

retaining walls (Baldwin and others, 1987). Stabilization 

of source areas for landslide-initiated debris flows has not 

been attempted in Davis County.

Transportation-zone modifications are generally 

designed to reduce the incorporation of channel material 

into debris flows and improve the ability of the channel to 

pass debris surges downstream. Scour of unconsolidated 

material in streambeds and undercutting of unstable 

streambanks are two of the most important processes 

contributing to the growth of debris-flow surges (Hungr 

and others, 1987). Check dams are small debris-retention 

structures placed in unstable channel areas to prevent 

incorporation of material from that part of the channel 

into debris flows. These check dams are used extensively 

in Europe and Japan to arrest or reduce debris-flow 

surges (Hungr and others, 1987). Streambed stabilization may also be achieved by lining the channel. The 

ability of stream channels to pass debris surges downstream may be improved through removal of channel 

irregularities, enlargement of culverts combined with 

installation of upstream removable grates to prevent 

blockage, and construction of flumes, baffles, deflection 

walls, and dikes (Jochim, 1986; Baldwin and others, 

1987). Structures crossing potential debris-flow channels 

may be protected by bridging the channels with sufficient clearance to allow debris surges to pass under 

structures, construction of debris sheds designed to 

allow debris flows to pass over structures, and designing 

structures to withstand debris-flow impact, burial, and 

reexcavation (Hungr and others, 1987). Transportationzone modifications in Davis County have been restricted 

to some stream channels below canyon mouths and 

consist mainly of dikes and deflection walls constructed

in the 1920's and 1930's and removal of channel irregularities and lining of channels in the 1980's. Stream 

channels above canyon mouths have generally not been 

modified.

Defense measures in the deposition zone are designed 

to control both the areal extent of deposition and damage 

to any structures located there (Hungr and others, 1987). 

Defense measures include deflection devices, impact 

walls, and debris basins. Deflection devices are used to 

control the direction and reduce the velocity of debris 

flows (Baldwin and others, 1987). Types of deflection 

devices include pier-supported deflection walls, debris 

fences (a series of steel bars or cables placed horizontally 

at increasing elevations above the stream channel), 

bernis, splitting-wedge walls (reinforced concrete wall in 

the shape of a "V" with the point facing uphill), and 

gravity structures like gabions (hollow wicker-works or 

iron cylinders filled with earth) (Baldwin and others, 

1987; Jochim, 1986).

Impact walls are designed to sustain the instantaneous 

force of impact from debris flows while containing the soil 

and vegetation debris until it can be removed (Baldwin 

and others, 1987). This impact force may be as high as 

125 lb/ft3 (19,640 N/m3) (Hollingsworth and Kovacs, 

1981). Types of impact walls employed in the United 

States include concrete walls, soldier pile walls, and soil 

and (or) rock gravity walls (including gabions) (Baldwin 

and others, 1987).

Two types of debris basins, open and closed, are 

commonly employed to reduce debris-flow hazards. Both 

types are designed to constrain the area of debris deposition to predetermined limits laterally, upstream, or 

downstream (Hungr and others, 1987). Open debris 

basins commonly have a basin-overflow spillway 

designed to direct excess material to an insensitive area 

or back into the stream channel, but straining outlets to 

remove water from entrapped debris are not generally 

provided. Closed debris barriers and basins can be 

located in the lower part of the transportation zone as 

well as in the deposition zone or on the alluvial fan 

(Hungr and others, 1987). Any suitable location along the 

lower part of the debris-flow path can be chosen to erect 

a barrier across the path and create a basin upstream. 

Closed debris barriers are provided with both straining 

outlets to pass water discharges and spillways to handle 

emergency debris overflows (Hungr and others, 1987). 

Both types of debris basins require access for maintenance and for removal of entrapped debris. Debris 

basins, both open (constructed in the 1930's) and closed 

(constructed in the 1980's), are the primary debris-flow 

hazard reduction technique employed in Davis County. 

Figure 60 shows the location of these debris basins. The 

Davis County debris basins vary greatly in storage
DEBRIS-FLOW HAZARDS: A GUIDE FOR LAND-USE PLANNING 147

01 234 5 6789 km 

 Debris Basin

FIGURE 60. Location map for debris basins in Davis County.
148 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

DAVIS COUNTY

Salt Lake City

UTAH

5 10 Kilometers

EXPLANATION

Location of Figure 62

FIGURE 61. Location map for figure 62.

capacity, and their adequacy to contain the debris from 

events of various magnitudes has generally not been 

evaluated.

SUMMARY OF METHODS USED IN MAP 

PREPARATION

Preliminary surficial geologic mapping by A.R. Nelson 

and S.F. Personius (unpublished mapping, 1987) was 

used to define debris-flow hazard areas at the mountain 

front. These maps differentiate active alluvial fans, 

where deposition during debris-flow and hyperconcentrated-streamflow events may occur, from areas 

not subject to debris flows, including older fans that are 

no longer active. Upper Holocene alluvial fans and 

undivided young alluvial fans, as mapped by A.R. Nelson 

and S.F. Personius (unpublished mapping, 1987), were 

combined and redesignated younger Holocene (active) 

alluvial fans. These fans represent areas that are considered susceptible to debris-flow hazards. In addition, all 

mountainous areas with slopes greater than 30 percent 

are considered to be susceptible to debris-flow initiation. 

The adequacy of existing debris basins or structures built 

to divert debris flows was not considered during preparation of the special study zone maps. The existence and 

adequacy of these structures should be considered for 

site-specific studies, however.

The frequency of occurrence (recurrence) of debrisflow events in a drainage basin depends on climatic 

factors as well as the availability of debris. Recurrence 

intervals vary among drainage basins and depend on the 

magnitude of the event (volume of sediment transported). For example, the recurrence interval for sedimentation events exceeding 40,000 yd3 (30,600 m3) of 

material deposited at the Ricks Creek debris basin has 

been calculated to range between 55 and 1,590 yr, but the 

recurrence interval for sedimentation events exceeding 

65,000 yd3 (49,700 m3) of material deposited at the Rudd 

Creek debris basin has been calculated to range between 

155 and 5,845 yr (Keaton and others, 1988). These 

numbers are significant because the volumes given represent the capacity of debris basins constructed at the 

mouths of Ford (Ricks Creek) and Rudd Canyons, 

respectively (Keaton and others, 1988). Recurrence 

intervals for debris-flow events of different magnitudes 

are not currently available for the other Davis County 

drainages.

RECOMMENDED USE OF MAPS IN LAND-USE 

PLANNING

The debris-flow hazard special study zone maps (figures 61 and 62) show areas where site-specific studies 

addressing debris-flow hazards are recommended prior 

to development. These maps are at a scale of 1:24,000 and 

are designed to show potential hazard areas for planning 

purposes only. It is recommended (see table 15) that 

debris-flow hazards be evaluated and any necessary 

hazard reduction measures be described by an engineering geologist in site-specific reports. The reports are 

then submitted by the developer to the planning commission prior to approval for all construction in the debrisflow hazard special study zone. Because of the relatively 

small scale of the maps, the possibility exists that some 

small hazard areas are not shown; studies concerning 

debris flows are therefore recommended for critical 

facilities even outside the special study zones. The imporTABLE 15. Matrix indicating recommended report requirements for 

debris-flow hazards, Davis County, Utah

Type of development

Debris-flow hazard 

special study zone

Inside Outside

Critical facilities such as lifelines and highoccupancy buildings.

Industrial and commercial buildings 

(other than high occupancy).

Residential subdivisions

Residential single lots___________

Yes1 

Yes2

Yes2 

Yes2

Yes1 

No

No 

No

If a debris basin is present above site, debris-flow special study must address adequacy of 

debris basin, both hi terms of design and maintenance.

If a debris basm is present above the site, debris-flow special studies are not required.
DEBRIS-FLOW HAZARDS: A GUIDE FOR LAND-USE PLANNING 149

FIGURE 62. Example of a debris-flow hazard special study zone 

map for the east Layton area of northern Davis County, Utah. 

Cross hatching indicates areas where debris-flow hazard studies 

are recommended prior to planning commission approval of 

proposed development. SNR, area where debris-flow studies 

should not be required; DS, debris slide; DF, debris flow; a, 

active (historic) slope failure; AF, younger Holocene (active)

tance in terms of life safety of such structures merits this 

precaution, and studies need only consider the hazard 

and either confirm that it does not exist or perform the 

necessary study if a potential hazard is found.

SCOPE OF SITE INVESTIGATIONS

The scope of investigations for site-specific reports 

evaluating debris-flow hazards for proposed developalluvial fan. This figure was reproduced from a portion of the 

debris-flow hazard special study zone map, Kaysville Quadrangle, 

Davis County, Utah, and is based on information from A.R. 

Nelson and S.F. Personius (unpublished mapping, 1987), G. 

Kappeser (written commun., 1986), Bryant (1984), Olson (1981), 

and M. Lowe (unpublished mapping, 1987).

ment should include (1) an analysis of the potential for 

the drainage basin to produce debris flows based on the 

presence of debris slides and colluvium-filled slope concavities and an estimate of the largest probable volumes 

likely to be produced during a single event; (2) an 

analysis of the stream channel to determine if the channel 

will supply additional debris, impede flow, or contain 

debris flows in the area of the proposed development; (3) 

an analysis of manmade structures upstream that may 

divert or deflect debris flows; and (4) recommendations
150 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

concerning any channel improvements, flow modification 

and catchment structures, direct protection structures, 

or flood-proofing measures, if necessary, to help protect 

the proposed development.

For critical facilities within the special study zone, any 

debris basins upstream from the site must be evaluated 

in terms of the storage capacity to reduce the debris-flow 

hazard. The quality of maintenance on these debris 

basins should also be addressed. The U.S. Army Corps of 

Engineers (1988) has evaluated the adequacy of many of 

the central Davis County basins to contain the 100-yr 

debris-flow event volumes, but Davis County is challenging the methodology used in determining the values for 

those 100-yr event volumes (Williams and others, 1989). 

Wieczorek and others (1983), Pack (1985), and Keaton 

and others (1988) identified factors to be considered 

when evaluating debris-flow hazards, and these references should be consulted during site investigations. Sitespecific reports should be reviewed by the county, and, 

once approved, should be forwarded to the planning 

commission along with review comments. The planning 

commission then has sufficient information to make decisions regarding the proposed development.

REFERENCES

Bailey, R.W., and Croft, A.R., 1937, Contour trenches, control floods, 

and erosion on range lands: Washington, D.C., U.S. Government 

Printing Office, Emergency Conservation Work Forestry Publication 4, 22 p.

Baldwin, J.E., II, Donley, H.F., and Howard, T.R., 1987, On debris 

flow/avalanche mitigation and control, San Francisco Bay area, 

California, in Costa, J.E., and Wieczorek, G.F., eds., Debris 

flows/avalanches Process, recognition, and mitigation: Geological 

Society of America Reviews in Engineering Geology, 

v. 7, p. 223-236.

Bryant, Bruce, 1984, Reconnaissance geologic map of the Precambrian 

Farmington Canyon Complex and surrounding rocks in the 

Wasatch Mountains between Ogden and Bountiful, Utah: U.S. 

Geological Survey Miscellaneous Investigation Series Map 1-1447, 

scale 1:50,000.

Butler, Elmer, and Marsell, R.E., 1972, Cloudburst floods in Utah, 

1939-69: Utah Department of Natural Resources, Division of 

Water Resources, Cooperative Investigations Report 11, 103 p.

Campbell, R.H., 1975, Soil slips, debris flows, and rainstorms in the 

Santa Monica Mountains and vicinity, southern California: U.S. 

Geological Survey Professional Paper 851, 51 p.

Copeland, O.L., 1960, Watershed restoration: A photo-record of conservation practices applied in the Wasatch Mountains of Utah: 

Journal of Soil and Water Conservation, v. 15, no. 3, p. 105^120.

Costa, J.E., 1984, Physical geomorphology of debris flows, in Costa, 

J.E., and Fleisher, P.J., eds., Developments and applications of 

geomorphology: New York, Springer-Verlag, p. 268-317.

Hollingsworth, Robert, and Kovacs, G.S., 1981, Soil slips and debris 

flows Prediction and protection: Association of Engineering 

Geologists Bulletin, v. 18, no. 1, p. 17-28.

Hungr, Oldrich, VanDine, D.F., and Lister, D.R., 1987, Debris flow 

defenses in British Columbia, in Costa, J.E., and Wieczorek, G.F., 

eds., Debris flows/avalanches Process, recognition, and mitigation: Geological Society of America Reviews in Engineering Geoll ogy, v. 7, p. 201-222.

Jochim, C.L., 1986, Debris-flow hazard in the immediate vicinity of 

Ouray, Colorado: Colorado Geological Survey Special Publication 

30, 63 p.

Keaton, J.R., Anderson, L.R., and Mathewson, C.C., 1988, Assessing 

debris flow hazards on alluvial fans in Davis County, Utah: 

Proceedings of the 24th symposium on engineering geology and 

soils engineering, p. 89-108.

Marsell, R.E., 1972, Cloudburst and snowmelt floods, in Hilpert, L.S., 

ed., Environmental geology of the Wasatch Front, 1971: Utah 

Geological Association Publication 1, p. N1-N18.

Olson, E.P., 1981, Geologic hazards of the Wasatch Range, Part 1, 

Ward Canyon to south side Ogden Canyon: U.S. Department of 

Agriculture, Forest Service, R-4 Intermountain Region, unpublished maps of selected quadrangles within U.S. Forest Service 

boundaries, scale 1:24,000.

Pack, R.T., 1985, Multivariate analysis of relative landslide susceptibility in Davis County, Utah: Logan, Utah State University, 

Ph.D. dissertation, 233 p.

Pierson, T.C., and Costa, J.E., 1987, A rheologic classification of 

subaerial sediment-water flows, in Costa, J.E., and Wieczorek, 

G.F., eds., Debris flows/avalanches Process, recognition, and 

mitigation: Geological Society of America Reviews in Engineering 

Geology, v. 7, p. 1-12.

U.S. Army Corps of Engineers, 1984, Wasatch Front and central Utah 

flood control study, Utah: Sacramento District, 180 p.

U.S. Army Corps of Engineers, 1988, Mudflow modeling, one- and 

two-dimensional, Davis County, Utah: Omaha District, 53 p.

Varnes, D.J., 1978, Slope movement types and processes, in Schuster, 

R.L., and Krizek, R.S., eds., Landslides Analysis and control: 

Washington D.C., National Academy of Sciences, Transportation 

Research Board, Special Report 176, p. 12-33.

Waitt, R.B., Pierson, T.C., Maclead, N.S., Janda, R.J., Voight, B., 

and Holcomb, R.T., 1983, Eruption-triggered avalanche, flood, 

and lahar at Mount St. Helens Effects of winter snowpack: 

Science, v. 221, no. 4618, p. 1394-1397.

Wieczorek, G.F., 1987, Effect of rainfall intensity and duration on 

debris flows in central Santa Cruz Mountains, California, in Costa, 

J.E., and Wieczorek, G.F., eds., Debris flows/avalanches Process, recognition, and mitigation: Geological Society of America 

Reviews in Engineering Geology, v. 7, p. 93-104.

Wieczorek, G.F., Ellen, Stephen, Lips, E.W., Cannon, S.H., and 

Short, D.N., 1983, Potential for debris flow and debris flood along 

the Wasatch Front between Salt Lake City and Willard, Utah, and 

measures for their mitigation: U.S. Geological Survey Open-File 

Report 83-635, 45 p.

Williams, S.R., Lowe, Mike, and Smith, S.W., 1989, The discrete 

debris-mud flow risk analysis method: Proceedings of the 1988 

conference of the Arid West Committee of the Association of State 

Floodplain Managers, Las Vegas, Nevada, October 19-21, 1988, 

p. 157-167.
LIQUEFACTION HAZARDS: A GUIDE FOR LAND-USE PLANNING,

DA VIS COUNTY, UTAH

By MIKE LowE15

ABSTRACT

Ground shaking during earthquakes may cause saturated sandy soils 

to 'liquefy" as a result of increased pore-water pressures. Soil liquefaction can result in bearing capacity failure, ground oscillation, lateral 

spreading, or flow landsliding. The potential for liquefaction is dependent both on soil and ground-water conditions and on the severity and 

duration of ground shaking. In general, an earthquake of Richter 

magnitude 5 or greater is needed to induce soil liquefaction.

Five lateral-spread landslides that are believed to have resulted from 

liquefaction during prehistoric earthquakes have been mapped in Davis 

County. Also, generalized maps depicting liquefaction potential in 

Davis County are available and can be used to indicate hazard areas 

where site-specific studies should be required prior to development. 

The purpose of this report is to make recommendations concerning how 

these maps should be used as part of the development approval 

process.

It is recommended that planning commissions require site-specific 

liquefaction-hazard evaluations for all critical facilities such as lifelines 

and high-occupancy buildings. For industrial and commercial building 

sites, it is recommended that liquefaction-hazard evaluations be 

required only in areas with susceptibility ratings that are high or 

moderate on the liquefaction-potential maps. Site-specific studies are 

generally not recommended for residential subdivisions or single lots 

because of the lower risk in terms of life loss and property damage in 

such structures, and the relatively high costs of study and mitigation.

INTRODUCTION

Ground shaking during earthquakes causes a variety 

of phenomena that can damage structures and threaten 

lives. One such phenomenon is termed soil liquefaction. 

Ground shaking tends to increase the pressure in the 

pore water between soil grains, which decreases the 

stresses between the grains. The loss of intergranular 

stress can cause the strength of some soils to decrease 

nearly to zero. The soil then behaves like a liquid and 

therefore is said to have liquefied. When liquefaction 

occurs, foundations may crack, buildings may tip, buoyant buried structures such as septic tanks and storage 

tanks may rise, and even gentle slopes may fail as 

liquefied soils and overlying materials move downslope.

15 Davis County Planning Department, Farmington, Utah.

The potential for liquefaction depends both on soil and 

ground-water conditions and on the severity and duration of ground shaking. Soil liquefaction most commonly 

occurs in areas of shallow ground water (less than 30 ft, 

or 9 m) and loose sandy soils such as are found in western 

Davis County. In general, an earthquake of Richter 

magnitude 5 or greater is needed to induce liquefaction 

(Kuribayashi and Tatsuoka, 1975,1977; Youd, 1977). For 

larger earthquakes, liquefaction is more likely to occur 

and will occur at greater distances from the epicenter 

(the point on the Earth's surface directly above the focus 

of the earthquake). Earthquakes of Richter magnitude 

7.0-7.5 are the largest expected along the Wasatch front 

(Schwartz and- Coppersmith, 1984). During such earthquakes, liquefaction has occurred up to 170 mi (273 km) 

from the epicenter (1977 Romanian earthquake, magnitude 7.2) (Youd and Perkins, 1987).

Anderson and others (1982) have produced maps 

depicting liquefaction potential for Davis County. It is 

the purpose of this report to discuss the nature of the 

hazard, the potential consequences, and commonly used 

techniques to reduce the hazard, and to recommend how 

these maps should be used by Davis County and its cities 

for land-use planning. A major goal is to translate 

technical information so that government officials and 

the general public can appreciate the need to reduce 

liquefaction hazards.

ACKNOWLEDGMENTS

Gary E. Christenson (Utah Geological Survey), Loren 

R. Anderson (Department of Civil and Environmental 

Engineering, Utah State University), Jeffrey R. Keaton 

(Sergent, Hauskins and Beckwith), Craig Barker 

(Weber County Planning Department), Barry Burton 

and Tim Stephens (Davis County Planning Department), 

and William J. Kockelman and Hal Olsen (U.S. Geological Survey) kindly reviewed this paper and provided 

valuable suggestions. Bill Black (Utah Geological Survey) drafted the figures.

151
152 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

TABLE 16. Ground slope and expected failure mode resulting from

liquefaction 

[modified from Youd, 1978a; Anderson and others, 1982]

Ground surface slope Failure mode

Less than 0.5 percent

Less than 0.5 percent, 

liquefaction at depth.

0.5 to 5.0 percent 

Greater than 5.0 percent

Bearing capacity 

Ground oscillation

Lateral-spread landslide 

Flow landslide

NATURE OF THE LIQUEFACTION HAZARD

Liquefaction itself does not necessarily cause damage, 

but it may induce ground failure of various types that can 

be very damaging. The four types of ground failure that 

commonly result from liquefaction are loss of bearing 

strength, ground oscillation, lateral-spread landslides, 

and flow landslides (Youd, 1978a, b; Tinsley and others, 

1985). Youd and others (1975) relate these types of 

ground failure to the slope of the ground surface (table 

16).

Loss of bearing strength beneath a structure can occur 

during ground shaking when the underlying soil liquefies 

and loses strength (Tinsley and others, 1985) in areas 

where slopes are generally less than about 0.5 percent 

(Anderson and others, 1982) (fig. 63). The soil mass can 

then deform, allowing buildings to settle and (or) tilt 

(Tinsley and others, 1985). Buoyant buried structures 

such as gasoline storage or septic tanks may float upward 

in liquefied soils (Tinsley and others, 1985). Among the 

more spectacular examples of a bearing capacity failure 

was the tilting of four 4-story buildings, some as much as 

60 degrees, in the Kwangishicho apartment complex 

during the 1964 Niigata, Japan, earthquake (National 

Research Council, 1985). Buried septic tanks rose as 

much as 3 ft (1 m) during the same earthquake (Tinsley 

and others, 1985).

UPWARD FLOW OF WATER

Before liquefaction After liquefaction

FIGURE 63. Tilting of a building due to liquefaction and loss of bearing 

strength in the underlying soil. Liquefaction reduces shear strength 

of the soil, which provides foundation support, allowing the building 

to settle and tilt (Youd, 1984, in National Research Council, 1985).

Ground oscillation takes place when liquefaction occurs 

beneath soil layers that do not liquefy and where slopes 

are too gentle for lateral displacement to occur (Tinsley 

and others, 1985). Under these conditions, "liquefaction 

at depth commonly decouples overlying soil blocks, 

allowing them to jostle back and forth on the liquefied 

layer during an earthquake" (National Research Council, 

1985) (fig. 64). The decoupled layer vibrates in a different 

mode than the underlying and surrounding firm ground, 

causing fissures to form and impacts to occur between 

oscillating blocks and adjacent firm ground (National 

Research Council, 1985; Tinsley and others, 1985). Overlying structures and buried facilities can be damaged as 

a result of ground settlement, the opening and closing of 

fissures, and sand boils, which commonly accompany the 

oscillations (Tinsley and others, 1985).

Where the ground surface slope ranges between 0.5 

and 5.0 percent, failure by lateral spreading may occur 

(Anderson and others, 1982). Lateral spreads occur as 

surficial blocks of sediment are displaced laterally downslope as a result of liquefaction in a subsurface layer

Soil 

Boils

Water table

Liquefied Zone

Before liquefaction After liquefaction

FIGURE 64. Diagram of liquefaction-induced ground oscillation. Liquefaction (cross-hatched zone) causes the surface layer to decouple from the 

surrounding firm ground, resulting in ground settlement, the opening and closing of fissures, and sand boils (Youd, 1984, in National Research 

Council, 1985).
LIQUEFACTION HAZARDS: A GUIDE FOR LAND-USE PLANNING 153

Stream channel

Before liquefaction

Sand 

Boil

INITIAL SECTION

Sand 

Boil

Liquefied Zone \ After liquefaction

DEFORMED SECTION

FIGURE 65. Diagram of a lateral spread. Liquefaction occurs in the 

cross-hatched zone (Youd, 1984, in National Research Council, 1985). 

The ground surface slopes slightly to the right.

(National Research Council, 1985) (fig. 65). The surface 

layer commonly breaks up into blocks bounded by fissures, which may tilt and settle differentially with 

respect to one another (National Research Council, 

1985). The ground surface can be displaced laterally 

several yards, perhaps tens of yards, depending on soil 

and ground-water conditions and the duration of earthquake shaking (Tinsley and others, 1985). As shown in 

table 17, significant damage to structures may result 

from lateral spreading.

Lateral-spread landsliding can be especially destructive to pipelines, utilities, bridge piers, and other structures with shallow foundations (Tinsley and others, 

1985). Lateral-spread landslides with ground displacements of only a few feet caused every major pipeline 

break in San Francisco during the 1906 earthquake 

(Youd, 1978a); hence, liquefaction was largely responsible for the inability to control the fires that caused 85 

percent of the damage to the city (Tinsley and others, 

1985).

Where ground surface slopes are steeper than about 

5.0 percent, slope failure may occur in the form of flow 

landslides (Anderson and others, 1982) (fig. 66). Flow 

failure is the most catastrophic mode of liquefactioninduced ground failure (Tinsley and others, 1985). Flow 

landslides consist chiefly of liquefied soil or blocks of 

intact material riding on a liquefied layer (National 

Research Council, 1985). Flow failures can cause soil 

masses to be displaced tens of yards; under favorable 

conditions, flow failure has displaced materials for miles 

at relatively high velocities (Tinsley and others, 1985). 

Extensive damage due to flow landslides occurred in 

Seward and Valdez, Alaska, during the 1964 Alaska 

earthquake (Tinsley and others, 1985). A flow landslide

TABLE 17. Relationship between ground displacement and damage

to structures 

[from Youd, 1980]

Ground displacement Level of expected damage

Less than 4 in. 

4 in. to 1 ft 

1 to 2 ft 

More than 2 ft

Little damage, reparable 

Severe damage, reparable 

Severe damage, nonreparable 

Collapse, nonreparable

during the 1906 San Francisco earthquake knocked a 

powerhouse near the Mount Olivet Cemetery from its 

foundation (Youd, 1973).

REDUCTION OF LIQUEFACTION HAZARDS

Earthquake-induced soil liquefaction or liquefactioninduced ground failures have the potential to cause 

damage to most types of structures. Structures that are 

particularly sensitive include buildings with shallow 

foundations, railway lines, highways and bridges, buried 

structures, dams, canals, retaining walls, port structures, utility poles, and towers (National Research Council, 1985). The National Research Council (1985) identifies several alternative approaches that can be taken if 

earthquake-induced liquefaction is determined to be a 

threat to existing or proposed structures. For an existing 

structure the choices include (1) retrofitting the structure and (or) site to reduce the potential for liquefactioninduced damage, (2) abandoning the structure if the 

retrofit costs exceed the potential benefits derived from 

maintaining the structure, or (3) accepting the risk.

Possible actions that may be taken if a liquefaction 

hazard exists at the site for a proposed structure include 

(1) improving site conditions to lower the potential for 

liquefaction, (2) designing the structure to withstand the

Before 

liquefaction

Flow-Failure Deposit

After 

liquefaction

FIGURE 66. Diagram of a flow failure. Liquefaction beneath the 

ground surface causes loss of shear strength, allowing the soil mass 

to flow down the steep slope (Youd, 1984, in National Research 

Council, 1985).
154 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

effects of liquefaction, (3) avoiding the risk by moving the 

proposed development to a less hazardous site, (4) insuring the development so that, if liquefaction-induced 

damage occurs, funds will be available to repair the 

damage, or (5) accepting the risk if the potential for and 

consequences of liquefaction are clearly understood.

Structural solutions to reduce the effects of liquefied 

soils can take several forms. For buildings, foundationsupport problems in liquefiable soils may be avoided by 

using end-bearing piles, caissons, or fully compensated 

mat foundations designed for the predicted liquefaction 

phenomena at the site (National Research Council, 

1985). Methods of improving liquefiable soil foundation 

conditions are (1) densification of soils through vibration 

or compaction, (2) grouting, (3) dewatering with drains 

or wells, and (4) loading or buttressing to increase 

confining pressures (National Research Council, 1985). 

Costs of site improvement techniques range from less 

than $0.50 to more than $500.00 per cubic yard of soil 

foundation material treated (National Research Council, 

1985).

INFORMATION FOR DAVIS COUNTY ON 

LIQUEFACTION POTENTIAL

The results of the liquefaction study are summarized in 

four maps. Each map consists of two parts: a southern 

and a northern half of Davis County (Anderson and 

others, 1982). The base maps are 50 percent reductions of 

U.S. Geological Survey 7W (topographic) quadrangles 

and have a scale of 1 in. =4,000 ft (scale 1:48,000). The 

four maps are Selected Geologic Data Map, Soils and 

Ground Water Data Map, Ground Slope and Critical 

Acceleration Map, and Liquefaction-Potential Map. Figure 67 shows the location of figure 68, which is a 

reproduction of a portion of the Anderson and others 

(1982) Liquefaction Potential Map (South Half) for Davis 

County.

A summary of the methods used in preparing the maps 

follows; for a detailed discussion of the technical aspects 

of map preparation, refer to Anderson and others (1982). 

Maps prepared by Anderson and others (1982) take into 

consideration soil and ground-water conditions and 

earthquake probability in determining liquefaction 

potential in Davis County. Soil and ground-water conditions were evaluated on the basis of subsurface data, 

chiefly boreholes and cone penetrometer tests, obtained 

from private engineering consultants, State and local 

government agencies, and tests run as part of the 

liquefaction-potential investigation. A calculation of the 

level of ground shaking needed to induce liquefaction was 

then made at each data point. Peak horizontal ground 

acceleration was used as the measure of ground shaking,

DAVIS COUNTY

Salt Lake City

UTAH

i r 

0 5 10 Kilometers

EXPLANATION

Location of Figure 68

FIGURE 67. Location map for figure 68.

and the level needed to induce liquefaction under a 

particular set of soil and ground-water conditions was 

termed the critical acceleration. The liquefaction potential in Davis County has been rated on the basis of the 

probability that the critical acceleration needed to induce 

soil liquefaction will be exceeded during a 100-yr return 

period (table 18). Local geological conditions were also 

considered in refining liquefaction-potential boundaries 

(Anderson and others, 1982). As shown on the Selected 

Geologic Data Map, five slope failures covering more 

than 10 mi2 (26 km2) in three areas of Davis County have 

been mapped and interpreted as prehistoric lateralspread failures, probably induced by past earthquake 

ground shaking (Van Horn, 1975, 1982; Miller, 1980; 

Anderson and others, 1982).

The liquefaction-potential rating for a given location 

can be determined by locating the site on the Liquefaction Potential Map. The approximate probability of 

ground shaking sufficient to induce liquefaction at that 

site in the next 100 yr may then be determined by 

referring to the proper category in table 18. The 

expected mode of ground failure if liquefaction occurs at 

a given location may be evaluated by determining the 

approximate ground surface slope at the site on the 

Ground Slope and Critical Acceleration Map and referring to table 16. Contours depicting areas of less than 0.5 

percent, 0.5 to 5.0 percent, and greater than 5.0 percent
LIQUEFACTION HAZARDS: A GUIDE FOR LAND-USE PLANNING 155

,*iiii*<i:-^' "' ;& 

 '' \?&f

*' ±*f. " :;- 

W-. :.;-:"v'i

^f

to 

Scale 

.5 1'mile

A

frSf: ""4"" " -Wp>'4*cx " '^^--^-i-'Ji- i-'ni T?. V^1 ^.. ^VT* ' "-'''"**» r!-fe-:F2 CvS?%:

if 11-" x-,^^ *P-Hi^.^&R^,

%'$* JU -SS'«i ... .1-»l -

i/*$i$$} ^^§jJMl':)ft^

FIGURE 68. -Liquefaction-potential map for the Centerville and northern Bountiful area of southern Davis County. High, Mod. (moderate), and 

Very Low refer to liquefaction potential ratings determined by Anderson and others (1982). This figure was reproduced from a portion of the 

Liquefaction Potential Map (South Half) for Davis County, Utah, by Anderson and others (1982).

slope are included in this map. To differentiate between 

the two failure modes bearing capacity and soil oscillation in areas of less than 0.5 percent slope, the depth of 

the liquefiable layer must be known. This depth can be 

determined for specific sites by using the Soils and 

Ground-Water Data Map to determine the depth to 

liquefiable soils and the nature of overlying and underlying units. However, the map does not interpret depths 

to liquefiable layers between data points, so the two 

failure modes can only be differentiated at specific sites 

where data were collected.

RECOMMENDED USE OF MAPS IN LAND-USE 

PLANNING

These maps are at a regional scale and, although they 

can be used to gain an understanding of probable potential of a given area for liquefaction during earthquake 

ground shaking, they are not designed to replace sitespecific evaluations. Mapped areas rated as having a low 

liquefaction potential may contain isolated areas with a 

high liquefaction potential, and areas rated as having a 

high liquefaction potential may contain isolated areas
156 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

TABLE 18. Criteria used to evaluate liquefaction potential 

[Anderson and others, 1982]

Liquefaction 

potential

High 

Moderate 

Low 

Very low

Critical acceleration 

needed to induce 

liquefaction (g)

Less than 0.12 

Between 0.12 and 0.20 

Between 0.20 and 0.30 

More than 0.30

Approximate probability 

that the critical acceleration needed to induce 

liquefaction will be 

exceeded during the 

next 100 yr (percent)

Greater than 50 

Between 10 and 50 

Between 5 and 10 

Less than 5

The unit of measure g is the force of gravity.

that are not prone to liquefaction. Site-specific studies of 

liquefaction potential should be conducted where this 

information is needed.

Large areas of Davis County have moderate to high 

potential for liquefaction during earthquake ground 

shaking, including most of the area west of State Highway 89. The liquefaction potential maps provide a general indication of where the hazard may exist and serve 

as a means of evaluating the need for site-specific studies. Because of the distribution of data points and the 

relatively small scale of the maps, this information does 

not preclude the necessity for site-specific evaluations. 

The point data may be useful in a site evaluation, 

depending on the quality of the data. Liquefaction potential should be evaluated (see table 19) and any necessary 

mitigative measures should be recommended in site 

investigation reports submitted by the developer prior to 

planning commission approval. Areas of moderate to 

high liquefaction potential need not be avoided because 

structural measures and site modification techniques are 

available to reduce hazards. Reports addressing liquefaction potential in such areas are recommended for large 

structures but not for single-family dwellings, according 

to the engineers and geologists who conducted the 

liquefaction-potential study (Anderson and others, 1987). 

This is because the cost of reducing liquefaction hazards

TABLE 19. Matrix indicating recommended report requirements for 

liquefaction hazards, Davis County, Utah

Type of development

Liquefaction-potential rating 

High/moderate Low/very low

Critical facilities including life- Yes

lines and high-occupancy

buildings. 

Industrial and commercial Yes

buildings (other than high

occupancy).

Residential subdivisions No1 

Residential single lots______No1

Yes

No

No 

No

1 Appropriate disclosure should be required.

commonly exceeds the value of single-family dwellings 

(L.R. Anderson, personal commun., August 31, 1987), 

and liquefaction is generally not a life-threatening 

hazard.

SCOPE OF SITE INVESTIGATIONS

A liquefaction-potential evaluation should be part of a 

standard soil foundation investigation for the proposed 

development. Initial evaluations for liquefaction potential should be based on depth to ground water and on soil 

types. If soil and ground-water conditions indicate that 

liquefiable soils may be present, standard penetration 

tests and (or) cone penetration tests should be conducted 

to determine critical accelerations needed to induce 

liquefaction. A site-specific liquefaction-potential report 

should include accurate maps of the area of the proposed 

development, the location of boreholes and test pits, and 

the site geology. Logs of boreholes and test pits should 

be included in the report, and any ground water encountered should be noted. The location of and depths to 

liquefiable soils should be noted, and the probability 

should be determined that the critical accelerations 

needed to induce liquefaction in these soils will be 

exceeded for appropriate time periods. Recommendations for hazard reduction techniques should be included. 

The county planing department and county engineer 

should meet to plan the site-specific liquefaction studies 

and decide what types of information should be obtained.

A useful guide for preparing reports has been published by the Utah Section of the Association of Engineering Geologists (1986). Site-specific reports addressing liquefaction hazards should be reviewed by the 

county and, once approved, submitted to the planning 

commission along with review comments, so that the 

planning commission has sufficient information available 

to make decisions regarding the proposed development.

REFERENCES

Anderson, L.R., Keaton, J.R., Aubry, Kevin, and Ellis, S.J., 1982, 

Liquefaction potential map for Davis County, Utah: Logan, Utah, 

Department of Civil and Environmental Engineering, Utah State 

University, and, Salt Lake City, Utah, Dames and Moore Consulting Engineers, 50 p.

Anderson, L.R., Keaton, J.R., Bay, J.A., and Rice, J.D., 1987, 

Liquefaction potential mapping, Wasatch Front, Utah, in 

McCalpin, James, ed., Proceedings of the 23rd annual symposium 

on engineering geology and soils engineering: Boise, Idaho Department of Transportation, p. 1-17.

Kuribayashi, Eiichi, and Tatsuoka, Fumio, 1975, Brief review of 

liquefaction during earthquakes in Japan: Soils and Foundations, 

v. 15, no. 4, p. 81-92.

 1977, History of earthquake-induced liquefaction in Japan: 

Japan Ministry of Construction, Public Works Research Institute 

Bulletin, v. 31, p. 26.
LIQUEFACTION HAZARDS: A GUIDE FOR LAND-USE PLANNING 157

Miller, R.D., 1980, Surficial geologic map along part of the Wasatch 

Front, Great Salt Lake Valley, Utah: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1198, scale 1:100,000.

National Research Council, 1985, Liquefaction of soils during earthquakes: Washington, D.C., National Academy Press, 240 p.

Schwartz, D.P., and Coppersmith, K.J., 1984, Fault behavior and 

characteristic earthquakes Examples from the Wasatch and San 

Andreas fault zones: Journal of Geophysical Research, v. 20, 

p. 261-285.

Tinsley, J.C., Youd, T.L., Perkins, D.M., and Chen, A.T.F., 1985, 

Evaluating liquefaction potential, in Ziony, J.I., ed., Evaluating 

earthquake hazards in the Los Angeles region An earth science 

perspective: U.S. Geological Survey Professional Paper 1360, p. 

263-315.

Utah Section of the Association of Engineering Geologists, 1986, 

Guidelines for preparing engineering geologic reports in Utah: 

Utah Geological and Mineral Survey Miscellaneous Publication M, 

2 p.

Van Horn, Richard, 1975, Largest known landslide of its type in the 

United States A failure by lateral spreading in Davis County, 

Utah: Utah Geology, v. 2, no. 1, p. 83-87.

 1982, Surficial geologic map of the Salt Lake City North 

Quadrangle, Davis and Salt Lake Counties, Utah: U.S. Geological 

Survey Miscellaneous Investigation Series Map 1-1404, scale 

1:24,000.

Youd, T.L., 1973, Liquefaction, flow, and associated ground failure: 

U.S. Geological Survey Circular 688, 12 p.

 1977, Discussion of "Brief review of liquefaction during earthquakes in Japan" by Kuribayashi, Eiichi, and Tatsuoka, Fumio, 

1975: Soils and Foundations, v. 17, no. 1, p. 82-85.

 1978a, Major cause of earthquake damage is ground failure: 

Civil Engineering, v. 48, no. 4, p. 47-51.

 1978b, Mapping liquefaction-induced ground failure potential: 

Proceedings of the American Society of Civil Engineers, Journal of 

Geotechnical Engineering Division, v. 4 no. 674, p. 433-446.

 1980, Ground failure displacement and earthquake damage to 

buildings: American Society of Civil Engineers conference on civil 

engineering and nuclear power, 2d, Knoxville, Tenn., 1980, v. 2, 

p. 7-6-2-7-6-26.

 1984, Geologic effects Liquefaction and associated ground

failure: U.S. Geological Survey Open-File Report 84-760, p.

210-232. 

Youd, T.L., Nichols, D.R., Helley, E.J., and Lajoie, K.R., 1975,

Liquefaction potential, in Studies for seismic zonation in the San

Francisco Bay region: U.S. Geological Survey Professional Paper

941-A, p. A68-A74. 

Youd, T.L., and Perkins, D.M., 1987, Mapping of liquefaction severity

index: Journal of Geotechnical Engineering, v. 113, p. 1374-1392.
TECTONIC SUBSIDENCE HAZARD: A GUIDE FOR LAND-USE 

PLANNING, UTAH AND JUAB COUNTIES, UTAH

By ROBERT M. ROBISON 16

ABSTRACT

Tectonic subsidence (seismic tilting) is the downwarping and tilting 

of the valley floor relative to the mountains during a surface-faulting 

earthquake (>M 6.5). The maximum vertical subsidence occurs at the 

base of the fault and decreases toward the valley. Two historic 

earthquakes in the Intermountain Seismic Belt are used as models for 

the Wasatch fault zone (WFZ): the 1959 Hebgen Lake, Mont., and the 

1983 Borah Peak, Idaho, earthquakes. Although the maximum subsidence was 20 ft (6 m) at Hebgen Lake, the average offset of the WFZ is 

expected to produce surface offset of about 6-9 ft (2-3 m) with less 

tectonic subsidence. The affected area could extend for about 10 mi (16 

km) basinward from the fault with maximum tilt within about 3 mi (5 

km). The lateral extent of subsidence is controlled by the length of fault 

rupture, which is expected to coincide with segment lengths that are 

generally 15-20 mi (24-32 km). The recurrence interval for tectonic 

subsidence along a particular fault segment is the same as that of 

surface-faulting earthquakes, ranging from hundreds to several thousands of years.

Hazards associated with tectonic subsidence in Utah and Juab 

Counties include shoreline flooding along Utah Lake and other bodies 

of water tilted by faulting, inundation from shallow ground water, and 

damage to facilities that cannot tolerate small changes in gradient, such 

as waste-water treatment facilities. Tectonic subsidence maps for the 

WFZ that show areas of potential flooding and tilting have been 

prepared for Utah and Juab Counties. However, the maps are based on 

theoretical models and are approximations of what may actually occur. 

Site-specific studies are recommended for certain vulnerable facilities 

within zones of flooding and maximum tilting such as electricitygenerating plants, waste-water treatment facilities, and other structures that, if tilted or inundated, could cause public health and safety 

problems as well as economic losses. The site-specific report should 

determine the depth to ground water and the site elevation with 

respect to projected lake and ground-water levels and should recommend hazard reduction techniques. Mitigation could include provisions 

to relevel after subsidence or to build more freeboard or tolerance for 

containers that hold toxic or other dangerous materials. Reports would 

be reviewed by the county geologist and county engineer.

INTRODUCTION

Tectonic subsidence is the warping, lowering, and 

tilting of a valley floor that accompanies surfacerupturing earthquakes on normal (dip-slip) faults such as

1 Utah County Planning Department, Prove, Utah.

the Wasatch fault zone (WFZ). Subsidence occurred 

during the 1959 Hebgen Lake, Mont., earthquake and 

the 1983 Borah Peak, Idaho, earthquake, and there is 

geologic evidence for tectonic subsidence, such as backtilting adjacent to the fault zone, during prehistoric 

earthquakes along the Wasatch Front (Keaton, 1987). 

Inundation along the shores of lakes and reservoirs and 

the ponding of water in areas with a shallow water table 

may be caused by tectonic subsidence. Also, tectonic 

subsidence may adversely affect certain structures that 

require gentle gradients or horizontal floors, particularly 

waste-water treatment facilities and sewer lines 

(Keaton, 1987). In this report, I discuss the consequences 

of possible tectonic subsidence in Utah and eastern Juab 

Counties (fig. 69) and make recommendations concerning 

the use of hazard maps for mitigation of subsidence 

hazards in land-use planning.

ACKNOWLEDGMENTS

Special thanks are given to Gary E. Christenson (Utah 

Geological Survey), Stephen F. Personius, and William 

J. Kockelman (U.S. Geological Survey) for their support 

and review of this paper. Jeff Keaton (Senior Engineering Geologist, Sergent, Hauskins and Beckwith Consultants) is responsible for a large portion of the research on 

tectonic subsidence along the Wasatch Front and provided valuable comments in his review. Craig Nelson 

(Salt Lake County geologist) and Mike Lowe (Davis 

County geologist) also made helpful suggestions.

CHARACTERISTICS OF TECTONIC SUBSIDENCE

Tectonic subsidence, also termed seismic tilting, 

occurs during large-magnitude earthquakes (>M 6.5) 

generated along normal faults that have accompanying 

deformation or displacement at the ground surface. The 

extent of seismic tilting is controlled chiefly by the 

amount and length of surface displacement and normally

158
TECTONIC SUBSIDENCE HAZARD: A GUIDE FOR LAND-USE PLANNING 159

UTAH COUNTY

American V Location of Figure 71.

 Fnrk ^* a

EASTERN JUAB COUNTY

FIGURE 69. Map showing the location of Utah and northeastern Juab

Counties.

occurs only along the portion of the fault that experiences 

surface deformation. The area of subsidence is controlled 

by the length of the fault rupture, and subsidence should 

extend only a short distance beyond the ends of the fault 

rupture.

The WFZ consists of 10-11 distinct segments, which 

probably break independently and average about 

20.6-22.7 mi (33.3^36.6 km) in length (Machette and 

others, 1989). The WFZ segments in Utah and eastern 

Juab Counties are the Provo (unrestricted) and Nephi, 

which are 43 mi (69.5 km) and 26.4 mi (42.5 km) long, 

respectively (Machette and others, 1989); these are discussed further elsewhere (Robison, "Surface-fault rupture: A guide for land-use planning, Utah and Juab 

Counties, Utah," this volume).

The probability that tectonic subsidence will occur is 

the same as that for a large earthquake (>M 6.5), 

namely, 340-415 yr for the average composite recurrence 

interval for large earthquakes on the WFZ. However, 

for any given individual segment, the average recurrence interval is 2035-2070 yr (Machette and others, 

1989). Because of the dispersion in the timing of events 

and the catastrophic losses that will occur during a 

large-magnitude earthquake, the most conservative estimate, 340-415 yr, should be used. This figure becomes 

even more significant when the timing of the most recent 

event, about 400 yr ago (Machette and others, 1989), is 

considered.

Two earthquakes have occurred in the northern Basin 

and Range province that are models for the WFZ; the 

largest is the 1959 Ms 7.5 Hebgen Lake, Mont., earthquake (Doser, 1985). The area of tilting, measured 

perpendicular to the fault, extended up to 10 mi (16 km) 

from the fault at Hebgen Lake (Meyers and Hamilton, 

1964). The amount of subsidence at Hebgen Lake is 

larger than that expected for the "characteristic earthquake" (Schwartz and Coppersmith, 1984) of the 

Wasatch Front and was not used as a direct analog for 

the Utah and Juab Counties area. The maximum subsidence at Hebgen Lake was 20 ft (6 m), whereas the WFZ 

has an expected offset of 6-9 ft (2-3 m) (Schwartz and 

Coppersmith, 1984). Also, the hazard maps for Utah and 

Juab Counties will show average expected offset for the 

WFZ, not the largest displacement that has occurred 

locally. The second earthquake model, the 1984 Borah 

Peak event, also formed subsidence, but lack of preearthquake survey and profile control eliminated evaluation of 

tectonic subsidence adjacent to the fault (Keaton, 1987).

The expected area of subsidence for the WFZ extends 

for about 10 mi (16 km) west of the fault zone, the 

majority of the deformation being within about 3 mi (5 

km) (Keaton, 1986). The maximum amount of subsidence 

should occur at the fault and decrease gradually on the 

downdropped valley block (Keaton, 1986).

Tectonic subsidence may cause flooding (Smith and 

Richins, 1984) (fig. 70). The amount of inundation along 

shorelines will depend on lake levels at the time of the 

event. Several zones of flooding have been delineated by 

Keaton (1986) for Utah Lake that correlate to lake 

elevations of 4485, 4490, and 4495 ft (1368,1370, and 1371 

m). These levels cover the range of lake fluctuations 

since 1935, when the lake reached its historical low of 

4478 ft (1365 m). The normal operating or "compromise" 

level of the lake is about 4490 ft (1370 m). Also plotted on 

the maps prepared for the counties are areas where the 

ground water may pond in the event of seismic tilting. 

Ground water was considered to be 3 ft from the ground 

surface prior to subsidence. A portion of the tectonic 

subsidence maps prepared by Keaton (1986) was adapted 

and is shown in figure 71. Also, the east shore of Mona 

Reservoir in Juab County may experience flooding due to 

tectonic subsidence similar to the shoreline of Utah 

Lake.

MITIGATION

The two major types of hazards associated with tectonic subsidence are tilting of the ground surface and
160 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

Preearthquake shoreline

Lake shoreline inundation zone

Postearthquake

Postearthquake Sag pond 

Buildings t Ponded shallow ground water 

\

Lake u

Waste-water 

o

treatment plant

Postearthquake shoreline

Preearthquake shoreline

Preearthquake 

Buildings Waste-water treatment plant

B

Sewer line

Postearthquake

Postearthquake shoreline

Buildings

Waste-water treatment plant

=e

Water table

Submerged shoreline Flooded basement

FIGURE 70. (A) Map (not to scale) showing surface rupture and 

tectonic subsidence accompanying a hypothetical earthquake along 

the Wasatch fault zone. Areas that may be inundated with water 

after an earthquake are shown with a checkerboard pattern. A 

cross-sectional view between points A-A' is given as a reference in 

parts B and C to show the possible effects from tectonic subsidence. 

(B) Cross-sectional view between points A-A' (from part A) showing 

an imaginary plane (water table) at its preearthquake position. 

Buildings and a waste-water treatment plant are represented to

illustrate some of the possible effects of tectonic subsidence. Subsidence would probably not be as uniform as depicted in this figure. Also, 

most of the deformation would likely occur adjacent to the fault, and 

total effects may extend over a much wider area. (C) Cross-sectional 

view between points A-A' (from parts A and B) showing potential 

Postearthquake effects from tectonic subsidence. Note the areas of lake 

flooding as well as flooding from shallow ground water. Gravity-flow 

systems such as waste-water treatment plant may experience problems 

from reversed flows.
TECTONIC SUBSIDENCE HAZARD: A GUIDE FOR LAND-USE PLANNING 161

\

EXPLANATION

Provo segment of Wasatch fault zone

4490ft t

(1368 m) I Limit of potential Utah Lake flooding (lake level 

V. at 4490 ft/1368 m at time of earthquake!

Area of potential ponding from shallow ground water

, . Waste-water treatment plant showing direction and 

-0.4 ft/mi magnitude of expected ground tilt

(7.6 cm/km)

-5ft (1.5m) Contour showing amount of subsidence

FIGURE 71. Map showing area of potential tectonic subsidence in part of Utah Valley, based on an M 7-7.5 earthquake 

with about 6-9 ft (2-3 m) of surface rupture. Heavy (numbered) lines around Utah Lake indicate potential 

postearthquake shorelines at three possible elevations of the lake at the time of the event (modified from Keaton, 

1986).
162 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

flooding from lakes, reservoirs, or shallow ground water 

(fig. 70). Because subsidence may occur over large areas 

(tens of square miles), it is generally not practical to 

avoid the use of potentially affected land except in 

narrow areas of hazard due to lake shoreline flooding. 

For gravity-flow structures such as waste-water treatment plants that are within areas of possible subsidence, 

it is advisable to consider the tolerance of such structures 

to slight changes in gradient. Some structures may have 

to be releveled after a large-magnitude earthquake. 

Critical facilities that contain dangerous substances 

should have safety features to protect the structure, its 

occupants, and the environment from both tilting and 

flooding.

Flooding problems along lakes from tectonic subsidence can be reduced using standard techniques. Structures can be raised above expected flood levels and dikes 

can be built. Land-use regulations around lakes or reservoirs can prohibit or restrict development in a zone 

along the shoreline that may be inundated. A buffer or 

safety zone of several feet of elevation above projected 

lake levels could be adopted to protect against natural 

rises from wet periods, storm waves, and earthquakeinduced seiching, as well as hazards associated with 

tectonic subsidence.

Rises in the water table accompanying tectonic subsidence may cause water to pond, flood basements, and 

disrupt buried facilities, chiefly along a zone 3 mi (5 km) 

wide adjacent to the fault (Keaton, 1987). In addition, 

shallow ground-water conditions in areas where 

earthquake-induced liquefaction could also occur may 

compound mitigation problems. In areas of shallow 

ground water or standing water, structures can be 

elevated and basements flood proofed.

USE OF HAZARD MAPS

Keaton (1986) has mapped the areas of potential tectonic subsidence along the WFZ in Utah and Juab 

Counties and estimated the amount of tilting and flooding. This mapping is based on a theoretical model, and it 

must be considered preliminary and approximate but will 

be adopted as published (Robison, 1988). Tectonic subsidence is a poorly understood phenomenon along the 

Wasatch Front, and these maps represent an initial 

attempt to depict the nature and extent of the hazard. 

The principal application of the maps is to make land-use 

planners and others aware of the hazard and to indicate 

those areas where further study may be necessary. 

Site-specific studies concerning tectonic subsidence are 

recommended only for critical facilities in areas of potential flooding. However, certain vulnerable facilities, such

as high-cost waste-water treatment plants and 

hazardous-waste facilities, should also consider potential 

tilting. It would also be prudent to consider this hazard 

for other types of development within the area of potential subsidence and to take precautions, but specific 

reports are not required by the county.

SCOPE OF SITE INVESTIGATIONS

Site-specific studies of tectonic subsidence hazards 

should determine the depth to ground water and the site 

elevation with respect to projected lake and groundwater levels. These results would then be compared with 

expected amounts of subsidence shown on the map by 

Keaton (1986). Recommendations regarding hazard 

reduction should be based on the extent of flooding or 

ground tilt indicated. These reports will be reviewed by 

the County Surveyor and County Geologist. The hazard 

maps of Keaton (1986) will be amended as more accurate 

information becomes available.

REFERENCES

Doser, D.I., 1985, Source parameters and faulting processes of the 

1959 Hebgen Lake, Montana, earthquake sequence: Journal of 

Geophysical Research, v. 90, no. B12, p. 4537-4555.

Keaton, J.R., 1986, Potential consequences of tectonic deformation 

along the Wasatch fault: Utah State University, Final report to 

the U.S. Geological Survey for Earthquake Hazards Reduction 

Program, Grant 14-08-0001-G1174.

 1987, Potential consequences of earthquake-induced regional 

tectonic deformation along the Wasatch Front, north-central 

Utah, in McCalpin, James, ed., Proceedings of the 23rd annual 

symposium on engineering geology and soils engineering: Boise, 

Idaho Department of Transportation, p. 19-34.

Machette, M.N., Personius, S.F., Nelson, A.R., Schwartz, D.P., and 

Lund, W.R., 1989, Segmentation models and Holocene movement 

history of the Wasatch fault zone, Utah, in Schwartz, D.P., and 

Sibson, R.H., eds., Proceedings of conference XLV Fault segmentation and controls on rupture initiation and termination: U.S. 

Geological Survey Open-File Report 89-314, p. 229-242.

Meyers, W.B., and Hamilton, W., 1964, Deformation accompanying 

the Hebgen Lake earthquake of August 17, 1959: U.S. Geological 

Survey Professional Paper 435-1, p. 55-98.

Robison, R.M., 1988, Surface fault rupture hazard and tectonic subsidence maps for the Wasatch Front, Utah: Geological Society of 

America Abstracts With Programs, v. 20, no. 6, p. 465.

Schwartz, D.P., and Coppersmith, K.J., 1984, Fault behavior and 

characteristic earthquakes Examples from the Wasatch and San 

Andreas fault zones: Journal of Geophysical Research, v. 89, no. 

B7, p. 5681-5698.

Smith, R.B., and Richins, W.D., 1984, Seismicity and earthquake 

hazards of Utah and the Wasatch Front Paradigm and paradox, 

in Hays, W.W., and Gori, P.L., eds., A workshop on "Evaluation 

of regional and urban earthquake hazards and risk in Utah," 

Proceedings of conference XVII: U.S. Geological Survey OpenFile Report 84-763, p. 73-112.
HAZARDS FROM EARTHQUAKE-INDUCED GROUND FAILURE 

IN SENSITIVE CLAYS, VIBRATORY SETTLEMENT, AND FLOODING

DUE TO SEICHES, SURFACE-DRAINAGE DISRUPTIONS, AND 

INCREASED GROUND-WATER DISCHARGE, DA VIS COUNTY, UTAH

By MIKE LOWE17

ABSTRACT

There are a number of potential hazards associated with earthquakes 

along the Wasatch Front that have not been sufficiently studied to 

determine probability of occurrence for various exposure periods or to 

produce maps showing areas at risk. These potentially damaging but 

poorly understood hazards include ground failure in sensitive clays, 

vibratory settlement in granular materials, and flooding due to seiches, 

surface-drainage disruptions, and increased ground-water discharge. 

Many of the consequences of these hazards are identified in this report. 

Additional study is required before these hazards can be considered in 

city and county planning. Some of these hazards, however, can be 

evaluated at the site-specific level and should be considered for major 

construction projects and, in particular, for critical facilities.

INTRODUCTION

A variety of phenomena that can cause damage to 

property and (or) threaten lives may accompany earthquakes. The principal hazards are addressed in other 

reports covering surface-fault rupture, ground shaking, 

liquefaction, tectonic subsidence, and landslide and rockfall hazards. It is the purpose of this report to discuss 

other potentially damaging but less well-understood phenomena associated with earthquakes, including ground 

failure due to loss of strength in sensitive clays, subsidence caused by vibratory settlement in granular materials, flooding caused by seiches in Great Salt Lake, 

flooding due to surface-drainage disruptions, and flooding from increased ground-water discharge. A major 

goal is to translate technical information so that government officials and the general public can appreciate the 

need to reduce earthquake hazards.

ACKNOWLEDGMENTS

Gary E. Christenson (Utah Geological Survey), Tim 

Stephens and Barry Burton (Davis County Planning

17 Davis County Planning Department, Farmington, Utah.

Department), Craig Barker (Weber County Planning 

Department), and William J. Kockelman and Robert L. 

Schuster (U.S. Geological Survey) kindly reviewed this 

paper and provided valuable suggestions.

GROUND FAILURE DUE TO LOSS OF 

STRENGTH IN SENSITIVE CLAYS

NATURE AND CAUSES

Fine-grained lake deposits underlie much of western 

Davis County. Near Farmington these deposits are 

about 810 ft (247 m) thick (Feth and others, 1966), and 

some areas of Davis County may be underlain by as much 

as 1,000 ft (300 m) of sediments (Parry, 1974) deposited 

by lakes occupying the Great Salt Lake basin during the 

last 15 million years (Currey and others, 1984). Much of 

these lake sediments are silicate clays, some of which are 

classified as sensitive (Parry, 1974).

Most clays lose strength when disturbed; sensitive 

clays are those that experience a particularly large loss of 

strength. The sensitivity of clays is defined as the ratio of 

shear strength in an undisturbed condition to shear 

strength after being remolded (severely disturbed) 

(Costa and Baker, 1981). One proposed origin for these 

clays holds that the platy clay particles were deposited in 

an edge-to-edge "house of cards" (flocculated) structure 

in saline (generally marine) environments in which the 

sodium and other cations in the water provided bonding 

strength (Rosenqvist, 1953, 1966). Later, when this 

saline water is leached out by fresh ground water, the 

clays are left in an unstable arrangement, subject to 

collapse and liquefaction when disturbed or shaken. 

After disturbance, the clays may revert from a flocculated soil structure, in which ground water fills the 

interstitial pore spaces, to a dispersed soil structure, in 

which the interstitial water is expelled, often liquefying 

the clay (Costa and Baker, 1981).

163
164 ASSESSMENT OF REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

EFFECTS

The principal effect of disturbance of sensitive clays is 

ground failure. The kinds of ground failures associated 

with sensitive clays are similar to those accompanying 

liquefaction and include flow failures, slump-type landslides, and lateral spreads or translational landslides 

(Earthquake Engineering Research Institute, 1986; 

Costa and Baker, 1981). Liquefied sensitive clays may 

flow downhill on slopes of 1° or less (Costa and Baker, 

1981). One triggering mechanism for ground failure in 

sensitive clays is intense ground vibration generated by 

earthquakes. The most devastating damage resulting 

from the 1964 Anchorage, Alaska, magnitude 8.6 earthquake was the result of translational landslides accompanying failure in sensitive clays. The largest of these 

landslides, located in the Turnagain Heights residential 

area, damaged 75 homes (Hansen, 1966).

The potential for ground failure in sensitive clays 

is related to the intensity and duration of ground shaking 

and to the sensitivity of the clays. Clays with sensitivities of 10 or more may be prone to failure during seismic 

ground shaking (Earthquake Engineering Research 

Institute, 1986). Clays exceeding sensitivities of 10 have 

been identified in Davis County along the Weber River 

and at the Interstate 15 Fairish Lane overpass (Parry, 

1974), indicating that sensitive clays are present and 

may be widely distributed in Davis County. The intensity and duration of ground shaking needed to induce 

failure in these sensitive clays have not been investigated, and therefore the probability that this type of 

ground failure would occur in Davis County cannot be 

currently determined.

HAZARD REDUCTION

Earthquake-induced ground failure due to sensitive 

clays has the potential to cause damage to most types of 

structures. Possible actions that may be taken if sensitive clays are present include (1) improving site conditions by converting the clays from a flocculated soil 

structure to a dispersed soil structure (preconstruction 

vibration techniques, etc.) and (or) dewatering the site 

and (2) designing the structure to withstand the effects of 

the potential ground failure using structural solutions 

such as end-bearing piles (placed below the sensitive 

clay), caissons, or fully compensated mat foundations 

designed for the anticipated failure type.

LAND-USE PLANNING

Maps have not been produced that show the extent of 

sensitive clay deposits in Davis County, but assessment 

of this hazard can be undertaken at the site-specific level

as a standard part of foundation investigations. The 

assessment involves laboratory tests (unconfined compression tests) in which axial loads are applied to unconfined cylindrical samples, first in an undisturbed state 

and then in a remolded state (Spangler and Handy, 

1973). The ratio of the strength of the soil under undisturbed versus disturbed conditions is then determined. 

Additional study is needed to determine the levels of 

ground shaking necessary to cause ground failure in 

sensitive clays before this hazard can be considered in 

regional land-use planning. Sensitive clays are a factor 

that should be considered in site-specific studies for all 

major construction, however, including critical facilities.

SUBSIDENCE CAUSED BY VIBRATORY 

SETTLEMENT IN GRANULAR MATERIALS

NATURE AND CAUSES

Loose granular materials such as some sands and 

gravels can be effectively compacted by vibration. The 

material assumes a denser form when particles move 

closer together and decrease the volume. Earthquakeinduced ground shaking is one source of vibrations that 

may cause this type of subsidence. During the 1964 

Alaska earthquake, vibratory settlement caused the 

ground to subside at some locations by as much as 5.9 ft 

(1.8 m) (Costa and Baker, 1981). Large areas of western 

Davis County are underlain by clean sand and gravel 

deposited in Pleistocene Lake Bonneville, where the 

potential for settlement may exist. Also, the county has 

many areas of fill that may be susceptible to vibrationinduced settlement. No studies have been conducted in 

Davis County to determine what levels of ground shaking are necessary to induce vibratory settlement in 

susceptible soils. Therefore, the probabilities that this 

hazard would occur are unknown.

EFFECTS

Differential settlement can occur if foundations are 

built across deposits with varying physical properties 

such as sorting and texture, possibly resulting in severe 

building damage as one part of the foundation settles 

more than another (Costa and Baker, 1981). Structural 

failure of building members (Dunn and others, 1980) and 

foundation cracking may also be caused by excessive 

settlement. Earthen fill is commonly used for construction of railway embankments, highway foundations, 

bridge abutments, and dikes and levees. Even minor 

differential settlement can cause extensive damage to 

these structures. If not adequately compacted during 

placement, these fills may be susceptible to this hazard 

because of the granular material commonly used
HAZARDS FROM EARTHQUAKE-INDUCED GROUND FAILURE 165

(Schmidt, 1986). Utility lines and connections may be 

severed due to vibratory settlement. Rate of settlement 

is an important factor that must be considered in evaluating the potential for damage (Dunn and others, 1980). 

Settlements due to earthquake ground shaking would be 

nearly instantaneous.

HAZARD REDUCTION

Structural methods to reduce damage due to settlement include supporting structures on piles, piers, caissons, or walls that are founded below the susceptible 

material (U.S. Bureau of Reclamation, 1985). Where 

structural measures to reduce vibratory settlement in 

granular soils are not possible, actions that may be taken 

to mitigate the hazard include (1) removing or precompacting the in situ granular materials prior to construction to improve site conditions, and (2) making sure that 

fills are properly engineered and compacted.

LAND-USE PLANNING

Maps delineating areas susceptible to vibratory settlement have not been completed for Davis County. Also, 

the level of ground shaking necessary to induce settlement varies with conditions, and assessment of this 

hazard must be undertaken at specific sites as a standard 

part of a foundation evaluation. Vibratory settlement, 

therefore, may not be properly considered in regional 

land-use planning in Davis County. Standard penetration 

and cone penetrometer tests are commonly used to 

evaluate the potential for vibratory settlement (Dunn 

and others, 1980). The potential for vibratory settlement 

should be evaluated for all major construction, especially 

for critical facilities.

FLOODING CAUSED BY SEICHES 

IN GREAT SALT LAKE

NATURE AND CAUSES

A seiche is the oscillation of the surface of a lake or 

other landlocked body of water, similar to the oscillations 

produced by sloshing water in a bowl or a bucket when it 

is shaken or jarred (Nichols and Buchanan-Banks, 1974). 

Seiches vary in period from a few minutes to several 

hours. The magnitude of oscillation of the water surface 

is determined by the degree of resonance between the 

water body and the periodic driving force such as earthquake ground shaking and wind. When the periodic 

driving force is oscillating at the same frequency at which 

the water body tends to oscillate naturally, the magnitude of the oscillation is greatest and may cause unusually large waves (seiches) that "break at considerable 

height and with great suddenness along the coastline" 

(Costa and Baker, 1981).

The effects of seiches are in part determined by water 

depth, lake size and shape, and the configuration of the 

local shoreline. These parameters determine the lake's 

natural period of oscillation and inherent system of long 

waves, much as the natural frequency of a pendulum is 

determined by its physical characteristics (Lin and 

Wang, 1978). "The system of long waves includes an 

infinite number of species of waves, usually called the 

normal modes; the fundamental mode refers to the wave 

with the longest wavelength" (Lin and Wang, 1978). It is 

the fundamental mode that is generally observed during 

surging and seiching (Lin and Wang, 1978). The period of 

the fundamental mode of Great Salt Lake's south basin is 

6 h (Lin and Wang, 1978). Studies from other areas have 

shown that seiches may raise and lower a water surface 

from inches to many yards, causing damage from wave 

action as well as severe flooding (Blair and Spangle, 

1979).

Seiches may be generated by wind, landslides, and (or) 

earthquakes (ground shaking, surface-fault rupture, and 

earthquake-induced landslides). The principal area at 

risk from seiches in Davis County is the shore of Great 

Salt Lake. Wind seiches in Great Salt Lake have been 

studied, and the maximum wave amplitude generated by 

this type of seiche is expected to be about 2 ft (0.6 m) (Lin 

and Wang, 1978). No systematic or theoretical studies of 

landslide or earthquake-induced seiching in Great Salt 

Lake have been completed. Seiches were reported along 

the southern shoreline of Great Salt Lake at Saltair and 

at the trestle at Lucin during the magnitude 6 Hansel 

Valley earthquake of October 5, 1909 (Williams and 

Tapper, 1953). The elevation of Great Salt Lake was 

4,202.0 ft (1280.77 m) on October 1,1909 (U.S. Geological 

Survey lake elevation records). The seiche generated by 

the 1909 Hansel Valley earthquake overtopped the Lucin 

cutoff railroad trestle, which had an elevation of 4,214.85 

ft (1284.69 m) (Southern Pacific Transportation Company records). Assuming the reports that the seiche 

overtopped the trestle are true and that lake and trestle 

elevation records were accurately reported, the seiche 

wave was more than 12 ft (3.7 m) high.

EFFECTS

Damage from seiches is primarily related to flooding, 

erosion, and forces exerted by waves. Seiches are a 

potential hazard to shoreline development and in-lake 

structures and are a concern to the proposed interisland 

diking project in Great Salt Lake.
166 ASSESSMENT OP REGIONAL EARTHQUAKE HAZARDS AND RISK ALONG THE WASATCH FRONT, UTAH

HAZARD REDUCTION

Dikes that are protected against erosion on the lakeward side and engineered breakwaters can be used to 

protect development or dissipate wave energy. Shoreline 

buildings can also be floodproofed, elevated, and constructed or reinforced to withstand the lateral forces of 

seiches (Costa and Baker, 1981).

LAND-USE PLANNING

Maps have not been produced that show areas that 

may be affected by seiches in Davis County. No comprehensive studies of landslide or earthquake-generated 

seiches have been completed for Great Salt Lake, but 

eyewitness accounts of the seiche generated by the 1909 

Hansel Valley earthquake suggest that maximum wave 

amplitudes generated by earthquakes may far exceed 

maximum wave amplitudes associated with wind seiches. 

Landslide and earthquake-generated seiches are a hazard to shoreline development and in-lake construction 

and should be taken into consideration during planning 

phases of development in Great Salt Lake and within the 

proposed Great Salt Lake Beneficial Development Area 

(Utah Division of Comprehensive Emergency Management, 1985).

FLOODING DUE TO SURFACE-DRAINAGE 

DISRUPTIONS DURING EARTHQUAKES

Flooding may be caused by earthquake ground shaking, surface-fault rupture, ground tilting, and landsliding 

during earthquakes if water tanks, reservoirs, pipelines, 

or aqueducts are ruptured or if stream courses are 

blocked or diverted. The areas where such flooding may 

occur can be predicted to some extent by defining where 

such structures and streams cross known active faults, 

active landslides, and potentially unstable slopes. Damming of streams by landslides can cause upstream inundation and, if the landslide dam subsequently fails, cause 

catastrophic downstream flooding (Schuster, 1987). 

Maps delineating active faults and landslides are available at the Davis County Planning Department. Sitespecific studies addressing earthquake and slope-failure 

hazards should be completed prior to construction for all 

major water-retention structures or conveyance systems, so that mitigative measures can be recommended. 

Studies can be done for existing facilities to evaluate the 

possible extent of flooding and to recommend drainage 

modifications to prevent damaging floods. Potential 

flooding from diversion of stream courses is more difficult to evaluate but should be considered during hazard 

evaluations for critical facilities.

INCREASED GROUND-WATER DISCHARGE DUE 

TO EARTHQUAKES

The effects of earthquakes on ground-water systems 

have not been extensively studied and, consequently, are 

not well understood. During the 1983 Borah Peak, Idaho, 

earthquake, local surface flooding and erosion were 

caused by increases in spring flow and expulsion of water 

from shallow bedrock aquifers. Resulting increases in 

streamflow of more than 100 percent occurred following 

the earthquake, and flow remained high for about 2 

weeks before declining to near original levels (Whitehead, 1985). Although this earthquake appeared to be 

one in which the ground water was especially affected, 

similar effects may occur during large-magnitude earthquakes in the vicinity of Davis County. Increased flow 

from springs in mountain drainages will be confined to 

stream channels, and adherence to Federal Emergency 

Management Agency flood-plain regulations should 

effectively reduce the risk. Increased flow from springs 

on the valley floor may result in ponded water and 

basement flooding.

CONCLUSIONS AND RECOMMENDATIONS

This report identifies a variety of phenomena associated with earthquakes that can damage property and 

threaten lives. Although many of the consequences of 

these hazards have been identified, the probability of 

occurrence has not been evaluated for Davis County, and 

maps that delineate areas in Davis County where hazards associated with these phenomena may occur are not 

available. Much study is required before these phenomena can be considered in regional planning for Davis 

County. However, some of these hazards can be evaluated on a site-specific basis; such studies should be 

considered for major construction projects, particularly 

critical facilities.

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the Earth: New York, John Wiley and Sons, 498 p.

Currey, D.R., Atwood, Genevieve, and Mabey, D.R., 1984, Major 

levels of Great Salt Lake and Lake Bonneville: Utah Geological 

and Mineral Survey Map 73, scale 1:750,000.

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HAZARDS FROM EARTHQUAKE-INDUCED GROUND FAILURE 167

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