The Loma Prieta, California, Earthquake of 

October 17, 1989-Loss Estimation and 

Procedures 

SUSAN K. TUBBESING, Editor 

SOCIETAL RESPONSE 

DENNIS S. MILETI, Coordinator 

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1553-A 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1994 
DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary 

U.S. GEOLOGICAL SURVEY 

Robert Me Hirsch, Acting 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 

Manuscript approved for publication, June 8, 1993 

Library of Congress Cataloging in Publication Data 

The Loma Prieta, California, earthquake of October 17, 1989. 

(U.S. Geological Survey professional paper ; 1553) 

Includes bibliographical references. 

Contents: Strong ground motion and ground failure 1 Thomas D. O'Rourke, editor ; Thomas L. Holzer, 

coordinator. ch. F. Marina District - Societal response / Susan K. Tubbesing, editor ; Dennis S. Mileti, 

coordinator. ch. A. Loss estimation and procedures. 

1. EarthquakesÃ‘California-Lom Prieta Region. 2. EarthquakesÃ‘California-Sa Francisco Bay Area. I. Series. 

QE535.2.U6166 1992 55 1.2'2'097946 92-32287 

For sale by the Book and Open-File Report Sales, U.S. Geological Survey, 

Federal Center, Box 25286, Denver, CO 80225 
CONTENTS 

By Susan K. Tubbesing 

Review, evaluation, and revision of the ATC-20 

postearthquake building safety evaluation 

procedures to include the Lorna Prieta 

earthqu&e--------------------------------------------------- 3 

By Robert A. Bruce 

Casualties and emergency medical response---------------- 9 

By Michael E. Durkin, Charles C. Thiel Jr., and 

James E. Schneider 

Study methods and progress report: A case-control 

study of physical injuries associated with the 

earthquake in the county of Santa Cmz ---------------- 39 

By Robin M. Wagner, Nicholas P. Jones, and 

Gordon S. Smith, and Frederick Krimgold 

Preliminary statistics on losses associated with 

ground deformation ......................... ------ --- ------ 63 

By Craig E. Taylor, Hope A. Seligson, David Fowler, 

and Craig W. Tillman 
THE LOMA PRIETA, CALIFORNIA, EARTHQUAKE OF OCTOBER 17,1989: 

SOCIETAL RESPONSE 

LOSS ESTIMATION AND PROCEDURES 

INTRODUCTION 

By Susan K. Tubbesing, 

Earthquake Engineering Research Institute, Oakland, Calif. 

This Professional Paper includes a collection of papers on 

subjects ranging from evaluation of building safety, to human injuries, to correlation of ground deformation with 

building damage. What these papers share is a common goal 

to improve the tools available to the research community to 

measure the nature, extent, and causes of damage and losses 

due to earthquakes. These measurement tools are critical to 

reducing future loss. 

Unlike the other authors, Bruce makes no effort to predict 

future losses but, rather, focuses on evaluating the efficacy 

of a specific procedure, ATC-20, designed to evaluate the 

safety of damaged buildings. Developed by the Applied 

Technology Council and introduced in large training ses-' 

sions just weeks before the Loma Prieta earthquake, this 

method was put into widespread use immediately after the 

earthquake. Bruce evaluates the effectiveness of this methodology and proposes various revisions to improve its accuracy and usefulness in future earthquakes. 

The papers by Durkin and others and Wagner and others 

focus on human injuries. Durkin's looks at injuries and illnesses throughout the entire earthquake-affected region, 

with specific attention to causality. The paper includes a 

section dealing with the delivery of health services, and on 

the basis of this work, the authors recommend approaches 

to improve emergency response and the development of 

casualty-estimation models. 

The paper by Wagner and others reports on an epidemiological study of various risk factors that resulted in physical injuries in Santa Cruz, California, during the first 72 

hours after the earthquake. This ongoing investigation is 

being carried out by an interdisciplinary team, in an effort 

to provide a better understanding of the relative contributions that the built environment and behavior make to 

earthquake-related casualties. 

Taylor and others focus on losses resulting from ground 

deformation based on data gathered from more than 700 

buildings in San Francisco. Their study demonstrates a 

weak correlation between loss and ground failure in the 

general vicinity of the city. The authors suggest a number 

of ways in which data may be improved and studies developed to compile superior, much improved loss data in the 

future. 
THE LOMA PRIETA, CALIFORNIA, EARTHQUAKE OF OCTOBER 17,1989: 

SOCIETAL RESPONSE 

LOSS ESTIMATION AND PROCEDURES 

REVIEW, EVALUATION, AND REVISION OF THE ATC-20 

POSTEARTHQUAKE BUILDING SAFETY EVALUATION PROCEDURES 

TO INCLUDE THE LOMA PRIETA EARTHQUAKE 

By Robert A. Bruce, 

Applied Technology Council, Redwood City, Calif. 

CONTENTS 

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ABSTRACT 

The Loma Prieta earthquake caused damage to thousands of buildings and immediately created the need for 

hundreds of inspectors to assess these buildings for safety 

of occupancy or limited entry. The Applied Technology 

Council (ATC) had published ATC-20, "Procedures for 

Postearthquake Safety Evaluation of Buildings" one month 

before the earthquake and had held two large training seminars to introduce the book. This fortuitous introduction and 

distribution of the publication resulted in its wide use for 

the earthquake recovery. 

The extensive use of the ATC-20 revealed the strengths 

and shortcomings of its methodology. To take advantage of 

this assessment of the methodology by hundreds of users, 

the National Science Foundation funded a project to use the 

Loma Prieta experience to evaluate and revise ATC-20. 

This project, ATC-20-2: Review, "Evaluation and Revision 

of the ATC-20 Postearthquake Building Safety Evaluation 

Procedures," is ongoing. Building evaluation aspects being 

reconsidered or introduced include evaluation records management, format and use of posting placards and evaluation 

forms, asbestos in damaged buildings, "windshield" (driveby) survey evaluation procedures, agreement with related 

publications, structural degradation assessment, removal of 

goods from red-tagged buildings, repair cost estimation, and 

training and qualifications of the volunteers. 

INTRODUCTION 

The need for an organization, legal framework, and methodology for voluntary assistance by design professionals to 

earthquake-stricken communities was recognized in California in 1978 by an agreement between the Structural Engineers Association of California (SEAOC) and the California 

Office of Emergency Services (OES). This agreement provided a structure for SEAOC engineers to volunteer through 

OES to building jurisdictions requesting assistance in the 

evaluation of buildings for safety of entry and occupancy. In 

1983, a similar agreement was made between the American 

Society of Civil Engineers (ASCE) and OES to provide for 

the evaluation of lifeline facilities such as bridges, pipelines, 

airports, roads, and water- and wastewater-treatment plants 

and for the geotechnical evaluation of soil-related damage. 

Engineers volunteering through these agreements enjoy certain liability immunities and workers compensation benefits. 

Under the SEAOC-OES agreement, engineers volunteered 

in the 1983 Coalinga and 1984 Morgan Hill earthquake recoveries. The response to these earthquakes revealed to the 

SEAOC Disaster Emergency Services (DES) Committee the 

need for a written manual on the methodology of safety 

evaluation of buildings. 

The DES Committee recognized that there were three main 

types of postearthquake hazards in buildings: overall or partial building frame collapse; falling hazards; and other hazards such as fire, gases, asbestos, and so forth. For each of 

these hazard types, the needs in developing a methodology 

were to describe agreed-upon evaluation methods, debate 
A4 LOSS ESTIMATION AND PROCEDURES 

and resolve those methods and issues where there was disagreement, and further expand the methodology of safety 

evaluation to cover all building types and damage scenarios. 

Work on such a manual was begun in 1984 by the DES 

committees of the four SEAOC chapter organizations. It 

soon became apparent that the development of the manual 

was beyond the means of volunteer committees. The 

SEAOC-DES committee approached the Applied Technology Council (ATC) to request their assistance in obtaining 

funding and producing the manual. Funding was obtained 

from the California Office of Emergency Services, the California Office of Statewide Health Planning and Development, and the Federal Emergency Management Agency. A 

subcontractor was chosen (R.P. Gallagher Associates) and a 

Project Engineering Panel (PEP) of engineers and building 

officials was selected. 

The 1987 Whittier earthquake occurred while the project 

was in progress. The Whittier earthquake differed from the 

Coalinga and Morgan Hill events in that it occurred in a 

heavily populated area. It demonstrated the extent of damage and need for numerous safety evaluation inspectors 

that can result from a relatively small magnitude (Richter 

5.9) event. For this earthquake, building inspectors from 

less-affected neighboring communities provided safety 

evaluation services for the recovery. 

The first printing of the project publication ATC-20, 

"Procedures for Postearthquake Safety Evaluation of 

Buildings" (Applied Technology Council, 1989a) and the 

companion ATC-20- 1, "Field Manual, Postearthquake 

Safety Evaluation of Buildings" (Applied Technology 

Council, 1989b) was in September 1989. ATC scheduled 

seminars in Los Angeles and San Francisco to introduce 

the publication. Each seminar was attended by about 500 

building officials and engineers, who received copies of 

the publication. 

The Loma Prieta earthquake occurred about one month 

later. It was quickly determined that damage was widespread. Later damage assessment studies would show that 

the modified Mercalli intensity zones VIII and VII for the 

earthquake included areas of seven counties and that about 

1,400 buildings were destroyed and about 27,000 buildings 

damaged. There was an immediate need for large numbers 

of safety evaluation volunteers in the stricken areas. 

BUILDING SAFETY EVALUATION AFTER 

THE EARTHQUAKE 

The need for safety evaluation volunteers was recognized 

within hours of the earthquake. They were requested 

through OES by the various jurisdictions, usually in accordance with the OES-SEAOC or OES-ASCE agreements. Beginning the morning after the earthquake, 

SEAOC and ASCE volunteer engineers were deployed to 

serve in the requesting jurisdictions. Two weeks later, 

SEAOC volunteers had served 670 person-days performing 

building evaluations (Structural Engineers Association Of 

California, 1991). ASCE volunteers performed evaluations 

of lifelines, soil conditions, and low-rise buildings. 

The principal building jurisdictions served by the safety 

evaluation volunteer engineers were the cities of Aptos, 

San Francisco, Los Gatos, Scotts Valley, Oakland, Watsonville, and Santa Cruz County. 

Most volunteers used the ATC-20 methodology, evaluation forms, and placards for building assessment. Evaluation forms and placards developed earlier by OES were 

used in some jurisdictions. As the recovery progressed, 

both the strengths and the shortcomings of the ATC-20 

methodology became apparent to the volunteers and 

jurisdictions. 

To improve the methodology, ATC was granted a contract with the National Science Foundation to review, evaluate, and revise ATC-20 to include the experience gained 

from the Loma Prieta earthquake building safety evaluation effort. This on-going project, ATC-20-2, "Review, 

Evaluation and Revision of ATC-20 Postearthquake Building Safety Evaluation Procedures," will result in an addendum to ATC-20 and additional and replacement pages for 

the ATC-20- 1 field manual. 

The project is guided by a Project Engineering Panel 

(PEP) selected for both their overall expertise and their 

specific experience in the Loma Prieta earthquake evaluation effort. The PEP members are: 

David R. Bonneville, H.J. Degenkolb Associates 

David J. Harnmond, Structural Engineer 

Fred Herman, City of Palo Alto 

William H. King, City of Los Angeles 

Larry. L. Litchfield, City of San Francisco Bureau 

of Building Inspection 

David L. Messinger, David L. Messinger & 

Associates 

Sherry D. Oaks, Colorado State University 

Richard A. Ranous, Southern California Earthquake Preparedness Project 

Debriefings have also been held to learn the experience of 

other Loma Prieta safety evaluation volunteers. About 40 

volunteers from the City of Los Angeles and Sacramento 

County have been debriefed (as of May 1992), and a further debriefing session is planned for San Francisco. 

EVALUATION OF THE USE OF THE ATC-20 IN 

EARTHQUAKE RECOVERY 

/ 

The significant needs for improvement or further work 

in postearthquake safety evaluation that were revealed as a 

result of the Loma Prieta earthquake evaluation effort are 

discussed below. Each will be considered in the ATC-20-2 

project. 
REVIEW, EVALUATION, AND REVISION OF THE ATC-20 POSTEARTHQUAKE BUILDING SAFETY EVALUATION AS 

RECORDS MANAGEMENT 

A building jurisdiction during earthquake recovery must 

immediately begin to effectively process building evaluation 

documents. This paperwork includes numerous requests for 

evaluations, completed written evaluations, and records of 

volunteer activity. This need occurs at a time when the staff 

is usually shorthanded and overworked, and when it is imperative that good records be kept to facilitate the recovery 

of aid funds. Representatives of many jurisdictions affected 

by the Loma Prieta earthquake have emphasized the importance of adequate preplanned, prerehearsed procedures for 

processing and managing evaluation documents. 

FORM AND USE OF POSTING PLACARDS 

The ATC-20 posting system of "inspected," "limited entry," and "unsafe" placards and an "area unsafe" designation had been adopted from earlier similar OES posting 

systems. Most building jurisdictions used this system or a 

similar OES posting system without significant incident 

for the Loma Prieta recovery. Others felt that it had certain 

shortcomings, as follows: 

1. A posting distinction differentiating a building which is 

hazardous to adjacent rights-of-way or properties from 

one which is only hazardous within was seen as necessary by some jurisdictions. This distinction allows jurisdictions to more vigorously demand owners to mitigate 

hazards to rights-of-way. Then, once the building is 

only hazardous within, the jurisdiction can proceed 

more slowly with the owner to affect repairs to the 

building. 

2. Some jurisdictions had a problem with the "area unsafe" 

designation, which allows part of a building to be posted 

"unsafe" and the remainder to be posted "inspected" or 

"limited entry." The jurisdictions would prefer that only 

one posting classification be given to each building. 

3. The "limited entry" posting is the most difficult posting 

to define and enforce. There is often confusion as to 

I what the entry and use limitations are and whether they 

are to be enforced by the jurisdiction or by the buildI ing owner. 

The desire for re-entry into even the most precarious 

buildings is often strong, especially for individuals whose 

livelihood is dependent on the belongings within. An account of the events influencing the removal of goods from 

damaged buildings is given in by Wilson (1991): 

The city was***under enormous pressure to provide access to damaged buildings. Residents wanted to remove***valued personal belongings*** cash and essential documents. Business owners wanted to 

remove inventory***computers ***files. At each afternoon's city council 

meeting they pleaded for access. ***We had to decide whether to err on 

the side of access or safety. The needs for access were urgent and compelling, but the dangers were real and manifest. ***many of the occupants of even the three most seriously damaged buildings were more 

than prepared to risk their lives to retrieve contents. ***Final decisions 

about access of course fell to me. 

The original intent of the ATC-20 methodology was that 

brief entry to remove goods was allowed in "limited entry7'-posted buildings. Entry was to be in accordance with 

the specific conditions written on the placard by the safety 

evaluation inspector. Goods could not be removed from 

"unsafe"-posted buildings until sufficient shoring, removal 

of falling hazards, and so forth was done to allow it to be 

reposted "limited entry." However, during the Loma Prieta 

earthquake recovery, the removal of goods from "unsafe"- 

posted buildings often occurred under the guidance of the 

jurisdiction or engineers, and the "limited entry" posting 

was often interpreted by the jurisdiction to allow more 

continuous occupancy. 

The meaning of the "unsafe" and "limited entry" placards 

must be well defined to differentiate (1) absolutely no entry, 

(2) limited entry for removal of goods when supervised by 

an engineer or the jurisdiction and (3) limited entry supervised by the owner. The PEP discussed modifying the "limited entry" posting to read "restricted use." The use 

restrictions would be clearly noted on the placard and would 

be enforced by the building ownerlmanager. Buildings 

where no entry is recommended or where entry must be 

strictly controlled by the jurisdiction would be posted "unsafe." The jurisdictions could choose to enforce this control 

by requiring that an engineer and contractor retained by the 

building owner obtain a permit for the task of evaluating and 

preparing the building for limited entry to remove goods. 

EVALUATION FORM REVISION 

The OES Evaluation Form and the ATC-20 Rapid Evaluation Form were most often used to record the evaluation 

information for use by the jurisdiction. Safety evaluation 

volunteers had both positive and negative comments on 

these forms. These and other existing or proposed forms 

have been reviewed by the PEP and by Loma Prieta earthquake safety evaluation volunteers with the aim of incorporating the best features of each. 

ASBESTOS IN DAMAGED BUILDINGS 

The ATC-20 document did not provide specific training in 

the recognition of asbestos hazards. During the Loma Prieta 

earthquake evaluation effort, several buildings appeared to 

have asbestos hazards and were ,appropriately closed. The 

greatest risk appears to be from damaged friable asbestos 

building materials and from free asbestos fibers previously 

in enclosed spaces being released due to damage to finishes 

and frame deformation. The risk is to both the safety evaluation volunteers and to future occupants (Pacific Asbestos 

Information Center, 1990; Chambers, 1988). 
A6 LOSS ESTIMATION AND PROCEDURES 

Friable asbestos-containing materials are those that can 

be easily broken by hand pressure. When these products 

are disturbed, they can easily release asbestos into the air. 

These products include certain sprayed acoustic ceilings, 

fireproofing, and pipe insulation. If damaged, friable asbestos-containing products are present in a building, it 

should be assumed that some level of asbestos will be 

present in the air. Even if asbestos fibers were not airborne 

prior to inspection they can easily and unknowingly be 

stirred up by the safety evaluation team. 

Asbestos sources other than friable materials are also 

possible. Nonfriable asbestos-containing materials include 

tightly bound asbestos fibers. They are less likely to release asbestos when disturbed or damaged. Crawl spaces, 

attics, and ceiling spaces may have had asbestos debris accumulation from the above sources before the earthquake. 

This debris can be easily become airborne and be inhaled 

by safety evaluation team. 

The health effects of asbestos can take 5 to 40 years to 

develop after the original exposure or exposures of breathing in the fibers. Three major illnesses, asbestoses, lung 

cancer, and mesothelioma, are caused by asbestos exposure. The effects of exposure are cumulative, and these diseases have no cure. No exposure level is considered safe. 

Safety evaluation volunteers should be knowledgeable 

about how to identify damaged asbestos products in buildings. Damage to a friable asbestos product should be considered cause for posting the building (or certainly the area) 

"unsafe," pending verification by trained asbestos professionals. Damage of this type would include cracked ceilings 

with acoustic coatings and damaged pipe insulation. Other 

damage which may warrant an "unsafe" posting would be 

cracking or separation at taped gypsum board joints, significant damage to vinyl flooring, and collapsed ceilings below 

structural soffits with pre-1978 sprayed-on fireproofing. 

"WINDSHIELD" SURVEY EVALUATION 

PROCEDURES 

This preliminary evaluation is carried out within hours of 

the earthquake, often by building inspectors, or firemen, to 

determine the scope of damage in the jurisdiction. The survey has been called a "windshield" survey because it is 

usually done by driving the streets and quickly assessing and 

recording obvious damage, usually without stopping to post 

structures. Safety evaluation volunteers could likely be requested and respond quickly enough to assist in this survey. 

A methodology for this survey procedure will be developed. 

AGREEMENT WITH RELATED PUBLICATIONS 

There are several other draft or published documents for 

California or nationwide use which are concerned with 

postearthquake safety evaluation. They are as follows: 

State of California Office of Emergency Services 

Post Disaster Safety Assessment Plan 

Structural Engineers Association Of Northern California Plan for Utilization of Damage Assessment Engineers (in draft) 

International Conference of Building Officials 

Building Department Guide to Disaster Mitigation Planning (Internal Conference of Building 

Officials, 199 1) 

Local Building Officials' Guide to the Utilization 

of Volunteer Engineers (Bay Area Regional 

Earthquake Preparedness Project, 1989) 

Persons working on these documents have been participating as PEP members or as guest project meeting attendees to coordinate their efforts so as to produce consistent, 

mutually beneficial documents. 

STRUCTURAL DEGRADATION ASSESSMENT 

Postearthquake safety evaluation and posting of buildings involves assigning an appropriate level of occupancy 

or entry to buildings with some degree of earthquake damage. It is essential that the evaluation and posting be appropriate to the actual risks of occupancy. Unconservative 

posting can place occupants at risk from falling hazards or 

collapse, whereas overly conservative posting will unnecessarily restrict residential and commercial users from occupancy of buildings and recovery of goods critical to 

their livelihoods. Building jurisdictions have typically 

been under great pressure after earthquakes to allow at 

least limited entry. 

Evaluating an earthquake-damaged building for safety of 

occupancy requires that its probable structural integrity, 

and eventually its posted level of occupancy or entry, be 

determined from its observed degradation. The inspector 

must decide to what degree the structural strength, stiffness, and stability of the overall structure and its parts have 

been lessened, based on observed degradation conditions, 

and then evaluate the resultant risk to occupancy or entry. 

As earthquakes are infrequent, engineers and building inspectors do not often practice building safety evaluation 

and have even less chance of verifying their decisions. 

Certain specific conditions have repeatedly been found 

to be difficult to assess. These conditions include the following: 

1. In reinforced concrete construction, how much structural 

degradation is indicated by given crack patterns, crack 

widths, and frame deformations? What is the relationship of crack width to reinforcement clamping and dowel action and reinforcement plastic elongation and 

fracture? How is element degradation related to overall 

frame strength and stability? Existing studies (Applied 

Technology Council, 1989a; Otani, 1988; Umemura, 

1989) have discussed these relationships but have not 
\ 

REVIEW, EVALUATION, AND REVISION OF THE ATC-20 POSTEARTHQUAKE BUILDING SAFETY EVALUATION A7 

fully developed the relationship of the degradation to 

risk. A further study of the known relationships between 

observed degradation and risk in reinforced concrete 

structures is especially needed. 

2. How are considerations similar to the above (without the 

reinforcement effects) applied to unreinforced masonry? 

3. How does an inspector best use the observed degradation of the nonstructural sheathing finishes (gypsum 

board, curtain walls, glazing) to estimate structural collapse risk and falling hazard risk? Finish degradation 

can indicate the structural degradation of a concealed 

frame, but this is dependent on the frame's stiffness. 

Cracked gypsum board in an unreinforced masonry 

building may be a symptom of concealed structural 

wall weakening, whereas cracked gypsum board in a 

steel moment frame building may only show that the 

gypsum board was stiffer but weaker than the frame. 

Cracked interior gypsum board often appears hazardous to occupants, who see it as a potential falling hazard and a sign of impending building collapse. Safety 

evaluation volunteers must be knowledgeable of all 

these considerations and confident in their assessment. 

This could be an important issue in a large event where 

there will be a large modified Mercalli intensity VI 

area containing numerous buildings with minor gypsum board damage. 

4. How can engineers correctly evaluate the safety hazards 

of mobile homes displaced from their support jacks? 

Mobile home construction, more often than site-built 

construction, uses the framing and the sheathing together compositely to achieve strength and stiffness. 

This composite construction is not well known to most 

safety evaluation volunteers. 

5. How can soils engineers assess the probability of further movement of slumped soil masses under buildings? This assessment can be important where the 

buildings on the displaced soils do not appear to be a 

collapse hazard. This was a common condition as a result of the 1964 Alaska earthquake. 

It will be beyond the scope of the ATC-20-2 project to fully 

research and develop all aspects of the technology of degradation assessment. Further research to improve this assessment could draw upon past laboratory test programs of 

structural and nonstructural elements, studies of overall frame 

stability, and the collected observations of actual earthquakedamaged buildings. It is unlikely that the degradation assessment methodology could ever become an exact procedure, 

but research leading to an improved methodology would be 

highly beneficial to the earthquake recovery process. 

REPAIR COST ESTIMATION 

Jurisdictions have often asked safety evaluation volunteers to estimate the cost to repair the observed damage. 

Volunteers often feel that they cannot provide these estimates with any usable accuracy because they are not experienced estimators and they do not know the full extent of 

damage and the local construction costs, reconstruction 

code requirements, or property values. Estimates are especially difficult for damaged unreinforced masonry buildings. Should jurisdictions ask for these estimates? 

Proponents of cost estimation by safety evaluation volunteers argue that early valuation is often needed to obtain 

outside assistance and for media inquiries and that the 

safety evaluation volunteers estimates are acceptably accurate. Opponents have argued that early repair cost estimates by safety evaluation volunteers tend to become fixed 

and cast doubt on later estimates and that the volunteers, 

working with insufficient information and under time pressure, will not make acceptably accurate estimates. 

It is often difficult to accurately estimate building repair 

costs. For example, cracked slabs-on-grade within buildings 

may permit occupancy, but the slabs are often irreparable. 

The building must then ultimately be demolished and rebuilt. 

Cripple wall collapses look drastic and make the building 

uninhabitable, but the house can often be readily lifted and 

repaired if the upper structure is reasonably undamaged. 

Veneer failures may expose decay and shear strength inadequacies, which compound the repair. In unreinforced masonry buildings, the decision on whether a given cracked or 

displaced masonry element can be structurally epoxied or 

must be replaced will have major cost implications. Slight 

differential settlements may require extensive foundation 

remedies. Archaic construction often cannot be rebuilt in kind. 

Recent experience has shown the difficulty even for experienced safety evaluation volunteers of making accurate estimates. In a 1987 damage assessment exercise by the Structural 

Engineers Association of Northern California, experienced 

teams of engineers assessed mock damaged buildings and 

were asked to fill in the cost of repair on the evaluation forms. 

Estimates by teams varied widely. In the Loma Prieta earthquake evaluation effort, the City of San Francisco asked that 

safety evaluation volunteers make repair estimates as they 

performed their evaluation work. City officials later observed 

that the estimates were often highly inaccurate. 

The PEP agreed that the safety evaluation volunteer 

should be asked to only estimate the percentage of loss 

(cost of repairltotal replacement cost). The jurisdiction, using their property valuation records, would then convert 

the percentage loss to a loss valuation. The ATC-20-2 will 

include training and guidelines for conducting a percentage loss estimate. It is not yet clear how the cost of required upgrades would be considered in this estimate. 

DEMOLITION CONSIDERATIONS 

The question of whether safety evaluation volunteers 

should be asked to recommend demolition is frequently 
A8 LOSS ESTIMATION AND PROCEDURES 

raised. The purpose of demolition during the immediate 

recovery is usually to eliminate hazards to a public rightof-way due to the collapse or falling hazards of an adjacent building. Closure of the threatened public right-ofway is the immediate remedy to the risk, but this can be a 

significant hardship for the community. Once a building 

no longer poses a threat to the public rights-of-way, its 

repair then becomes the problem of its owner and tenants, 

and the jurisdiction should no longer have a compelling 

need to order demolition. Thus the real issue to be addressed may be: Should safety evaluation volunteers be 

asked to make recommendations on how to mitigate a collapse or falling hazard to a public right-of-way? 

The safety evaluation volunteers can advise the jurisdiction as to what portions of the building are likely to fall or 

collapse and over what area of the public right-of-way 

they are likely to impact. They could further advise the 

jurisdiction as to whether they think that removal or shoring of the falling or collapse hazard is feasible. Service or 

recommendations beyond this point are inappropriate. Removal of a collapse or falling hazard, such as a precarious 

parapet or window glass panel, is best done by contractors. The design of shoring is not an appropriate task for a 

safety evaluation volunteer: it should be done by an engineer hired by the building owner or the jurisdiction. 

Once a building no longer threatens the adjacent public 

rights-of-way, the considerations regarding demolition can 

be more thoroughly weighed. The owner, aided by consultants, will consider the damage to the building, the cost 

of rehabilitation, its potential value if repaired, and what 

code will govern reconstruction. 

VOLUNTEERS TRAINING AND QUALIFICATIONS 

California Office of Emergency Services officials, safety 

evaluation volunteers, and building officials agree that better training is needed to prepare for safety evaluation 

work. This training has in the past taken the form of classroom sessions combined with field exercises where volunteers form teams and proceed to evaluate actual buildings 

with simulated damage and post appropriate placards. Further training could include other volunteers from related 

professions, such as architects and soils engineers. 

CONCLUSIONS 

The Loma Prieta earthquake provided an opportunity to 

use the existing postearthquake safety evaluation procedures. Any postearthquake evaluations are difficult by nature and are made more so by the circumstances and 

pressures. The consequences of erring conservatively or unconservatively are both significant. To be prepared for the 

inevitable "big one," it is imperative that we further develop evaluation knowledge and methodologies and train large 

numbers of engineers and other professionals in their use. 

REFERENCES CITED 

Applied Technology Council, 1989a, Procedures for postearthquake safety evaluation of buildings: Redwood City, California, ATC-20 Report, 152 p. 

1989b, Postearthquake safety evaluation of buildings: Redwood 

City, California, ATC-20 Field Manual, 114 p. 

Bay Area Regional Earthquake Preparedness Project, 1989, Local building officials' guide to the utilization of volunteer engineers: 15 p. 

Chambers, M.D., 1988, The Whittier Narrows, California, earthquake of 

October 1, 1987-Asbestos hazards in post-earthquake investigations: Earthquake Spectra, v. 4, no. 1, p. 31-34. 

International Conference of Building Officials 1991, Building department 

guide to disaster mitigation: Whittier, Calif., 79 p. 

Otani, Shunsake, 1988, Emergency guidelines for classification of risk 

levels of earthquake damaged reinforced concrete buildings: Bulletin of the New Zealand Society for Earthquake Engineering, v. 21, 

no. 4, p. 279-287. 

Pacific Asbestos Information Center, 1990, Answers to common questions about asbestos in homes and buildings: University of California, 12 p. 

Structural Engineers Association of California, 1991, Reflections on the 

Loma Prieta Earthquake, October 17, 1989: 174 p. 

Umemura, Hajime, and others, 1989, Post-earthquake inspection and 

evaluation of earthquake damage in reinforced concrete buildings, 

in Proceedings of the Ninth World Conference on Earthquake Engineering, v. VIII, Tokyo: p. 969-974. 

Wilson, R.C., 1991, The Loma Prieta quake: What one city learned: International City Management Association, 64 p. 
THE LOMA PRIETA, CALIFORNIA, EARTHQUAKE OF OCTOBER 17,1989: 

SOCIETAL RESPONSE 

LOSS ESTIMATION AND PROCEDURES 

CASUALTIES AND EMERGENCY MEDICAL RESPONSE 

By Michael E. Durkin, Michael E. Durkin & Associates, Woodland Hills, California; 

Charles C. Thiel Jr., Institute for Seismology and Earthquake Engineering, Stanford University; and 

James E. Schneider, Santa Cruz County Emergency Medical Services Agency, Santa Cruz, California 

CONTENTS 

Abstract .............................. ..................................... Introduction ................................................... ------------ Casualty data ------------------------------------------------------------- Regional fatalities ................................................. Santa Cruz hospitalization data ................................. Work-related casualty data ....................................... An Earthquake casualty index ......................................... 

Regional analysis of work-related and nonwork-related 

casualties (health-care demand) .................................... 

Number, type, and location of casualties ...................... Distribution of fatalities by place ............................... Distribution of hospitalized cases ............................... Work-related hospital admissions ............................... 

Data showing cause of injury or death------------------------- 

Casualty distribution by place ............................ 

Work-related injuries associated with structural 

collapse .................................................... 

Injuries not attributable to structural collapse ---------- Evasive action injuries --------------------------em--------- 

Injuries from toxic substances release ------------------- DIR data showing casualty distribution by type ------------- DIR casualty indices .............................................. 

Conclusions related to health-care demand analysis--------- 

Capacity of the health-care system (supply) ........................ Santa Cruz County emergency health-care delivery --------- 9- 1 - 1 emergency response ................................. 

Recommended 9- 1 - 1 EMS process for disaster 

periods --------------- - --- ----- ............................. 

Conclusions for EMS improvement---------------------- 

Hospitals ............................................................ Hospital administrator interviews ............................... 

Implications for emergency medical services----------------- 

Casualty-estimation modeling ......................................... Casualty estimation ............................................... 

Preliminary assessment of existing casualty-estimation 

models ............................................................ 

Analysis of existing earthquake casualty-estimation 

approaches ....................................................... 

Needs for revision and extension of models ------------------ Findings on the sources and frequency of earthquakecasualties ......................................................... 

Findings related to casualty-estimation methods------- 

Findings related to casualty-research methods --------- Findings related to physical setting data ---------------- 

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ABSTRACT 

Findings are presented from studies of casualties, 

health-care utilization (demand), and health-service response (supply) as a result of the Loma Prieta earthquake. 

Specific demand and supply factors are explored that are 

useful in developing both earthquake casualty-estimation 

models and more effective emergency-response procedures. 

Work-related injuries and illnesses were assessed from the 

entire affected region, including where the injured sought 

care, and a case study of emergency medical response in 

heavily damaged Santa Cruz County is presented. The casualty analysis found that (1) almost all fatalities and most 

serious injuries were associated with structural failure, 

(2) the majority of fatalities and serious casualties came 

from a small number of damaged structures, most notably 

the Cypress Street Viaduct collapse, (3) falling sections of 

unreinforced masonry buildings, striking passersby and 

falling on top of other buildings, caused deaths and serious 

injuries, (4) occupant contact with nonstructural elements 

and building contents was the major source of minor injuries, (5) although interior nonstructural elements and building contents posed a relatively low risk of serious injury to 

building occupants, certain elements and settings were particularly hazardous, and (6) occupant actions contributed to 

injuries-many victims were injured while attempting to 

take protective actions. 

The health-care utilization analysis found that 60 percent of the victims were treated in nonhospital settings. 

The emergency medical-response case study in Santa Cruz 

County found that (1) the 9-1-1 emergency response system was severely taxed, but remained functional and responsive, (2) advanced life-support ambulance transports 
A 10 LOSS ESTIMATION AND PROCEDURES 

were fewer than normal, (3) the medical system was able 

to accommodate the injury load because the county healthcare system was extensive. Although normal operations 

were initially disrupted, the three community hospitals did 

not suffer severe structural damage, and the demand for 

major medical care was light. A revised 9-1- 1 emergency 

medical service procedure is recommended for disaster periods and is expected to improve substantially disaster 

management of limited ambulance resources, while maintaining rapid call processing. 

Existing earthquake casualty-estimation procedures are 

reviewed to evaluate them in terms of our research results. 

The findings presented have three major implications for 

earthquake casualty modeling: (1) Structural damage potential remains the major predictor of serious earthquake 

casualties, but occupant contact with nonstructural elements remains a key source for minor injuries and a potentiality for major ones; (2) casualty estimates based 

exclusively on hospital utilization data may greatly underestimate the true medical need; and (3) future casualty 

models should estimate the resiliency of an entire regional 

health-care system. 

For instance, the spatial distribution of injuries, which applies to both supply and demand issues, shows that the 

extensive health-care system of the San Francisco Bay area 

was adequate to meet the care for relatively few injuries in 

this moderate earthquake. It is noteworthy that the injury 

severity and distribution patterns for the Loma Prieta earthquake are similar to those for other earthquakes. 

Three major topics are covered in this paper. First, examination of the types, severity, and distribution of casualties (demand for medical services). Second, examination 

of the medical care provided by the emergency medical 

services (EMS) and hospitals (supply of medical services). 

Lastly, implications of data from the Loma Prieta and other earthquakes on casualty-estimation modeling. For each 

major topic, findings and recommendations that warrant 

consideration by the appropriate research and applications 

community are presented. The most immediate of these is 

our recommendation for revision of the current 9- 1 - 1 dispatch systerh, which offers substantial improvement without additional capital expenditures. 

CASUALTY DATA 

INTRODUCTION 

Casualties have only recently been included in loss estimation studies for earthquakes, mostly because of the difficulty of acquiring accurate casualty data. Recent 

advances, however, in injury studies have made possible a 

new framework for loss estimation that includes data on 

injuries, as well as the capacity of the health-care system 

to respond (Durkin and Thiel,1990; Johns Hopkins University, 1989; U.S. Geological Survey, 1990). Casualty estimation consists of two facets: 

1. Estimating the demand--the number, type, and location 

of casualties requesting health services 

2. Estimating the supply--the capacity of the health-care 

system to respond to estimates of casualties 

These estimations are typically oversimplified in most 

casualty-estimate models because presenting data in absolute numbers does not identify subtle patterns important in 

determining the medical care needed (demand) and the 

medical care available (supply). For example, estimates are 

often distorted because only hospitalized injuries are reported, not doctor-treated injuries; nor are the circumstances, location, and distribution of injuries typically reported. 

Such inadequacies in supply and demand numbers are crucial because they affect decisions about the facilities, training, and loss-mitigating measures prior to a disaster. 

Injury data from the Loma Prieta earthquake offer the 

opportunity to improve the understanding of the relationship among supply, demand, and mitigation. From these 

data, patterns emerge from which conclusions can be made. 

The data sources we used for this study need to be put 

in the context of the different research approaches that we 

and other investigators have used to study Loma Prieta 

earthquake casualties. No single approach provides a complete picture, each having disadvantages as well as advantages. Given the weaknesses of any single method, we 

determined that the best method for developing a reliable 

picture was by comparing the findings of different approaches and looking for confirmation. We used the following types of analyses, as well as others that are still 

being developed: 

1. An analysis of earthquake-related fatalities for the entire affected region 

2. An analysis of Santa Cruz County earthquake-related 

injuries requiring hospitalization 

3. An analysis of work-related injuries and illnesses for 

the entire region 

We chose these analyses because fatalities and hospitalizations clearly depict earthquake severity and effects and because work-related injuries clarify the relationship between 

settings and effects as well as the personal characteristics 

of victims. 

REGIONAL FATALITIES 

Determining the number of and reasons for fatalities underlies any comprehensive earthquake-injury investigation 

because mitigation strategies, at the very least, should be 

directed at minimizing mortality. In fact, although present 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A1 1 

seismic codes are designed to minimize deaths, they do 

not necessarily prevent injuries. We based this analysis 

primarily on a review of data compiled by county coroner's offices in the affected counties and interviews with 

coroner's office personnel. Because relatively few fatalities were associated with the Loma Prieta earthquake, reasonably complete information was available. 

One limitation is that the factors related to any death 

were described by witnesses and determined through other 

circumstantial evidence, so we assume these sources to be 

accurate. A second problem is that coroner's reports do 

not contain information about others who escaped death in 

the same setting. Therefore, while it is possible to calculate gross epidemiological rates using census and other 

population data, it is difficult to derive place-specific fatality rates. With this shortcoming in mind, we investigated 

one location where place-specific rates could be obtained: 

the Cypress Street viaduct in Oakland. Given that so many 

casualties were concentrated at the Cypress viaduct we reviewed and analyzed data collected by the California 

Highway Patrol on casualties in that setting. The California Highway Patrol study was a good example of a placespecific, historical cohort, epidemiological analysis in that 

it systematically documented fatalities as well as examined 

the behavior of the injured and uninjured on and near the 

Cypress viaduct. 

Finally, our regional fatality data was supplemented by 

work-related casualty data (see section "Work-Related Casualty Data" below). 

SANTA CRUZ HOSPITALIZATION DATA 

The rationale for investigating those hospitalized from 

Loma Prieta earthquake injuries is similar to that for fatalities: Given limited resources, injury-prevention strategies 

should first be designed to reduce the sources of major 

injury; thus these strategies should be based on an empirical understanding of the types of serious injuries. 

Unlike subjective reports of injury type, hospital documentation provides an objective medical diagnosis. Emergency room data are, however, not used because people use 

emergency rooms as their initial point of medical contact 

for a variety of reasons and may not have severe injuries. 

Studies that rely exclusively on hospital emergency-room 

gross numbers tend to overestimate severe injuries; also, 

they may underestimate the number of minor injuries because many with minor injuries do not go to an emergency 

room. 

We restricted our study to Santa Cruz County in order to 

calculate the gross, earthquake-related hospitalization rates 

using the current county census data. The degree to which 

our data can be generalized to other counties is not clear; 

however, we have supplemented this data with regional, 

work-related hospitalization data. 

WORK-RELATED CASUALTY DATA 

The Loma Prieta work-related injury and illness data are 

especially important because the timing and location of 

previous California earthquakes resulted in relatively few 

documented injuries in work settings. The California Department of Industrial Relations (DIR) collects specific data 

on occupational injury and illness as part of its ongoing 

responsibilities (California Department of Industrial Relations, 1989). California employers are required to report all 

Workman's Compensation claims to DIR. Each report includes details of the victim's personal characteristics, the 

type of injury, the physical setting where the injury happened, the victim's activities before and at the time of injury, the injury mechanism(s), and the setting(s) where the 

victim received medical care. DIR maintains data on 100 

percent of work-related fatalities, and systematically samples 50 percent of disabling-that is, nonfatal-injuries and 

illnesses. A disabling injury or illness is one that causes the 

worker to be absent from work for a full day (or shift period after the time of occurrence). This definition is used in 

Workman's Compensation cases, and, as such, they do not 

usually tax the health care system. 

Immediately following the earthquake, DIR agreed to 

identify those fatal and "disabling" (according to the 

above criteria) cases that were earthquake-related. A total 

of 17 work-related fatalities and 325 "disabling" injuries 

and illnesses was identified. The work-related casualty 

analysis in the following sections is based on these data. 

The DIR set aside approximately 100 additional nonfatal 

cases. We excluded these cases from this analysis because 

they did not fit the "disabling" criteria and therefore were 

not part of a systematic sample. 

Compared to other data sources, the Loma Prieta workrelated injury and illness data have the following advantages and disadvantages. Unlike medical documentation 

such as hospital emergency-room logs and medical 

records, which contain scant information about how or 

where injuries occurred, the DIR data contain detailed descriptions of the circumstances surrounding each injury 

and its place of occurrence. This locational data can subsequently be correlated with damage data from visual inspections or public records and can serve as a basis for 

estimating physical setting performance. A second advantage is that the work-related injury accounts were prepared 

within hours or days of the event. They therefore do not 

have the problem of personal recall accuracy that can lessen the reliability of survey data collected months and even 

years after an event. The third advantage is that, unlike 

studies restricted to a small geographic area, the DIR data 

base is regional and therefore can be used to explore regional differences in injury patterns. 

The disadvantages of the DIR data typify other data 

sources, all of which call for additional investigation. One 

disadvantage is that, like studies that depend exclusively 
LOSS ESTIMATION AND PROCEDURES 

Table 1.-Spatial distribution by county of work-related fatalities and disabling injuries and illnesses 

[(From Durkin and others (1991); seventeen fatal injuries were attributed to the period of shaking; one heart attack was 

attributed to the earthquake. One additional work-related fatality in Santa Cruz was not reported to DIR, but independently 

confirmed, and is not included here. Numbers and percentages do not include San Benito County. N, number of cases; Pet.. 

percentage of total] 

County Fatalities Non-fatal disabling injuries Total 

During shaking After shaking 

N Pet. N Pct. N Pet. N Pet. 

Santa Clara - 2 11.1 105 37.5 11 25.0 118 34.5 

Alameda - - - 10 55.5 5 7 20.4 6 13.6 73 21.3 

San Mateo - - - - 40 14.3 4 9.1 44 12.9 

San Francisco 5 27.7 27 9.6 10 22.7 42 12.3 

Santa Cruz - - 1 5.5 26 9.3 6 13.6 3 3 9.6 

Monterey . . . - - - - 4 1.4 2 4.5 6 1.8 

Contra Costa - - - - - 6 2.1 0 .O 6 1.8 

Marin - - - - - - - - - 3 1.1 0 .O 3 .9 

Sonoma - - - - - - - - 2 .7 0 .O 2 .6 

Sacramento - - - - - - 0 .O 1 2.3 1 .3 

Not specified - - - - 10 3.6 4 9.1 14 4.1 

Totals 18 99.8 280 100.0 44 99.9 342 100.0 

on hospital emergency-room data, the DIR reports tend to 

underestimate the total number of injuries. In the case of 

work-related injuries this underreporting appears due primarily to underreporting by victims. However, underreporting is probably confined primarily to less severe 

injuries because victim compensation, especially to those 

fatally or severely injured, is dependent on reporting. A 

second disadvantage of current work-related injury data is 

that place-specific injury rates cannot be calculated without further follow-up investigations to determine the population at risk in particular situations. A third difficulty is 

determining whether work-related injuries are representative of nonwork-related injuries in type and scope; data 

here are too preliminary for answers. 

AN EARTHQUAKE CASUALTY INDEX 

As aptly pointed out by Steinbrugge (1982) in his seminal 

work on building damage, casualties vary greatly with situation and setting. Durkin and Thiel (1990) have developed 

an injury index to aid in classifying injuries for casualty 

estimation purposes. Injuries vary greatly-from scratches, 

cuts, and abrasions that can be self or nonprofessionally 

treated (a so-called Red Cross training level) to those requiring specialized medical care. The first type do not degrade severely with delay (becoming life threatening) from 

professional treatment, whereas the latter can quickly become life threatening. There are three distinct components 

to categorizing injury severity: the type of assistance needed to move the patient to the medical provider, the skill 

level required to treat the injury, and the degree to which 

the injury becomes more serious with lack of treatment. 

Recognizing that these distinctions have serious implications for preparedness planning and for public policy decisions, we have developed an injury index (see table 9). The 

scale reflects the degree of medical skill required and the 

ability of the injured to transport himself to the care provider; an important factor not considered in the table is the 

degree to which the injury could become life threatening if 

not treated quickly. This index is not meant to replace currently used medical severity scales, but for possible use as 

a planning tool in earthquake preparedness. 

REGIONAL ANALYSIS OF WORKRELATED AND NONWORK-RELATED 

CASUALTIES (HEALTH-CARE DEMAND) 

NUMBER, TYPE, AND LOCATION OF 

CASUALTIES 

Our health-care demand study includes the spatial distribution of casualties at the regional level, the relationship 

of building damage to casualties, the physical setting performance and occupant actions that contributed to injury, 

and the distribution of injuries by type. The California Office of Emergency Services (OES) reported that there were 

approximately 3,800 casualties (deaths and injuries) attributable to the earthquake (Housner and Thiel,1990). The 

accuracy of this estimate is suspect because the consistency of data-collection methods among reporting agencies is 

unclear, but the data are associated with hospital and 

emergency-room reports from the medical community. 

Table 1 presents the distribution of work-related disabling casualties by county. All but one of the fatalities 

and 86 percent of the nonfatal work-related casualties happened during the period of shaking; 14 percent of the non- 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A13 

fatal work-related casualties occurred in the earthquake's 

aftermath. Two-thirds of the deaths took place in Alameda 

County and about one-third in San Francisco County. Santa Cruz County had only one work-related death. Workrelated fatalities accounted for 27 percent of the total 63 

deaths attributed directly to the earthquake. 

The vast majority, 90 percent, of the nonfatal work-related casualties were reported in the 5 counties closest to the 

epicenter. Injury frequency declined with distance from 

the epicenter as a function of decreasing earthquake intensity (on the modified Mercalli intensity scale, see fig. l), 

with the exception of Alameda County, where the Cypress 

viaduct collapse generated numerous injuries. Santa Clara 

County accounted for over 37 percent of work-related injuries during the earthquake. Santa Cruz County, where 

the heaviest damage occurred, accounted for less then 10 

percent of the total work-related injuries. 

Table 1 also gives the injury data reported by the OES, 

which shows that the percentage of work-related casualties 

(Dm) to total casualties (OES) remains nearly constant 

between counties. The DIR percentage for Alameda County is high, owing to the one catastrophic collapse of the 

Cypress viaduct; that for Santa Cruz County is lower, owing to agriculture and tourism as its principal industries. 

(As will be noted later, there were apparently few tourists 

in the county at the time of the earthquake.) The information available on DIR injuries, because of careful auditing 

and recordkeeping, offers a new resource for understanding some aspects of casualties to comparable populations 

for which casualty data are not readily obtainable. 

DISTRIBUTION OF FATALITIES BY PLACE 

The Loma Prieta earthquake was directly or indirectly 

responsible for at least 65 deaths. A total of 43 deaths resulted from injuries sustained in Alameda County; 13 in 

San Francisco County; 6 in Santa Cruz County; 2 in Santa 

Clara County; and 1 in Monterey County. At least 18 of 

these 64 deaths (28 percent) were considered work related. 

Table 2 summarizes the cause and geographic location of 

these fatalities, as well as their frequency and proportional 

Figure 1.Ã‘Generalize isoseismal map of the damage impacts of the Lorna Prieta earthquake according to the modified Mercalli intensity (MMI) scale. MMI VII is termed strong 

shaking and is described by the types of effects observed: weak unreinforced buildings 

damaged; unreinforced masonry chimneys broken at roof lines; disruption of building contents; plaster cracked. MMI VIII is termed very strong shaking: damage to nonearthquakeresistant structures can be significant, with some collapses, particularly those in poor condition; damage to nonstructural elements in modem, seismically resistant buildings; substantial disruption of building contents and toppling of unanchored equipment. From Housner 

and Thiel(1990). 
LOSS ESTIMATION AND PROCEDURES 

Table 2.-Fatalities by structural type and location 

[(From Durkin and others (1991)l 

Type of failure Place of fatal injury Fatalities Percent 

of 

Total 

Structural failure: 

Bridges: 

Reinforced concrete: 

Cypress Viaduct, - - - - - . - Oakland . - - - . - - - . - - . - - 42 65.0 

Steel truss: 

San Francisco Bay Bridge . . . . . . San Francisco . - . . - . - - . . 1 1.5 

Buildings: i 

Unreinforced masonry: 

Exterior wall falls on cars - . - - . . Downtown San Francisco . 5 8.0 

Exterior wall pieces: 

Strike victim outside . . . .. . . . .. Watsonville . . - - - . - - - - - 1 1.5 

Roof collapse due to 

adjacent building collapse . . . Santa Cruz . - - - - - - - - - - - 3 5.0 

Wood frame: 

Apartment building collapse. . . Marina District: San Francisco 3 5.0 

Other structures: 

Transmission tower collapse . . . Los Altos . - - - . - - - - - - - . 1 1.5 

Water tower collapse . . . . . . . . Monterey . - - - - - ., - - - - - - 1 1.5 

Total related to structural failure 57 88.0 

Other causes: 

Landslide . - - - - - - - - - - - - - - - - - - - Falls/s tairway . - - - - - - - - - - - - - - - Employee evacuationheart attack . - Smoke inhalationhire . - - - - - - - - - - Carbon monoxide inhalation1 

generator 

Gunshot wound1 directing traffic . . Vehicle collision with horses , - - - - - Total related to other causes . - 

Total fatalities . - - - - - - - - - - - - 

Oakland. - - - - - - - - - - - - - 1 1.5 

San Francisco , - - - - - - - - - 1 1.5 

Santa Cruz . - - - - - - - . - - . 1 1.5 

8 12.0 

65 100.0 

distributions. Of these 65 earthquake-related fatalities, 43 

(66 percent) were concentrated in Oakland at the Cypress 

viaduct collapse; 11 other deaths (17 percent) were confined to three other locations in San Francisco and Santa 

Cruz. Of these 11, 5 died within close proximity to each 

other in downtown San Francisco, 3 perished in a San Francisco Marina District residential building, and 3 others died 

in two separate buildings in the Santa Cruz central business 

district. 

Structural failure was the underlying cause of most fatal 

injuries. Of the 65 fatalities, 57 (88 percent) were associated with some type of structural failure. All but on'e of the 

18 work-related fatalities (94 percent) were the direct result of structural failure or its complications (for example, 

fire). Fatalities occurred in the collapse of a nonductile, 

reinforced concrete structure (the Cypress viaduct), the 

failure of two 50-ft spans of the San Francisco-Oakland 

Bay Bridge, the partial or complete failure of unreinforced 

masonry buildings, the collapse of a four-story woodframe apartment building, the collapse of an agricultural 

water tower, and the collapse of a transmission tower 

(U.S. Centers for Disease Control, 1989; San Francisco 

County Coroner's Office, 1990). 

Two-thirds of the fatal injuries and three-quarters of 

those related to structural failure occurred in the Cypress 

viaduct collapse (California Highway Patrol, 1990). Table 3 

provides a breakdown of the cause and place of fatalities, 

and their frequency and rate, for the two freeway levels 

and for surface streets in the collapse vicinity. One-quarter 

of the vehicle occupants involved in this collapse perished. 

However, table 3 shows a place differential, similar to that 

found in the collapse of reinforced concrete buildings, between fatalities on the upper and lower decks. Almost half 

of the vehicle occupants on the lower deck died, whereas 

less than 10 percent of upper deck occupants perished. 

Lower deck fatalities were primarily due to vehicles being 

crushed by falling spans or bent caps. Fire caused by exploding fuel tanks was also associated with some fatalities. 

Upper deck fatalities happened 'in vehicles that fell or 

were pitched off the upper deck and fell to the street be- 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A15 

Table 3.Ã‘Casualt frequency and rates for the Cypress viaduct collapse 

[Data from California Highway Patrol (1990). Injury index is interpretation of authors. Note that some data are for a range of 

injury indexes, which are described in text; therefore total numbers and percentages do not add up to the number of 

occupants. N, number of cases; Pct, percentage of total] 

Casualty Injury index Lower deck Upper deck Surface Total 

(table 9) streets 

(N = 77) (N = 85) (N = 7) (N= 169) 

N Pet. N Pet. N Pet. - N Pet. 

Uninjured- - - - - - 0 4 5.2 11 12.9 4 57.1 19 11.2 

Injured - - - - - - - .- 1-6 38 49.3 67 78.8 3 42.9 108 63.9 

Pain - - - - - - - 1 7 9.0 14 16.5 1 14.3 22 13.0 

Visible . - - - - 2 10 13.0 19 22.3 0 0.0 29 17.2 

Severe - - - - - 4-6 21 27.3 34 40.0 2 28.6 57 33.7 

Fatalities - - - - - - - 7 35 45.4 7 8.2 0 0.0 42 24.8 

low. All of the 10 work-related fatalities occurred when 

the upper deck collapsed on vehicles: Apparently 8 were 

crushed in their vehicles by collapsing concrete; 1 person 

was killed when his truck toppled off the freeway; the 

tenth victim died from bums while trapped in wreckage. 

In another "bridge-related" incident, which occurred 30 

minutes after the earthquake, a 23-year-old female drove 

into the gap created by the collapse of the upper deck closure span of the San Francisco Bay Bridge suffering fatal 

injuries (Housner and Thiel, 199 1). 

The failure of unreinforced masonry (URM) buildings 

contributed to nine fatalities, including six work-related 

deaths. In San Francisco, five motorists, in three separate 

vehicles, were killed when parts of the exterior wall of a 

five-story URM building collapsed on top of their vehicles. 

All of these fatalities were work related. In downtown Santa 

Cruz, two victims were inside a single-story URM commercial building when its roof collapse was triggered by a wall 

failure in the adjacent multistory URM building. Just down 

the street, a similar collapse incident killed a person inside 

a two-story department store. Finally, in Watsonville, falling 

exterior wall and parapet material fatally injured a woman 

outside of a bakery housed in a URM structure. 

Three were killed when the top two stories of a fourstory, wood frame San Francisco Marina District apartment building collapsed onto the first (residential) floor. 

Two were killed in an apartment while an infant, being 

evacuated by its mother, died in a collapsed stairwell. Two 

additional fatalities are related to the failure of other structures: A communications technician was killed by a falling 

transmission tower in Los Altos; the other victim died in 

the collapse of an agricultural water tower. 

Eight deaths (12 percent) were related to causes other 

than structural failure. One of these was due to slope failure. The victim, discovered five days after the earthquake, 

was found buried under earth from a Santa Cruz cliff that 

apparently gave way during the earthquake. 

Two San Francisco deaths were attributed to stairway falls 

either during or immediately after the earthquake. In one 

case, a 59-year-old man was observed to fall down a 10-foot 

flight of stairs. In the other instance, a 68-year-old female 

tourist was found lying on the floor of a darkened basement 

garage at the foot of the stairway leading to a hotel lobby. 

Other fatalities included a public agency supervisor who 

suffered a fatal heart attack after evacuating his agency, a 

third San Francisco resident who apparently died from 

smoke inhalation during a fire caused by an earthquakeinduced gas leak, a 34-year-old male who died from carbon monoxide inhalation from an emergency generator in 

Alameda County, and a civilian who was shot while directing traffic in San Francisco after the earthquake (this 

death was considered indirectly earthquake related by the 

San Francisco Coroner's office). Finally, perhaps the most 

bizarre death, attributed indirectly by the Santa Cruz Coroner's office to the earthquake, happened approximately 7 

hours after the event when a pickup truck, traveling a 

darkened Santa Cruz freeway, crashed into three horses, 

killing the driver and all of the animals. 

DIR data show that the 18 work-related fatalities (28 percent of all fatalities) were concentrated in five locations, all 

included within those deaths discussed above. Of the 18, 

10 died in the Cypress viaduct collapse; 5 died within 

close proximity to each other in downtown San Francisco; 

one reported death was in the Santa Cruz central business 

district. An additional death was independently confirmed 

but not reported to DIR and therefore not discussed (or 

considered in our numbers) here. Two others died in Santa 

Clara County. All but one fatality was the direct result of 

structural failure or its complications (for example, fire). 

No work-related deaths were attributable to the performance of nonstructural elements or building contents. 

DISTRIBUTION OF HOSPITALIZED CASES 

Next to fatalities, the most serious earthquake casualties 

were those requiring hospital admission, in addition to hospital emergency-room or outpatient treatment. The proportion 
A16 LOSS ESTIMATION AND PROCEDURES 

of emergency-room cases that are actually admitted to a 

hospital, as opposed to being examined or treated or both and 

released, is one way to gage the relative severity of earthquake-related injuries. In the 72-hour period after the earthquake, the three Santa Cruz County hospitals, Dominican, 

Community, and Watsonville, admitted only 23 patients with 

serious earthquake-related injuries. This number stems from 

a medical record review, as part of a county and local hospital's postearthquake medical assessment, of the 981 cases 

seen in hospital emergency rooms during the 72-hour interval; 76 of these cases were seen more than once in the 72- 

hour period. Table 4 shows the probable medical cause of 

these emergency room cases. It shows that 55 percent of all 

cases were potentially earthquake related and 22 percent 

were clearly earthquake related. The geographic distribution 

of these 98 1 cases within the county shows a concentration in 

population centers. - 

A total of 11 5 patients (1 1.7 percent) of the 98 1 required 

hospital admission. Their case records contain significantly 

more detail than those cases not hospitalized. Table 5 proTable 4.-Probable medical cause for hospital cases during the 72-hour 

period after the earthquake 

[N, number of cases; Pct, percentage of total] 

Medical cause N Pct. 

Illness.. . - . . . - - .. . - .- .. - - - - . - - 360 36.7 

Other (for example, OBGYN) - . - - - - - 6 .6 

Unknown------.--.----.------ 79 8 .O 

Total--..--.---..------..-- 445 45.4 

Injury 

Clearly earthquake related- - - - - - 2 15 21.9 

Clearly not earthquake related. . . - 15 1.5 

Uncertain cause- - . - - . - - - - - - - 3 06 31.2 

Total - - . - - - . - - - - - - - - - - - - - - - 536 54.6 

Total cases - - - - - - - - - - - - - . - - - - 98 1 99.9 

vides a breakdown, by medical cause, of these 115 patients (11.7 percent of the total cases). This number 

includes both direct admissions to hospitals (81 percent) 

and transfers from other hospitals (19 percent). Of these 

115 admissions, only 23 were judged earthquake related. 

Data from tables 4 and 5 allow estimation of the frequency for earthquake-related injuries requiring hospital 

treatment from the total of earthquake injuries. Taking the 

23 serious earthquake-related injuries, if only earthquakecaused injuries are considered, the frequency of serious injuries is 10.7 percent (23/215), whereas if all of the causeuncertain injuries are assumed to be earthquake related, 

then the frequency is 4.4 percent (231521). The California 

Department of Health Services, in association with Santa 

Cruz County, Johns Hopkins University, and the authors, 

is completing a detailed study of Santa Cmz County injuries. When completed this study will provide a means for 

more precise assessment of injury frequency. 

Table 6 gives the probable medical cause of these 23 

hospitalized cases. Heavy building contents, such as packing crates, were the source of the hospitalized injuries from 

building contents. Only one-fifth of the serious injuries was 

due to structural failure. Unlike the overall fatality distribution, falls were responsible for over half (13123) of the 

Santa Cruz earthquake-related hospitalizations. Closer scrutiny reveals that the elderly were the most frequent fall 

victims. Whereas a younger individual might escape a fall 

with minor bruises, the elderly victims in this group were 

more likely to suffer a fractured hip requiring several days 

of hospitalization. In several cases, it appeared that the 

earthquake injury provided a convenient opportunity for the 

physician to treat a pre-earthquake condition. 

These data clearly support the observation that serious 

injuries, those requiring hospitalization, did not represent 

a substantial fraction of all the injuries that occurred in 

the earthquake within Santa Cruz County and probably 

regionwide. 

Research is now underway to further assess data from 

Loma Prieta and other worldwide earthquakes with the obTable 5.-Cause of hospital admissions for the 72-hour period after the earthquake in Santa Cruz County 

[Hospitals make a distinction between admissions and transfers from other hospitals; N, number of cases; Pct, percentage 

of total] 

Medical cause 

Percent of 

Admissions Transfers Total hospital 

cases 

(table 4) 

N Pct. N Pct. N Pct. 

Illness - - . . . . . . . . . . . . . - 56 60.9 9 39.1 65 56.5 6.6 

Injury, earthquake related . . . 16 17.4 7 30.4 23 20.0 2.2 

Injury, not earthquake related 13 14.1 7 30.4 20 17.4 2.0 

Other (for example, OBGYN) 5 5.4 --- --- 5 4.3 0.5 

Unknown.. . . . . . . . . - . . . 2 2.2 --- --- 2 1.7 0.2 

Total .------------.- 92 100.0 23 99.9 115 99.9 11.7 

Table 6.-Earthquake-related hospitalized injuries in Santa Cruz County 

[N, number of cases; Pct, percentage of total] 

Cause of injury 

Falls: 

Direct - - - - . - - - Indirect . - - - - - . 

Structural failure: 

URM - - - - - - . - Unknown- - - - - Building contents 

Toxics (indirect) 

Total hospitalized 

Pct. 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE 

Table 7.-Distribution of nonfatal, disabling1 work-related injuries and illnesses in Santa Cruz 

County 

[(From Durkin and others (1991); N, number of injuries; Pet, percentage of total; leaders (--), no data] 

Cause of injury During shaking After shaking Total 

N Pct N Pct N Pct 

Due to structural collapse: 

Cypress viaduct. ........... 8 2.9 0 .O 8 2.5 

San Francisco Bay Bridge ..... 2 .7 0 .O 2 .6 

Unreinforced masonry related: 0 .O 

Falling wall material ......... 2 .7 0 .O 2 .6 

Falling ceiling1 building collapse . 2 .7 0 .O 2 .6 

Floor failure~burning building ... 0 .O 1 2.1 1 .3 

Total .................. 14 5.0 1 2.1 15 4.6 

Not due to structural collapse: 

Hit by falling object ......... 43 15.5 0 .O 43 13.2 

Hit or bumped by overturning 

object.. .............. 36 13.0 0 .O 36 11.1 

Thrown into or bumped into 

object.. ............... 57 20.6 0 .O 57 17.5 

Fall-related injuries .......... 72 26.0 16 33.3 88 27.1 

Other stairway related ........ 0 .O 6 12.5 6 1.8 

Sprains due to shaking ........ 6 2.2 0 .O 6 1.8 

Strained taking evasive action ... 23 8.3 0 .O 23 7.1 

Holding on.. .. ^. ......... 7 2.5 0 .O 7 2.2 

Helping someone. .......... 1 0.4 3 6.2 4 1.2 

Vehicle related. ............ 2 0.7 1 2.1 3 .9 

Toxic material exposure ....... 0 .O 12 25.0 12 3.7 

Moving objects. ........... 0 .O 3 6.2 3 .9 

Clean-uphepair ............ 0 .O 2 4.2 2 .6 

Steppedlslipped on object. ..... 1 .4 3 6.2 4 1.2 

Emotional ................ 2 .7 1 2.1 3 .9 

Other .............. 2 .7 0 .O 2 .6 

Unknown. ...........-... 11 4.0 0 .O 11 3.4 

Total. ................. 263 95.0 47 97.8 310 95.2 

Total Injuries ............. 277 100.0 48 99.9 325 99.8 

^'Disabling" is defined in text in the section "Work-Related Casualty Data." 

jective of developing empirically supportable casualty-estimation models. 

counters and other objects. Finally, two victims fell from 

some height (one from five stories); two others tripped and 

fell while evacuating a building, and a fifth felt that a fall 

may have complicated her pregnancy. 

WORK-RELATED HOSPITAL ADMISSIONS 

DIR data show that of the 25 work-related cases requiring hospital admission, 8 were related to structural failure, 

10 were associated with building contents, 1 was connected to the failure of a nonstructural ceiling system, 5 were 

fall related and, 1 person was burned by cooking grease. 

Six of the eight structure-related injuries occurred at the 

Cypress viaduct collapse; one at the San Francisco Bay 

Bridge failure; and one at a URM collapse. Heavy objects 

that toppled, including a roll of newsprint, a wine barrel, a 

metal locker, a file cabinet, and a store display, accounted 

for five building-content injuries. An airline employee suffered a possible paralysis when hit by a falling gate podium. Four injuries resulted when people were thrown into 

DATA SHOWING CAUSE OF INJURY OR DEATH 

I 

DIR data are particularly useful in relating casualties to 

specific structures, environments, or actions. Despite their 

potential underreporting of injuries, these data offer a useful breakdown of types and causes. 

CASUALTY DISTRIBUTION BY PLACE 

Table 7 summarizes the causes of the fatalities and injuries. While all but one fatality were associated with stmctural failures, only 7 percent of the injuries were related to 
A 18 LOSS ESTIMATION AND PROCEDURES 

such failures. Approximately 85 percent of the injuries were 

caused by earthquake shaking, while the other 15 percent 

occurred after the earthquake shaking. These latter casualties were associated with individual behavior or accidents 

that would not have occurred if the earthquake had not 

caused the damage or behavior associated with the injury. 

The fact that about 20 percent of after-earthquake injuries 

were caused by toxics is of some concern, especially since 

these are disabling injuries and few sites with non-agricultural chemicals were damaged. This percentage may suggest that future toxics-related injury rates can be expected 

to be much higher, both in absolute numbers and in proportions. The nature of these data are discussed below. 

WORK-RELATED INJURIES ASSOCIATED WITH 

STRUCTURAL COLLAPSE 

Like fatalities, work-related injuries associated with 

structural collapse were concentrated at the Cypress viaduct and the San Francisco Bay Bridge and also scattered 

among a small number of URM buildings. There were 8 

vehicle-related injuries at the Cypress viaduct collapse, 2 

at the Bay Bridge, and 4 from URM failure. Two of the 

four documented URM-related injuries resulted from falling masonry hitting passersby; the other two victims were 

inside URM's when the ceiling collapsed. A fireman who 

fell when the floor of a burning building collapsed suffered the only postshaking injury due to structural failure. 

INJURIES NOT ATTRIBUTABLE TO STRUCTURAL COLLAPSE 

Fall-related injuries comprised those most frequently reported to the DIR as unrelated to structural collapse. This 

type of injury accounted for almost 26 percent of those 

occurring during and after shaking. The four most common fall-related injuries during the shaking were due to 

stairway falls; falls off ladders, scaffolding, and loading 

docks; and simply being knocked down by the strength of 

the shaking. Falls were also responsible for 33 percent of 

the postshaking injuries. Postshaking fall victims were primarily individuals attempting to evacuate buildings 

through darkened stairways. 

Being thrown into or bumping into a desk, doorway, or 

other object was reported by over one-fifth of the victims, 

making such impacts the second most frequent cause of 

shaking-related injuries. Although being hit by a falling 

object is commonly thought to be the predominant earthquake-injury mechanism, the DIR data support this assertion only for those injuries resulting from the structural 

failure of URM buildings. Only about 16 percent of the 

"nonstructural" injuries were due to falling nonstructural 

elements such as ceiling tiles or light fixtures. Furthermore, only 13 percent of the shaking-related injuries were 

associated with building contents, such as filing cabinets, 

overturning and striking building occupants. In addition, 

approximately 10 percent reported straining of the back or 

extremities while taking evasive action such as attempting 

to get under a desk. 

EVASIVE ACTION INJURIES 

Many nonfatal injuries were associated with building occupants taking protective action. At least 60 percent of 

those injured during the period of shaking were engaged in 

some form of protective action at the time of their injury 

(table 7). A total of 43 percent of this number was either 

attempting to evacuate a building, move to a safer place 

within a building, or, if already outside, move away from a 

structure. Typical evacuation injuries included tripping 

while running down stairs, and jumping off loading docks 

while attempting to exit. One-quarter of those injured were 

either attempting to take shelter under a desk or table or 

were already underneath. A total of 14 percent was injured 

while standing in doorways or holding onto doors. 

INJURIES FROM TOXIC SUBSTANCES RELEASE 

Emergency medical authorities are concerned about the 

health threat posed by hazardous-material releases during 

and after an earthquake. Our analysis of work-related injuries found 12 individuals exposed to toxic substances. The 

victims were predominantly managers and security and 

maintenance personnel who encountered or spent long periods of time in hazardous settings while searching buildings, directing evacuations, or participating in clean-up 

operations. The exposures were localized--confined to a 

single building area--and each involved one or two people. 

Two' security guards evacuating a multistory college science building were exposed to unknown chemical fumes 

while passing through a science lab; a security guard in an 

industrial facility reported exposure to chemicals of unknown origin while conducting an evacuation. In addition, 

two workers at a semiconductor manufacturer and a janitorial supply warehouse employee inhaled chemical fumes 

while evacuating their respective facilities. The second 

group of toxic-related injuries happened during the postearthquake cleanup period. Two janitorial supply warehouse workers reported exposure to spilled bathroom bowl 

cleaner; a hardware store clerk inhaled fumes from a 

spilled insecticide container; an electronics manufacturing 

manager was exposed to sodium hydroxide fumes when 

chemicals spilled from production line tubs; and a maintenance worker claimed to have inhaled dust particles while 

repairing damaged ceiling light fixtures. Finally, a retail 

store janitor slipped on spilled cleaning chemicals and suffered burns and blisters. All of these injuries were relatively minor, resulting in emergency room and physician visits 

for examination but no hospital admissions. 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE 

Table 8.-Frequency of disabling injuries during and after shaking in Santa Cruz 

County 

[From Durkin and Thiel (1991); N, number of injuries; Pet, percentage of total] 

Disabling injury type During shaking 

N Pct 

148 35.4 

97 23.2 

35 8.4 

40 9.7 

31 7.4 

29 6.9 

6 1.4 

10 2.4 

9 2.2 

5 1.2 

5 1.2 

2 .4 

After shaking 

N Pct 

38 54.3 

12 17.1 

5 7.1 

0 .o 

5 7.1 

2 2.9 

6 8.6 

0 .o 

0 .o 

2 2.9 

0 .o 

0 .o 

Total 

N Pct 

186 38.1 

109 22.3 

40 8.2 

40 8.2 

36 7.4 

31 6.4 

12 2.5 

10 2.0 

9 1.8 

7 1.4 

5 1.1 

2 .4 

Possible paralysis . - 1 .2 0 .O 1 .2 

Total.. . . . . . . 418 100.0 70 100.0 488 100.0 

DIR DATA SHOWING CASUALTY DISTRIBUTION 

BY TYPE 

DIR data also provide a useful breakdown of injury 

type, although limited to work-related injuries. Table 8 

shows the distribution of nonfatal work-related injuries 

and illness by type. Strains, sprains, and contusions combined to constitute almost 60 percent of the shaking-related injuries and over 70 percent of the postshaking ones. 

Strains and sprains resulted mostly from falls and evasive 

action such as diving under a desk, bracing oneself in a 

doorway, or trying to hold onto something for stability. 

The chief causes of contusions were bumping against a 

wall, floor, doorway, or piece of equipment, or being 

struck by a falling or overturning object. 

Fractures and lacerations added up to almost 16 percent 

of the total injuries reported by DIR. Most fractures were 

relatively minor, involving the hands, wrists, feet, and ankles. Over half of the fractures resulted from falls. Seven 

fractures were caused by falling or overturning objects. 

Two Cypress viaduct victims and one URM collapse victim sustained the most serious fractures. However, one office worker suffered a broken neck and back, requiring 

hospitalization, when struck by a filing cabinet. Most lacerations were also relatively mild. 

DIR CASUALTY INDICES 

The casualty index (table 9) was applied to the DIR data. Table 10 gives the distribution of injury severity for the 

DIR data, using the definitions of table 9. The lowest two 

injury classes are certainly underrepresented because the 

DIR requirement for inclusion is that at least one day of 

work be lost after the injury. Category 1 and 2 injuries not 

resulting in one lost work day would be excluded. The 

current information available is not sufficient to make fine 

distinctions; however, it is sufficient to conclude that very 

few, no more than 7 percent, of the injuries required the 

use of hospitals, notwithstanding that many more people 

sought hospital attention for injuries. This frequency 

should be considered as an upper bound of the actual frequency since there is probably underreporting for Index 1 

and 2. Significantly, none of the aftershaking injuries were 

sufficiently serious to require hospital care. 

CONCLUSIONS RELATED TO HEALTH-CARE 

DEMAND ANALYSIS 

Our assessment of the characteristics of injuries, particularly serious injuries, in the Loma Prieta earthquake led to 

the following findings. These conclusions are the major 

findings of our research effort to date. They will be supplemented and revised as analysis continues and additional 

data now being collected and assessed are integrated. 

Earthquake Casualties 

1. Structural failure led to 98 percent of the direct earthquake fatalities and 88 percent of the total earthquake 

fatalities. I 

2. High-risk structures, especially the Cypress viaduct 

and unreinforced masonry buildings, were major 

sources of serious injuries. 

3. ,Well-designed, modern, earthquake-resistant structures posed little casualty risk in this earthquake. 

Earthquake-related hospitalized injuries in Santa Cruz 

County 

4. Occupant contact with nonstructural building elements, 

especially building contents, was a major source of 
LOSS ESTIMATION AND PROCEDURES 

Table 9.-Injury index scale for earthquake casualties in Santa Cruz County 

[These index values are based on the seriousness of the initial injury, as determined from the services required to 

treat the injury; the index can be enhanced by incorporating the degree to which an injury will progress to a 

more serious level if medical attention is not provided] 

Injury Level of Skill level of Transportation of Type of facility 

index seriousness provider injured needed 

First Aid. . - 

Outpatient. . 

Hospitalized . 

Serious. . - - 

Severe. - - - . 

-- None; can be self 

administered 

Red Cross level 

training 

Nurse, physician 

General practice 

physician 

Specialized 

physician, surgeon 

Specialized 

physician, surgeon 

, -- None 

None 

To skilled person if 

not on-site; can 

convey self 

To skilled person if 

not on-site; needs 

assistance 

Attended care during 

transportation 

Attended care during 

transportation; 

relocation to another 

facility possibly 

required -- 

-- None 

None 

Clinic, medical 

office, emergency 

room 

Clinic or general 

services hospital: 

stay for observation 

General services 

hospital 

State-of-the-art 

hospital 

Table 10.-Work-related injuries by casualty index (table 9) that occurred during and 

after the earthquake in Santa Cruz County 

[The injuries given for index 3 to 8 are estimated upper boundaries. The total injuries for index 1 and 

2 are probably underrepresented; N, number of injuries; Pct, percentage of total] 

Injury During shaking After shaking Total 

index N Pet. N Pet. N Pet. 

18~2.. 40 13.6 4 8.1 44 12.9 

3..... 208 70.7 4 1 83.7 249 72.8 

4,5,6.. 25 8.5 0 .O 2 5 7.3 

7.,.. 17 5.8 1 2.0 18 5.3 

8..... 4 1.4 3 6.1 7 2.0 

Total . . 294 100.0 49 99.9 342 100.3 

minor injuries but was associated with few serious 

injuries. 

5. Falls caused over half the Santa Cruz County 

hospitalizations. 

6. The elderly were the principal fall victims. 

7. Only 20 percent of the serious injuries in Santa Cruz 

County were due to structural failure, and these were 

principally caused by URM buildings. 

8. Heavy building contents were associated with the few 

serious nonstructural injuries. 

9. Total minor and first-aid level injuries (injury index 1 

and 2; table 9) in the earthquake are underrepresented 

in the Loma Prieta injury data. 

Work-Related Injuries 

10. Most work-related injuries were relatively minor. 

11. 60 percent of the shaking-related injuries and 70 percent of the indirect earthquake injuries were minor 

strains, sprains, and contusions. 

12. Falls were the largest single source of work-related 

injuries. 

13. Disabling work-related injuries, those causing 1 day 

or more lost work, were concentrated in a few locations. Half were building-failure related. 

14. Nonstructural elements and building contents posed 

relatively little threat of serious injury. Heavy objects 

were responsible for the six serious injuries associated with building contents. 

15. Only about 7 percent of DIR injuries required 

hospitalization. 

16. 60 percent of DIR injuries were treated outside a hospital setting (emergency room, outpatient clinic, or 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE 

Table 11 .-Index of treatment for nonfatal, disabling work-related injuries and illnesses that occurred during or after the earthquake 

[From Durkin and others (1991); N, number of injuries; Pct, percentage of total] 

Ultimate treatment setting During shaking After shaking Total - 

N Pct. N Pct. N Pct. 

Self-treated (no formal treatment) . 40 14.6 4 8.9 44 13.8 

Physician's office or clinic. ..... 120 44.0 23 51.1 143 45.0 

Hospital-based outpatient ...... 88 32.2 18 40.0 106 33.3 

Hospital inpatient. .......... 25 9.2 0 ,, .O 25 7.9 

Total ................ 273 100.0 45 100.0 318 100.0 

1 "Disabling" is defined in text in the section "Work-Related Casualty Data." 

hospital-based physician); total number of DIR injuries was about 2 to 2A times the number of DIR hospital-treated injuries. 

Hospital case records 

17. From 22 percent to 54 percent of hospital cases seen 

were earthquake related. 

18. Only about 2 percent of emergency-room contacts led 

to hospital admission and were earthquake related. 

CAPACITY OF THE HEALTH-CARE 

SYSTEM (SUPPLY) 

Health-care supply is a combination of a number of 

components, which include local hospitals, emergency 

medical services, private clinics, and physicians. The adequacy of the supply in an emergency situation such as a 

major earthquake is a function not only of the physical 

condition of the supply, but also of its potential utilization. 

Our findings have three major implications for earthquake 

casualty modeling: First, structural damage potential remains the major predictor of serious earthquake casualties, 

but because nonstructural performance remains a key 

source of minor injuries and a potential risk for major 

ones, we should evaluate and prioritize nonstructural hazards in terms of their relative risk. Second, casualty estimates based exclusively on hospital utilization data may 

greatly underestimate the true medical demand. Third, future casualty models should estimate the resiliency of the 

entire regional health-care system. Table 11 provides a 

breakdown for DIR cases of the numbers and proportion 

of victims who treated themselves or sought treatment at 

various treatment settings. Of the 318 cases for which data 

is available, about 14 percent sought no formal medical 

care for their injuries, even though these injuries were sufficiently severe to cause at least one day's work loss, and 

45 percent sought treatment at a private physician's office 

or nonhospital clinic. In sum, approximately 60 percent of 

the total DIR cases were treated outside of the hospital 

setting; of the remainder, about one-third received treatment at a hospital-based outpatient setting (for example, 

emergency room, outpatient clinic, hospital-based physician). Less than 10 percent of those injured during the 

shaking required hospital admission, and no postshaking 

injured needed such care. 

The heavy utilization of private physicians and nbnhospital-based clinics after the Loma Prieta earthquake is one 

indication of both the relatively low severity of most injuries and the absence of disruption to the normal healthcare system. An analysis of injury type and severity (tables 

10 and 11) indicates that most of the 106 injuries seen in 

the hospital setting could have been treated in physicians' 

offices or nonhospital clinics. That is, the vast majority of 

injuries (81 percent, 106/106+25) did not require the sophisticated technical environment of a hospital. These data 

suggest that about three-fourths of those who used a hospital may not have needed to do so. 

The DIR data show heavy utilization of familiar, local, 

health-care resources and thus call into question the usefulness of setting up services in unfamiliar locations. It has 

been conjectured that an efficient way to manage earthquake medical services is to establish casualty collection 

points (CCP) at several locations within a community. 

However, when the Santa Cmz County emergency medical services officer was asked whether CCP's were needed, his response, based on patient behavior, corroborated 

findings from the DIR data: 

No. The public will always seek help where it is most familiar. The 

traditional focus of health care for the public are the hospitals and medical clinics. If casualty collection points were to be established, they 

would need to be located near hospitals and clinics. I believe CCP's 

would have been needed only if the hospitals had sustained enough structural damage to render the buildings unsafe. This was not the case for the 

Loma Prieta earthquake. 

The total number of DIR injuries is about 2.5 times the 

number of DIR hospital-treated injuries. This observation 

has great potential importance for future casualty estimation and data collection. Since it was found that the county 

distribution of injuries was comparable to the OES distribution, then it is reasonable to assume that the actual number of total injuries may be approximately 2.5 times the 
A22 LOSS ESTIMATION AND PROCEDURES 

number reported by studies that rely on hospital emergency room records as their only basis. 

SANTA CRUZ COUNTY EMERGENCY 

HEALTH-CARE DELIVERY 

An analysis of one county, Santa Cruz, provides useful 

insights into the operation of major health-care components after a major earthquake. Santa Cruz County was 

selected for detailed analysis because it was the most severely impacted by the Loma Prieta event, data were 

available, and county officials were very cooperative. The 

following section reviews 9-1-1 emergency and hospital 

response. Health-care delivery systems in Santa Cruz 

County, including 9- 1 - 1 emergency medical services, hospitals, clinics, and mental health agencies, were challenged 

beyond any previous disaster experience. At the time of 

the earthquake the county was served by three hospitals: 

Watsonville Community, Dominican (Santa Cruz), and 

AM1 Community (Santa Cruz) Hospitals; AM1 has subsequently been absorbed by Dominican. The County Emergency Operations Center (EOC) operated in the disaster 

mode for one week after the earthquake, coordinating a 

myriad of disaster operations. Although other studies are 

underway by the authors and other researchers, particularly those at Johns Hopkins University, only 9-1-1 emergency medical services and initial observations by medical 

administrators will be discussed below. 

9-1-1 EMERGENCY RESPONSE 

Requests for 9- 1- 1 emergency services reached unprecedented levels at the county communications center within 

minutes of the earthquake, even though many telephone 

lines were not functioning. Although there is not yet an 

accurate count, over 1,000 calls from the public were reported that night, many times the normal volume. Numerous requests for ambulance services were dispatched, but 

the number of victims who actually received their services 

is not known. Not all calls were for emergency purposessome callers asked if there had been an earthquake. Despite the high volume of calls and confused radio communications, the emergency medical and rescue teams 

managed to respond to requests for their services. 

The 9-1-1 system in Santa Cruz County is centrally organized and serves the entire county. Because of the earthquake, operators felt a sense of urgency to make sure that 

every call was taken, lest a major problem not be identified 

because of the busy 9-1-1 system. The usual careful, information-intensive inquiry process was foreshortened to a 

brief conversation to assure minimal time spent on each 

call. For medical calls, they reduced their inquiry to simply 

whether this was a medical emergency or not and, if so, the 

location where the ambulance should be sent. There was 

no interrogation to confirm the callers' response that it was 

a medical emergency and no information was obtained on 

the medical severity or other characteristics of the call. 

Using standard emergency-management procedures, the 

ambulance dispatcher was given a small card that only indicated the location to which an ambulance was to be dispatched and a time stamp indicating when the call was 

received. There were no notations that indicated severity, 

number of victims, and so forth that could have assisted in 

assigning priority. In most instances requests for ambulances were processed in the order that they were received. The 

dispatcher spread the unanswered calls out on a small table 

and made calls essentially in time order of receipt as ambulances became available. 

During this period there were initially six EMS (emergency medical service) vehicles (ambulances) and crews 

on duty; this rapidly increased to 10 as additional crews 

were assembled. At the time of the earthquake, telephone 

technicians were in the process of some equipment work, 

a task rapidly completed once it was clear that an earthquake had occurred. 

All 9- 1 - 1 communications center ambulance dispatch 

cards and disaster report notes were collected to determine 

the volume and types of medical calls responded to during 

the earthquake. Each record was ordered sequentially by 

the date and time the call was received and the outcome 

was reviewed; that is, did the paramedic unit contact, treat, 

or transport a patient. A total of 230 dispatch requests 

were recorded during the 72-hour study period, including 

one duplicate. Determining the dispatch outcomes for the 

first 7 hours (up to midnight) after the earthquake proved 

problematic, as over 60 percent of the records did not include this information. These outcomes were of particular 

interest to this investigation, as nearly one-third of ambulance dispatches in the first 72 hours occurred from the 

time of the earthquake until midnight. After midnight, 

however, the unknown outcomes dropped to less than 10 

percent as radio communications traffic decreased significantly and generally less chaos prevailed; this allowed for 

more complete documentation of dispatch information. 

This investigation then sought to reconstruct all dispatch 

outcomes from sources other than the 9- 1- 1 records. 

Most of the 9-1-1 medical dispatch outcomes were reconstructed through interviews with the paramedics on 

duty the night of the earthquake and cross-referencing prehospital and hospital medical records. The results showed 

that for the period ending midnight the night of the earthquake, just over one in three dispatches resulted in a paramedic team transporting a patient or multiple patients to 

the hospitals. Most patients were brought to either Dominican Hospital or Watsonville Hospital; only three patients 

were transported to AM1 Community Hospital. Initially, 

AM1 was reported to have significant structural damage, 

and a diversion order was issued because field paramedics 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE 

believed that the hospital was overloaded treating its own 

patients; subsequently, the order was canceled. The overall 

9- 1- 1 call volume was significantly higher for 2 days after 

the earthquake but thereafter was near normal. The heaviest volume of ambulance transports was received by Watsonville Hospital on Wednesday (10/18/89), which was 

surprising because Dominican normally receives twice the 

volume of patients of Watsonville. 

During the 72 hours after the earthquake a total of 229 

calls was logged that resulted in ambulance dispatch. Figure 2 graphically locates the destination for ambulance 

runs during this 72-hour period. 

Figure 3 shows the cumulative number of 9-1-1 calls resulting in ambulance dispatches for the 72 hours after the 

earthquake. The most substantial increase in call volume 

was during the hours after the earthquake. Time of day 

and seasonal experience from previous years were not 

available so that this volume could be compared. On the 

basis of aggregate data, table 12 shows that on an average 

day in late 1988 there were about 37 dispatches (3 per 

hour) that resulted from 9-1-1 calls; the dashed lines in 

figure 3 indicate the average slope for normal data. Clearly, the number of dispatches was unusually high, by a factor of three, during the 72 hours immediately after the 

earthquake, but quickly dropped to a rate only of about 50 

percent above normal and stayed at this level for the 72- 

hour period. The responsible official on duty October 17 

stated that until about midnight there were typically 5 to 

Table 12.-Comparisoil of 9-1-1 outcomes for earthquake period to a 

previous normal period 

[From Thiel and others (1992)l 

Location Transports Other4 Total runs 

South county1 - - - - - - - - - 8.6 2.9 11.5 

Northcounty2------ - -- 19.3 6.2 25.5 

Average per day - - - - - - - 27.9 9.1 37.0 

Pct. Pct. 

Pre-earthquake - - - - - - - - 75 25 

October 173 - - - - - - - - - - 59 4 1 

72 hours after earthquake3 - 69 3 1 

Determined from total for last half of 1988. 

Determined from total for last quarter of 1988. 

Number of transports and dead-on-arrivals 

plus treat-and-release divided by total number 

dispatched less unknown dispositions. 

Cancelled, unknown disposition, or unable to 

locate. 

Santa Cruz 

Figure 2.Ã‘Geographi distribution of Santa Cruz County 9-1-1 emergency dispatches during the first ' 

hours after the earthquake. The distribution closely follows population centers; few rnidcounty, rural 

runs were made, in part due to road conditions and absence of calls for assistance. From Thiel and 

others (1992). 
A24 LOSS ESTIMATION AND PROCEDURES 

10 calls awaiting dispatch of an ambulance. Thus, it is reasonable to conclude that the system was saturated during 

the 7 hours after the earthquake. Figure 4 shows the processing sequence for a 9-1-1 call; an ambulance is dispatched to the site, unless the call is canceled in route. 

Table 13 gives the number of dispatches resulting in transport or cancellation for the 7-hour period after the earthquake and for the following 72-hour period. There are still 

a number of dispatches for which outcome is unknown. 

The emergency response showed several ways that EMS 

personnel were resourceful in addressing abnormal circumstances: several patients were treated and released by 

the EMS crews; multiple individuals were transported in 

one run to a hospital; patients were directed to other 

means of transport if available; and no action was taken 

when the crew determined that their services were not critical. There was an unusually high number of dispatches 

where the ambulance arrived and found that other medical 

resources were already on the scene. The average time period from receipt of the call to completion ranged from 30 

to 42 minutes for successive days (30, 35, 40, 42); however, the distribution indicated that the average was heavily 

affected by a few long cases, associated with victim extrication from automobiles. 

One of the striking observations from table 13 is the unusually low number of advanced life support (ALS) transOct 18 Oct 19 Oct 20 Oct 21 

Figure 3.-Cumulative number of 9-1-1 calls that resulted in ambulances being dispatched for the 72 

hours after the earthquake. The solid lines are average slopes for before and after midnight, October 

17; dashed lines are estimates of average slope for normal rates based on data for late 1988. From 

Thiel and others (1992). 

Unknown Dead 

disposition Standby No action on arrival Dominican Hospital 

Community Hospital 

Watsonville Hospital 

Cancelled Service Unable Treat 

in route call to locate & release 

b Other 

Figure 4,-Node diagram of processing and disposition of 9-1-1 calls; see table 13 for frequencies. From Thiel and 

others (1992). 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE 

Table 13.-Disposition of 9-1-1 calls in Santa Cruz County 

for October 17 and the 72-hour period after the earthquake 

[From Thiel and others (1992). EMS, emergency medical services; 

ALS, advanced life support vehicle; BLS, basic life support vehicle] 

Disposition of 9- 1 - 1 calls October 17 

(7 hours)l 72-hour 

periodl 

Total 9- 1 - 1 EMS 

dispatches2 ... x7 ...... Unknown disposition ..... 

Canceled in route . . - - . - - Service call ........... Arrive: 

Standby ............ Unable to locate ....... 

Patient found: 

No action ........... 

Dead on arrival ....... Treat and release ...... 

Transport: 

EMS transport: ALS .... EMS transport: BLS .... 

Other transport. ...... Location of transport: 

To Dominican Hospital . . 

To Community Hospital . 

To Watsonville Hospital . 

To other medical providers 

Table 14.-Type of transport provided (advanced life support versus basic life support) by date 

and total admissions to each of the three hospitals in Santa Cruz County 

[From Thiel and others (1992); leaders (--), no transport] 

-- - 

~ate'(0ctober 1989) 

Transports1 admissions 17 17A 18 19 20 20A Total 72 hours 

Advanced life support.. .. 3 10 10 18 6 8 37 

Basic life support.. ..... 20 69 -- .. .. .- 94 

'Totaltransports ...... 23 79 10 18 6 8 131 

Admissions: (postearthquake): 

Dominican.. ...... 13 45 14 26 14 20 67 

Community.. ....... 5 17 8 9 3 4 23 

Watsonville ......... 6 21 19 8 6 8 3 9 

Other ............. 2 7 1 0 0 0 3 

Total ............. 26 90 42 43 23 32 134 

Average admissions2.. ... 8 28 28 28 20 28 .. 

~atio3.. ...........- 3.2 3.2 1.5 1.5 1.1 1.1 .. 

I A, results adjusted to reflect 24-hour equivalent values. 

See table 12 for average pre-earthquake transports. 

Ratio of total post-earthquake admissions to average admissions for each column. 

Table 15.-Dispatch locations of 9-1-1 emergency calls for October 17 and 20 

[From Thiel and others (1992); N, number; Pct, percentage of total; NA, not applicable] 

Electric power was out at the dispatch center for 

approximately 20 minutes at about 7: 10 p.m. on 

October 17; therefore, no calls were received nor 

dispatched during this time. 

This total represents only those calls evaluated as 

requiring EMS assistance; the total number of 

incoming calls is unknown. 

October 17 October 20 

Location N Pct. N Pct. 

Commercial building ..... 20 29.4 3 11 

Convalescent home. ..... 6 8.8 3 11 

Medicallemergency services 10 14.7 1 4 

Mobile home.. ........ 4 5.9 2 7 

Outdoors ............. 4 5.9 14 5 0 

Residence ............ 8 11.8 5 18 

Others, principally unknown 16 N.A. 9 , N.A. 

Total ............. 68 100 37 10 1 

ports. All Santa Cruz ambulances and crews are ALS 

capable and trained. Table 14 indicates that when adjusted 

for the short day (7 hours on October 17 and 17 hours on 

October 20), the number of ALS cases is no higher during 

the last 7 hours of October 17 than for subsequent days; 

indeed it seems lower. For the first 7 hours, only 13 percent (3123) of transports were ALS; for the subsequent 65 

hours, 32 percent (341168) of transports were ALS. It is 

likely that crews provided ALS treatment only in the most 

severe cases on October 17; on subsequent days, the reduced numbers of 9-1-1 dispatch requests allowed crews 

more time to treat individual patients. Another possible explanation is the low incidence of vehicular accidents on 

October 17, as discussed later. 

The sources of 91 1-initiated EMS calls on October 17 and 

from October 17 to 20 are indicated in table 15. Commercial 

sites, convalescent homes, and medical service providers 

accounted for almost 70 percent of the calls on October 17. 

Date N 

Table 16.-Vehicular accidents after 5~*m. l a0 

resulting in 9-1-1 dispatches 17A - - - - - - 3.4 

18 ....... 5.0 

[From Thiel and others (1992); A, 19 - . - - . - - 5.0 

results adjusted to reflect 24- 20 to 5 p.m. - 7.0 

hour equivalent values] 20A ...... 9.9 

It is surprising that so few calls came from residences, 

where most people at risk are assumed to have been during 

the earthquake. Data for October 20, a more normal day for 

which such information is available, indicate a diversified 

mix of call locations, with calls substantially reduced from 

commercial sites and increased from outdoor accidents 

(such as vehicles). We consider this day to be more representative of a nondisaster period than are the previous two 

days. Table 16 reveals the number of vehicular accidents 

from the detailed 91 1 records of October 17 and 20. The one 
A26 LOSS ESTIMATION AND PROCEDURES 

October 1 7 accident, which occurred near midnight, involved one car running into three full-grown horses. Further, emergency personnel on-duty October 17 confirmed 

that few vehicular accidents appear to have occurred that 

day. In contrast, table 15 reveals a substantial increase in 

vehicular accident calls on October 20. It is possible that 

people were substantially more careful driving or chose not 

to drive during the immediate postearthquake period. If so, 

EMS services may not need to reserve significant resources 

after earthquakes to cover expected serious auto accidents. 

The number of victims transported in response to 9-1-1 

calls (table14) appears high on October 17 but decreases 

rapidly on subsequent days. Unfortunately, data on all 

transports are not yet available for analysis. Compared to 

normal ambulance transport rates, transport rates are substantially (75 percent) higher for the 7 hours after the 

earthquake and then are about 50 percent higher than normal for the next 2 days. These rates seem to indicate that 

the demand for 9-1-1 transport returned to normal very 

quickly. The actual rate would be somewhat higher for 

October 17, if an adjustment for time of day was made, 

because evening hours until midnight are typically a lower 

demand period. 

Based on the findings of the 9-1-1 medical incidents, 

and information not herein reviewed, the following recommendations were made to the county: 

1. Residents of the summit area or any remote area susceptible to road damage (for example, mountainous 

landslides) during an earthquake should consider the 

possibility of either a delayed response or no response 

at all from ground-based EMS units. In these areas, familiarity between residents and local fire departments 

should be encouraged so that they can have at least 

minimal medical aid provided for them until they are 

able to receive hospital treatment. 

2. The county should consider whether the practice of simultaneously dispatching two paramedic ambulances 

to the same 9-1-1 incident should continue in disaster 

situations. (Of note: The very first medical dispatch by 

9-1-1 following the earthquake sent two Santa Cruz 

paramedic units to an incident in the Aptos area. Fortunately, in this case, the private ambulance paramedics 

decided that it would be better for the Aptos Fire Department paramedic unit to handle their own transports 

so that the Santa Cmz units could remain available for 

what became a series of back-to back 9-1-1 incidents 

that followed this call.) 

3. Consideration should be given to whether a public-information campaign should be used to inform the public not to call 9-1-1 following an earthquake unless 

they have an actual emergency. The 9-1-1 communications center received many unnecessary calls in the 

hours following the earthquake. Some victims, however, may take this notice to the extreme. Watsonville 

physicians reported that they treated patients for earthquake injuries who came to their clinics and hospital 

days after they were injured; by then, some of the injuries were infected. When the physicians asked the patients why they delayed seeking help for their injuries, 

they responded that they did not want to burden the 

doctors, whom they thought would be busy treating seriously injured victims. 

4. The public should be encouraged to learn first aid and 

CPR because medical response teams may be delayed 

or unavailable during a disaster. A woman's life was 

saved immediately after the earthquake because a bystander provided her with CPR during what was a considerable length of time before a paramedic ambulance 

arrived. 

5. The public should be made aware that driving following an earthquake may pose a risk to their safety because roads will be damaged, traffic control signals 

will not be working, and animals may be running loose 

on roadways. For example, a woman was seriously injured in Watsonville the day after the earthquake when 

the car she was in struck a protruding part of an earthquake-damaged bridge. 

RECOMMENDED 9-1-1 EMS PROCESS FOR DISASTER 

PERIODS 

Notable from the data in table 13 were the 13 calls (19 

percent) in the first 7 hours where the patient was not located by the ambulance crew; that is, the patient was not at 

or near the dispatched location. This number would probably be higher if the 13 unknown disposition cases (table 

13) could be resolved. In the following 65 hours there was 

only one additional "unable to locate" dispatch outcome. 

During this latter period the normal method of processing 

incoming 9-1-1 EMS calls had been reinstituted. 

These data have implications for how 9-1-1 dispatch can 

be improved. The following findings relate to these management issues: 

1. Immediately after the earthquake and for several hours 

thereafter, the 9- 1- 1 system was saturated with calls. 

2. The volume of calls was so high that a short-cut procedure was used by the emergency medical dispatchers to 

process the calls in minimum time. 

3. The ambulance dispatchers were only given the time 

the call was requested, as stamped, and the location for 

the dispatch. There were no notations on the cards that 

indicated severity, number of victims, and so forth that 

could have assisted in assigning priority. 

4. There was an unusually small number, 34 percent, of 

the calls that resulted in a transport, compared to norm 

of 75 percent. 

5. There was only a small number of ambulances, from 6 

to 10, available during the earthquake; they had an average time from assignment to completion of 20 minutes. 

The backlog of waiting calls, at times, was 24 or more. 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A27 

Clearly there was a conflict between the need for handling the incoming flood of calls and the need to manage 

effectively the use of the small number of emergency ambulances available. There is no evidence to suggest that 

any of the individual elements of the 9- 1-1 EMS ambulance system performed poorly or were ineffective in carrying out their assigned and implied tasks. However, there 

is doubt as to whether the system on the whole effectively 

managed the small ambulance resource available. Fortunately the level of medical emergency associated with this 

earthquake in Santa Cmz County was modest and the inadequacies determined by our assessment did not result in 

serious medical consequences. The Loma Prieta earthquake caused a small number of casualties compared to 

that expected for major earthquakes expected near large 

urban centers (Federal Emergency Management Agency,1980). The system of 9-1-1 dispatch, as well as almost 

all emergency plans, used in Santa Cruz County could 

well have had major negative consequences if a more 

pressing medical emergency had occurred in the county. 

The issue presented by these findings is how to maximize the provision of available medical services through 

the 9- 1 - 1 system. This entails a process to1. Systematically handle unusually large call volumes 

quickly, and only process those with emergency needs. 

2. Set priorities for management of a limited number of 

ambulances that results in provision of needed medical 

services. 

Figure 5 shows the process used in Santa Cruz County 

after a 9-1-1 call was identified as being a medical emergency. It's simplicity allows for the maximum possible 

speed in processing incoming calls but provides for no information to assist ambulance dispatchers in establishing 

priority among requests. 

The difficulty in determining priorities using the usual 

medical inquiry evaluation tools during the 9-1-1 call is 

that it consumes much more time than is reasonably available during a disaster, even for trained emergency medical 

dispatchers. An analysis of emergency medical records for 

Santa Cruz County indicates that only a small proportion of 

the earthquake injuries were medically severe and relatively few resulted in hospital admission (Durkin and others, 

1991). 

These findings and observations lead us to propose an 

alternative 9- 1 - 1 medical services procedure, depicted in 

figure 6, for use during a medical emergency period. We 

believe that this process will shorten many, if not most, 

calls. The only calls that are lengthened are those for 

which an ambulance is needed. Of more than 1,000 calls 

during the first hours after the earthquake, only 66 resulted 

in ambulance dispatches. Given similar conditions, we believe that use of our procedure would not significantly increase 9-1-1 response time but would enhance proper 

allocation of medical resources. 

The abbreviated procedure could be immediately invoked 

when the on-site EMS supervisor, or someone of comparable authority, determines that a disaster condition exists. 

The local supervisor must make this decision promptly on 

the basis of locally available information: The indicators 

could be felt shaking, confirming that an earthquake occurred, or large numbers of calls. It is recommended against 

waiting for State or regional notification that an emergency 

exists, because such a declaration is dependent, in part, on 

requests for emergency assistance (for example, 9- 1- 1 

calls) and probably will occur some time after the earthquake and well into the emergency period. Although there 

appears to be no legal precedent for such a call-handling 

procedure, there also appear to be no legal restrictions to 

adopting such a procedure when a disaster exists, because 

such procedures are authorized and regularly employed 

within the medical community (triage, for example). 

To reduce the large number of "unable to locate" dispatch outcomes, it is proposed that the first medical question put to a caller is whether the patient can be transported 

to care by other means. This is not meant to be an interrogation, and no medical advice or evaluation is intended, or 

given. The objective is to reduce the demand for ambulance service when there is an alternative. If the answer is 

"yes," the caller is told to move them there by this means 

and the call is terminated promptly, after possibly suggesting a nearby hospital based on where the call comes from. 

If the answer is "no," then the issue is what priority should 

be assigned to the call. Our experience with emergency 

conditions indicates that there is only the capacity to deal 

with two priority levels for dispatch of ambulances under 

these type circumstances. It is proposed to have the operator assign one of two priorities to the call: 

Priority 1 : Life-threatening condition 

Priority 2: Non-life-threatening condition \ 

Although there are very effective protocols for determining injury severity, the call volume does not allow for asking 

1 call as medical -> ;.::;:Ã -> 

Figure 5.-Sequence of steps used to respond to 9-1-1 calls in Santa Cruz County after the Loma Prieta earthquake. From Thiel 

and others (1992). 
A28 LOSS ESTIMATION AND PROCEDURES 

and answering the battery of questions, with supporting descriptions, required to use them. It is proposed that the priority of the call be determined through a brief answer to the 

question "Why is an ambulance needed?" The operator is 

not to engage in discussion of terms, or to provide or offer 

advice. The purpose is to quickly gain the caller's perspective of why the ambulance is required. The operator then 

assigns the call a priority, without discussion with the caller 

or revealing the evaluation. An additional benefit of this 

procedure is that it also allows the operator to redirect those 

cases that require a different type of assistance. The operator 

then asks for the location information necessary for dispatch 

and asks the caller to call back if transport is provided some 

other way. The call is terminated and the dispatch card 

passed to the ambulance dispatcher. When there is substantial demand above capacity, priority should be given to the 

priority 1 cases regardless of the waiting time; ALS-capable 

units would preferentially be assigned to these cases. PossiIncoming 

9-1-1 call 

Type of emergency 

determination 

............ a: : Police 

[ I Hazardous 1 '- 

materials a 

Redirect call 

to other 

emergency service 

bly, the response protocol would increase a priority 2 case 

to priority 1 after a given length of time from receipt, say 1 

hour. 

It could be argued that callers are a poor judge of the 

medical characteristics required to make a judgment of 

whether a condition is life threatening. For this reason the 

caller is not asked to answer medical questions. Rather, 

the caller is asked to give a brief reason for the need for 

medical transportation, among which might be: has a severed arm; is bleeding from the mouth; is unconscious after 

being hit by a brick; fell off a bicycle and has a sore elbow. It is expected that the first thing the caller states will 

have sufficient content that an informed assessment of the 

category for dispatch priority can be made. Undoubtedly 

errors will be made, where individuals in need of ambulance service do not receive it because of the assignment 

priority. But it is even more likely that persons not needing service would tie up the 9-1-1 EMS system. The enRequest that 

the transport andterminate call 

Evaluated as 

Assignment by 

operator 

circumstances; 

assigned priority 2 

.................. 

Assignment decision made 

Victim extraction : by the operator based 1 or other emergency . on response toquestion without 

requirement 1 . further discussion 

................... 

Obtain dispatch information 

Ask caller to call 

9-1-1 to cancel, if transported 

by other means 

1 Pass record 1 

and priority to ambulance 

dispatcher 

Figure 6.-Proposed sequence of steps to be used by 9-1-1 operators for medical needs during the emergency period after a damaging 

earthquake, or other large-scale disaster. From Durkin and Thiel (1992). 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A29 

couragement to use other available transportation may 

cause some victims to suffer added injury by being improperly transported, but many more will be given timely 

assistance by the same process. 

There are potentially serious medical consequences of 

improper movement of patients who have some types of 

injuries, particularly spinal, and our questioning procedure 

does not allow identification with certainty those patients 

who should be moved and transported only by trained personnel. There is the expectation that many callers will decline to move patient's with such injuries; however, this is 

conjectural. If the order of the questions were reversed, 

asking first "Why is an ambulance or paramedic services 

needed?', then the operator could assess whether it was 

appropriate to ask the transport question. This would help 

sort out the cases where severe injury would be caused by 

unskilled handling. However, the transport question is 

open ended and likely to add considerably to total call 

time not only to those for which the question is relevant. 

Evidence from 9-1- 1 Santa Cruz data leads to the conclusion that any procedure that prevents some calls from being taken is likely to be abandoned quickly. Thus, the 

initial order of questions recommended is preferred, but 

with the recognition that the mix of serious injuries in this 

particular earthquake may not be representative of more 

severe earthquakes. 

The recommended protocol has similarities to the widely 

discussed "Simple Triage And Rapid Treatment" (START) 

disaster medical treatment process. START is used when 

there are multiple victims at a site; the first step (simple 

triage) is to ask in a loud voice for everyone to stand up 

who can. These people are asked to get themselves to 

treatment off-site. Those remaining are then treated in priority order using standard emergency medical triage practices. The recommended 9-1-1 EMS procedure starts with 

the same type of transportation question, except that someone else does the transporting. The wide acceptance of the 

START process for field disaster treatment leads to the 

conclusion that our recommended 9- 1- 1 EMS process is 

sound. 

Like other emergency management functions, training of 

the operators will be required for the system to function 

efficiently and effectively. That already takes place, yet it 

is the natural tendency of an individual to err on the side 

of assuming the worst when there is inadequate information to make considered judgments. The current 9-1-1 

EMS protocols focus on the worst cases under normal operating conditions. However, the consequences of continuing to use such procedures during a disaster period could 

have catastrophic implications for many seriously injured. 

Training and the participant evaluations of performance in 

table-top exercises will quickly uncover the consequences 

of too great a proportion of high priorities. Such a system 

as proposed is an easily implementable approach to disaster period 9- 1 - 1 medical dispatch management. 

CONCLUSIONS FOR EMS IMPROVEMENT 

It is our judgment that adoption of the simple emergency 

procedure given in figure 6 for 9-1-1 medical calls offers 

the opportunity to substantially improve the performance 

of the emergency medical transport system at virtually no 

cost. Simply reducing the proportion of nontransport outcomes in Santa Cruz during the 7 hours after the earthquake from the 34 percent observed to the 75 percent 

usual proportion effectively increases the number of ambulances available by a factor of two! It is not often we 

have the opportunity to achieve a doubling of capacity by 

a simple, no-cost management change. 

The findings and recommendations presented here were 

developed from experience in Santa Cruz County, where the 

telephone system continued to function in almost all areas 

and where there were relatively few major injuries. Other 

investigations are underway to determine whether those 

mostly rural areas that lacked telephone service had EMS 

needs that went unserviced. If the telephone system had been 

inoperative, either because of the intensity of the earthquake, 

power loss to the telephone system or damage to the response center, then the 9-1-1 response system would have 

been unavailable as a primary mode for providing EMS 

services. Experience shows that most serious injuries in 

earthquakes will be found in areas that experience the greatest concentrated building, particularly structural, damage. 

Such damage may eliminate local telephone service, thus, 

rendering the telephone 9-1-1 system ineffective as a means 

of identifying where EMS services are most needed. It is 

important that the EMS response plans include alternative, 

nontelephone-dependent approaches for locating the injured 

in heavily damaged areas and targeting emergency medical 

services to these areas. Identifying those areas and targeting 

immediate EMS response may be just as important to improving EMS effectiveness as is more effectively managing 

the 9- 1 - 1 EMS response functions already discussed. 

Although the focus has been on the problems of the 

emergency medical component of the 9-1-1 system during 

an earthquake disaster, the observations extend to all of 

the other services that the 9-1-1 system is designed to 

serve during an emergency, or other disaster. Large earthquakes are expected to -have large demands, often dubious 

ones, for fire, search and rescue, toxics removal, and 

heavy rescue. These demands are typically larger than the 

capacity of the local service, even when augmented by resources from other communities. The same procedure suggested here for ambulance and paramedic services can and 

should be applied to these other emergency services. 

HOSPITALS 

Almost immediately after an earthquake, all hospitals began triaging and treating patients who arrived by private 
A30 LOSS ESTIMATION AND PROCEDURES 

vehicles, ambulances, and police and fire vehicles. Meanwhile, hospital-damage survey teams were reporting that 

they had lost essential services from the earthquake such as 

water supply and X-ray. A temporary loss of telephone and 

two-way radio communications at all three hospitals created 

confusion, as they were not able to accurately estimate resources needed, expected number of casualties, or exchange 

other vital information. Because of earthquake damage to 

equipment and facilities and high volumes of casualties, 

some patients received limited treatment and diagnosis and 

others with less than serious injury or illness were instructed 

to return the next day for treatment. The damage was so 

great at Watsonville Hospital that 17 patients had to transfer 

to other hospitals. Clearly, the hospitals were challenged 

well beyond any previous disaster experience. 

Nonhospital medical facilities were called into action to 

assist emergency medical efforts in the county. In particular, Salud Para la Gente, a medical clinic located in Watsonville, treated many earthquake victims in the downtown 

area, perhaps greatly reducing the patient load at Watsonville Community Hospital. Their efforts, however, were not 

limited to medical treatment but included comprehensive 

assistance to the nonmedical needs of earthquake victims. 

The emergency medical response to the earthquake was 

unprecedented by any previous disaster experience. Santa 

Cruz County had experienced five Presidentially declared 

disasters in the 1980's, but none had required the mobilization and actions of so many medical resources as did the 

Loma Prieta disaster. 

A major effort is underway to review emergency department records at the three Santa Cruz County hospitals for 

the period ending 72 hours after the earthquake. A total of 

1,057 patient records have been collected, reviewed, and 

abstracted, with the cooperation of the county, State, and 

Johns Hopkins University, in association with Durkin and 

Associates. The distribution of patients by hospital was 

454 from Watsonville Community, 390 from Dominican 

Santa Cruz, and 213 from AM1 Community. The total of 

1,057 admissions from all sources, earthquake and nonearthquake causes, was drawn from a current county population of approximately 229,000. The follow-up data 

collection and reconciliation process is still in progress. 

Over 95 percent of the patients seen at the local hospitals 

were residents of the county, and over 97 percent were 

from the normal patient catchment area for the county (less 

than 3 percent of the patients were not residents of the 

county or did not live within close proximity to the hospitals). Therefore, the transient population treated within the 

study period at the local hospitals was minimal compared 

with the resident population. Also noted was that patients 

who lived in the north county sought help almost exclusively in the north county-either Dominican or AM1 

Community Hospital-and south county residents sought 

help at Watsonville Hospital. Comparative data of normal 

volumes of injury versus illness patients is not yet available; however, the medical records managers at the three 

hospitals reported significantly higher volumes of emergency department admissions after the earthquake. Preliminary data suggest that over half of the earthquake-injured 

patients were treated in the hospital emergency departments in the hours beginning the morning of October 18 

until the end of the study period October 20 at 5:04 p.m. 

Seventeen patients, 13 injury cases and 4 medical cases, 

were transferred from Watsonville Hospital in the hours 

after the earthquake. Twelve patients were transported by 

helicopter-two to Dominican Santa Cruz Hospital (one 

medical, one trauma) and ten (two medical, eight trauma) 

to hospitals in Santa Clara and Monterey Counties. Five 

patients were transported by ground ambulances-four to 

Dominican Santa Cruz Hospital and one to a hospital in 

Monterey County. With one exception, all transfers were 

postearthquake, emergency-department admissions. All patients were classified as critical care transfers, and all received critical-level care at the receiving hospitals. All 

injury transfers were earthquake-caused injuries. One 

transfer patient later died as a result of her earthquakecaused injuries. Six transfer patients are known to have 

required major surgery because of their earthquake-caused 

injuries, and some of them were later transferred to other 

hospitals for further definitive care. \ 

HOSPITAL ADMINISTRATOR INTERVIEWS 

Three hospital administrators were interviewed in person 

to determine their impressions of their hospital's operations during the disaster. Some special notes regarding the 

disaster response of the hospitals follow: 

The hospitals enacted their disaster plans within 30 

minutes after the earthquake and remained in the disaster mode from 4 days to 1 week. 

Only Watsonville Hospital evacuated pre-earthquake 

patients. 

Only Watsonville Hospital transferred patients from 

their facility, and only Dominican Hospital received 

transfer patients from other facilities (all from Watsonville Hospital). 

Electrical power was lost at all three hospitals (as was 

the case in the entire county), but only Watsonville 

Hospital experienced difficulties with its generators as 

a direct result of earthquake damage. 

Each hospital had staff and nonstaff volunteers spontaneously report for duty after the earthquake, and no 

management problems were reported regarding their 

actions. 

Each hospital provided stress debriefing/counseling 

sessions for staff and their families within one week 

after the earthquake; attendance was voluntary. 

Each hospital lost vital diagnostic services as a result 

of earthquake damage to equipment. 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A3 1 

8. No problems were reported with patient transfers to 

Dominican Santa Cruz Hospital and Monterey and 

Santa Clara County hospitals from Watsonville Hospital, in spite of no formal transfer agreements to that 

effect . 9. No medical teams were sent to field sites from any 

hospital. 

10. The hospital administrators predicted they could have 

seen between 50 and 100 percent more casualties in 

their emergency departments during the night of the 

earthquake, even though some of their essential hospital services became nonfunctional as a result of the 

earthquake. 

IMPLICATIONS FOR EMERGENCY MEDICAL 

SERVICES 

Numerous implications for health-care supply and demand emerge from these data. For the Loma Prieta disaster, the demand was relatively small because the numbers 

were scattered and the severity was light. The supply was 

therefore adequate because the health-care system was extensive, the hospitals remained operational, and the demand for major medical care was light. Any future 

casualty estimation model should take into account an 

overall resiliency of the health-care system for various levels of demand. 

Most earthquake fatalities and serious injuries (injury intensity 4 or higher; see table 1) resulted from structural 

failure. The majority of serious casualties came from a 

small number of damaged structures, consistent with experience in other recent earthquakes. Falling sections of 

URM buildings, striking other buildings, were once again 

sources of severe injuries. 

Well-designed, modern, earthquake-resistant structures 

posed relatively little serious casualty threat to their occupants. Minor injuries constituted the bulk of injuries in these 

structures. A substantial threat is posed by structures with 

high collapse potential, even if they do not collapse. Experience worldwide suggests that a relatively small number of 

damaged structures provide the vast majority of serious casualties (Durkin and others, 1989a). Interior nonstructural 

elements have a relatively low likelihood of causing fatalities or serious injury. Building contents also have a relatively 

low likelihood of causing fatal or serious injuries. For example, no Loma Prieta work-related fatalities could be attributed to nonstructural elements or building contents. 

Although, 10 of the 25 Loma Prieta work-related injuries 

noted as requiring hospital admission were due to nonstructural elements or building contents, this number represents 

less than 8 percent of the total injured by such elements. 

However, despite the low overall probability for serious 

injury, some physical objects (for example, tall metal lockers, wine barrels, heavy filing cabinets, and so forth) and 

some settings are particularly hazardous and can cause serious injuries. In some cases, protective actions taken by 

building occupants increased their probability for minor and 

moderate injuries from physical objects. Thus there is still a 

need to (1) determine the probability for serious injury associated with all settings and (2) identify those settings 

which are most hazardous and prioritize them in terms of 

relative risk. 

Most Loma Prieta injuries were treated by the normal 

health-care system. Emergency medical services were not 

overloaded. Most medical attention was provided by the 

local medical community, not by external resources. 

What do some of these preliminary observations mean? 

For emergency medical planning, in particular, and the 

health-care system, in general, they suggest that there are 

three principal patient-demand sources after earthquakes. 

The first is from collapse of high-risk, high-occupancy 

structures that yield large numbers of serious, life-threatening injuries. The second is from the failure of high-risk, 

low-occupancy structures, like URM's, that are often distributed within the community in known places (Durkin 

and others, 1986, 1989b). The third is from the normal 

injury mix from low to moderate building damage, that is 

nonbuilding collapse; these injuries are probably distributed proportional to the population and do not create excessive demands on the health-care system, because there are 

not likely to be massive numbers of severe casualties concentrated in a local area. 

The distribution of casualties for the Loma Prieta earthquake provides a rich source of data for future estimation 

of losses. The distribution shows the need for analysis by 

region, by building type, and by severity. Other indications 

may well emerge in future studies. However, casualty estimation still suffers from the absence of reported data on 

nonhospitalized injuries. Indeed, the strategies that currently estimate injuries ignore these doctor-treated injuries 

(for example, FEMA's casualty estimation for Memphis 

and St. Louis). Until ways of recovering these data are 

determined, reliable predictors of the larger injury effects 

of an earthquake will not be available. 

Current Loma Prieta studies have adequate data on fatalities and hospitalized injuries. However, injury data based 

only on hospital-source data are likely to considerably underestimate injuries, particularly for the lower injury intensity. The number historically collected in the United States 

from such sources may be 2 112 times lower than actual 

numbers, if the ratios from Loma Prieta DIR injuries are 

characteristic of other nationwide earthquakes. Furthermore, the number of injuries attributable to an earthquake 

but occurring after the shaking may be significant. 

It is important that strategies be developed for estimating 

these unreported injuries. Although some of these injuries 

might indeed be slight, others could be severe. More important, lesser injuries still use health-care resources. Furthermore, we project that a higher magnitude earthquake would 
A32 LOSS ESTIMATION AND PROCEDURES 

have increased the severity of these minor injuries. Finally, 

the unreported injuries help us establish connections between building damage and injury types. Therefore, they are 

important for a number of estimating purposes. 

Studies such as this are increasing our understanding of 

factors influencing casualty estimation in different building 

types. Such factors include a broad understanding of the 

relationship between shaking intensity, building damage, 

and casualty; of the relative influence of intervening variables such as occupant actions, space utilization, nonstructural elements, and building contents; and of the need in 

any casualty loss-estimation methodology to elaborate not 

only the causes of the loss but also the impact of the loss. 

CASUALTY-ESTIMATION MODELING 

The casualty data collected, and still being analyzed at 

this writing, can provide a sound basis for development 

and widespread application of a comprehensive earthquake 

casualty-estimation methodology-one that combines and 

further develops the most effective existing casualty-estimation techniques, reflects current data, and is sensitive to 

different regional contexts of the United States. As part of 

a longer term U.S. Geological Survey-sponsored research 

effort, the authors are developing earthquake casualty-estimation procedures for a wide variety of potential applications. This section addresses the following three subject 

areas: (1) our initial research findings from an assessment 

of both Loma Prieta and other earthquake data; (2) deficiencies in currently available data bases and estimation 

methods; and (3) programmatic recommendations for future research and process development. 

A scientifically based procedure for estimating earthquake casualties is potentially valuable to a variety of users-both public and private, including the health, design 

and construction professions-in the following areas of 

primary, secondary, and tertiary injury prevention: 

1. Preparedness and response planning for providing 

emergency medical services after earthquakes, encompassing both health-care supply and demand issues. 

Supply issues include the availability of medical facilities (considering their degree of damage) and the management of available personnel, medications, and 

equipment in search and rescue and medical care delivery; demand issues relate to where casualties occur and 

what are their requirements (extraction, transportation, 

mix of injury types, types of diagnostic and treatment 

equipment needed). 

2. Pre-earthquake preparedness programs, including information, education, and training, aimed at the general 

public and high-risk populations to reduce their vulnerability when earthquakes occur. 

3. Mitigation actions that can reduce the likelihood of casualties when earthquakes occur. These are at two levels: those actions occupants can take to protect 

themselves from injury from contents (attaching cabinets, replacing brick chimneys) and those that design 

professionals (architecture, engineering, interior design) 

can incorporate into structures and interior space use. 

4. Setting insurance rates, terms of coverage and financial 

reserves; for example, life, health, workman's compensation, and liability. 

5. Determination, in legal actions, where earthquake casualty liability lies. 

CASUALTY ESTIMATION 

Earthquake casualty estimates have been available for 

over 20 years. The majority of them were made in response to specific needs, usually preparedness, and focused on specific earthquake scenario's. They generally 

were gross estimates for use in policy determination, not 

for specific medical planning. The estimates were usually 

for large areas (Federal Emergency Management Agency, 

1990) or for large numbers of buildings (National Academy of Sciences, 1988). These estimates typically had the 

following problems:. 

They lacked a significant data sample on which to base 

the estimation procedure 

They have not been tested in accordance with what data 

has been available 

They were based on overly simplistic assumptions about 

casualties and health services 

Unfortunately, there has been very little research or systematic data collection directed at developing more accurate and useful estimation procedures. 

The major casualty-estimation approaches are (1) the 

nonbuilding-specific approach, (2) the building-specific approach, and (3) the composite approach. The nonbuilding 

specific approach is a "top-down" approach that develops 

casualty estimates for a geographic area which are based 

on gross mortality and morbidity ratios. The building-specific approach is a "bottom-up" approach that relates casualties to the performance of specific building types. The 

composite approach combines specific building-type loss 

estimates with gross mortality and morbidity casualty ratios. The more sophisticated casualty-estimation processes 

rely on fragility curves or damage probability matrices to 

express casualty rates as a function of shaking intensity 

and building damage. 

The earliest casualty estimates were the widely circulated 

National Oceanic and Atmospheric Administration by Steinbrugge and others. They characterized casualties in three 

categories and determined the relative occurrence of casualties by ratios: for every death there are 4 injuries requiring 

hospitalization and 30 that do not. The number of fatalities 

was based on building type and the severity of shaking, with 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A33 

the ratio of fatalities to those exposed given per 10,000 

occupants; for example, they assumed 4 fatalities in 10,000 

for wood frame houses (1 in 2,500 chance of death) and 

5,000 per 10,000 for URM buildings (1 in 2 chance). These 

procedures were applied first to the Berkeley campus of the 

University of California in late 1970, and subsequently to 

other University and State University campuses. 

The ATC- 19 project developed damage-estimation procedures for many different types of buildings (Applied 

Technology Council, 1985). Their approach yielded estimates of the probability of different damage levels for different ground motions (modified Mercalli intensity) by 

building type and height. They also estimated the likelihood of death and injury at different damage levels and 

provided a nominal differentiation of injuries: They were 

classified as either serious or not serious, with the assumption that the latter required hospitalization. Unfortunately, 

there were gross methodological difficulties in this approach to damage estimation. 

The FEMA approach represents the most sophisticated 

study for a regional area to date; see the estimates for St. 

Louis City and County (Federal Emergency Management 

Agency, 1990) and the Six City Study (Federal Emergency 

Management Agency, 1985). Unfortunately these estimates 

categorize casualties as either fatalities or injuries, with no 

distinction for severity or degree of medical treatment. 

In all these studies, having no information on the distribution by injury type, severity, and location, there is no 

way to know what medical resources will be needed and 

where; in the absence of such information, planning may 

well assume the worst. Also, significant gaps are present 

in conceptual approaches that restrict casualty estimates to 

building type and degree of damage; for example, recent 

studies have documented significant life loss and injuries 

from earthquake-induced landslides. Another limitation is 

that there has not been enough attention given to other 

built elements that might suffer significant damage and 

pose a significant safety threat; for example, property 

walls in Chile and bus kiosks in the Philippines were 

sources of fatalities. In addition, it was found in the 1985 

Chile earthquake (Durkin and others, 1986) that many 

people successfully evacuated their homes only to be injured by falling unreinforced masonry property walls. 

PRELIMINARY ASSESSMENT OF EXISTING 

CASUALTY-ESTIMATION MODELS 

The first two authors (Durkin and Thiel) are engaged in 

an ongoing research effort to develop casualty-estimation 

procedures, working toward an empirically and judgmentally based, maximum likelihood model to describe the types 

and severity of casualties likely for different building types, 

occupancies, and ground motions. This work is in progress, 

and conclusions and the specifics of the models are not yet 

appropriate for discussion. This research includes assessing 

an extensive data base, from domestic and foreign earthquakes, to determine relative injury rates due to: 

Damage to structural systems 

Damage to nonstructural systems 

Damage and performance of other physical setting elements, such as equipment or contents falling or moving, 

caustics, fire or other hazardous-materials release, and accidents such as tripping while exiting. 

Injury sources and performance of a building and its 

contents are being classified as to where the injury occurred. Finally, the medical implications of the injury 

types are being assessea; for example, injuries are classified by the degree to which they would likely have been 

more severe if the earthquake had been more severe, using 

a classification system that indicates the typical level of 

emergency medical attention 'required. These results are 

being formulated to provide a qualitative, as well as quantitative, indication of the demand likely for the health-care 

assistance. Our (Durkin and Thiel) classification levels 

will be consistent with the types of qualitative damage 

scales developed for ATC-13 and by Thiel and Zsutty 

(1987) for historical building-damage studies. 

During the initial phases of this research effort, a series 

of hypotheses was developed that provided the basis for 

collection and evaluation of historical injury data. Among 

the hypotheses were the following: 

Injuries in wood-frame dwellings are not usually life 

threatening. 

For any particular level of damage, measured as a percentage of replacement value, the severity of injury increases with the brittleness of the building lateral force 

resisting system. 

Falling sections from URM buildings striking other 

buildings are substantial sources of injury. 

Injuries caused by household and office equipment and 

furnishings are not usually life threatening. 

The occurrence of injuries from household and office 

equipment and furnishings increases with the flexibility of 

the building. 

First providers of medical assistance are typically not 

medical professionals. 

The current building code for emergency egress, based 

on fire requirements, does not provide adequate 

protection of escape routes from earthquake-damaged 

buildings (rows of lateral files are now prevalent in offices 

and often line corridors). 

"Duck-and-cover" recommendations lead to a heightened probability of minor injury but may reduce probability of major injuries. 

Broken glass and downed electrical lines are minimal 

causes of injury, and seldom cause higher classes of injury. 

Transportation of the injured can be a critical element 

for their survival. 
A34 LOSS ESTIMATION AND PROCEDURES 

Search and rescue retrievals in the period right after 

damage occurs is critical for survival of the seriously injured; the success of such retrievals strongly diminishes 

over time. 

For modern, earthquake-resistant construction, minor injuries are a larger proportion of total injuries than most 

assume. 

For nonearthquake-resistant construction, major injuries 

are a large proportion of total injuries. 

Most critical medical attention is provided by the local 

community not by external resources. 

These hypotheses indicate the types of data under examination by an empirical examination of historic data, most 

notably Loma Prieta, Coalinga, Mexico City, San Salvador, Japan and Chile: Housner and Thiel (19901, Durkin 

and others (19831, Durkin (1989a), Durkin (1987), Murakami and others (1989), and Durkin (1986). A comprehensive set of hypotheses, not all believed to be true, has 

been developed to assure that data collected is sufficiently 

complete to address the types of questions that are of potential importance to building design and management as 

emergency preparedness. Additional data are being collected from the Loma Prieta and Philippine (Roces, 1990a, b) 

earthquakes to supplement this analysis. 

As pointed out by Steinbrugge (1982) in his seminal work 

on earthquake damage, casualties vary greatly, from a preponderance of scratches, cuts, and abrasions that can be self 

or nonprofessionally treated (a so-called Red Cross training 

level) to a relatively small proportion of injuries requiring 

specialized medical care. The first type do not degrade severely (become life threatening) with delays until treatment, 

whereas the latter can quickly become life threatening. Research to date suggests that there are three distinct components to categorizing injury severity: the type of assistance 

needed to rescue and move the patient to the medical provider, the skill level required to treat the injury, and the 

degree to which the injury becomes more serious with lack 

of treatment, which is an important element of the casualtyestimation procedure under development. 

It is apparent that different building types pose different 

types of casualty risk. Data are not historically inclusive 

enough to determine risk for many types of construction, 

but they are sufficient to offer empirically defensible conclusions for a few building types: adobe, URM buildings, 

wood-frame residences, and nonductile concrete frames. 

These conclusions provide anchor points for estimation of 

the risk for other types of buildings, much in the manner 

that ATC-13 used information on performance of a few 

building types to determine risk for a larger range of 

building types. The clearest single casualty-related factor 

turns out to be the size and number of building elements 

likely to fall at a particular damage level during an earthquake; for example, URM building's propensity to shed 

parapets, nonductile frame's propensity to collapse, and 

brittle infill wall's tendency to topple. Buildings with great 

flexibility, particularly wood frame, appear to pose relatively low likelihood of serious injury. 

Our analysis increases the understanding of factors influencing casualty estimation in various building types. Such 

factors include a better understanding of the relationships 

between shaking intensity, building damage, and casualty; 

the relative influence of intervening variables such as occupant actions, space utilization, nonstructural elements, 

and building contents; and the need in any casualty-estimation methodology to elaborate not only the causes of 

the loss but also the impact of the loss (for example, a 

building collapse can result in a range of fatal and nonfatal 

injuries that have varying immediate consequences for 

search grid rescue and emergency medical response and 

longer-term consequences for health care). 

ANALYSIS OF EXISTING EARTHQUAKE 

CASUALTY-ESTIMATION APPROACHES 

Normally, casualty-estimation processes determine earthquake casualties in the following manner. First, structural 

engineers or other trained personnel inventory buildings 

that fit prespecified conditions; for example, inventory all 

of the buildings in a particular geographic area or all critical facilities such as hospitals by structural type. Buildinginventory techniques can range from simply documenting 

the presence and location of potentially hazardous buildings, through rapid, visual screening (Applied Technology 

Council, 1987a), to more detailed structural investigations 

of individual buildings (Applied Technology Council, 

1987b). Second, ground-shaking levels and other geologic 

parameters in particular areas are estimated, either by relying on previous geotechnical studies or by commissioning 

such investigations. Third, researchers construct fragility 

curves for specific building types, ground motion, and geologic conditions. Fragility curves are then applied to the 

aggregated building inventory to determine how many 

buildings are likely to occupy each damage state in a particular earthquake scenario. Average occupancy rates are 

then used to determine the population at risk. Finally, planners incorporate a casualty coefficient, derived from expert 

consensus, to determine the expected number of casualties. 

NEEDS FOR REVISION AND EXTENSION OF 

MODELS 

Our review of previous methods and empirical data from 

recent worldwide earthquakes found significant gaps in conceptual approaches that tie casualty estimates only to building, type and expected degree of damage. This analysis 

revealed the following specific areas where present models 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A35 

can be revised and (or) extended to enable more comprehensive and meaningful earthquake-casualty estimations. 

The first need is to incorporate a wider range of geotechnical factors. Present casualty estimates are based almost 

exclusively on structural failure caused by ground shaking, 

to the exclusion of potential casualties from other geologic 

events like landslides. This omission likely evolved from 

the United States having experienced relatively few casualties from earthquake phenomena other than simple ground 

shaking. Experience elsewhere suggests the importance of 

these other types of phenomena: Probably half of the fatalities in the 1990 Philippine earthquake were due to landslides sweeping buses, cars, pedestrians, and homes off 

mountainous roads and hillsides (Durkin and Thiel, 1992); 

many fatalities in the 1987 San Salvador earthquake occurred when single-family residences collapsed and fell 

down hillsides. Other types of earthquake phenomena may 

produce high structural damage with relatively little safety 

risk, as did the 1964 Turnagain slide in Alaska. 

A second need, related to the impact of different earthquake phenomena, is to assess the relative extent to which 

different types of geotechnical performance and resultant 

structural failures contribute to earthquake casualties. For 

instance, liquefaction may cause significant structural damage but lead to few casualties, as was the case in the 1985 

Chile and 1989 Loma Prieta earthquakes. Alternatively, 

structural collapse resulting from slope failure, also documented in the Philippines, may lead to significant fatalities. 

A third need is to incorporate the numerous physical setting hazards other than complete building collapse. Irrespective of their validity, casualty coefficients used in past 

United States casualty estimations were applied only to 

occupants of collapsed buildings, to the exclusion of those 

at risk from other types and degrees of structural failure. 

These estimates assumed that the overwhelming majority 

of serious casualties would occur inside collapsed buildings and thus did not give enough attention to other physical setting types and elements that might experience 

significant structural damage and pose a significant life 

safety threat. One such type is the complete collapse of 

structures other then buildings; for example, the Cypress 

viaduct collapse caused most of the Loma Prieta earthquake fatalities. In the 1985 Chile earthquake, numerous 

residents evacuated their homes only to be killed and injured by collapsing masonry property walls. Partial building collapse is another important type of structural failure 

largely ignored by present casualty-estimation methods. 

The second major cause of Loma Prieta fatalities was falling parapets and sections of masonry exterior walls which 

fell on people outside of buildings. 

A fourth need is to incorporate estimates of mortality 

and morbidity due to the performance of nonstructural elements and building contents. Although our recent research 

indicates that nonstructural elements such as ceiling tiles 

and building contents such as office equipment and household furnishings have a low likelihood of causing fatal injuries, such elements are responsible for numerous minor 

and moderate injuries that tax emergency health services 

and incapacitate individuals. 

A fifth need is to develop better techniques for relating 

populations at risk to earthquake hazards. The threats posed 

by an entire physical setting need to be documented and 

incorporated, particularly urban design issues. The concept 

of physical setting is particularly useful in understanding 

factors that contribute to earthquake injuries because it combines physical elements with occupant behavior. Therefore, 

it is possible to evaluate the interaction of environment and 

behavior in terms of normal activity and space utilization, 

and in terms of emergency actions. The physical setting 

approach also has the advantage of including potentially 

hazardous physical elements outside the building itself, for 

instance the lethal Chilean property walls. In addition, the 

physical setting approach also allows a more comprehensive 

and detailed hazard assessment of specific geographic areas. 

For example, planners can analyze a specific intercity area by 

a number of different dimensions, including the proximity of 

specific medical resources to the areas of potential collapse, 

street width, population density, the probable ability of 

skilled medical personnel to reach victims, and the size of 

emergent groups that are likely to aid or hinder rescue efforts. 

Ideally, casualty estimates should describe the damage 

potential of all physical setting elements, both natural and 

built. Specifically, better descriptions are needed of the exact mechanisms of structural failure that contribute to fatalities and injuries, beyond building collapse, to identify 

other causes of morbidity and mortality, including those 

injury-producing mechanisms that span the spectrum of 

non-contactlnondamage injuries to crushing injuries. Better documentation is needed of the circumstances surrounding typical injuries, and the personal characteristics 

and specific actions of building occupants that make them 

more or less susceptible to injury must be identified and 

described. Finally, a model is needed that interrelates how 

this information relates to different building types, building uses, and damage levels. 

The sixth need is to expand our conceptual framework 

to include more supply-side issues (availability and management of health-care resources). It is clear that the rapid 

provision of appropriate medical care can save lives and 

reduce injury severity. Recent research shows that, even in 

building collapses, many seriously injured occupants are 

freed very quickly and can benefit from the rapid provision of specialized medical care. However, as discussed 

above, the Santa Cruz County EMS system response in 

the Loma Prieta earthquake shows that many ambulance 

trips were wasted because the disaster response system 

was not set up to deal adequately with injury severity. Unfortunately, most EMS approaches categorize casualties as 

either fatalities or injuries, with no distinction for severity 

of medical conditions. Thus, there is no way to know what 
A36 LOSS ESTIMATION AND PROCEDURES 

medical resources are needed in a particular location. If it 

is known what the injury severity is likely to be, then the 

estimates can be adjusted. Other supply-side factors that 

existing estimation processes do not include are the impact 

of loss of transportation and utility systems. For example, 

medical conditions due to the inability of emergency medical equipment and personnel to reach the injured because 

of severed transportation arteries are not currently estimated. Similarly, the impact of interrupted utilities on the delivery of health-care services is not considered. 

The seventh and final need is to redesign current loss and 

casualty-estimation processes so that they more fully assist 

policy formulation and implementation. Although processes used in the United States give planners gross building 

damage and casualty estimates (normally expressed in 

terms of expected numbers of deaths and serious injuries), 

these methods are not sufficiently developed. They fail to 

provide policymakers and emergency service agencies with 

an empirical basis for selecting among alternative policy 

strategies or for assessing the effectiveness of strategies 

once in place. For example, shaking of a URM building 

has a higher likelihood of causing serious injuries than the 

same level of shaking to a steel or wood-frame building. 

Therefore, given a program to decrease serious injuries, 

creating selective retrofit policies for URM buildings only 

is a more efficient use of limited resources than policies 

including all buildings, regardless of their level of damageability. Similarly, the ability to estimate the relative injury 

potential of different nonstructural elements and building 

contents is essential in allocating limited resources to fixing these facets only that have a likelihood of causing serious injuries, rather than all of them. 

FINDINGS ON THE SOURCES AND FREQUENCY 

OF EARTHQUAm- CASUALTIES 

This analysis increases our understanding of factors influencing casualty estimation in United States building types. 

Such factors include a better understanding of the relationships between shaking intensity, building damage, and casualty; the relative influence of intervening variables such as 

occupant actions, space utilization, nonstructural elements, 

and building contents; and the need in any casualty-estimation methodology to elaborate not only on the causes of the 

loss but also on the impact of the loss (for example, a building 

collapse can result in a range of fatal and non-fatal injuries 

that have different immediate and longer-term consequences). Although our work is in progress and therefore not ready 

to be fully documented, there are several important preliminary findings presented below that are organized by subject. 

FINDINGS RELATED TO CASUALTY-ESTIMATION METHODS 

1. Past United States earthquake-casualty estimates were 

largely speculative, owing to the absence of an earthquake-injury data base. The estimates tended to be 

based first on simple ratios of casualties to damage and 

second on casualty ratios (minor, major, death) developed from other injury experience. 

2. Recent United States earthquake-casualty estimates still 

lack a sufficient empirical basis; their casualty assumptions have not been tested with available data. 

3. Recent United States earthquake-casualty estimates are 

based on overly simplistic assumptions about casualties and how the health-service delivery system works. 

4. Casualty assumptions are not comprehensive. 

5. Health-service assumptions ignore utilization patterns. 

6. Hypothesized ratios of the number of fatalities to the 

number of casualties need revision and further refinement in light of current data. For example, Mexico 

City (1985 earthquake) results indicate more fatalities 

than hospital admissions, whereas Loma Prieta has 

many times more admissions than fatalities. 

7. The problem of estimating casualties by degree of injury severity is one of statistical estimation, with associated probabilities for different levels of injury, not one 

of deterministic estimation. 

FINDINGS RELATED TO CASUALTY-RESEARCH METHODS 

1. Early earthquake injury studies did not adequately categorize injury type and severity. 

2. Few previous studies considered the role of physical 

setting in earthquake injuries. 

3. Previous studies did not link earthquake injuries to 

physical setting elements. 

4. Research has ignored the role of occupant behavior in 

earthquake-injury susceptibility. 

5. Historical data has tended to record only specific injury 

data and not include what happened to others at risk in 

the same place or similar situations. This may have 

tended to inflate earthquake casualty rates. 

6. Traditional, institutionalized methods for injury data collection (for example, medical record procedures) do not 

systematically collect information, such as injury location, contributing physical element, and injury circumstances, that is useful to earthquake-casualty estimation. 

FINDINGS RELATED TO PHYSICAL SETTING DATA 

1. Current methods for describing physical setting performance (for example, building damage-classification 

schemes) are inadequate for explaining or predicting 

many earthquake injuries. 

2. Methods for collecting postearthquake damage data lack 

sufficient detail to be very usehl in casualty studies. 

3. Preearthquake hazard-assessment methods (see Applied 

Technology Council, 1987a) need refinement to be 

useful in predicting earthquake casualties. 
CASUALTIES AND EMERGENCY MEDICAL RESPONSE A37 

4. Physical settings are difficult to reconstruct after an 

earthquake. Documentation is often nonexistent for 

older buildings and for newer buildings, especially 

heavily damaged ones, is frequently restricted by the 

owners. 

FINDINGS RELATED TO EARTHQUAKE CASUALTIES AND 

BUILDING PERF'ORMANCE 

1. The majority of earthquake fatalities and serious injuries have resulted from structural failure. 

2. A majority of serious casualties have come from a 

small number of damaged facilities, consistent with 

statistical experience from other disasters. This is apparent immediately in recent United States experience 

(SO+ dead at the Cypress viaduct from the Loma Prieta 

earthquake and 40+ at the Veterans Hospital in San 

Fernando (1971) were the majority killed in their respective earthquakes; similar for foreign events) but 

has not become a basis for emergency planning. 

3. Well-designed, modern, earthquake-resistant structures 

pose relatively little serious casualty threat to their occupants. The substantial threat is structures in classes 

that pose collapse hazards even if they do not collapse. 

4. Nonstructural elements have a low likelihood of causing serious injury. 

5. Building contents, such as office equipment and household furnishings, have a low likelihood of causing serious injury. 

What do some of these preliminary observations mean? 

For emergency medical planning they suggest that there 

are two principal patient-demand sources. The first is from 

building collapse that yields large numbers of serious, lifethreatening injuries. The second is from the normal injury 

mix from low to moderate building damage-that is, nonbuilding collapse. These injuries are probably distributed 

proportionally to the population and do not create excessive demands on most health-care systems, because there 

are not likely to be massive numbers of severe casualties 

concentrated in a local area. This suggests that the primary 

emphasis of emergency medical planning should be first in 

areas where there are large numbers of high-hazard, structures and second where there are collapse-hazard structures, often widely distributed within a community. 

The locating of collapse-hazard structures within a 

community is not overly difficult. The major contributors 

to building damageability include, among others, site location and characteristics, structural system, and architectural configuration. Classifying a structure and its site, 

however, is not the end of the hazard-determination process, because classification according to any one category 

(for example, unreinforced masonry) can be very misleading, giving either a false sense of security or peril. This is 

because earthquake engineering is not yet a precise endeavor; the identification of the damageability of a structure is a problem in statistics, with results given in rather 

broad ranges, not specific numbers. 

ACKNOWLEDGMENTS 

The authors gratefully acknowledge the support of the 

U.S. Geological Survey and the Santa Cruz County Emergency Medical Services Agency. This work was partially 

supported by research grants to Michael E. Durkin and 

Associates on casualty estimation from the U.S. Geological Survey (USGS Grants No 14-08-0001-Gl785, 14-08- 

0001 -GI 862, 14-08-000 1-G2002, 14-08-000 1 -G 1974) as 

part of the National Earthquake Hazards Reduction Program (NEHRP). Co-investigators include Charles C. Thiel 

Jr., Anne H. Coulson, Christopher Rojahn, Donald Cheu, 

and the Applied Technology Council. This work also utilized data collected under a series of previous grants on 

earthquake casualties and health services from the National Science Foundation, also part of the NEiHRP. 9-1-1 response data were collected with the support of the Santa 

Cruz County Emergency Medical Services Agency, Santa 

Cruz, California, under a grant from the California Emergency Medical Services Authority. Ms. Teri De Vried of 

the Seismic Safety Commission provided access to the 

DIR data. The paper gained significantly from the insights 

offered by the 9- 1- 1 emergency dispatchers, paramedics, 

hospital administrators; emergency medical services personnel of Santa Cruz County; of particular note were the 

assistance and insights of Donald Hiatt, R.N., Director of 

Emergency Medical Services for Santa Cruz County. The 

assistance of the staff of the Work Injury and Statistics 

Section, California Department of Industrial Relations, 

was invaluable in making available work-related injury 

and illness data for analysis. 

REFERENCES 

Applied Technology Council, 1985, Earthquake damage evaluation data 

for California: Redwood City, Calif., ATC-13 Report, 492 p. 

1987% Evaluating the seismic resistance of existing buildings: 

Redwood City, Calif., ATC-14 Report, 370 p. 

1987b, Rapid visual screening of buildings for potential seismic 

hazards-a handbook: Redwood City, Calif., ATC-21 Report, 185 p. 

Benuska,, Lee, 1990, ed., Loma Prieta earthquake reconnaissance report: 

Earthquake Spectra, v. 6, supp. 1, 1990, 448 p. 

California Highway Patrol, 1990, 1989 Lorna Prieta earthquake report: 

Sacramento, Calif., 50 p, 

California Department of Industrial Relations, 1989, Work injuries and 

illnesses: Sacramento, Calif., Department of Industrial Relations, 

123 p. 

Durkin, M.E., 1986, Casualties, hospital response and response of the 

health care system, in The Chilean earthquake of March 3, 1985: 

Earthquake Spectra, v. 2, no. 2, p. 487-497. 

1987, Casualties, search and rescue, and response of the health 

care system, in The San Salvador earthquake of October 10, 1987: 

Earthquake Spectra, v. 3, no. 3, p. 621-634. 
A38 LOSS ESTIMATION AND PROCEDURES 

1989a, The role of the physical setting in earthquake injuries: The 

Mexico experience, in Lessons learned from the 1985 Mexico 

Earthquake: El Cerrito, Calif., Earthquake Engineering Research Institute, p. 205-208. 

1989b, The role of building evaluation in earthquake hazard reduction, in Preiser, W.F.E., ed., Building evaluation: Advances in 

methods and applications: Plenum Publishing, p. 67-80. 

1991, Estimating casualties in earthquakes: An assessment, in 

Proceedings of the Fourth International Conference on Seismic Zonation: El Cerrito, Calif., Earthquake Engineering Research Institute, p. 293-300. 

Durkin, M.E., Aroni, S., Colson, A., 1983, Injuries in the Coalinga earthquake, in The Coalinga earthquake of May 2, 1983: El Cerrito, Calif., Earthquake Engineering Research Institute, p. 277-279. 

Durkin, M.E., and Thiel, C.C., Jr. 1990, Integrating earthquake casualty 

and loss estimation, in Workshop on Modeling Earthquake Casualties for Planning and Response, December 4-6, 1990, Pacific Grove, 

Calif., Proceedings: Sacramento, Calif., VSP Associates. 

1992, Improving measures to reduce earthquake casualties: Earthquake Spectra, v. 7, p. 95-1 13. 

Durkin, M.E., Thiel, C.C., Schneider, J.E., and De Vried, T., 1991, Injuries and emergency medical response in the Loma Prieta earthquake: Bulletin of the Seismological Society of America, v. 81, no. 

5, 2143-2166. 

Federal Emergency Management Agency, 1980, An Assessment of the 

Consequences and Preparedness for a Catastrophic California Earthquake: Findings and Actions Taken: Washington, D.C., 59 p. 

Federal Emergency Management Agency, 1985, Central United States 

earthquake preparedness project: An assessment of damage and casualties for six cities in the central United States resulting from 

earthquakes in the New Madrid seismic zone: Washington, D.C., 

330 p. 

Federal Emergency Management Agency, 1990, Estimated future earthquake losses for St. Louis City and County, Missouri: Washington, 

D.C., Federal Emergency Management Agency, Earthquake Hazard 

Reduction Series 53, 199 p. 

Housner, G.W., and Thiel, C.C., 1990, Competing against time, report to 

the Governor from The Board of Inquiry on the 1989 Loma Prieta 

earthquake: Sacramento, Calif., Office of Planning and Research, 

264 p. 

Johns Hopkins University, 1989, International workshop on earthquake 

injury epidemiology for mitigation and response, July 10-12, 1989, 

Proceedings: Baltimore, Md., 502 p. 

Murakami, H.O., and Durkin, M.E., 1989, Studies of occupant behavior 

in earthquakes-Review and perspectives, in Proceedings of the 

Ninth World Conference on Earthquake Engineering: Tokyo, Japan, 

Maruzen, v. 7, p. 681-686. 

National Academy of Sciences, 1988, Estimating Losses from Future Earthquakes, Panel report and technical background, Washington, D.C. 

Roces, C.R., White, M.E., Dayrit, M.M., and Durkin, M.E.,1992, Risk 

factors for injuries due to the 1990 earthquake in Luzon, Philippines: Bulletin of the World Health Organization, v. 70, no. 4, 

p. 509-514. 

Roces, C.R., N.I. Pator, I.L. Gopez, C. Lim-Quizon, R.U. Rayray, R.R. 

Gavino, E.S. Salva, M.B. Brizuela, EC. Diza, E.V. Falcon, J.M. Lopez, M.E.G. Miranda, R.A. Sadang, N.S. Zacarias, M.M. Dayrit, 

1990b. "Earthquake Disaster-Luzon Philippines," Morbidity and 

Mortality Weekly Report, Centers For Disease Control, Atlanta, Ga., 

August 31, 1990, v. 39, no. 34, p. 573-577. 

Steinbrugge, K.V., 1982, Earthquakes, volcanoes and tsunamis: An anatomy of hazards: New York, Scandia America, 392 p. 

Thiel, C.C., G.W. Housner, and L.T. Tobin, 1991, State Response to the 

Lorna Prieta Earthquake: Competing Against Time: Bulletin of the 

Seismological Society of America, v. 81, no. 5, October 1991, 

p. 2127-2142. 

Thiel, C.C., Schneider, J.E., Hiatt, D., and Durkin, M.E., 1992, 9-1-1 

EMS process in the Loma Prieta earthquake: Journal of Prehospital 

and Disaster Medicine, v. 7, no. 4, p. 348-358. 

Thiel, C.C., and Zsutty, T.C., 1987, Earthquake characteristics and damage statistics: Earthquake Spectra, v. 3, no. 4, p. 747-792. 

U.S. Centers for Disease Control, 1989, Earthquake-associated deathsCalifornia: Morbidity and Mortality Weekly Report, v. 38, no. 45, 

p. 767-770. 

U.S. Geological Survey, 1990, Proceedings of conference XLIX: meeting 

of the US ad hoc working group on earthquake-related casualties: 

U.S. Geological Survey Open-File Report 90-244, 155 p. 
THE LOMA PRIETA, CALIFORNIA, EARTHQUAKE OF OCTOBER 17,1989: 

SOCIETAL RESPONSE 

LOSS ESTIMATION AND PROCEDURES 

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STUDY METHODS AND PROGRESS REPORT: 

A CASE-CONTROL STUDY OF PHYSICAL IN JURIES ASSOCIATED 

WITH THE EARTHQUAKE IN THE COUNTY OF SANTA CRUZ 

By Robin M. Wagner, Nicholas P. Jones, and Gordon S. Smith, The Johns Hopkins University; and 

Frederick Krimgold, Virginia Polytechnic Institute and State University 

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Preliminary progress report on case-control study ----------------- Hospital and dead cases .......................................... 

Population sample: Noninjured controls and population 

ABSTRACT 

A case-control study in progress is examining the risk 

factors for physical injuries associated with the Loma Prieta 

earthquake. The study explores how the physical environments 

and personal behaviors of residents of the County of Santa 

Cruz contributed to their risk of being physically injured or 

killed during the shaking of the main earthquake and in the 

subsequent 72 hours. This paper describes in detail the study 

design and methods. Information on risk factors and injuries 

was collected in the County of Santa Cruz through a structured 

interview and review of medical records during the field 

period, which ended in August 1991. The risk factors for 

physical injury examined include age of building, type of 

structure, occupant behavior, and sociodemographic characteristics. preliminary results of the data collection efforts (for 

example, the number of cases and controls targeted for an 

interview and ascertained) are reported here. The collected 

data are currently being coded for data entry and subsequent 

analysis. Final study findings will be published when available. 

INTRODUCTION 

Obtaining reliable and accurate estimates of casualties 

associated with earthquakes has posed serious challenges. 
A40 LOSS ESTIMATION AND PROCEDURES 

Such estimates have varied, in part, because there is no 

universally accepted definition of earthquake-related 1 deaths and injuries. Furthermore, documentation of injuries has generally taken a lower priority than rescue and 

treatment activities in the face of disaster. The Loma Prieta earthquake was no exception. Initial press accounts put 

the total death toll in the hundreds (Shilts and Sward, 

1989a, b), an overestimate by a factor of three to four, and 

even the scientific literature could not agree on a final total 

count, offering a range of 60 to 67 deaths (Journal of 

Emergency Nursing, 1990; McNutt, 1990; Morbidity and 

Mortality Weekly Report, 1989; and Plafker and Galloway, 

1989). One year after the event, there was still no reliable 

information on injury morbidity associated with the earthquake (Jones and others, 1990). The work described below 

attempts to overcome these and other problems that have 

characterized previous research in this area. 

This paper describes recent efforts made, since the Loma 

Prieta earthquake, to assess, both qualitatively and quantitatively, the morbidity and mortality associated with that 

event. This study, when complete, will not only provide 

useful information relative to this specific event, but will 

also augment substantially the literature available in disaster-specifically earthquake-epidemiology. As the research is still in progress, the material and data presented 

herein must be considered preliminary only. Unfortunately, 

since most of the efforts to date have focussed on study 

design, data collection, and coding, few quantitative data are 

available for presentation at this stage. Reported herein, 

therefore, are descriptions of the study design, implementation, and future plans, as well as preliminary assessments 

made from the data processed to date. Specifically the authors are unable to report injury rates, risk factors, and so 

forth, at this stage, owing to the ongoing status of the project. 

PURPOSE OF STUDY 

A case-control epidemiology study of the risk factors for 

physical injuries in the County of Santa Cruz, associated 

with the Loma Prieta earthquake, is being conducted. 

Earthquake-related injuries that occurred during the shaking of the main earthquake and the next 72 hours are 

being examined. The study population is restricted to persons who were residents of the County of Santa Cruz and 

were physically present in the County at the time of the 

earthquake. 

The specific primary aims of this study are: 

1. To assess the relative risk for physical injury associated 

with different physical environments (for example, 

buildings, vehicles, outside), with entrapment, and with 

personal behaviors in the disaster and postdisaster 

phases of the Loma Prieta earthquake. 

2. To assess the relative risk for other potential risk factors for physical injury including preexisting medical 

conditions and mobility, drug and alcohol use, and sociodemographic characteristics. 

3. To estimate the absolute risk of physical injury mortality and morbidity associated with the Loma Prieta 

earthquake in the County of Santa Cmz. 

A secondary aim of this study is to determine if physically injured cases who sought treatment at a hospital 

were different from those who did not seek such care. For 

example, selection factors for treatment that will be examined include injury severity, possession of health insurance, and sociodemographic characteristics. 

BACKGROUND AND SIGNIFICANCE 

Earthquakes are one of the most feared natural disasters, 

causing injury and physical damage in developing and developed nations alike. Despite the fact that earthquakes 

have killed at least 1.3 million people in this century 

(Smith, 1990), they have received scant attention from epidemiologists. 

PREVIOUS STUDIES 

A critical review of the scientific literature on the causes 

of earthquake-related deaths and injuries leads to the following general conclusions. First, there is a paucity of epidemiological investigations of earthquakes, despite their 

great lethality (Smith, 1990). This dearth has arisen from 

inadequate funding and, until recently, from a relative lack 

of interest in the subject area by researchers (Tierney, 1990). 

Second, almost all of the published epidemiological studies 

on earthquake-related injuries are descriptive rather than 

analytical1, precluding the ability to establish and quantify 

the magnitude of the relationship between significant risk 

factors and injuries. Only four earthquakes, prior to the 

Loma Prieta, have been examined through analytical studies 

of earthquake-related injuries: the 1976 Guatemalan (Glass 

and others, 1977); 1980 Italian (de Bruycker and others, 

1983, 1985); 1988 Armenian (Armenian and others, 1992; 

Noji, 1990); and 1990 Philippine (Morbidity and Mortality 

Weekly Report, 1990) earthquakes. 

Third, documentation of deaths and, in particular, nonlethal injuries is often incomplete in the aftermath of disaster, 

'~escri~tive injury studies investigate the experiences of injured or 

killed individuals only. The background rate of exposure to the same 

hazards (for example, collapsing buildings) in the noninjured persons is 

not considered. Analytical injury studies are superior to descriptive ones, 

in that they compare the experiences of injured persons to noninjured 

ones to identify and quantify significant risk factors for injury. Analytical 

studies permit researchers to test hypotheses that particular hazards are 

associated with injuries. 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A4 1 

particularly in less-developed countries. Fourth, injuries are 

often vaguely and inconsistently defined in the previous 

epidemiological studies. For example, the definition of injuries may include conditions other than physical trauma 

(Sanchez-Carrillo, 1989), as well as any affliction treated 

after the disaster, whether or not it was earthquake-related 

(de Ville de Goyet and others, 1976). Investigators often 

employ different schemes to classify injury severity levels 

(Coulson, 1989). Fifth, most previous epidemiological 

studies of earthquakes have been conducted solely by 

health researchers, even though the topic calls for an interdisciplinary approach which draws on structural engineering, geology, architecture, epidemiology, and emergency 

medicine. 

The majority of studies on the risk factors for earthquake-associated injuries actually appears in the earthquake engineering literature. These studies have generally 

been executed along strict disciplinary lines without input 

from health professionals. Thus, despite their quantitative 

approach, these engineering studies do not employ standard epidemiologic methods or meet minimal criteria generally required by epidemiologists to accurately and reliably 

assess risks. For example, some surveys of earthquake victims are not based on random probability samples of a 

clearly defined study population (Arnold, 1986; Durkin, 

1985 (San Fernando earthquake)); others do not report 

sufficient information to evaluate the sampling methodology (Mochizuki, 1988; Miyano and Mochizuki, 1988; Ohta 

and others, 1980; Ohta and Omote, 1977); still others sample highly select groups (Mochizuki and others, 198Q2, 

making it difficult to generalize the results to the rest of 

the population. Many of these studies either do not report 

or have unacceptably low case ascertainment or survey response rates.3 The survey instruments, when described, do 

not always appear to measure well the stated variables of 

interest (Ohta and others, 1977, 1980), although this may 

result from inadequate translations of the questionnaires 

published in the English-language scientific literature? 

Despite these limitations, the literature has identified a 

number of potentially important risk factors for injuries associated with earthquakes. These include characteristics of 

the earthquake itself (magnitude, intensity, distance from 

the epicenter, time of day, and season), geological and top- 

'~hese researchers targeted college graduates because they thought respondents with higher education would have better memories than those 

with less schooling. 

'For example, results based on case ascertainment rates of less than 30 

percent were reported for building occupants in the 1985 Mexico and 

1986 San Salvador earthquakes (Durkin and others, 1988). 

?he Ohta questionnaires were administered in Japanese but translated 

into English for publication. 

ographic conditions (soil type, cliffs, or mountains), postearthquake weather (rain which may cause landslides and 

extreme cold), the nature of the built environment (the degree of seismic resistance of buildings and other human 

engineered structures, such as bridges), the presence or absence of secondary hazards (fires, hazardous materials 

spills, tsunamis), sociodemographic features of the affected 

population (population density, age, and sex), and human 

behavior during and after the event (Stratton, 1989; Tierney, 1990). An extensive critique of the earthquake injury 

risk factor literature will be published later (Jones and others, 1993a). 

CASE-CONTROL STUDY OF THE EARTHQUAKE 

This study in progress aims to build and improve upon 

previous work. It is being conducted by an interdisciplinary 

research team which includes epidemiologists (including an 

injury specialist), an engineer, and an architect. As an analytical epidemiological study, it will be able to explore and 

refine hypotheses of the contribution of the built environment and behaviors to earthquake-related casualties. Physical injuries are clearly defined with respect to qualifying 

medical conditions, severity level, time of occurrence, and 

earthquake-relatedness. Risks posed by structural and nonstructural components of buildings are distinguished from 

those associated with building contents. 

The County of Santa Cruz was chosen for study rather 

than other regions affected by the Lorna Prieta earthquake 

for the following reasons. Although the media concentrated 

on the San Francisco Bay area, the earthquake was centered 

in the County of Santa Cruz and caused widespread damage and destruction in the County. The County of Santa 

Cruz also presented unique opportunities for ascertaining 

persons injured in the County. The County had a relatively 

small total population at the time of the earthquake (approximately 235,000). It was difficult to leave the County 

by ground transportation after the earthquake, since it is 

isolated by natural barriers (the Pacific Ocean and Santa 

Cruz Mountains), and the few roads leading out of it were 

inaccessible for days, owing to earthquake-induced damage. Furthermore, medical treatment options in the County 

were thought to be restricted to the County's three hospitals, since doctor's offices and clinics were reportedly 

closed for several days after the earthquake.5 

5~n exception to this is that one clinic, Salad Para la Gente, which 

sustained serious structural damage during the quake, set up an outdoor 

temporary clinic in the downtown Plaza of Watsonville following the 

quake. The outdoor clinic provided limited services for minor injuries to a 

predominantly Hispanic clientele. According to Salud's Director, Barbara 

Garcia, persons with serious injuries were referred to a County hospital. 
A42 LOSS ESTIMATION AND PROCEDURES 

PUBLIC HEALTH IMPACT OF THE STUDY 

Injury prevention strategies can intervene at a number of 

different phases of an earthquake: the predisaster, disaster, 

and postdisaster phases (Noji and Sivertson, 1987). Interventions aimed at the predisaster phase prevent or limit 

people's exposure to the disaster; those directed toward 

the disaster phase limit the impact of the disaster while it 

is occurring; and those targeted at the postdisaster phase 

minimize the consequences of injuries incurred during the 

disaster. Examples of interventions for earthquakes include 

keeping people from living or working in seismically active regions and improving the design of buildings and 

(or) retrofitting them (for example, anchoring houses, 

bracing walls, and so forth) to prevent their collapse during the shaking (predisaster phase); instructing people on 

protective actions to take during the mainshock (disaster 

phase); and developing techniques to more rapidly rescue 

and treat victims trapped by rubble (postdisaster phase). 

This case-control study will evaluate risk factors for the 

predisaster, disaster, and postdisaster phases. Thus, the lessons learned from this study can hopefully be used to design more effective injury prevention plans for future 

earthquakes. 

Finally, this project is the first case-control study of 

earthquake-related injuries in a region in which many 

buildings have been designed or retrofitted to resist seismic forces. Thus, in contrast to the earlier studies which 

have concentrated on lesser developed nations, the results 

of this investigation are likely to be generalizable to future 

earthquakes in California and industrialized nations, such 

as Japan, which have well-conceived and enforced seismic 

building codes. This information should be valuable since 

there is a probability of approximately two-thirds that an 

earthquake at least as strong as the Loma Prieta earthquake will strike California in the next 30 years (U.S. 

Geological Survey, 1990). 

PRELIMINARY STUDIES 

BACKGROUND 

This case-control study is one of several collaborative 

projects examining the health impacts of the Loma Prieta 

earthquake. The efforts of the participating research teams 

are being coordinated by the California Department of 

Health Services, the State's public health agency. This 

study builds on an ongoing descriptive, case-series study 

of the medical consequences associated with the earthquake in the County of Santa Cruz. The Johns Hopkins 

University team has played a leading role in the design 

and execution of both studies, in collaboration with California health authorities. 

A major goal of the descriptive study is to determine the 

circumstances, causes, and nature of deaths and physical 

injuries requiring hospital treatment that occurred in the 

County of Santa Cruz and were associated with the earthquake. These cases are also part of the case-control study. 

Hospital cases were identified by reviewing the medical 

records of all persons who visited the emergency room of 

any one of the three hospitals in the County of Santa 

Cruz-Dominican Santa Cruz, AM1 Community, and Watsonville Community ~os~itals~-for any reason in the 72 

hours after the earthquake. County residents who were 

flown by helicopter to a hospital outside of the County 

were also identified as hospital cases. Helicoptered cases 

were identified through a review of the logs of all local 

helicopter ambulance services as well as through contact 

with the California Department of Forestry and Fire Protection. The latter agency used some of its helicopters to 

transport County residents to hospitals outside the County. 

Dead cases were identified by media reports and a visit to 

the County of Santa Cruz Coroner's Office. Dead cases 

and hospital cases whose medical records indicated they 

were "injured" or they visited the hospital for "unknown" 

(that is, unrecorded) reasons were targeted for a follow-up 

interview. Those with "unknown" diagnoses were targeted 

so as not to miss anyone who might have been injured. 

The medical records of County of Santa Cruz hospital 

visitors were abstracted by 19 volunteers with medical 

training under the supervision of Santa Cruz County Office of Emergency Medical Services and Watsonville 

Community Hospital, collaborators in the project. Autopsy 

and coroner's reports were obtained from the Coroner's 

Office for the dead cases. 

The interviewing phase of the descriptive study began 

on July 19, 1990, and was completed by March 3 1, 1991. 

PRELIMINARY RESULTS OF THE 

DESCRIPTIVE STUDY 

During the case ascertainment period (the 72 hours after 

the main earthquake), six persons died from earthquakerelated physical injuries that occurred in the County. The 

three County of Santa Cruz hospitals recorded 1,057 visits 

to their emergency rooms, representing 990 persons (some 

people went to a hospital more than once in the 72 hours 

after the quake). Of these 990, 630 visitors (64 percent) 

had diagnoses of "injured" or "unknown." The remainder 

(36 percent) had "illness" diagnoses. A critical review of 

all the medical abstracts resulted in some of the "injured" 

or "unknown" persons to be judged ineligible (that is, not 

earthquake-related) whereas a few from the "illness" category had sufficiently ambiguous diagnoses to be included 

for an interview. This review resulted in 565 persons who 

'~orninican has recently acquired AM1 and converted it into a drug 

treatment center, nursing home, and intermediate care hospital. 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A43 

Table 1 .-Distribution of target population of County of Santa Cruz hospital cases by hospital and medical outcome recorded on the medical abstract 

Medical Outcome 

Hospital In jury I1 lness Unknown Total 

Watsonville 21 5 4 3 3 252 (44.6 pet1 

Dominican 193 0 14 207 (36.6 pet) 

AM1 - 104 - 0 - 2 106 (18.8 pet! 

Total 512 (90.6 pet) 4 (0.7 pet) 49 (8.7pct) 565 (100.0 pct) 

Table 2.-Distribution of ascertained County of Santa Cruz hospital cases that completed interviews as of December 26, 

1990 by hospital and medical outcome recorded on the medical abstract * 

Medical Outcome 

Hospital Injury Illness , Unknown Total 

Watsonville 

Dominican 

AM1 

Total 426 (91.6 pet) 4 (0.9 pet) 35 (7.5 pet) 465 (100.0 pet) 

* n=463 and n=2 for totally and partially completed interviews, respectively. 

Table 3.-Distribution of ascertained County of Santa Cruz hospital cases that refused to be interviewed as of December 26, 

1990, by hospital and medical outcome recorded on the medical abstract* 

Medical Outcome 

Hospital Injury I1 lness Unknown Total 

Watsonville 6 0 1 7 (23.3 pet) 

Dominican 13 0 1 14 (46.7 pet) 

AM1 - 8 - 0 - 1 9 (30.0 pet) 

Total 27 (90.0 pet) 0 (0.0 pet) 3 (10.0 pet) 30 (100.0 pet) 

* Includes final refusals (refusal conversion failed) (n=17) and refusals 

for whom refusal conversion' process had not been completed (n=13). 

visited a County of Santa Cruz hospital-including one of 

the six persons killed by the earthquake-or their proxies 

being targeted for an interview. Four additional persons 

were identified as injured and flown to an out-of-county 

hospital. Thus, the total pool of potential cases was 574 

(565 County hospital cases (including 1 dead case) plus 5 

other dead cases and 4 non-County hospital cases). 

A total of 482 potential cases or proxies were interviewed (477 completed interviews and 5 break-offs), representing 83 percent of the total. Another 31 (5 percent) 

refused. About 11 percent were lost to follow-up. 

Tables 1 and 2 show that the 465 County hospital cases 

who were interviewed as of December 26, 1990, (a final 

- 

analysis is not yet available), were highly representative of 

the target population from which they came with respect 

to both medical outcome and hospital visited. Table 3 

shows that refusals obtained as of December 26, 1990, 

were disproportionately higher than expected from the two 

north County hospitals (Dominican and AM1 Hospital) and 

lower from the south County hospital (Watsonville). The 

reasons for this are unknown. However, Dominican Hospital acquired AM1 in a highly publicized takeover during 

the interview phase, and this may account for some of the 

negative responses. 

A more complete description of the case population and 

ascertainment methods is presented in the following section. 

-- - - - -- -- 
A44 LOSS ESTIMATION AND PROCEDURES 

STUDY DESIGN AND METHODS 

OVERVIEW OF METHODS 

This case-control study examines how the physical environments and personal behaviors of the County of Santa 

Cruz residents contributed to their risk of being physically 

injured or killed in the County by the Loma Prieta earthquake. Physical environments are characterized broadly as 

being inside a building, in or on a vehicle, or outside (near a 

building or entirely away from one). Risk factors specific to 

each environment, such as collapsing chimneys or landslides, are also being explored. Within the building environment, hazards from structural and nonstructural components 

of buildings are being distinguished from dangers posed by 

building contents. Behaviors of interest include the protection and rescue of oneself and other people, pets, or things, 

as well as clean-up activities in earthquake-damaged areas. 

The outcomes of interest are earthquake-related physical 

injuries that occurred during the shaking of the main earthquake (the disaster phase) and the subsequent 72 hours (the 

postdisaster phase). Injuries are characterized by their type, 

affected body parts, cause, and level of severity. 

Information on both injuries and risk factors was obtained through a structured interview of cases and controls, or their proxies if necessary. 

Injury information on cases was also obtained from 

medical records and autopsy reports. Interviews were generally conducted by telephone. They were administered in 

English and Spanish. 

Interviews are a standard tool in epidemiology (Schlesselman, 1982). They provide unique advantages over other 

methods of data collection for certain classes of information. For example, interviewing individualsis the best method currently available to investigate human behaviors 

during an unanticipated event (such as an earthquake) in a 

large-sized sample. 

To be eligible for the case-control study, participants had 

to have been living and present in the County at the time of 

the earthquake. The case group consisted of hospital and 

dead cases. For comparison, a population-based sample of 

current County residents was selected using a random digit 

dial of listed and unlisted residential telephone numbers. The 

sample was divided into two groups: noninjured controls 

and population cases, the latter group comprising individuals who incurred an earthquake-related injury but were not 

treated at a County hospital or flown by helicopter to a 

hospital outside the County. The noninjured controls were 

frequency matched to hospital and dead cases on general 

area of residence at the time of the earthquake. Three residential strata were defined by aggregates of contiguous zip 

codes in the County. The goal was to interview two noninjured controls for each hospital or dead case. 

The injury status of individuals from the population sample was not determined in advance of the interview. Injury 

information collected in the interview was used to assign 

persons post-hoc to the appropriate category. Based on the 

results of the pilot testing, 20 percent of the population 

sample was expected to have incurred an earthquake-related injury and thus qualify as population cases? With such a 

background injury rate, it would be necessary to interview 

2.5 members of the population sample for each hospital or 

dead case to achieve the desired 2:l ratio of noninjured 

controls to hospital/dead cases. Population cases will be 

studied separately from hospital and dead cases. 

Hospital and dead cases or their proxies were interviewed from July 19, 1990, to March 31, 1991. Noninjured controls and population cases were interviewed over 

the period of March 24, 1991, to August 3 1, 199 1. 

The collected data is currently being coded for data entry. Three basic types of analyses will be performed. First, 

hospital and dead cases will be compared to noninjured 

controls to assess the significant risk factors for injury. 

Second, hospital and dead cases will be compared to population cases to evaluate the selection factors for seeking 

medical care among the injured. Third, several descriptive 

studies will be undertaken to assess the total morbidity 

and mortality in the County of Santa Cruz associated with 

the earthquake. 

TARGET POPULATION 

The case-control study target population was the residents 

of the County of Santa Cruz at the time of the earthquake. 

The County is highly diverse with respect to geography and 

the demographic composition of its population. At the time 

of the earthquake, the County's population was approximately 235,335 (California Department of Finance, 1990). Approximately two-fifths of the population lived in one of the 

four incorporated cities-Santa Cruz, Watsonville, Capitola, 

and Scotts Valley-whereas the remainder lived in unincorporated areas of the County (table 4). The two major cities 

are Santa Cruz (n=51,082) and Watsonville (n=30,882) 

which are located in the coastal parts of north and south 

County, respectively. 

The populations in the north and south County are quite 

distinct. The residents of north County are predominantly 

white and English speaking and have a relatively high socioeconomic status. Many are employed in the computer 

and electronics industries. Nearby Silicon Valley and tourism drive the local economy. A large university, University 

of California at Santa Cruz, draws many students and professionals to the area. 

^his background rate is in keeping with the results of the case-control 

study of the 1988 Armenian earthquake, in which 30 percent of the selected controls were found to have been injured but not hospitalized (Armenian and others, 1992). 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES 

Table 4.-Population characteristics of the County of Santa Cruz, January I, 1990, estimates 

Source: California Department of Finance (1990, p. 51)] 

Locat ion Number (Percent) of People 

Incorporated cities 

Santa Cruz (north County) 51,082 (22 pet) 

Watsonville (south County 30,882 (13 pet) 

Capitola (north County) 10,450 (4 pet) 

Scotts Valley (north County) 9,460 (4pct) 

Total incorporated 101,874 (43 pet) 

Unincorporated areas 133,461 (57 pet) 

Grand Total 235,335 (100 pet) 

In contrast, Watsonville has an agricultural economy 

with a large Hispanic population that fluctuates seasonally 

due to migrant farm workers. Many of the Hispanics are 

poor, and an undetermined number are undocumented. A 

significant fraction of the Hispanic community lives in severely overcrowded dwellings; often two or three families 

live in a house designed for one family. Others live in 

converted garages, shacks and labor camps. 

The County of Santa Cruz can also be categorized by 

geography. Much of the County's population lives along 

the coastal regions in relatively urbanized cities. These 

coastal cities, running from north to south, include Davenport, Santa Cruz, Live Oak, Capitola, Soquel, Aptos, Rio 

del Mar, La Selva Beach, Freedom, and Watsonville. The 

rest of the population lives in the Santa Cruz Mountains, 

which run from the northwest to the southeast parts of the 

County. Cities in the mountains include Boulder Creek, 

Ben Lomond, Brookdale, Felton, Los Gates, Mt. Herman, 

and Scotts Valley in the north, and Corralitos in the south. 

The mountainous population itself is quite diverse and different from the coastal residents. The residents range from 

wealthy growers, commune dwellers, and artists to persons 

in communities as poor as ~~~alachia.~ Most are white 

and generally very self-reliant-an attitude which may affect medical seeking behaviors. 

Geography also serves to isolate the population from 

neighboring counties. The County is bounded by the Pacific 

Ocean and the Santa Cruz Mountains. Only a few highways 

lead out of the County, and some of these were closed for 

days after the earthquake due to landslides and other damage. 

This geographic and demographic diversity is likely to 

have influenced the types of risk factors for injury and opportunities for medical treatment experienced by the population during and after the earthquake. 

In fact, the catchment areas for the three County hospitals-the main source of hospital cases-have almost no 

'personal communication from a number of local and Federal officials. 

including 1990 U.S. Census workers. 

overlap. Watsonville Hospital serves the south County 

area. Dominican and AM1 are located about 1 mile from 

one another in the Santa Cruz city area and serve the north 

coastal and mountainous regions. This can be seen in 

table 5, which presents the distribution of target population 

of the County hospital cases by hospital visited in the ascertainment period and city of residence at the time of the 

earthquake. Almost all of the potential cases from Watsonville went to Watsonville Hospital (184 out of 191), 

whereas the vast majority of Santa Cruz residents went to 

either Dominican or AM1 Hospitals (155 out of 158). 

DEFINITION OF STUDY GROUPS 

prising hospital and dead cases, and a population sample, 

divided into noninjured controls and population cases. The 

hospital and dead cases are a subset of those from the descriptive study, having to meet more stringent requirements for entry into the case-control study. The eligibility 

criteria for both studies are summarized and compared in 

table 6. The study group definitions for the case-control 

study are described in the following two sections. 

The case-control study consists of a case group, comCASE GROUP: HOSPITAL AND DEAD CASES 

I 

Hospital cases were defined by the following criteria: (1) 

they were residents of the County at the time of the earthquake; (2) they were physically injured in the County during the shaking from the mainshock, or in the subsequent 

72 hours as a result of the earthquake or its aftershocks; 

and (3) they were treated at a County hospital or were 

flown by helicopter to a hospital outside the County within 

72 hours of the earthquake. 

Dead cases met the following criteria: (1) they were residents of the County at the time of the earthquake and (2) 

they were killed in the County by physical injuries during 

the shaking from mainshock, or in the subsequent 72 hours 

as a result of the earthquake or its aftershocks. 
LOSS ESTIMATION AND PROCEDURES 

Table 5.-Distribution of potential cases by hospital visited and city of residence 

Cities within County Hospital 

of Santa C~UZ Watsonville Dominican AM1 Total 

Aptos 

Ben Lomond 

Boulder 

Creek 

Brookdale 

Capi tola 

Corralitos 

Felton 

Freedom 

La Selva Beach 

Live Oak 

Los Gatos 

Mt. Herman 

Santa Cruz 

Scotts Valley 

Soquel 

Watsonville 

Zayante 

Cities outside County 11 

of Santa Cruz 

No residence information 3 6 

To make the sampling frame for hospital cases and noninjured controls comparable, hospital cases were excluded 

if: (1) they lacked a home phone at the time of the interview or (2) they were living in institutional or commercial 

facilities at the time of the interview. These exclusion criteria will be waived if it can be determined from the interview that the case's condition is a consequence of the 

earthquake. For example, cases living in motels, shelters, 

or tents because the earthquake destroyed their homes are 

not excluded. The residential phone requirement will be 

waived for cases who usually had a home phone but who 

lacked one at the time of the interview because of earthquake-related circumstances. 

POPULATION SAMPLE: 

NONINJURED CONTROLS AND POPULATION CASES 

A random sample of current County of Santa Cruz residents was taken for comparison to the case group. This 

population sample comprised two groups, noninjured controls and population cases. 

Noninjured controls were defined by the following criteria: (1) they were residents of the County when the earthquake occurred; (2) they were present in the County when 

the earthquake occurred; (3) they were alive at the time of 

the interview; (4) they were residents of the County at the 

time of the interview; and (5) they were not injured because of the earthquake in the ascertainment period. 

Population cases satisfied criteria (1) through (4) used 

for the noninjured controls, plus two additional ones: (5) 

they sustained an earthquake-related injury during the ascertainment period and (6) as a result of these injuries, 

they did not seek treatment at a County hospital or were 

not flown by helicopter to a non-County hospital during 

the ascertainment period. Individuals who met the population case criteria and who sought treatment at other medical facilities (for example, private doctor's offices, clinics) 

were classed as population cases. 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A47 

Table 6.-Comparison of case and control definitions in the case-series and case-control studies 

Case series study 

Cases 

Group Criteria 

Hospital Dead 

Case-control study 

Cases Population sample 

Population Noninjured 

Hospital Dead cases controls 

Injured during shaking and (or) in Yes 

next 72 hours in County 

Earthquake-related injuries Yes 

Visited a County hospital or flown Yes 

by helicopter ambulance to out-ofcounty hospital 

Resident of County at time of quake Not required 

Resident of County at time of Not required 

i nterview 

Had home phone at time of interview Not required 

Living in an institutional facility Included 

at time of interview 

Yes Yes Yes Yes 

Yes Yes Yes Yes 

Somet imes Yes Sometimes No 

Notrequired Required Requ i red Requ i red 

Not required Not required Not required Required 

Not required ~equiredl NA- Requ i red 

Included ~xcluded~ NA- Excluded 

No 

N A 

No 

Required 

Required 

Required 

Excluded 

Alive at the time of the interview Not required Not required Not required Not required Required Required 

cases without phones at the time of the interview will be included if their phone status was related to the earthquake (for example, 

they were institutionalized after their injuries, or they lived in temporary shelters because their homes were destroyed by the earthquake). 

^cases living in institutions at the time of the interview for reasons related to the earthquake will be included, 

NA means "not applicable. " 

CASE ASCERTAINMENT 

(HOSPITAL AND DEAD CASES) 

Hospital and dead cases in the case-control study are a 

subset of those in the case-series study. Thus, the former 

were ascertained in the same manner as the latter as described in the section, "Preliminary Studies." 

As noted in that section, the review of medical records 

and helicopter logs resulted in 574 persons being targeted 

for an interview. Another five persons were ascertained in 

the process of tracing the cases who were identified from 

the medical records and helicopter logs. These five persons 

met the case definition and were interviewed. Thus, the 

final total population targeted for an interview was 579. 

Reviews of the records of hospital and dead cases for 

whom an interview was obtained are underway to determine 

if they met the eligibility requirements for the case-control 

study. Preliminary results of this review are presented in the 

section, "Preliminary Progress Report on Case-Control 

Study." 

POPULATION SAMPLE SELECTION PLAN 

A population-based stratified random sample of current 

County residents was selected using a random digit dial of 

listed and unlisted residential phone numbers in the County. 

Selected individuals were screened for eligibility on the 

I 

residency requirements (that is, living and present in the 

County at the time of the earthquake) before being enrolled. 

As indicated above, the population sample included both 

persons who were not injured by the earthquake (noninjured controls) and those who were injured but did not go 

to a hospital (population cases). The injury status of enrolled individuals was not determined before the interview 

began. Thus, participants were assigned to the appropriate 

study group after the interview was completed. 

To increase statistical power, an attempt was made to 

select two noninjured controls for each hospital or dead 

case. It was estimated that 20 percent of the County population and selected sample would have been injured (see discussion below). Thus, it was deemed necessary to choose 

2.5 eligible individuals .to achieve the desired 2:l ratio of 

noninjured controls to hospital and dead cases. 

Noninjured controls were frequency matched to hospital 

and dead case on general area of residence at the time of 

the earthquake, which is likely to be an important confounder (see section, 'Target ~o~ulation").~ Matching 

closely on residential location was not done because this 

could result in overmatching on building type, a primary 

risk factor of interest. 

In theory, residential strata should be as similar within 

and as different between strata as possible with respect to 

the geography and sociodemographic characteristics. This 

ideal was approximated by creating three strata of contiguous zip codes which were geographically distinct (table 7; 
A48 LOSS ESTIMATION AND PROCEDURES 

fig. 1). Stratum 1 covered the north mountainous areas, 

where most of the County's mountaih population lived. 

Stratum 2 corresponded to the north coastal region and included the cities of Santa Cruz, Capitola, Soquel, and Aptos. Stratum 3 covered the entire south County, including 

Watsonville, where most of the County's Hispanic population lived. 

Noninjured controls were assigned to a stratum as part 

of the initial screening process. A random sample of listed 

and unlisted residential phone numbers for the County was 

computer generated.1o Each number had an equal probability of being selected. Enrolled individuals were asked 

for their home zip code at the time of the earthquake before the interview began. Their answer determined the 

stratum into which they fell. Once the proper number of 

noninjured controls was selected for a stratum, additional 

persons initially selected from that stratum were not enrolled. 

The matching information, home zip code at the time of 

the earthquake, was also obtained for hospital and dead 

cases from the questionnaire. 

This sampling plan, unusual for a case-control study, 

was adopted because it was deemed both important and 

feasible. It was important because it would facilitate the 

9~ confounder (for example, residential stratum) for a risk factor of 

interest (for example, being in a building when mainshock began) can 

make it appear that there is a relationship between the risk factor of interest and the outcome of interest (for example, injury) when, in truth, there 

is none, and vice versa. Technically, a risk factor, C, is a confounder for 

the risk factor of interest, R, if: (1) C is an independent risk factor for the 

outcome of interest, I, and (2) C is distributed differently among the different levels or categories of R (for example, the distribution of residential stratum is different among those in a building and those not in a 

building when the shaking began), and (3) R does not cause C or viceversa. One method to control or adjust for a confounder is to match cases 

and controls on that confounder. This is done when it is thought that a 

random sampling plan without matching may not produce enough cases 

and controls at each level of the confounder to examine the independent 

effect of other risk factors, holding the effect of the confounder constant, 

in the analysis phase. A disadvantage of matching is that one cannot examine the association between the confounder (for example, residential 

stratum) as a risk factor and the outcome of interest (for example, injury). Thus, in general, one tries to minimize the number of risk factors 

that are matched. In this study, matching on residential stratum was performed because this variable was thought to be a potential confounder, 

and a sampling plan was desired that would ensure an adequate number 

of cases and controls in each of the three strata. This matching will not 

preclude analyses of risks associated with other unmatched and potentially important risk factors (see section, "Purpose of Study"), including sociodemographic characteristics such as age, sex, and level of education. 

 h he telephone numbers were provided by the consulting firm Survey 

Sampling, Inc. (SSI), which had performed a Waksberg-like technique on 

all of the residential telephone prefixes in Santa Cruz County. SSI identified all "working blocks" of telephone numbers in the County. Details of 

the process will be provided in future reports. 

Table 7.-Control selection strata by general area of residence in the County of , 

Santa Cruz at the time of the earthquake 

Zip code City 

Stratum 1: North 

Mountainous County 

95005 Ben Lomond 

95006 Boulder Creek 

95007 Brookdale 

95018 Fel ton 

95030 Los Gatos 

95041 Mount Herman 

95066 Scotts Valley 

Stratum 2: North Coastal 

County (predominantly 

nonmountainous) 

Aptos 

Capitola 

Davenport 

Santa Cruz 

Live Oak 

UC Santa Cruz 

Santa Cruz 

Soquel 

Stratum 3: 

South County 

95076 Watsonville 

9501 9 Freedom 

study of persons injured by the earthquake who would not 

otherwise be ascertained as hospital and dead cases. The 

number of such persons was expected to be high. In the 

pilot test of the draft questionnaire-to refine the questions for inclusion in the final version~on asmall random 

sample of County residents", it was found that 20 percent 

reported an earthquake-related injury of any severity level 

that was not treated at a hospital.12 This rate, if borne out 

in the full-scale study, would translate into some 47,000 

earthquake-related injuries in County residents. 

The medical significance of injuries among population 

cases was also considered. Most population cases were expected to have minor injuries. However, the great majority 

llsee section, "Questionnaire and Interview" for a brief description of 

the pilot testing procedures. 

^~n elevated background rate is consistent with the results of the 

case-control study of the Armenian earthquake, in which an even higher 

proportion (30 percent) of the selected controls was found to have been 

injured but not hospitalized (Armenian and others, 1992). 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A49 

of all injuries caused by the earthquake was anticipated to 

be moderate to minor in nature. Only five County residents 

were killed^, and only 33 persons had injuries serious 

enough to be admitted to a hospital. Most of the moderately injured were probably seen at a County hospital or helicoptered out of the County within the ascertainment 

period, since alternative care was largely unavailable. Furthermore, the medical abstracts indicated that many of the 

hospital visitors sustained relatively minor injuries. Thus, 

considerable overlap in the level of injury severity among 

the hospital and population cases with minor injuries was 

expected. Therefore, collecting information on the population cases was seen as essential in estimating the true 

earthquake-related injury burden in the County. 

The sampling plan was deemed feasible because the expected 20 percent background injury rate was high enough 

to provide sufficient numbers of population cases to study 

in a meaningful fashion. In fact, population cases composed 

15 percent of the population sample that was interviewed 

(see section "Preliminary Progress Report on Case-Control 

Study"). This injury rate was still adequate to produce 

enough population cases to study. 

RISK FACTORS FOR PHYSICAL INJURY 

13~he sixth person killed in the County was a resident of Napa, Cali- presents an the risk factors for physical 

fornia. injury that were examined in the interview. The primary risk 

Figure 1.Ã‘Sant Cruz County residence strata. Bold lines are zip-code boundaries; light lines are County and city,boundaries. 
LOSS ESTIMATION AND PROCEDURES 

Table 8.-Risk factors for physical injury 

During the shaking of the main In the 72 hours after the shaking 

earthquake of the main earthquake stopped 

Physical environment 

Inside a building 

Inside a vehicle 

Outside, within 20 feet of a building 

Outside, further than 20 feet 

from a building 

0 ther 

Physical environment 

Inside a building 

Inside a vehicle 

Outside 

0 t her 

Being trapped Being trapped 

~rotective/rescue behaviors 

Oneself 

Other people 

Pets 

~hings/belongings 

~escue/retrieval behaviors 

Oneself 

Other people 

Pets 

~hings/belongings in buildings 

Clean-up activities 

factors of interest were physical environments, entrapment, 

individual behaviors, and their interactions. Potential confounders, including demographic characteristics, were also 

explored. Risks posed during each time period-during the 

shaking of the mainshock and in the next 72 hours-were 

examined separately. 

Physical environments were broadly defined as being inside a building, in or on a vehicle, outside and within 20 feet 

of a building, outside and further than 20 feet from a building, and "other." The category of "other" would include, for 

example, persons in a car which is inside an enclosed garage. 

Risk factors within each environment will be explored 

through subgroup analysis. For example, for those within a 

building during the shaking, the hazards associated with 

falling furniture, collapsing walls, gas leaks, exposed live 

wiring, and so forth will be examined. The type of building 

will also be explored (that is, buildings were broadly classified as residential, commercial, industriallfarm, or public1 

institutional). The age, construction materials, and number of 

floor levels of the building, as well as respondent's location 

within it (floor level, room, and so forth) will be determined. 

Respondents were also asked whether or not the building was 

bolted to its foundation. The year of construction is considered a potential risk factor because seismic building codes 

changed and improved over time; thus, for example, older 

brick buildings (which have not been retrofitted) are expected to be more hazardous than newer ones. For practical 

reasons (for example, knowledge limitations of layperson 

respondents), the only attempt made through the questionnaire to infer structural type was through a description of 

building materials (for example, wood, brick, and so forth).14 

For those outside further than 20 feet from a building, the 

dangers posed by landslides, floods, and human-made structures such as collapsing bridges and fences will be explored. 

Entrapment, or inability to move, can be caused by both 

physical objects which restrict movement, or by injuries 

(which themselves could be the result of physical objects). 

The interview distinguished between these two types of entrapment, which will be treated separately in analysis. Elements of entrapment which were examined include the 

causative agent(s), the duration of entrapment, and the place 

of entrapment. The duration of entrapment was broken 

down into the intervals between first being trapped, discovered by others (when relevant), and rescued or self-freed. 

Personal behaviors examined include actions taken to protect oneself, other people, pets, and belongings or things. 

Rescue or retrieval of other persons, pets, and things were 

also explored as well as clean-up in earthquake damaged 

areas. Behaviors specific to each environment were scrutinized. For example, for those in a building during the shaking, standing in a doorjamb, holding onto to something, 

getting under a table or desk, and running outside were 

examined. For those in a moving vehicle during the shaking, actions evaluated included continuing to drive, pulling 

over and stopping, getting out of the vehicle, and so forth. 

Demographic characteristics which were collected include 

age, sex, marital status, occupation, ethnic origin, level of 

education, number of dependents, and home ownership. The 

importance of being with other people, including dependents 

or disabled persons, during the shaking was examined. Other 

risk factors which were explored include preexisting medical 

conditions and mobility, prescription drug use, and alcohol 

consumption in the 2 hours before the mainshock. 

OUTCOME MEASURES FOR PHYSICAL IN JURY 

^verification of building type required a field follow-up after preliminary data analysis (Jones and others, 1993b). 

Injuries directly and indirectly associated with the earthquake were included in the study but will be analyzed sep- 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A5 1 

arately. Directly related injuries were defined as those 

caused by the seismic forces during the shaking of the 

mainshock or its aftershocks. This class of injuries also 

included persons injured in the postdisaster period while 

engaged in protective, rescue, retrieval, or clean-up activities because of the earthquake. For example, this category 

would include persons injured while cleaning up or retrieving belongings from their earthquake-damaged homes. 

Indirectly related injuries were those whose relationship to 

the earthquake is less clear. For example, a person injured 

in a car accident because of excess alcohol consumption 

due to stress brought on by the earthquake would fall into 

this category. 

Outcomes which were excluded from this study are: (1) 

intentional physical injuries, that is, injuries that were selfinflicted or caused by assaults, and (2) medical conditions 

other than injuries which may or may not have been associated with the earthquake, including but not limited to 

psychological trauma, communicable diseases, cardiovascular events, and complications of pregnancy. 

The outcomes of interest are earthquake-related physical 

injuries that occurred during the shaking from the mainshock and the subsequent 72 hours. Injuries were defined 

as physical trauma of any severity level. Multiple injuries 

to the same person were described individually. Information collected on each injury included the type of injury, 

affected body part, the cause of the injury, and the location 

of the person when the injury occurred. Injuries that occurred during the shaking from the mainshock will be analyzed separately from those that occurred in the subsequent 

72 hours. 

Each injury will be coded using the Abbreviated Injury 

Scale 1990 Revision (AIS) (Association for the Advancement of Automotive Medicine, 1990). The 1990 AIS assigns a unique seven digit number to each injury diagnosis. 

The code describes an injury according to body region 

where it occurs, the type of anatomical structure affected 

(nerves, and so forth), the specific nature of the injury or 

anatomic structure (for example, abrasion, amputation, loss 

of consciousness, cervical injury, and so forth), the severity 

level of injury, and the AIS severity score. 

The AIS severity score is an anatomically based system 

that categorizes injuries by six body regions using a six 

point ordinal scale ranging from minor (AIS=l) to currently unbeatable (AIS=6) injuries. The other four scores are 

AIS 2=moderate, AIS 3=serious, AIS 4=severe, and AIS 

5=critical. A score of nine is assigned for injuries of unknown severity. AIS scores reflect not only potential lethality but also diagnostic certainty, as well as the 

expected duration and degree of recovery with or without 

medical treatment (Association for the Advancement of 

Automotive Medicine, 1990). 

The AIS severity scores are based on only anatomical 

injury and not physiological status. This property means 

that a particular injury can have only one AIS score that 

does not change with time. In contrast, injury severity systems which include physiological parameters, such as the 

Trauma Score, may produce many scores for the same injury as the patient's physiological status changes with 

time. The AIS' anatomical basis also means that it is a 

measure of the severity of the injury itself and not of the 

consequences of injury such as death or disability, the latter which may be affected by availability and efficacy of 

treatment (Association for the Advancement of Automotive Medicine, 1990). 

AIS scores will be computed from interview data (all 

case groups) and from medical abstracts and autopsies 

(hospital and dead cases only). The scoring from each 

source (interview and medical records) will be done separately and blinded. AIS scoring employs precise medical 

information of sufficient detail usually found only in medical records. 

Injury Severity Scores (ISS's) will be computed separately from AIS's derived from the interview data (all case 

groups) and from medical recordslautopsies (hospital and 

dead cases only). Analyses which rely on the ISS will be 

done twice, using each set of ISS's. 

For the purposes of analysis, outcomes for each individual will be described in two ways: (1) the absence or presence of physical injury of any level and (2) the overall 

level of injury severity. Overall injury severity is a measure of the total impact of all injuries a person may have. It 

will be assessed using the ISS (Baker and others, 1974). 

The ISS is the sum of the squares of the highest AIS severity code in each of the three most severely injured ISS 

body regions. The ISS body regions are slightly different 

from the AIS classifications but are intraconvertable. The 

ISS has a range of 1 to 75. The maximum score of 75 is 

produced in one of two ways: either a person has three 

AIS level 5 injuries, or at least one AIS level 6 injury. 

DATA COLLECTION PROCEDURES 

MEDICAL ABSTRACTS 

The majority of relevant County hospital records were 

abstracted by the team described above from November 

1989 to June 1990; the rest were abstracted in September 

199 1. The helicopter-mediated visits to out-of-County hospitals will be abstracted by the same team in future work. 

The summary judgment of medical diagnosis was used to 

determine which County hospital visitors to target for a 

follow-up interview. 

HELICOPTER AMBULANCE LOGS 

The premedical care logs of all local ambulance services 

were reviewed for the ascertainment period by the California 

Office of Emergency Services. In addition, the California 
A52 , LOSS ESTIMATION AND PROCEDURES 

Department of Forestry and Fire Protection was contacted 

for a list of persons they helicoptered to neighboring County 

hospitals. Persons whose premedical care record indicated 

they were injured or did not list a diagnosis were targeted 

for a follow-up interview. 

QUESTIONNAIRE AND INTERVIEW 

Information on potential hazards, injuries, and other factors of interest was collected through a structured interview. The same questionnaire was administered to cases 

and controls, and their proxies when necessary. 

The questionnaire was developed in English, and translated into Spanish to accommodate the large Hispanic population that lives in the southern part of the County. The 

translation was done by a doctoral student in public health 

who has extensive experience in health survey design and 

translation. Like most of the Hispanic residents of the 

County, the translator is of Mexican descent and was able 

to translate the questionnaire into an appropriate Spanish 

dialect. The Spanish version was back-translated into English by two qualified persons selected by the translator. 

The English version was pilot tested in June and July 1990 

on a random sample of approximately 30 County residents 

who were not hospital cases; the Spanish version was 

comparably tested on a sample of 10. The versions were 

modified based on the lessons learned from pilot testing. 

The questionnaire had eight parts, sections A to H. Section A collected demographic information and determined 

the physical environment (in a building, in a vehicle, or 

outside) in which the case or control was when the main 

earthquake began. The answers given in section A directed 

the respondent to either section B, C, or D. These sections 

asked about exposures, human behaviors, and injuries during the 15-second shaking period of the mainshock for 

those in a building (section B), in or on a vehicle (section 

C), or outside (in close proximity to a building or away 

from buildings entirely) (section D) when the earthquake 

began. Section E gathered information about hazards and 

injuries in the 72 hours after the mainshock. It also queried 

about being trapped and rescued during the shaking and 

subsequent 72 hours and evaluates the use and efficacy of 

the 91 1 emergency response system. Section E was administered to all respondents. Section F collected information 

on health care utilization. It was given only to those who 

reported an injury during the shaking or the next 72 hours. 

Section F also collected information on disabilities associated with the reported injuries. Section G gathered more 

demographic information, and data on drug and alcohol 

use, physical mobility, health insurance and preexisting 

medical conditions. Section H was the closing section of 

the interview and asked for future contact information. 

The questionnaire took approximately 30 minutes to an 

hour to administer depending on the experiences of the respondent. The interview was conducted by a staff of 

trained bilingual interviewers located in the County. It was 

done in either English or Spanish depending on the preference of the respondent. It was generally administered by 

telephone at the respondent's home. However, interviews 

were conducted at a work phone, or in person through 

home visits if the respondent requested it. In-person interviews were also done for hospital and dead cases (or their 

proxies) who could not be reached by home phone because either they lacked a home phone or the study could 

not trace the phone number. 

Proxy interviews were obtained for dead cases or for hospital cases who died since the ascertainment period. Proxies 

were sought for hospital cases who were unavailable during 

the interviewing phase, or who refused to do the interview. 

Proxy interviews were also done for study subjects who 

were under 13 years old, or who were too mentally or physically disabled to do the interview. 

For respondents under 13 years old, proxy interviews were 

requested of parents or guardians. For other categories, 

proxy interviews were sought from adult next of kin. However, when next of kin were unavailable, other adults who 

were knowledgeable about the respondent were solicited. 

Minors between 13 and 17 years old were interviewed 

directly. However, permission to do the interview was first 

obtained from parents or guardians. 

RECRUITMENT AND ENROLLMENT OF 

HOSPITAL AND DEAD CASES 

The recruitment and enrollment of hospital and dead 

cases began on July 19, 1990, and was completed on March 

3 1, 199 1. The process involved tracing, contacting, and obtaining informed consent from cases or their proxies in 

order to administer the interview. 

TRACING METHODS AND COMMUNITY OUTREACH EFFORTS 

Tracing efforts began with the information contained in 

the medical records. However, phone numbers and addresses were either missing or outdated for many cases. Therefore, the following additional sources were employed to 

trace cases or their proxies: (1) individuals including neighbors, friends, relatives, and apartment managers; (2) private 

and public agencies (for example, nonprofit social service 

groups, the Red Cross, churches, and government agencies 

including U.S. Postal Service, Voter Registration, California 

Department of Motor Vehicles, Planning Departments of the 

incorporated cities and unincorporated areas of the County); 

(3) a national credit bureau; (4) former and current employers; (5) Federal Express, (6) publicly available sources 

(newspapers, Directory Assistance, hard-bound and on-line 

criss-cross directories); and (7) a prominent Hispanic community organizer hired as a consultant to the study. 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A53 

Tracing methods were chosen to protect the confidentiality 

of cases. No information about the study or the case was 

divulged to past or current employers. When speaking with 

other categories of individuals, or public and private agencies, interviewers identified themselves as from the study but 

did not reveal that the case was injured or visited a hospital. 

A bilingual community outreach campaign was initiated 

in August 1990 with the assistance of the community organizer. The purpose of the campaign was to familiarize 

the community with the study, and to encourage people 

who met the hospital case definition to contact the study 

for an interview. Flyers in Spanish and English were prepared and distributed to social service agencies, labor 

~ camps, churches, employment agencies, supermarkets, and 

other public places. Radio and television public service 

announcements on the study ran on local stations. The 

major County newspapers donated advertisement space to 

explain the study. The authors were also interviewed by 

local radio stations and newspapers. 

CONTACT AND ENROLLMENT 

In general, the study first contacted cases or their proxies 

at their homes by phone. When this was not possible, initial contact was made through other phone numbers (when 

available), home visits, or mailings which asked the targeted individuals to call the study, collect if necessary. Phone 

contact and home visits were made by the interviewers. 

When a household was contacted, the interviewer asked 

to speak to the case or his or her proxy, if necessary. Once 

the desired person was reached, she was read an introductory script describing the study. To confirm that the proper 

person had been contacted, the interviewer asked for the 

case's age. When relevant, the interviewer also asked if 

the case visited the appropriate hospital in the 72 hours 

after the earthquake. If the reported age was within three 

years of that noted on the medical record or autopsy, and 

(or) the respondent confirmed a recorded hospital visit, the 

respondent was read an informed consent statement which 

describes the study's purpose, risks, and benefits. Respondents who granted consent were considered enrolled. The 

questionnaire was administered immediately after consent 

was given whenever possible. If this was not possible, the 

interview was scheduled for a later time. 

If the reported age or hospital visit did not match the 

information in the medical records or autopsy report, the 

respondent was thanked, the session was ended, and the 

search for the correct respondent was continued. 

1991. The selection protocol was pilot tested in the first 

half of March 1991. 

In general, the recruitment and enrollment process involved identifying eligible households by calling lists of 

randomly generated County telephone numbers.15 Each randomly generated phone number was called up to six times, 

before it was discarded in favor of another one. The six calls 

were made at different times of day and on different days of 

the week. The interviewers proceeded down a list of such 

numbers until an eligible participant from a residence was 

enrolled. Persons reached at nonresidential numbers-businesses, government offices, jails, hospitals, nursing homes, 

and so forth-were not eligible for enrollment. 

When a household was reached, the interviewer asked to 

speak to an adult. Once an adult was on the phone, the 

interviewer confirmed that the correct number was dialed 

and that it was a home phone. If the number was nonresidential, the session was terminated. If it was residential, 

the interviewer determined whether the household was eligible, that is, whether it was located in the County. If the 

household was eligible, the adult-the informant-was 

asked to list all the current residents in the household in 

descending order of age. The sex and relationship to the 

informant was also obtained for each listed member. The 

interviewer recorded this information on a numbered roster form. A potentially eligible respondent from the numbered list was selected using a random number table. A 

proxy was obtained for selected respondents who were 

physically or mentally unable to answer questions, or who 

were under 13 years old. 

When the selected person or proxy came to the phone, 

she was asked the questions on residency which determined eligibility. If the selected individual did not meet 

the residency requirements described earlier, another person on the list was randomly selected. The same steps 

were repeated until an eligible person was identified from 

the household. The selected individual was read the informed consent statement. If consent was granted, the interview began or was rescheduled. If consent was denied, 

the interviewer attempted refusal conversion. If this failed, 

contact with the household was terminated. 

DATA MANAGEMENT AND QUALITY CONTROL 

MANAGEMENT OF INTERVIEW DATA ( 

Each study participant was assigned a unique identification number. A packet of materials was assembled for each 

hospital and dead case that included tracing information, 

interviewing materials, and a tracking sheet to record the 

RECRUITMENT AND ENROLLMENT 

OF THE POPULATION SAMPLE 

The population sample was recruited starting in the mid- ''see section "Population Sample Selection Plan" for a description of 

die of March 1991 and was continued through August how the numbers were generated. 
A54 LOSS ESTIMATION AND PROCEDURES 

time, day, and outcome of contacts. The packet for population sample members included the interview as well as materials for the selection of an eligible household member. 

Once an interview was completed, the interviewer filled 

out a final disposition summary sheet and reviewed his or 

her work for accuracy, neatness, and completeness. The interviewer supervisors and (or) study coordinator then editchecked the interview and went over any problems with the 

interviewer who conducted it. When information was incorrectly or incompletely ascertained, the interviewer was instructed to call the respondent back. The specific questions 

asked or reasked were noted on the final disposition sheet. 

A DBASE file was created to assist in tracing cases and 

monitor interviewing progress in cases and controls. Once a 

final disposition was reached, the information was recorded 

on the hard copy and was later transferred to the data base. 

After the interviewing phase was completed, the data base 

was stripped of identifying information (names, and so 

forth) to protect the confidentiality of those interviewed. 

INTERVIEWER TRAINING 

All interviewers received two days of training at the time 

of hire on general interviewing techniques, and procedures 

specific to the study. They received another two days of 

training on the population sample selection protocol in 

March 199 1. The importance of maintaining the confidentiality of information collected was highly stressed. The 

training included role playing with the interview and doing 

practice interviews on noncase County residents. Additional experience was obtained during the pilot testing phases. 

The interviewers were periodically monitored while interviewing to improve quality control. 

CODING QUESTIONNAIRES 

The answers to close-ended questions on the questionnaires were preceded. Coding of the open-ended questions 

is currently being done by the Johns Hopkins team. Spanish comments have been translated into English before 

being coded with the English responses. For a subset of 

the data, coding assignments to each open-ended question 

will be made independently by at least two persons so that 

interrater reliability can be assessed. Coders will also be 

asked to assign codes to the same data on different days to 

assess intrarater reliability. 

DATA ENTRY 

Data entry of the coded questionnaires and the medical 

abstracts was subcontracted to a data entry firm in Baltimore, Maryland. The data was keypunched twice and verified for accuracy. The Johns Hopkins team is currently 

doing additional analyses of the data tape to check for 

consistency and accuracy. 

ASSESSMENT OF BIAS IN SELF-REPORTED INFORMATION 

Information collected in the interview has two sources 

of potential bias, bias in the accuracy and in the repeatability of self-reported information. Accuracy for hospital 

and dead cases will be assessed by comparing the degree 

of correspondence between injury information reported in 

the interview and that contained in the medical records or 

autopsies. 

Medical records are generally considered to be more accurate and complete than retrospective self-reports. However, this assumption is questionable for the first 12 to 24 

hours after the earthquake, when the hospitals (especially 

Watsonville) were overwhelmed with visitors and treatment took a higher priority than keeping records. The hospitals reportedly resumed their normal routines after the 

first 24 hours. To adjust for variable degrees of completeness of the medical records, the accuracy analysis will be 

stratified by hospital and day of arrival at the emergency 

room. 

Accuracy for all study groups will also be assessed by 

comparing self-reports of successfully reaching the 911 

system to another dataset containing the logs of all 911 

calls received in the 72 hours after the earthquake. The 

911 dataset was compiled by study collaborator, Jim 

Schneider. 

STATISTICAL ANALYSIS 

Three basic types of analysis will be performed on the 

collected data: (1) a case-control analysis, which compares 

hospital and dead cases to noninjured controls to evaluate 

the significant risk factors for earthquake-related injury; 

(2) a study of selection factors for seeking medical treatment among the injured, which compares hospital cases to 

population cases that did not seek medical attention; and 

(3) descriptive analyses which estimate total injury morbidity and mortality in the County of Santa Cruz related to 

the earthquake. 

CASE-CONTROL ANALYSIS 

The relationship(s) among the injury and various risk 

factors will be analyzed through a series of steps. Exploratory data analysis will be employed to identify significant 

risk factors. Injury outcomes for each case will be characterized in two ways: (1) the presence or absence of injury 

(a binary outcome variable) and (2) the overall level of 

injury severity as measured by the ISS (an ordinal outcome variable). Separate analyses will be performed for 

cases who were injured during shaking, versus those who 

were injured in the next 72 hours. Some cases were injured in both time periods, and attempts will be made to 

model the dependence of being injured in the postshaking 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A55 

phase on being injured during the mainshock. Separate 

analyses will also be conducted for injuries directly and 

indirectly related to the earthquake. 

When the outcome variable is the presence or absence of 

injury, odds ratios can be computed. Univariate and bivariate analysis will first be performed followed by multiple 

logistic regression to characterize the independent risk factors and their interactions adjusted for confounders. The 

relative odds associated with being in different physical 

environments, broadly defined (that is, building, vehicle, 

outside) will be evaluated. Subgroup analyses will also be 

performed for risks within each physical environment. 

The ISS has a range of 1 to 75, with higher values representing greater injury severity. When the ISS is the outcome variable, it will be used to create categories of injury 

severity (for example, mild, moderate, severe, lethal, and 

so forth). ISS ranges will define each category. Logistic 

regression will be done where the outcome variable is defined as injury severity class (for example, severe vs. moderate; severe vs. all other) and the dependent variables are 

the same as before. Several categorization schemes have 

been used by other investigators and will be explored here 

(MacKenzie and others, 1986; Copes and others, 1988). 

MEDICAL TREATMENT SELECTION 

FACTORS ANALYSIS 

The selection factors for medical treatment among the 

injured will be evaluated in several ways. Injury severity as 

a selection factor will explored by comparing the distribution of ISS's for hospital cases to the distribution for population cases with back-to-back stem and leaf plots. Multiple 

logistic regression will also be performed where the outcome variable will be sought or did not seek medical treatment (that is, y=l for hospital cases and y=0 for population 

cases). The independent variables will be the various potential selection factors including but not limited to perceived 

and actual injury severity level, possession of health insurance, entrapment due to the earthquake, preexisting medical 

conditions and mobility, the needs of others, and sociodemographic features such as age, sex, and ethnic origin. 

DESCRIPTIVE ANALYSES 

The total burden of physical injury in County of Santa 

Cruz residents associated with the Loma Prieta earthquake 

will be estimated. Both hospital and population cases, 

appropriately weighted, will be used to this end. Total morbidity and mortality will be calculated as well as age-, sex-, 

ethnic origin- and injury severity level-specific rates in the 

County population. Casualty rates for the disaster and postdisaster phases will be calculated, as will rates for injuries 

directly and indirectlyrelated to the earthquake. 

The ability to estimate rates is a special feature of this 

study. It is not possible to do this with most case-control 

study designs. However, it is possible to estimate rates in 

this study because estimates are available for both the size 

of the total population at the time of the earthquake and 

the fraction of the total sampled for each of the three geographic strata. 

Spatial analyses of injuries will also be performed in 

collaboration with study collaborator, Jim Schneider. 

Spot maps which distinguish cases by injury severity, 

physical environment, time period of injury, and so forth 

will be made. The relationship between injuries, distance 

from the epicenter, and zone of earthquake intensity will 

be investigated. 

PRELIMINARY PROGRESS REPORT ON 

CASE-CONTROL STUDY 

The following preliminary results should be interpreted 

with caution as they have not yet been thoroughly validated. Validation efforts are currently underway, the results of 

which will be reported in the future. 

HOSPITAL AND DEAD CASES 

As noted in section "Preliminary Results of the Descriptive Study," the size of the target population of potentially 

eligible hospital and dead cases was 579. Interviews were 

obtained for 482, or 83 percent of the target population. 

Another 31, or 5 percent refused to do the interview, and 

66, or 11 percent were lost to follow-up. 

Completed interviews were provisionally reviewed to 

evaluate which respondents were eligible for the case-control and descriptive studies. Recall that the eligibility criteria are more stringent for the former than for the latter 

study. Nearly three-fourths of those interviewed (n=358) 

are definitely eligible for both studies, including 10 percent (n=48) who moved out of the County of Santa Cruz 

after the earthquake. Twelve percent (n=58) are ineligible 

for either study because they were not injured or their injuries were clearly not earthquake related. About 5 percent 

(n=26) are eligible only for the case-series study because 

they were not County residents at the time of the earthquake or they lacked home phones at the time of the interview. Seven percent (n=36) met the residency and phone 

requirements of the case-control study but had injuries 

whose relationship to the earthquake is questionable. This 

last group will be included in the case-control study but 

will be analyzed separately from other cases. Finally, less 

than one percent (n=4) are possibly eligible for the caseseries but not the case-control study. 

Thus, the number of hospital and dead cases which qualify 

for the case-control study ranges from 3 10 to 394, depending 
A56 LOSS ESTIMATION AND PROCEDURES 

on the stringency of the case definition. The most stringent 

definition includes only those definitely eligible cases who 

had not moved outside the County by the time of the interview (that is, 358-48=3 10). The most lenient definition includes those who are definitely eligible for the case-control 

study, including those who moved out of the County, plus 

those for whom the earthquake relatedness of their injuries 

is unclear (that is, 358+36=394). 

To date, all but 3 (0.8 percent) of the 394 hospital and 

dead cases have been assigned to one of the three residential strata used to match noninjured controls to cases (the 

remaining three cases require additional information to 

classify). At the time of the earthquake, 38 cases (9.6 percent) resided in the north mountainous part of the County 

(stratum I), 179 (45.4 percent) lived in the coastal northern and midcounty area that includes the city of Santa 

Cmz (stratum 2), and 174 (44.2 percent) lived in the 

southern part of the County that includes Watsonville 

(stratum 3). 

POPULATION SAMPLE: NONIN JURED 

CONTROLS AND POPULATION CASES 

The reader is again cautioned that the figures, provided 

below, are preliminary and await verification. 

A total of 2,749 telephone numbers were called as part 

of the population sampling plan. Of these numbers, 780 

(28.4 percent) were nonhousehold numbers (for example, 

businesses, disconnected numbers, FAX or modem numbers, and so forth). Another 1,823 (66.3 percent) were determined to be households. The status of another 146 

numbers (5.3 percent) was unknown because no answer 

was ever obtained upon calling them. 

Of the 1,823 households contacted, 538 (29.5 percent) 

were ineligible because they were either located outside of 

the County boundaries or contained residents who had 

moved to the County after the earthquake. Another 432 

households (23.7 percent) were ineligible because they 

were contacted after the residential stratum from which 

they came was filled (see section "Population Sample Selection Plan"). Four households (0.2 percent) posed a language barrier which precluded doing the interview, six 

eligible households (0.3 percent) had otherwise eligible respondents who were not available during the study period 

(for example, were serving in the Persian Gulf War), and 

five households (0.3 percent) contained a person who had 

been previously interviewed by the study. 

One hundred thirty-six households (7.5 percent) refused 

to cooperate with the study, despite efforts to persuade 

them to do otherwise. An unknown proportion of these refusals almost certainly came from ineligible households, 

as many of them occurred before household eligibility 

could be determined; nearly a third of the cooperating 

households were found to be ineligible, suggesting that 

some of the uncooperative ones were ineligible as well. 

Study efforts at refusal conversion~conducted within the 

appropriate guidelines of informed consent-were quite 

successful. Initially, 299 households refused to participate 

in the study. It was eventually possible to convince 163 of 

them (54.5 percent of the refusals) to cooperate. 

Finally, 701 of the 1,823 households were eligible (25.5 

percent) and provided one eligible person each to interview 

(resulting in 696 completed interviews and 5 break-offs). 

These 701 respondents comprise the population sample for 

the case-control study. 

The population sample was distributed in the following 

manner. At the time of the earthquake, nearly 20 percent 

(n=138) lived in stratum 1, 45.6 percent (n=320) lived in 

stratum 2, and 34.7 percent (n=243) resided in stratum 3. 

Just over 15 percent (n=106) of the population sample reported an earthquake-related injury and thus were classed 

as population cases. The majority of these injuries were 

minor, although a systematic review of injury severity has 

not yet been done. The remainder were noninjured controls (n=594) or had an unknown injury status (n=l).16 

The proportion of reported earthquake-related injuries 

varied by stratum. The northern and mid-County coastal 

area had the lowest proportion of injuries, with 12.2 percent (n=39) of the 320 stratum 2 respondents reporting 

one. The northern mountainous region had the highest percentage of injuries, with 18.1 percent (n=25) of the 138 

stratum 1 respondents saying they were injured. The 

heavily Hispanic south County area followed closely behind, with 17.3 percent (n=42) of the 243 stratum 3 respondents reporting an injury. 

FUTURE DIRECTIONS 

Further characterization of injuries and their associations 

with potential risk factors is underway. These results will 

be reported when available. 

SAMPLE SIZE AND STATISTICAL 

POWER 

The maximum sample size of the case group (that is, 

hospital and dead cases) was fixed by design. Of the 482 

interviewed to date, almost 400 hospital and dead cases 

were provisionally found to qualify for the case-control 

study. 

Statistical power increases as the ratio of noninjured controls to cases increases to about four when the prevalence 

^one break-off interview ended before the injury status was determined. 
I 

STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A57 

of exposure to a risk factor of interest is low in controls7. 

Balancing additional costs of doing extra interviews against 

a desire for greater power, a ratio of 2: 1 noninjured controls 

to each hospitalldead case was sought with a 1: 1 ratio as an 

absolute minimum. Because controls were matched to cases 

on residential stratum, this translated into seeking a 2:l 

ratio in each stratum. 

Due to resource constraints, the 2:l goal was met only 

for stratum 1. The minimum goal of a 1:l ratio was exceeded for strata 2 and 3. The ratios that were achieved 

were 3.0 (1 13/38), 1.6 (28 1/179), and I. I (2001174) noninjured controls per case for strata 1, 2, and 3, respectively. 

The total sample size for noninjured controls was 594. 

Thus, the overall ratio of noninjured controls to hospital 

and dead cases was 1.5 (5941394). 

The statistical power actually achieved is likely to be 

somewhere between having one and two controls per case, 

all other relevant factors held constant (for example, sample size of cases, type 1 error, exposure rate of risk factor 

in controls, relative risk). Therefore, power calculations 

discussed below are presented as a range, assuming the 

contro1:case ratio of 1: 1 and 2: 1, all other factors held 

equal. A 5 percent significance level (type 1 error) is also 

assumed. 

Most analyses will be conducted on subgroups of the 

total. For example, cases injured during the shaking will 

be analyzed separately from those injured in the next 72 

hours. Approximately 75 percent, or 300, of the cases are 

expected to have been injured during the shaking.'* One 

might wish to estimate the relative risk of injury among 

those in a building versus other physical environments 

when the earthquake began. The power to detect a significant relative risk of injury with 300 cases for a variety of 

relative risk values (1.25-20.0) and levels of exposure to a 

risk factor in controls (0.1-0.9) was calculated. l9 The 

power lies between 82 percent and 99.8 percent to detect 

any relative risks greater than or equal to two for any 

background exposure rate in controls of 80 percent or less. 

Sample size will be further reduced when doing subgroup analyses restricted to each physical environment. 

The power to detect a significant relative risk of injury 

with 100 cases was calculated for the same range of relative risks and exposure rates in controls, and the same significance level as for the preceding example. The power 

lies between 80 percent and 99.4 percent to detect a rela- 

^personal communication with Dr. Walter Stewart, Associate Professor of Epidemiology, Johns Hopkins University, Baltimore, Md. 

1 

 h his conclusion is based on a preliminary analysis of a subset of 

cases eligible for the case-control study. 

^power calculated from the formula (6.9) in Schlesselman (1982, 

p. 151). 

tive risk of three or more for exposure rates in controls 

less than or equal to 70 percent. For a relative risk of 2.0, 

the power ranges from 24 percent to 80 percent for exposure rates in controls between 0.1 and 0.9. 

STUDY LIMITATIONS 

CASE ASCERTAINMENT ISSUES 

Not all County hospital c ses were ascertained because 

some visits to the hospitals in ade in the 72 hours after the 

earthquake were not recorded. An estimated 30 to 40 people were treated at Watsonv'lle Hospital, and some small 

but unknown number were s 1 en at Dominican Hospital for 

whom no record was made. All of the missing persons are 

likely to have had minor injuries (they were treated and 

discharged). A few of these cases may have been picked 

up in the population sample, a determination which awaits 

further analysis. 

People who were injured in the 72 hours after the earthquake but who went to the hospital after 72 hours will not 

be ascertained as hospital cases. The magnitude of this 

problem is unknown but is expected to be small according 

to anecdotal reports of hospital personnel (Jim Schneider, 

County of Santa Cruz Office of Emergency Medical Services, 1990, personal commun.). Again, a few of these 

people may have been selected in the population sample. 

In contrast, all injuries that occurred in the population 

sample during the 72-hour ascertainment period will potentially be detected. 

SAMPLING FRAME ISSUES 

For practical reasons, the sampling frames were slightly 

different for hospital cases and the population sample. Noninjured controls and population cases had to be County residents at the time of the interview to get into the sampling 

frame, whereas hospital cases did not have to satisfy this 

criteria. As a result, hospital cases who left the County after 

the earthquake were included in the study. However, noninjured controls and population cases who have moved out of 

the. County since the earthquake were not included. The 

frames could be made comparable by excluding outmigrating hospital cases from the case-control study. This option 

was rejected since outmigration may be related to both risk 

factors (for example, earthquake-damaged residence) and 

injury severity levels. Although it is not possible to obtain a 

probability-based sample of noninjured controls who have 

left the County, it is possible to evaluate the importance of 

outmigrators in the hospital case group by studying how risk 

estimates change, if at all, by their inclusion or exclusion. 

Another difference in the sampling frames between hospital cases and controls is that a small subset of cases did 
A58 LOSS ESTIMATION AND PROCEDURES 

not have a home phone at the time of the interview whereas all controls did. Similarly, a few hospital cases lived in 

institutions at the time of the interview (for example, in 

jail, hospitals, and so forth), whereas all controls lived in 

private residences when interviewed. These distinctions 

arose from the different sampling methodologies used to 

ascertain cases and controls: cases were ascertained from 

medical records, independent of their home phone status 

or type of residence, whereas controls were ascertained 

from private residences using a randomly generated list of 

phone numbers. To make the sampling frames comparable, 

cases without home phones or living in institutions at the 

time' of the interview will be excluded from the analyses. 

This exclusion could result in some bias; it is well known 

that individuals who have home phones or who live in private residences may differ significantly from those who do 

not. One way the study will try to measure the degree of 

bias introduced by excluding hospital cases that lacked a 

home phone or lived in institutions at the time of the interview will be to examine how risk estimates change, if at 

all, by their inclusion or exclusion. 

It is important to note that the exclusion of persons who 

lack home phones or who live in institutions is an inherent 

limitation of the random digit dial sampling method. It is a 

commonly employed method, however, because it is relatively inexpensive and it generates a nonbiased, random 

sample of persons who have residential phones, which 

constitute the vast majority of the population.2o The standard alternative sampling method-multistage sampling of 

first blocks, then households within selected blocks, and 

then individuals within selected households-is far more 

expensive in time and money. The latter method requires 

sending staff into the field to do an up-to-date census of 

all residential units within selected blocks. Interviewers 

then must attempt to contact households in person, a task 

which to successfully complete may require many visits to 

homes spread out over a large geographic area. The study 

employed the random digit dial method for selecting controls for practical reasons-that is, resource limitations. 

INTERVIEWING TIMETABLE ISSUES 

Noninjured controls and populat~on cases were interviewed after hospital cases and proxies for dead cases. 

Several potential biases are introduced by this situation. 

There may be differential recall bias in self-reported information provided by the respondents. Many hospital cases 

or proxies were interviewed less than one year after the 

20~n fact, the 1980 U.S. Census indicated that 96 percent of County 

residents had a home phone. The comparable statistics from the 1990 

Census, which coincides more closely with the time period of the study, 

will be evaluated when available. 

disaster, whereas all controls were surveyed at least 17' 

months after the event. It can be argued that recall bias is 

less likely in this situation because the earthquake was a 

point source environmental exposure experienced by everyone in the County. In the field work, virtually everyone 

contacted indicated that people told their earthquake experience to others over and over again. This may enhance 

recall of the event. In any case, potential recall bias in the 

hospital case group can be examined by comparing the information contained in the medical records to self-reports 

to see if correspondence between the two sources declines 

with calendar time. 

There may also be interviewer bias because the interviewers were not blinded to the injury status of the hospital and dead cases. However, the effects of nonblinding 

should be mitigated in part by the fact that both injured 

and noninjured persons from the population-based sample 

were interviewed in the same time period-and injury status was not determined before the interview began. 

INFORMATION BIAS ISSUES 

Medical records were less complete in the first day following the earthquake when the emergency rooms of the 

County hospitals, especially Watsonville Hospital, were 

overwhelmed with patients. For some cases, no diagnosis 

information was recorded. Missing or incomplete information will preclude or compromise the ability to compute 

1SS9s from medical records. One possible solution to this 

problem is to evaluate the degree of record completeness 

by day of arrival at the emergency room. A stratified analysis by day of arrival at the hospital can be done to see if 

and how risk estimates are affected. 

Another form of information (and recall) bias may also 

affect the computation of AIS scores. The injury questions 

on the questionnaire were designed to solicit the same types 

of information necessary to assign AIS codes to them. However, most respondents are unlikely to be able to report their 

injuries at the detailed level the NS can accommodate. This 

problem should not preclude using the AIS on the interview 

data but may result in systematically underestimating true 

injury severity; when details on an injury are not specified, 

the AIS usually assigns a lower severity score. The accuracy 

of self-reports of injury severity will be assessed by examining the degree of correspondence between AIS scores 

based on interview data and those computed from medical 

records and autopsies. The latter procedure can be done only 

on hospital and dead cases. 

While the medical records-based ISS's are expected to be 

more accurate, their use will reduce the sample size for 

hospital cases since the medical records for at least 10 percent of these cases had no diagnostic details. The assumption of greater accuracy of medical records recorded during 

a disaster over interview data may also be incorrect. This is 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A59 

especially true for hospital visits made in the first 24 hours 

after the disaster, as noted above. 

OTHER ISSUES RELATED TO THE ISS 

The use of the ISS to measure injury severity presents 

several advantages, First, it has biological relevance in 

that it has been shown to correlate well with the probability of death (Greenspan and others, 1985). Second, it is the 

most widely used anatomically based injury severity scale, 

facilitating comparisons across injury studies (MacKenzie 

and others, 1986). Third, it has been shown to have relatively high inter- and intra- rater reliability for both blunt 

and penetrating injuries, even among persons without 

medical training (MacKenzie and others, 1985). 

A limitation of the ISS is there is some heterogeneity in 

mortality associated with some of the same value ISS 

scores. This heterogeneity may be the result of several factors: (1) the ISS measures only the most severe injury 

within a given body region, ignoring the effect of multiple 

injuries to that part; (2) combinations of injuries of different severity levels-with different mortality experiencescan produce the same ISS score; and (3) the ISS gives 

equal weight to each body region even though same level 

injuries to some regions (that is, head injuries) appear to 

be more lethal than others (Copes and others, 1988). This 

heterogeneity may be reduced by aggregating ISS scores 

into categories (Copes and others, 1988) as proposed in 

the "Statistical Analysis" section above. 

CONCLUSIONS 

Despite the limitations discussed in the preceding sections, 

it is believed that the studies described herein will provide a 

wealth of information relative to morbidity and mortality in 

the hma Prieta earthquake, and for earthquakes in general. 

It is clear from literature reviews that,there is a shortage 

of quality, quantitative data in this area. In conducting this 

study, at least some of the reasons for this scarcity became 

evident. Even in the U.S., collection of both the case and 

control data was difficult. The research team is most encouraged by the support it received in most phases of the 

study from a broad range of people (see "Acknowledgments" section). 

Successful completion of the analysis phase of the study 

will provide useful quantitative information to epidemiologists, engineers, planners, emergency medicine personnel, 

and so forth, relative to earthquake preparedness for future 

events. In addition, while it is recognized that this study 

provides a single-event perspective of injury patterns, it is 

hoped that it will form the basis for future studies in earthquakes in this country and abroad, thereby enabling comparative studies among events to be made. 

ACKNOWLEDGMENTS 

A large number of collaborators and consultants have 

participated and will continue to participate in the study. 

The authors would like to identify and gratefully acknowledge their contributions to the effort. 

The case-control and case-series studies are a collaborative 

effort among the Johns Hopkins University, the California 

Department of Health Services (California's public health 

agency), and various consultants; the three County of Santa 

Cruz hospitals, Dominican Santa Cruz, AM1 Community, and 

Watsonville Community Hospitals; and the County of Santa 

Cruz Office of Emergency Medical Services and its consultants. The Hopkins research team also hired two consultants, 

Ms. Mary Lou Gutierrez, who translated the questionnaire 

into Spanish, and Ms. Celia Organiste, who orchestrated the 

community outreach campaign in the County. 

Dr. Kirsten Waller is the California Department of Health 

Services' principal scientific advisor on the descriptive study. 

She wrote the medical abstract form in consultation with Prof. 

Gordon Smith, and co-authored early drafts of the questionnaire. She has been involved with the study since its inception 

and continues to provide assistance and advice on the collection of case data. Drs. Alex Kelter and Roger Trent are 

responsible for coordinating the efforts of the various study 

collaborators. They also oversee the sizable California Department of Health Services' budget allocated to the study. 

Peter Roeper, a consultant to the California Department 

of Health Services, acted as Study Field Coordinator from 

June through September 1990. He managed the interviewing operation and field staff in the first months of the 

study. He had primary responsibility for hiring and training the first group of interviewers in June 1990. He also 

contributed to the development of the questionnaire. 

Jim Schneider and Lisa Angell, emergency medical care 

specialists, organized and directed the medical abstraction 

of hospital case records. Mr. Schneider conducted a parallel study of the utilization of emergency medical services 

in the County in the 72 hours after the earthquake. Ms. 

Angell, the hospital base coordinator for Watsonville Hospital, is the primary liaison between the cooperating County hospitals and the descriptive and case-control studies. 

The Santa Cruz field staff consisted of the study coordinators, and 21 interviewers (their names are not listed here for 

brevity). Most of the interviewers were local college students. 

Three of the interviewers also served as interviewer supervisors. All of the interviewers were fluent in Spanish and English 

except for five. An additional student was hired to assist in 

translating Spanish interviews into English for coding. 

It would be negligent if the authors did not thank the 

people of the County of Santa Cruz for their support and 

cooperation. Without their willingness to provide the necessary data, this study would not have been possible. 

The authors also express their gratitude to the National 

Science Foundation (Dr. S. Liu and Dr. W. Anderson), the 
A60 LOSS ESTIMATION AND PROCEDURES 

National Center for Earthquake Engineering Research, and 

the California Department of Health Service for jointly 

providing the funding necessary to undertake the research. 

The field study was administered financially by Impact 

Assessment, Inc. of La Jolla, California. Their cooperation 

and understanding are also most appreciated. 

REFERENCES CITED 

Arnold, C., 1986, Occupant behavior related to seismic performance in a 

high-rise office building," in Third U.S. National Conference on 

Earthquake Engineering, v. 111, Charleston: El Cerito, Calif., Earthquake Engineering Research Institute, p. 1,755- 1,766. 

Armenian, H.K., Noji, E.K., and Oganesian, A.P., 1992, A case-control 

study of injuries arising from the earthquake in Armenia, 1988: Bulletin of the World Health Organization, v. 70, no. 2, p. 251-257. 

Association for the Advancement of Automotive Medicine, 1990, The 

abbreviated injury scale, 1990 revision: Des Plaines, Ill.? 74 p. 

Baker, S.P., O9Nei1l, B., Haddon, W., Long, W.B., 1974, The injury severity score: a method for describing patients with multiple injuries and 

evaluating emergency care: Journal of Trauma, v. 14, p. 187-196. 

California Department of Finance, 1990, Santa Cmz County population 

and housing estimates, January 1, 1990: Demographic Research 

Unit, Report E-5, Sacramento. 

Copes, W.S., Champion, H.R., Sacco? W.J., Lawnick, M.M.? Keast, S.L., 

Bain, L.W., 1988, The injury severity score revisited: Journal of 

Trauma, v. 28, p. 69-77. 

Coulson7 A.H., 1989, Epidemiologic concepts and earthquake injury research, in International workshop on earthquake injury epidemiology 

for mitigation and response: Johns Hopkins University, Baltimore, 

Md., p. 133-142. 

de Bmycker, M.? Greco, D., Annino? I., and others, 1983? The 1980 earthquake in southern Italy: rescue of trapped victims and mortality: 

Bulletin of the World Health Organization, v. 61, no. 6, p. 1021-1025. 

de Bmycker, M.? Greco, D., kchat, M.F., 1985, The 1980 earthquake in 

southern Italy: morbidity and mortality: International Journal of Epidemiology, v. 14, no. l7 p. 113-1 17. 

de Ville de Goyet? C., del Cid, E., Romero, A., Jeannee, E., and kchat, 

M., 1976, Earthquake in Guatemala: epidemiologic evaluation of 

the relief effort: Pan American Health Organization Bulletin? v. 10, 

no, 2, p. 95-109, 

19907 Disaster-related deaths from hurricane Hugo and the northern Californiaearthquake: Journal of Emergency Nursing? v. 16, no. 4, p. 295-297. 

Durkin, M., 1985, Behavior of building occupants in earthquakes: Earthquake Spectra, v. 1, no. 2, p. 271-283. 

Duckin? M., and Murakami, H.O., 1988, Casualties? survival7 and entrapment 

in heavily damaged buildings, in Proceedings of the Ninth World 

Conference on Earthquake Engineering, v. VIII, Tokyo-Kyoto, Japan: 

Japan Association for Earthquake Disaster Prevention, p. 977-982. 

1989, Earthquake-associated deaths-california: Mortality and Morbidity 

Weekly Report, v. 38, p. 767-770. 

1990, Earthquake disaster-Luzon, Philippines: Mortality and Morbidity 

Weekly Report, v. 39, no. 34, p. 573-577. 

Glass? R.I., Umtia, J.J., Sibony, S., Smith, H., Garcia, B., and Rizzo, L., 

August 12, 1977, Mquake injuries related to housing in a Guatemalan village: Science? v. 197, p. 638-643. 

Greenspan, L., Mckllan, B.A., Greig, H., 1985, Abbreviated injury scale 

and injury severity score: a scoring chart: Journal of Trauma, v. 25, 

no. 1, p. 60-64. ' 

Jones, N.P., Noji, E.K., Smith? G.S., and Krimgold, F., 1990, Preliminary 

earthquake injury epidemiology report, in Bolin, R., ed., The Loma 

Prieta earthquake, studies of short-term impacts: Monograph 50, University of Colorado7 Boulder, Institute of Behavioral Science, p. 33-43. 

Jones? N.P.? Noji, E.K., Smith, G.S., and Wagner, R.M., 1993a. Casualty 

in earthquakes, in Earthquake hazard reduction in the central United 

States: a time for examination and action: Conference Monograph, 

Central United States Earthquake Consortium, Memphis, p. 19-68. 

Jones, N.P., Wagner, R.M.? and Smith, G.S., 1993b. Injuries and building 

data pertinent to the Loma Prieta earthquake, County of Santa Cmz, 

in Earthquake hazard reduction in the United States: a time for examination and action: Conference Monograph: Central United 

States Earthquake Consortium, Memphis, p. 531-540. 

MacKenzie, E.J., Shapiro, S., and Eastham, J.N., 1985, The abbreviated 

injury scale and injury severity score: levels of inter- and intra-rater 

reliability: Medical Care, v. 23, no. 6? p. 823-835. 

MacKenzie, E.J., Shapiro, S., Moody, M., Siegel, J.H., and Smith, 1986, 

Predicting posttrauma functional disability for individuals without 

severe brain injury: Medical Care, v. 24, no. 5, p. 377-387. 

McNutt, S., 1990, Loma Prieta earthquake, October 17, 1989, Santa Cmz 

County, California: California Geology, p. 3-7. 

Miyano, M., and Mochizuki, T.? 1988, On the characteristics of human 

casualties due to earthquake? in Proceedings of the Second JapanU.S. Workshop on Urban Earthquake Hazards Reduction: Tokai 

Univ., Shimizu, Japan, Mhquake Engineering Research Institutdlnstitute of Social Science Safety, p. 210-212. 

Mochizuki? T., 1988, Dangerous factors in living environments to human 

caseloads, in Proceedings of the Second Japan-U.S. Workshop on 

Urban Earthquake Hazards Reduction: Tokai Univ., Shimizu, Japan, 

Earthquake Engineering Research Institutehnstitute of Social Science Safety? p. 202-203. 

Mochizuki, T., Hayasaka, S., and Kosaka, S., 1988, Human behavior and 

casualties in wooden houses with little ductility, in Proceedings of 

the Ninth World Conference on Earthquake Engineering, v. VII17 

Tokyo-Kyoto, Japan: Japan Association for Earthquake Disaster Prevention, p. 983-988. 

Morbidity and Mortality Weekly Report, 1989, Earthquake-associated 

deaths4alifornia: v. 38, p. 767-770. 

1990, Earthquake disaster-Luzon, Philippines: v. 39, p. 573-577. 

Noji, E.K., 1990, Epidemiologic studies from the 1988 Armenia earthquake: implications for casualty modelling, in Workshop on Modelling Earthquake Casualties for Planning and Response: VSP 

Associates, Inc. and California Emergency Medical Sewices Authority, Pacific Grove, CA, p. C-1-C-35. 

Noji? E.K., and Sivertson, K.T., 1987, Injury prevention in natural disasters: a theoretical framework: Disasters, v. 11, no. 4? p. 290-296. 

Ohta, Y., and Ohashi, M., 1980, A field survey on human response during 

and after an earthquake, in Proceedings of the Seventh World Conference on Earthquake Engineering? v. IX, Istanbul, Turkey: Ankara 

Turkish National Committee on Earthquake Engineering, p. 345- 

352. 

Ohta, Y.? and Omote, S., 1977, An investigation into human psychology 

and behavior during an earthquake, in Proceedings of the Sixth 

World Conference on Earthquake Engineering, v. I, Meemt, India: 

Sarita Prakashan? p. 702-708. 

Plafker, G., and Galloway, J.P., eds., 1989, kssons learned for the Loma 

Pcieta, California, earthquake of October 17, 1989: U.S. Geological 

Suwey Circular 1045,48 p. 

Sanchez-Cacillo, C.I., 1989, Morbidity following Mexico City's 1985 

earthquakes: clinical and epidemiological findings from hospitals and 

emergency units: Public Health Reports, v. 104, no. 5, p. 482-487. 

Schlesselman, J.J., 1982,-Case-control studies: design, conduct, analysis: 

Oxford University Press, 354 p. 

Shilts, R., and Sward, S., October 19? 1989a, Devastating reports from 

big quake area, disaster declared in 7 counties: San Francisco 

Chronicle, p. A1 . 1989b7 Hund~ds dead in huge quake, Oakland freeway collapses-Bay Bridge section fails: San Francisco Chronicle, p. Al. 

Smith, G.S., 19907 The application of epidemiology to the reduction of 

earthquake related casualties: Research needs, in Hays? W.W., ed., 
STUDY METHODS AND PROGRESS REPORT: A CASE-CONTROL STUDY OF PHYSICAL INJURIES A61 

Proceedings of Conference XLIX, a meeting of the U.S. ad hoc Tierney, K.J., 1990, Developing multivariate models for earthquake casuworking group on earthquake related casualties: U.S. Geological alty estimation, in Workshop on modelling earthquake casualties for 

Survey-Open File Report 90-244, p. 17-19. planning and response: VSP Associates, Inc. and California EmergenStratton, J.W., 1989, Earthquakes, chap. 4, in Gregg, M.B., ed., The pub- cy Medical Services Authority, Pacific Grove, Calif., p. D-1-D-24. 

lic health consequences of disasters: U.S. Department of Health and U.S. Geological Survey, 1990, The Loma Prieta earthquake of October 

Human Services, Public Health Service, CDC Monograph, p. 13-24. 17, 1989: Washington, D.C., 18 p. 
THE LOMA PRIETA, CALJFORNIA, EARTHQUAKE OF OCTOBER 17,1989: 

SOCIETAL RESPONSE 

LOSS ES7'IMATION AND PROCEDURES 

PRELIMINARY STATISTICS ON LOSSES 

ASSOCIATED WITH GROUND DEFORMATION 

By Craig E. Taylor, Dames & Moore, Inc., Los Angeles, Calif.; 

Hope A. Seligson, EQE Engineering, Costa Mesa, Calif.; 

David Fowler, Private Consultant, San Francisco, Calif.; and 

Craig W. Tillman, Dames & Moore, Inc., Los Angeles, Calif. 

CONTENTS INTRODUCTION 

Page 

A63 

63 

63 

.67 

67 

68 

70 

7 1 

73 

76 

76 

76 

This report surveys losses associated with ground deformation from the 1989 Loma Prieta, Calif., earthquake. We 

confined our study to structures located in four San Francisco ZIP code areas (fig. I), which experienced significant 

ground deformation. This report emphasizes strengths and 

weaknesses of alternative approaches to gathering earthquake loss data for areas of ground deformation and presents- preliminary loss statistics derived through this 

project. 

PREVIOUS WORK 

ABSTRACT 

Loss estimates made for buildings affected by ground 

deformation due to earthquakes have had limited reliability. As a consequence, public policy questions on the equity and efficiency of various earthquake-related landuse 

alternatives have been subject to considerable speculation. 

In this report, we develop, largely from secondary sources, 

earthquake loss data in four ZIP code areas of San Francisco. The many significant studies on ground deformation 

resulting from the Loma Prieta earthquake greatly assist in 

delineating hazards within these four areas. Moreover, data 

are available, at some expense, for estimating the replacement costs and general structural categories of buildings at 

risk. We review the loss data collected from more than 

700 buildings. Data suggest that for buildings suffering 

losses, the degree of building loss as a percentage of replacement value is weakly correlated with the degree of 

ground failure in the general vicinity. Because these study 

results are preliminary, we further indicate ways in which 

t these data may be improved and future studies developed 

to compile improved loss data. 

Loss data for buildings subjected to earthquakes characterized by strong ground motion are limited (Eguchi and 

others, 1989). Loss data are even more limited with respect 

to buildings affected by permanent ground deformation 

(here used to mean permanent soil displacement and also 

used interchangeably with ground failure). 

A partial review of previous loss data associated with 

ground deformation is provided in Rojahn and others 

(1985). Their study quotes Wood (1908) in reporting that in 

the 1906 San Francisco, Calif., earthquake, structures built 

on soft, moist sands and sediments near the shoreline or on 

filled swamps suffered damage five to ten times greater 

than similar structures built on hard ground or thinly covered ridges of rock. Rojahn and others (1985) also cited 

Youd (1978) in discussions of losses associated with 

ground deformation in the 1964 Alaska earthquake, the 

1920 Kansu, China, earthquake and the 1970 Peruvian 

earthquake. Based on an interpretation of Wood's (1908) 

data from the 1906 San Francisco earthquake, Rojahn and 

others (1985) proposed that a multiplicative factor of five 

be used to estimate increases in structural damage expected 

in areas prone to ground liquefaction. This factor applies 
A64 LOSS ESTIMATION AND PROCEDURES 

only if the mean building-loss estimate, owing to ground 

shaking, is less than 20 percent of the building replacement 

value. 

Loss data from the 1971 San Fernando Valley, Calif., 

earthquake (McClure, 1973) were re-examined by Wiggins 

and Taylor (1986). In the 1973 study, structural reviews 

were made for 169 dwellings in heavily damaged areas and 

217 factors were analyzed for each dwelling. As support for 

this previous research, Ralph Goers (Ralph Goers and Associates, unpub. commun., 1984) made available detailed 

field notes, which often clarified evidence of permanent 

ground displacement. These factors included actual repaircost estimates as well as damage estimates for a large number of structural and nonstructural components. Although 

statistical biases were evident in the selection of the stmctures, the biases were partially overcome through norrnalization of loss data in a more expansive study of losses to 

single-family dwellings in California earthquakes by SteinFigure 1 .Ã‘Sa Francisco ZIP code areas surveyed. Heavy line shows extent of 1852 shoreline. 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION 

brugge and Algermissen (1 990). Wiggins and Taylor (1 986) 

used regression analyses on these data to confirm that a 

statistical correlation exists between higher observed structural damage and the following dwelling characteristics: 

exterior wall framing of wood stud and cripples, 

no visible connection of wood sill or ledger to footings, 

interior partition finish of gypsum lath and plaster or 

metal lath and plaster, 

site grading of fill, engineered or not, and 

crawl space or split level below first floor. 

As part of the review and augmentation of McClure's 

data for the Wiggins and Taylor (1986) study, M. Legg 

(written commun., 1984) used geologic data on ground 

displacement, along with field notes by surveyors, to identify structures whose damage was affected by permanent 

ground displacement. Legg (written comrnun., 1984) identified additional structures as being in fault rupture zones 

based on the map of surficial fault ruptures in Oakeshott 

(1975). These additional cases could, on occasion, be 

compared with the surveyor field notes when the actual 

location of fissures was identified. 

Dwellings affected by ground failure were then separated 

according to type of ground failure: dwellings in tectonic 

fault-rupture zones; dwellings in landslide areas or areas of 

significant lateral spread; dwellings that suffered differential settlement ground-failure effects; and dwellings identified as being in areas with minor ground cracking, such as 

lurch cracks or minor liquefaction effects. Differences between these categories were in some instances gradational, 

such as when a minor lateral spread appears as lurch cracking or even differential settlement. Wiggins and Taylor 

(1986) devised the following measures of severity of 

ground failure: For fault rupture areas, maximum displacement of a given fault segment was used (Sharp, 1975; 

Legg and others, 1982); for landslide/lateral spread, maximum displacement width of individual cracks at the site 

(Ralph Goers, unpub. data, 1972) was used, and for differential settlement and minor liquefaction, a modified Mercalli intensity (MMI) scale was used only as it pertains to 

shaking intensity. 

A comparison of the data showed that the amount of 

structural damage associated with fault rupture and landslidellatefa1 spread appears to correlate with the degree of 

ground displacement (fig. 2; Wiggins and Taylor, 1986) 

and that the use of MMI as a measure of severity for differential settlement and minor liquefaction/lurching does 

not correlate well with the associated amount of structural 

damage for the limited cases examined (figs. 2, 3; Wiggins 

and Taylor, 1986). Figures 2, 3, and 4 all show that when 

detailed field survey loss data are gathered, it is sheerly 

speculative to maintain that building loss resulting from 

ground deformation is a multiplicative factor of normal 

building loss at the same intensity. Figures 3 and 4 appear 

to show that structural damage associated with minor liquefactionJdifferentia1 settlement is similar to damage that 

would otherwise be expected as a result of strong ground 

shaking at MMI X. 

Steinbrugge and Algermissen (1990) provided less detailed data on a much larger sample of dwellings for the 197 1 

I I I I I I J 

0 50 100 150 200 250 300 350 

DISPLACEMENT (cm) 

Figure 2.-Loss ratios versus displacement for structural damage associated with ground failures related to 

tectonic faulting and landslides (Wiggins and Taylor, 1986). 
Table 1 .-Dwelling loss ratio as a percentage of market value in high intensity areas of the 1971 Sun Fernando Valley earthquake 

Areas without ground deformation Areas with ground deformation 

Construction 

date Number of Loss ratio Number of Loss ratio 

dwellings (percent)- dwellings (percent)- 

Pre- 1940 ........ 589 

1940-49 ......... 4,117 

Post- 1949 ........ 5,596 

Total 10,515 8.1 1,560 15.3 

' Includes dwellings not categorized by construction date. 

Average loss (building and contents) as a percentage of market value. 

San Fernando Valley earthquake than did Wiggins and Taylor 

(1986). Steinbmgge and Algermissen's (1990) loss data are 

limited by (1) the lack of detailed structure distinctions, 

especially structural foundation details; (2) the use of market 

value rather than replacement value as a basis for loss ratios; 

(3) the use of total dwelling losses (losses for both building 

and contents); (4) the use of subjective estimates for damage 

(for example, for slight damage to interior finishes) rather 

than actual repair costs; and (5) the absence of clear descriptions as to how geologic effects (ground deformation) were 

categorized. With these restrictions in mind, table 1 can be 

derived from tables 2 and 6 in Steinbrugge and Algermissen 

MODIFIED MERCALLI INTENSITY 

Figure 3.-Loss ratios versus modified Mercalli intensity for structural 

damage associated with ground failures related to differential settlement (Wiggins and Taylor, 1986). 

" VI VI I VIII I X x 

MODI FIE0 MERCALLI INTENSITY 

Figure 4.-Loss ratios versus modified Mercalli intensity for structural 

damage associated with ground failures related to liquefaction/lurch 

cracking (Wiggins and Taylor, 1986). 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION A67 

(1990). We derived multipliers from table 1 for comparison 

between areas with and without ground deformation. Total 

dwelling losses in areas with deformation were 2.9 times 

higher for pre-1940 buildings, 2.3 times higher for 1940 

through 1949 buildings, and 1.7 times higher for post-1949 

buildings. The overall average multiplier of 1.9 is far below 

the multiplier of 5.0 proposed by Rojahn and others (1985) 

for the 1906 San Francisco earthquake. Because the dwellings surveyed by Steinbrugge and Algermissen (1990) were 

in the highly damaged regions of the 1971 earthquake, the 

use of a simple multiplier approach for estimating effects of 

ground deformation is further called into question. 

The lack of more extensive studies of earthquake loss 

data has far-reaching implications. Controversies, such as 

those in a workshop on loss-control measures in a Federal 

earthquake insurance context (see Taylor and others, 1989; 

Taylor, Petak, and others, 1990), present special practical 

concerns because: 

Section 404 of the 1989 Robert T. Stafford Disaster Relief and Assistance Act requires that applicants produce 

cost-effective mitigations (these may require weighing 

benefits against costs; estimation of benefits for many 

landuse policies requires estimation of losses associated 

with ground deformation); 

earthquake insurance ratings depend on reliable data; and 

reliable data are required to evaluate the comparative 

practical worth of strong motion versus ground-failure 

studies and of structural loss-reduction measures versus 

landuse and geotechnical planning measures. 

Without more extensive data, informed judgments are difficult to make in establishing Federal, state, and local priorities and in determining the cost effectiveness of proposed 

mitigation measures. 

IDENTIFYING PERMANENT GROUND 

DEFORMATION WITHIN THE FOUR ZIP 

CODE AREAS 

Ideally, for each structure evaluated within the four San 

Francisco ZIP code areas (fig. I), one would have actual 

measurements of ground displacement at the site along 

with structural models that explain and clarify the types 

and amount of damage associated with the ground displacement. This would be in contrast to the types and 

amount of damage resulting from strong ground motion 

alone. For the Loma Prieta earthquake, detailed maps were 

developed of sand boils within the Marina District. Moreover, evidence exists, such as the Federal Emergency 

Management Agency's Damage Survey Reports (DSRs), 

for the usefulness of street and gutter damage as indices of 

permanent ground displacement. 

We selected Bennett's (1990) general contour map of longterm sediment settlement as one basis for analyzing losses 

associated with ground deformation in the Marina District 

(ZIP code 94123). Contours on this map are associated with 

four different artificial fills (fig. 5). Most sand boils are found 

in the area of fills laid down between 1906 and 1917. Bennett 

(1990) plotted the ratios of 1974 through 1989 settlement to 

1961 through 1974 settlement for regions in the Marina 

District (fig. 6); ratios greater than one indicated that more 

vertical settlement of sediments occurred in the 1974 through 

1989 period. (Bennett, 1990, primarily attributed settlement 

during this period to the Loma Prieta earthquake.) We used 

rapid evaluation forms filled out for the City and County of 

San Francisco to augment this general background mapping 

(see R.P. Gallagher and Associates, 1989; Oaks, 1990; and 

Seekins, in press, for survey details). (A general history of 

Marina District developments is found in Bonilla, 1990.) 

For the South of Market area (SOMA) (ZIP codes 94103, 

94105, and 94107), we used Seed and others' (1990) map 

(fig. 7). The liquefaction areas on this map roughly correspond to similar areas in the 1906 earthquake. However, 

massive and catastrophic liquefaction did not occur in the 

shorter duration, more distant 1989 earthquake. Instead, the 

map shows areas of "minor liquefaction and (or) pore-pressure generation and associated ground softening representing incipient or near liquefaction over much of this region" 

(Seed and others, 1990). 

The modified Mercalli intensity assigned to the Marina 

District is IX; the intensity assigned to the SOMA area is 

VII (Stover and others, 1990; Plafker and Galloway, 

1989); and an intensity of IX is ascribed to a portion of 

the SOMA area by Oaks (1990). These intensities are 

sometimes determined by strong motion data alone; however, some authors suggest that shaking and ground failure 

sometimes inextricably contribute to damage. 

EARTHQUAKE DAMAGE DATA 

For gathering earthquake damage and loss data for the 

four ZIP code areas, we have used numerous data sources, 

including: 

the city of San Francisco, which performed a rapid evaluation screening analysis based on Applied Technology 

Council Procedures for post-earthquake safety evaluation of buildings, commonly referred to as ATC-20; 

the Federal Emergency Management Agency (FEMA), 

which provided DSRs for public and private nonprofit 

applicants for ~ederal disaster assistance grants and loans; 

the Small Business Administration (SBA), which provided loss data relative to loans to small business and 

individuals adversely affected by the earthquake; 

the Individual and Family Grant Program (IFGP), State 

of California, which provided loss data for applicants; 

private insurers, who provided detailed data on losses to 

their insured properties; 

the State of California Department of Insurance (DOI), 

which requested detailed loss data from all primary insurers 
A68 LOSS ESTIMATION AND PROCEDURES 

(only preliminary DO1 data were available for use in this 

study); 

OTHER PRELIMINARY FINDINGS 

the State of California Office of the State Architect; and Preliminary findings by other investigators provided a 

comments by other investigators. valuable background for the systematic collection of earth- 

- Older alluvial deposits 

ARTIFICIAL FILLS 

["I 1906- 191 7 (principally 191 2) f^l 1869-1 895 

1895-1906 1851-1869 

eM3 Location of USGS borings 

Figure 5.Ã‘Genera locations of geologic units (the older alluvial deposits are generally south of Lombard Street) and the location of the different fills 

used to reclaim the Marina District. The central fill area is referred to as Marina Cove. (Data from Bennett, 1990.) 

Figure 6.-Ratios of 1974-1989 settlement to 1961-1974 settlement in the Marina District. Ratios less than one indicate that more vertical settlement of 

sediments took place before 1974 than after 1974. (Data from Bennett, 1990.) 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION A69 

quake loss data. We reviewed damage patterns for the Marina District and the SOMA. 

Celebi (1990) attributed damage in the Marina District to 

two main causes: structural deficiencies including foundations (for example, lack of strength and stiffness at the first 

story of many buildings) and soil-related phenomena (settlement and amplification). Other contributing causes were 

structural deterioration of concrete or timber members, 

buildings out of plumb owing to long-term settlement, deficient building-to-foundation anchorage, and pounding of 

structures against one another. In short, assessment of damage patterns must consider both structural and soil-related 

parameters. 

Diverse opinions have been expressed on the relative 

importance of liquefaction versus strong ground motion in 

causing damage. Tissel (1990) noted structural deficiencies 

Approximate Zone of Ground Problems .:,.a:, (settle, Pavement Cracking, etc.) 

Sand Boils Damage to Pier 45 

0 2000 4000 

Figure 7.-Apparent extent of soil liquefaction in San Francisco's Embarcadero and Old Mission Bay regions on October 17, 1989. 

Light, unlabeled lines show landward limit of bay mud deposits. Heavy line shows extent of 1852 shoreline. (From Seed and others, 

1990.) 
A70 LOSS ESTIMATION AND PROCEDURES 

of wood-frame buildings in the Marina District: soft story 

problems, no anchor bolts from the sill plate to the foundation, and lack of ties between brick veneer and the 

frame. In a survey of posted buildings (red, unsafe; yellow, limited entry; and green, no restrictions), Seekins and 

others (1990) maintained that the boundary of the hydraulic fill region' of the Marina does not correlate with damage patterns. Much of the damage in the Loma Prieta 

earthquake resulted from shaking alone (in other words, 

much damage was not related to the liquefaction of the 

fill). Boatwright and others (1990) maintained that, other 

than the blocks between Marina Boulevard and Beach 

Street, to the end of Scott Street, "the area underlain by 

the 19 12 hydraulic fill was less severely damaged than the 

areas to the west and south." Boatwright and others (1990) 

suggested that the small liquefaction settlements were part 

of a process that dampened the strong ground motion in 

the hydraulic fill area, so that strong-motion amplification 

and associated damage was actually less in this area. Baringer (1989) also noted that liquefaction contributed little 

to the damage because of the short duration of the earthquake. In a follow-up study based on revised City of San 

Francisco damage postings, Seekins (in press) reiterated 

that "while some of the structural damage in the Marina 

was due to liquefaction, or a combination of liquefaction 

and shaking, much of it was due to shaking alone." However, Bennett (1990) maintained that all demolished buildings and most tilted buildings are in areas of fill. 

"Seventy-three percent of the red tag [sic] buildings are 

located in the areas that have been filled, and except for 

the red-tagged buildings on the beach deposit, ninety one 

percent of the red-tagged buildings are located where settlement was at least 25 mm." 

Astaneh and others (1989) reported that much of the 

structural damage in the Marina District had been initially 

attributed to strong shaking, but on closer inspection, they 

found that many structures suffered partial bearing failures, differential settlement of interior column footings, 

and sand intrusions in garages and basements. In the 

SOMA, they found pockets of settlement-induced damage, 

especially to unreinforced concrete buildings and buildings 

not supported on deep piles. 

VARIATIONS IN THE MEANING OF LOSS 

Discussions of loss-data surveys and findings often 

make important distinctions among the various meanings 

of the term "loss." Steinbrugge and Algermissen (1990), 

for instance, draw a distinction between "personal" and 

"impersonal" viewpoints on loss. As an example, minor 

interior and exterior plaster damage can be an out-of-pocket cost for the homeowners who make their own repairs. If 

a professional is hired, the repairs and painting may cost 

$1,000. What constitutes a minor crack to one observer 

may be a major eyesore to another and entail considerable 

cash outlays. For those who are covered by insurance, 

grants, or loans, incentives exist not to perform the work 

on one's own and to repair and restore as much as outside 

funds will permit. The regulatory environment may also 

require that specific repairs be made, which increase repair 

costs. (Issues such as these are elaborated in Arnold, 

1990.) The relationship between loss and hazardous conditions is also complex. For example, some buildings that 

suffer significant losses may not be posted as either extreme hazards or dangerous to enter. In contrast, some 

buildings may be posted as hazardous even though they 

have not suffered direct loss but are at risk from adjacent 

damaged buildings, glass damage, broken gas mains, or 

asbestos exposure (Seekins, in press). 

From the standpoint of the secondary survey of losses 

that we have performed, additional complications arise: (1) 

Loss estimates may be based on different methods or different intents, (2) loss estimates from one information 

source may be incompatible with those from another, and 

(3) loss estimates from various sources may not be representative-data from insurance companies, for example, 

only cover insured losses, not losses to all affected buildings. Also, the actual loss may depend on regulations that 

are in place to govern repairs required; losses exceeding 50 

percent of replacement value may require total replacement. Depending on the municipality, repairs or replacement may be required to comply with current building 

regulatory standards (Lizundia, Rutherford and Chekene, 

written commun., 1992). SBA loss estimates, which are the 

most complete data sets available, depend on estimator's 

assessment of repair costs; these estimates may vary from 

the actual costs. FEMA's estimates depend on actual approved costs, based on receipts and detailed information on 

damage. Insurance company estimates reflect not only actual approved repair costs, but deductible levels, types of 

losses covered, and limits of liability. An insured building 

with a 10 percent deductible may have no insured losses 

recorded if actual approved repair costs are less than the 10 

percent deductible. If insurance covers only building contents, structural damage may go unrecorded; also if policy 

limits are below the replacement value of the structure, the 

insured loss will not represent the actual loss. 

The rapid ATC-20 evaluation performed by the city and 

county of San Francisco provided data on ground deformation and other data observed at the time the structures were 

posted as hazardous. As such, these data assist in loss estimation to the extent that they clarify what damage surveyors observed in comparison with final loss estimates. 

Potential discrepancies between ATC-20 postings and 

loss estimates are a concern. Other concerns arise from 

discrepancies in loss estimates from different sources. 

Comparisons between SBA loss estimates and insurance 

company estimates showed that some discrepancies could 

be explained by the deductible levels and (or) limits of 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION A71 

Table 2.-Initial summary of Loma Prieta earthquake damage estimates 

[SBA, Small Business Administration; FEMA, Federal Emergency Management Agency] 

Zone of SBAtFEMA No. of Average Buildings posted 

Zip code ground damage buildings loss red or yellow2 

area displacement1 estimates damaged ($1 

(total $1 No. Percent 

South of Market area 

94103 Yes $10,226,790 63 $162,330 22 34.9 

No $1 1,892,942 58 $205,05 1 19 32.8 

94105 Yes $787,322 5 $157,464 0 0 

No $2,652,199 22 $120,555 11 50.0 

94107 Yes $10,355,710 37 $279,884 19 51.4 

No $978,362 32 $30,574 3 9.4 

Marina District 

C $16,353,256 112 $146,011 47 42.0 

B 1 $8,849,921 67 $132,088 3 3 49.3 

D $5,991,400 63 $95,102 24 38.1 

B2 $5,352,264 11 1 $48,219 15 13.5 

Grand total . . . . . . . . . $92,126.566 726 $126.896 234 32.2 

Sand boils in the Marina were concentrated in areas A and C. A, Hydraulic fill placed principally in 1912 

(ratio 8.6); C, older fills (1869-1895; ratio 3.3);' B,, beach sands (Strawberry Island; ratio 2.5); D, filled tidal 

sloughfdraining marsh (1895 to 1906; ratio 1.8); B2, dune field (ratio 0.4). (Higher ratios are attributed to greater 

ground displacement; data from Bennett, 1990.) 

Buildings posted red (no entry) or yellow (limited entry) during initial damage survey by the city of San 

Francisco. 

liability on insurance policies or by the fact that full insurance payment amounts had not been determined at the time 

of the SBA survey. However, other discrepancies were 

very large and could not be explained without a detailed 

followup. In the HUD survey of residential structures damaged by the 1971 San Fernando Valley earthquake, actual 

documented repair costs were used as the standard for estimating earthquake losses (McClure, 1973). Therefore, it 

was assumed that actual payouts by insurers or Federal 

agencies would effectively serve as the final loss estimates 

for both groups (McClure, 1973). However, even if loss 

estimates are objective in the sense that they are the result 

of the application of various uniform standards, the actual 

payouts may differ depending on who pays for the claimed 

losses and in the extent to which the judicial system is 

involved in claims adjudication. 

THE NEED FOR REPLACEMENT COST 

ESTIMATES 

Based on data collected through the secondary surveys 

previously discussed, we developed table 2, which provides a summary of SBA/FEMA total dollar estimates of 

structural damage in the four San Fernando ZIP code areas. These estimates are further broken down by location 

in or out of ground-failure zones, and average losses are 

calculated. These average losses were used to determine 

that losses are higher in zones of ground failure. However, 

it is also possible that the average cost of buildings in 

zones of ground failures is greater. For this reason it is 

necessary to normalize losses to some value at risk such as 

structural replacement cost. 

The current standard for value at risk is building replacement value. This implies additional costs to restore a building to its original condition-including possible costs of 

upgrades to comply with current codes. Also, regulatory 

standards may need to be taken into account so that losses 

do not exceed replacement value. The use of building market value is less satisfactory than the use of replacement 

value, because building depreciation, which makes comparisons between damage to older and newer buildings difficult, must be taken into account. The use of appraised 

land values and improvements is an extremely indirect 

means of assessing building value. The land value is generally speculative, whereas structural replacement costs are 

ordinarily less speculative. In addition, building losses may 

depend on such factors as building type and age. The presence of more seismically vulnerable buildings in one locality may contribute to larger aggregate earthquake losses in 

that locality. To overcome these problems, we gathered 

data from the city and county of San Francisco on the 726 
LOSS ESTIMATION AND PROCEDURES 

Table 3.-Summary of estimates of replacement cost estimates per square foot 

[Leaders (- -), not applicable] 

General building usage type1 - 

Replacement cost ($) per square foot - 

Low rise Medium rise High rise 

Houses, condominiums, duplexes ....... 

Apartments, dormitories (not elsewhere 

specified) ..................... 

Public buildings: libraries, educational 

institutions, jails, police and fire stations . 

Commercial buildings (generally with no 

specific breakdown) .............. 

Restaurants, bars, banks, hotels and motels, 

convalescent hospitals, clubs, churches, 

theaters, service stations ........... 95 

Garages ....................... 3 3 

Hospitals ...................... 124 

Offices, convenience stores ........... 72 

Industrial offices .................. 72 

117 

65 

124 

Ill 

11 1 

Warehouses 52 72 - - ..................... 

Heavy industrial factories 59 7 8 - - ............ 

Omits the San Francisco land-use codes with which each of the general building-usage types were correlated. 

buildings for which loss data were available. Data include: 

year of construction, number of stories, square footage, 

landuse, building class (frame system), ZIP code, land value, improvements value (building market value after subtracting land value), tax valuation, notes, and damage 

inspection category (red, yellow, or green). 

In order to develop replacement costs, we first correlated 

San Francisco landuse codes with categories found respectively in Means Square Foot Costs (R.S. Means Company, 

Inc., 1991) and in Rojahn and others (1985, table 4.6). 

Next, we used the Local Cost Index table in Means Square 

Foot Costs to set prices at January 1990 (close to October 

1989) levels. This very approximate process resulted in 

broad categories for estimating replacement values of surveyed buildings for which square footage data were available. A more detailed valuation approach would only be 

justified for extremely high-value or unique buildings. 

A summary of the replacement costs per square foot basis 

that we used to estimate replacement costs is listed in table 

3. We have chosen not to use city and county of San Francisco estimates of improvements values as the basis for 

estimating building values at risk. Compared with the replacement values that we have calculated, improvements 

values show a wide scatter or variation relative to usage 

categories and square footage estimates (fig. 8). Almost half 

of the 726 buildings surveyed have improvements value 

estimates of less than 40 percent of replacement cost as 

estimated from table 3 and square footage data. While most 

improvements-value estimates are low relative to replacement-value estimates, more than 10 percent of the estimates 

of improvements values exceed estimates of replacement 

values, and a few exceed replacement values by more than 

a factor of two. Thus a wide scatter exists in estimates of 

improvements values, which in general are low relative to 

replacement values. 

A further test of the use of estimates of improvements 

values, replacement costs, and insurance liability limits, as 

estimates of building values at risk, is derived from examination of a small sample group from the database in which 

two or three of these factors were present in the database 

we have examined. In some cases, loss estimates of building values at risk may significantly exceed insurance policy estimates of limits of liability. Even for insurance 

policies that cover replacement costs, the basis for estimating limits of liability may depend on estimates of replacement costs per square foot; our gross-scale estimates in 

table 3 are similar to these estimates of replacement costs 

per square foot. Ratios of improvements estimates to insurance estimates had a mean value of 0.55 with a standard deviation of 0.13 (32 cases). Ratios of replacement 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION A73 

values estimates derived from table 3 and square footage 

data to insurance estimates had a ratio of 1.14 with a standard deviation of 0.14. These suggest that some degree of 

variability is to be expected in replacement-cost estimates 

(similar conclusions are drawn in Taylor, Elliot, and others, 1990). 

CONDITIONAL LOSS ESTIMATES AS 

PERCENTS OF REPLACEMENT VALUE 

The loss and replacement-cost estimates developed in 

our project mostly relate only to building-damage cases in 

which damage claims are made to some party, whether a 

governmental agency or a private insurer. Until we assimilate further data such as California DO1 data, biases are 

possible in our results because not all cases are included in 

our database. 

Alternative data sets may be compared in order to discern the possible biases in the loss data we have examined. 

For example, early data collected by the California DO1 

after the Loma Prieta earthquake contain data sets (2,4 and 

10 claims, respectively) on personal lines insurance claims 

in ZIP code areas 94103, 94105, and 94107. However, a 

large data set of 370 insurance claims was compiled for 

ZIP code area 94123. The average earthquake insurance 

claim payout amount in these 370 building damage cases 

was $21,700. To determine an average replacement value 

of $174,000 for these buildings, we used their fire policy 

insured values because fire policies have low deductibles 

and therefore have insured values that approximate actual 

building replacement values. (Our study does not cover 

earthquake losses that are due to fires.) If the typical earthquake insurance deductible in these cases was 10 percent 

of the replacement value, then the average claim payout 

represents a loss of $39,100 (about 22 percent of the replacement value). At the time of the Loma Prieta earthquake, 966 buildings were insured against earthquake 

damage in the 94123 ZIP code area. Because only 370 of 

these 966 insured buildings had adjusted losses above their 

policy deductibles, the average loss for the entire sample of 

966 buildings was well below 22 percent of building replacement value. (Source of information: R. Roth, Jr., California DOI, written commun., 1991.) In contrast to the 

DO1 data, the loss data surveyed in our study show an 

average loss for small residentially zoned properties (city 

and county of San Francisco zone R-1) (74 in sample) in 

ZIP code 94123 with $98,000 on an average replacement 

value of $222,000. The average claim in data we surveyed 

for these properties is about 44 percent of replacement value, which is well above the 22 percent estimated from DO1 

claims data. It should be borne in mind that the preponderance of claims data we surveyed were from the Small 

Business Administration. Only limited overlap with insurance data exists within our database. These overlaps may 

not include building contents losses and temporary living 

expenses and may reflect different loss estimation criteria. 

Our limited comparison of SBA and DO1 loss data strongly suggests that a more comprehensive comparison of these 

loss data should be made in order to clarify potential biases 

and to improve future earthquake loss projections for both 

the SBA and private insurers. 

RATIO OF IMPROVEMENTS VALUE ESTIMATES (SAN FRANCISCO COUNTY) 

TO REPLACEMENT VALUE ESTIMATES 

(DERIVED FROM TABLE 3) 

Figure 8.Ã‘Cumulativ distribution of ratio of improvements value estimates to replacement value estimates. Replacement value estimates derived from table 3. 
A74 LOSS ESTIMATION AND PROCEDURES 

A key question in our study was whether or not liquefaction-induced ground displacement was a significant contributing factor in overall building losses. We indirectly 

approached this question by aggregating the buildings surveyed into groups based on ground displacements (see 

table 2); yes and no zones of displacement were used for 

buildings in the SOMA (data from Seed and others, 1990; 

fig. 7), and buildings in the Marina district were grouped 

on the basis of the ratio of 1974 through 1984 settlement to 

1961 through 1974 settlement and the type of underlying 

artificial filllsediment (data from Bennett, 1990; figs. 5, 6). 

Our loss data show that mean damage ratios (losses as a 

percent of replacement value) are greater for wood-frame 

buildings located in zones in which ground failure is generally more severe (fig. 9). 

Figure 10 compares cumulative loss distributions for three, 

general ground-failure zones, a high zone (combining the 

South of Market ground failure zones, and the Marina A, C, 

and B, zones), a moderate zone (consisting of the Marina D 

zone), and a low zone (combining the Marina B2 zone and 

the South of Market zones with no ground failures). 

The cumulative loss distributions in figure 10 show that, 

regardless of percentile rank, greater losses are expected to 

occur as ground failure severity increases. For example, at 40 

percent of all cases (on the vertical scale) losses are 8 percent, 

14 percent, and 20 percent of replacement value, respectively, for the low, moderate and high ground-failure zones. 

The loss patterns shown in figures 9 and 10, however, 

need to be qualified because of three issues: (1) Unanalyzed hazard factors such as more severe ground shaking 

may or may not have been present in the higher groundfailure zones; (2) losses are conditional only-a thorough 

data set including all zero losses will modify the distributions and may modify any conclusions drawn; and (3) 

other structural vulnerability factors such as poor seismic 

resistance may have contributed to damage. 

In this project, our current data set does not permit us to 

address the first and second issues. We address the third 

issue only partially by using a multiple-regression analysis 

of the form 

Y = AiXl + A2X2 + A3X3 + Â (1) 

where 

Y is the building damage ratio (loss as a percentage 

of replacement value), 

XI is the degree of ground displacement, approximated 

by the yearly sediment settlement ratios listed in 

table 2 (the ground-failure region in the SOMA is 

assigned an 8.6, analogous to the Marina A zone, 

and the no-ground-failure region in the SOMA is 

assigned a 0.4, analogous to the Marina B2 zone), 

X2 is the building story height, subdivided into low-, 

medium-, and high-rise buildings; 

X3 is the building age; and 

Al, A2, A3, and e are coefficients to be determined. 

Application of this linear-regression model to our data 

base led to the following conclusions: 

Age had a zero coefficient of determination with respect 

to the damage ratio, or loss as a percentage of replacement value (nearly all the buildings surveyed were at least 

50 years old). 

Height category had a zero coefficient of determination 

with respect to the damage ratio (most buildings were 

low rise). 

Marina 

District 

Marina ; District ; 

south of ! District : D zone 

Mae area B2 zone : 

no failure i 

zone 1 

Marina 

District 

C zone 

Marina 

District 

A zone 

GROUND SETTLEMENT RATIO 

South of 

Market area 

failure 

zone 

Figure 9.-Mean damage ratio (average of damage ratios for wood-frame buildings surveyed) plotted against 

ground settlement ratios (discussed in table 2) for ground failure zones. 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION A75 

Sediment settlement regions had a small coefficient of To determine the effects of using a real variable Xl (condetermination with respect to the damage ratio, which tinuous in theory, polychotomous in application) to estimate 

for the analyses evaluated was highest (f = 0.097) when degree of ground deformation, we also regressed the logaboth the settlement categories and the damage ratios rithm of Y with a dependent indicator X (0 for no settlement 

were transformed by natural-logarithm functions (for ex- in the vicinity or if Xl < 0.5, and 1 for settlement). Figure 

ample, ln Y = alln XI + &). 11 summarizes the results; the coefficient of determination 

- High zone (mean = 33.5, std. dev. = 25.9) Moderate zone (mean = 23.0, std. dev. = 20.5) 

Low zone (mean = 15.2, std. dev. = 15.2) 

0 I0 20 30 40 50 60 70 80 90 I00 

LOSS (AS A PERCENTAGE OF REPLACEMENT VALUE) 

Figure lO.-Cumulative loss distribution by general ground failure zones for buildings having losses 

in San Francisco ZIP code areas surveyed, The high zone of ground failure combines the South of 

Market ground-failure zones and the Marina A, C, and B, zones; the moderate zone consists of 

the Marina D zone; and the low zone combines the Marina B2 zone and the South of Market 

zones with no ground failures. , 

I I 

0 1 

PRESENCE OF GROUND FAILURE (NO = 0, YES = 1) 

Figure 11.-Line regressing natural logarithms (Ln) of damage ratios (loss as a percentage of replacement value) for damaged buildings in the San Francisco ZIP code areas surveyed plotted against the 

presence of ground failure in the general vicinity. 
A76 LOSS ESTIMATION AND PROCEDURES 

(f = 0.12) is somewhat better, and the regression shows that 

the presence of settlement appears to influence the loss 

ratios. 

Our analyses show that considerable scatter exists in our 

loss data and that detailed follow-up studies are required 

to reduce this scatter. 

CONCLUSIONS 

Currently, for a public policy study, loss data from the 

SBA constitute the most comprehensive data on incurred 

losses. The quality of data available from insurance companies varies depending on their specific data-collection practices. Some insurers do not wish to release data and some 

do not systematically gather loss data. The California 

DOI's call for insurance loss data following the Loma Prieta earthquake resolves the data-release problem. However, 

the DO1 analysis of the loss data had only begun when this 

paper was written. Insurance regulators seem to be in the 

best position to improve the gathering of loss statistics. 

Still, only a portion of buildings at risk are voluntarily insured; and unfortunately, we do not know if the insured 

building stock is representative of the larger building stock. 

Losses are relative to whomever pays. Actual repair costs 

may be one standard of loss incurred. This standard is considered by governmental agencies or insurers. The actual 

loss to a governmental agency or insurer is the amount paid 

for the damages through the claims adjustment process. 

Improvements value estimates (estimates of the building 

market value after subtracting land value) can be exceptionally misleading in developing a normalized loss ratio (one 

in which losses are related to a standard measure of exposure at risk). In this project, we us~d cost-per-square-foot 

estimates along with data on square footage to derive estimates of building replacement values. These replacement 

value estimates compare well with insurance industry limits 

of liability estimates. However, variations arise with respect 

to estimates of values at risk, even though more detailed 

cost and bid procedures could reduce these variations. 

Tax assessor data assist in estimating building square 

footage and often contain additional information, such as 

building frame system and landuse category. If tax assessor 

improvements value estimates were regularly updated, these 

could be useful proxies for replacement value estimates. 

Our preliminary analysis of building loss data from the 

San Francisco ZIP code areas we surveyed show that a 

pattern can be developed to distinguish loss ratios (as a 

percentage of replacement value) for buildings in grounddeformation areas from loss ratios for buildings in areas that 

have little or no ground deformation. Considerable variability exists in individual building losses sustained relative to 

mean building losses for a given sample. 

The regression analyses of our building loss data shows 

only a small coefficient of determination (y2 = 0.097), 

which indicates a weak correlation, between the logarithm 

of loss (as a percentage of replacement value) and the logarithm of degree of sediment settlement (by ground-failure 

zone). A slight improvement (y2= 0.12) occurs if the presence of sediment settlement is treated as an indicator variable (with values of 0 and 1). Scatter in our data can be 

further removed by (1) use of a broader data base of building loss data, covering newer structures, undamaged structures, and higher rise structures and (2) more detailed 

followup evaluations of specific building structures to improve data development and to augment data with site-specific and building-specific hazard and vulnerability data. 

This report was prepared under U.S. Geological Survey 

grant number l4-O8-OOOl-Gl863. Opinions and conclusions 

expressed herein do not necessarily represent those of the 

USGS. In addition to the regional technical project monitor, 

T. Holzer, U.S. Geological Survey, we wish to thank the 

following people for their assistance on this project: J. Albert, city of San Francisco, Department of Public Works, 

Bureau of Building Inspection; B. Breedlove, California 

Senate Office of Research; M. Carroll, Department of Housing and Community Development, California Disaster Assistance Program; R. Eis, U.S. Geological Survey; G. 

Fulcher, Brighter Images; W. Garcia, California Department 

of Veterans Affairdcalifornia Veterans Loan Program; R. 

Golesorkhi, Dames & Moore; R. Gorrup, Federal Emergency Management Agency; ' W. Graf, Dames & Moore; R. 

Jenkins, US. Small Business Administration; D. Klink, Arkwright Mutual Insurance Company; R. Mairs, St. Paul Fire 

and Marine Insurance; G. May, Associated International Insurance Company; K. McGregor, Farmers Insurance Group; 

J. Kuehl and T. Morrison, Allstate Insurance; M. Mustacchi, 

photographer; J. Richmond, Individual and Family Grant 

Program; R. Roth, Jr., California Department of Insurance; 

R. Seed, University of California at Berkeley; L. Seekins, 

U.S. Geological Survey; M. Taylor, United Nations; H. Vergales, Government Employees Insurance Company; D. 

Wait, the Federal Emergency Management Agency; 

J. Westbrook, American International Adjustment Company; A. Ziezel, Jr., the Federal Emergency Management 

Agency. Review and editorial comments by B. Lizundia, 

Rutherford and Chekene; S. Tubbesing, Earthquake Engineering Research Institute; J. Hendley, U.S. Geological 

Survey; and an anonymous reviewer are also greatly 

appreciated. 

REFERENCES 

Arnold, Chris, 1990, Presentation at the 4th Annual National Earthquake 

Hazard Reduction Program (NEHRP) Workshop for the Puget 

Sound-Portland Area: April 1990, 
PRELIMINARY STATISTICS ON LOSSES ASSOCIATED WITH GROUND DEFORMATION A77 

Astaneh, A., Bertero, V., Bolt, B.A., Mahin, S.A., Moehle, J.P., and Seed, 

R.B., 1989, Preliminary report on the seismological and engineering 

aspects of the October 17, 1989 Santa Cruz (Loma Prieta) earthquake: University of California, Berkeley, Earthquake Engineering 

Research Center Report No. UCBIEERC-89/14, 51 p. 

Baringer, Marcia, 1989, Loma Prieta: Saved by a short, sharp shock: Science, v. 246, no. 4929, p. 1390-1391. 

Bennett, M.J., 1990, Ground deformation and liquefaction of soil in the 

Marina District in Effects of the Loma Prieta earthquake of the Marine District, San Francisco, California, U.S. Geological Suwey 

Open-File Report 90-253, p. Dl-D36. 

Benuska, Lee, ed., 1990, Loma Prieta earthquake reconnaissance report: 

Earthquake Spectra, no. 6, supp. 1,448 p. 

Boatwright, John, Seekins, L.C., and Mueller, C.S., 1990, Ground motion 

amplification in the Marina District, in Effects of the hma Prieta 

earthquake on the Marina District, San Francisco, California: U.S. 

Geological Suwey Open-File Report 90-253, p. Fl-F24. 

Bonilla, M.G., 1990, Natural and artificial deposits in the Marina District, 

in Effects of the Loma Prieta earthquake on the Marina District, San 

Francisco, California: U.S. Geological Suwey Open-File Report 90- 

253, p. 8-32. 

Celebi, M., 1990, Qpes of structural damage, in Effects of the Lorna 

Prieta earthquake on the Marina District, San Francisco, California: 

U.S. Geological Suwey Open-File Report 90-253, p. 33-38. 

Earthquake Engineering Research Center, 1990, Preliminary report on the 

principal geotechnical aspects of the October 17, 1989 Loma Prieta 

earthquake: University of California, Berkeley, Earthquake Engineering Research Center Report No. UCBIEERC-90105,51 p. 

Earthquake Engineering Research Institute (EERI), 1989, Loma Prieta 

earthquake, October 17, 1989; Preliminary reconnaissance report: El 

Cerrito, Calif.: Earthquake Engineering Research Institute Report 

89-03, 51 p. 

Eguchi, R., Taylor, C., Donovan, N., Werner, S., McGuire, R., Hayne, R., 

1989, Risk analysis methods in a Federal earthquake insurance program: Los Angeles, Dames & Moore, 125 p. 

Holzer, T.L., and O'Rourke, T.D., 1990, Summary and conclusions, in 

Effects of the Loma Prieta earthquake on the Marina District, San 

Francisco, California: U.S. Geological Sumey Open-File Report 90- 

253, p. 1-6. 

Idriss, I.M., 1990, Response of soft soil sites during earthquakes, in Proceedings, H. Bolton Seed Memorial Symposium, May, v. 2: Berkeley, Calif., BiTech Publishers, p. 273-289. 

Legg, M.L., Slosson, J.E., and Eguchi, R.T., 1982, Seismic hazard mapping for lifeline vulnerability analyses, in Mehmet Sherif, chairman, 

Proceedings of the Third International Earthquake Microzonation 

Conference, v. 3, Seattle, Wash., June 28-July 1: p. 1641-1652. 

Lew, H.S., ed,, 1990, Performance of structures during the Loma Prieta 

earthquake of October 17, 1989: U.S. Department oeCommerce, 

National Institute of Standards and Technology, NIST Special Publication 778, 201 p. 

McClure, F.E., 1973, Studies in gathering earthquake damage statistics: 

Washington, D.C., U.S. Coast and Geodetic Suwey, 128 p. 

National Research Council (NRC), 1989, Estimating losses from future 

earthquakes: Washington, National Academy Press, 231 p. 

Oakeshott, G.B., 1975, ed., San Fernando, California earthquake of 

9 February 1971: Sacramento, California Division of Mines and Geology Bulletin 196,463 p. 

Oaks, S.D., 1990, The damage assessment process; The application of 

ATC-20, The Loma Prieta earthquake: Studies of short-term impacts: Boulder, Colo., Institute of Behavioral Science, Program on 

Environment and Behavior, Monograph 50, p. 6-16. 

09Rourke, T.D., and Roth, B.L., 1990, Performance of pipeline systems 

in the Marina, in Effects of the Loma Prieta Earthquake on the Marina District: U.S. Geological Open-File Report 90-253, p. El-E8. 

O'Rourke, T.D., Stewart, H.E., Blackburn, F.T., and Dickerman, T.S., 

1990, Geotechnical and lifeline aspects of the October 17, 1989 

Loma Prieta earthquake in San Francisco: Buffalo, New York, National Center for Earthquake Engineering Research Technical Report 

NCEER-90-001,53 p. 

Plakfer, George, and Galloway, J.P., eds., 1989, Lessons learned from the 

Loma Prieta, California, earthquake of October 17, 1989: U.S. Geological Suwey Circular 1045,48 p. 

R.P. Gallagher Associates, Inc., 1989, Procedures for postearthquake 

safety evaluation of buildings: Redwood City, Calif., Applied Technology Council, ATC-20, 152 p. 

R.S. Means Company, Inc., 1991, Means square foot costs [12th ed.]: 

Kingston, Mass, 445 p. 

Rojahn, C., Sharpe, R., Scholl, R., Kiremidjian, A,, and Nutt, R., 1985, 

Earthquake damage evaluation data for California: Redwood City, 

Calif., Applied Technology Council, ATC-13, 492 p. 

Seed, R.B., Dickerson, S.E., Riemer, M.F., Bray, J.D., Sitar, N., Mitchell, 

J.K., Idriss, I.M., Kayen, R.E., Kropp, A., Harder, L.F., Jr., and 

)Power, M.S., 1990, Preliminary =port on the principal geotechnical 

aspects of the October 17, 1989 Loma Prieta earthquake: Berkeley; 

University of California, Earthquake Engineering Research Center 

Report UCBIEERC-90105, 137 p. 

Seekins, L.C., in press, Revised areal distribution of damage to surface 

structures in the Marina District of San Francisco from the Loma 

Prieta earthquake: Bulletin of the Seismological Society. 

Seekins, L., Lew, F., and Kornfield, L., 1990, Areal distribution of damage to surface structures, in Effects of the Loma Prieta earthquake 

on the Marina District, San Francisco, California: U.S. Geological 

Sumey Open-File Report 90-253, C 1 -C5. 

Sharp, R.V., 1975, Displacement on tectonic ruptures, in Oakeshott, G.B., 

ed., San Fernando, California earthquake of February, 1971: Sacramento, California Division of Mines and Geology Bulletin 196, 

p. 187-194. 

Steinbrugge, K.V., and Algermissen, S.T., 1990, Earthquake losses to single-family dwellings: California experience: U.S. Geological Survey 

Bulletin 1939, 65 p. 

Stover, C.W., Reagor, B.G., Baldwin, F.W., and Brewer, L.R., 1990, PEliminary isoseismal map for the Santa Cruz (Loma Prieta), California, earthquake of October 18, 1989 UTC: U.S. Geological Sumey 

Open-File Report 90-18,24 p. 

Taylor, C., Crouse, C.B., Porush, A., Eguchi, R., Kunreuther, H., Doherty, N., Butler, A., Kleffner, A., Petak, W., and Mittler, E., 1989, 

Workshop on Loss-Reduction Provisions of a National Earthquake 

Insurance Program: hs Angeles, Dames & Moore, 75 p. 

Taylor, C.E., Elliot, W., Cornell, H,, and Bdlantyne, D., 1990, The demonstration project on seismic loss estimation for water systems, in 

Kiremidjian, A.S., ed., Recent lifeline seismic risk studies: New 

York, The American Society of Civil Engineers, 166 p. 

Taylor, C., Petak, W., Mittler, E., Brown, J., Porush, A., Kunceuther, H., 

Crouse, C.B., Doherty, N., Butler, A., and Kleffner, A., 1990, Lossreduction provisions of a federal earthquake insurance program: 

Washington, D.C., The Federal Emergency Management Agency 

Publication 200, 208 p. 

Tissel, John, 1990, Performance of wood-framed structures in the Loma 

Prieta earthquake, in Raufaste, N.J., ed., Wind and Seismic Effects-Proceedings of the 22d Joint Meeting of the U.S.-Japan Cooperative Program in Natural Resources: Gaithersburg, Md., 

National Institute of Standards ad Technology, NIST SP 796, 

p. 324-330. 

Wiggins, J.H., and Taylor, C.E., 1986, Earthquake performance of lowrise construction, v. 2, Long Beach, Calif.: NTS Engineering Report 

86-1442, 189 p, 

Wood, H., 1908, Isoseismals-Distribution of apparent intensity, in The 

California Earthquake of April 18, 1906: Report of the State Investigation Commission, Carnegie Institution of Washington, p. 220- 

254. 

Youd, T.L., 1978, Major cause of earthquake damage is ground failure: 

Civil Engineering, p. 47-51.