Puget Sound Tsunami Sources Puget Sound Tsunami Sources

2002 Workshop Report 2002 Workshop Report

National Oceanic and Atmospheric Administration

United States Geological Survey

Washington State Department of Natural Resources

Washington State Military Department Emergency Management Division

A Joint Special Report A Joint Special Report
On the cover: Puget Sound has a history of tsunamis that includes

water waves generated by this landslide at the Tacoma Narrows. The

slide occurred three days after the magnitude-7.1 Olympia earthquake

of April 13, 1949. It generated a tsunami that reflected off the

opposite shore and propagated back to the coast on which the

landslide occurred.
NOAA OAR Special Report

Puget Sound Tsunami Sources—2002 Workshop

Report

A contribution to the Inundation Mapping Project of the

U.S. National Tsunami Hazard Mitigation Program

Workshop Report Committee:

Frank I. Gonz ́alez, compiler, with contributions from Brian L. Sherrod, Brian F. Atwater,

Arthur P. Frankel, Stephen P. Palmer, Mark L. Holmes, Robert E. Karlin, Bruce E. Jaffe,

Vasily V. Titov, Harold O. Mofjeld, and Angie J. Venturato

Sponsored by:

National Oceanic and Atmospheric Administration

U.S. Geological Survey

Washington State Department of Natural Resources

Washington State Military Department Emergency Management Division

Workshop Organizing Committee:

G. Crawford, F. Gonz ́alez (Chair), M. Holmes, H. Mofjeld, B. Sherrod, V. Titov,

A. Venturato, T. Walsh, C. Weaver

June 2003

Contribution 2526 from NOAA/Pacific Marine Environmental Laboratory
NOTICE

Mention of a commercial company or product does not constitute an endorsement by

NOAA/OAR. Use of information from this publication concerning proprietary products

or the tests of such products for publicity or advertising purposes is not authorized.

Contribution No. 2526 from NOAA/Pacific Marine Environmental Laboratory

For sale by the National Technical Information Service, 5285 Port Royal Road

Springfield, VA 22161

ii
Contents iii

Contents

Puget Sound Tsunami Sources Workshop History . . . . . . . . . v

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Earthquake Sources . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2 Priority Areas . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Seattle Fault .......................... 5

Tacoma Fault ......................... 7

South Whidbey Island Fault ................. 8

2.3 Event Descriptions ........................ 8

2.4 Recommendations ........................ 8

Tsunami Source Modeling .................. 8

Science Improvement ..................... 9

3. Delta Failure and Landslide Sources . . . . . . . . . . . . . . 9

3.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2 Priority Areas . . . . . . . . . . . . . . . . . . . . . . . . . . 12

River Delta Failures . . . . . . . . . . . . . . . . . . . . . 12

Non-deltaic submarine Landslides . . . . . . . . . . . . . . 12

Subaerial landslides . . . . . . . . . . . . . . . . . . . . . . 12

3.3 Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Historical precedent scenarios . . . . . . . . . . . . . . . . 12

Worst-case scenarios . . . . . . . . . . . . . . . . . . . . . 15

Non-deltaic submarine slide scenarios . . . . . . . . . . . 17

3.4 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 18

Tsunami source modeling . . . . . . . . . . . . . . . . . . 18

Science improvement . . . . . . . . . . . . . . . . . . . . . 18

4. Paleotsunami Field Evidence . . . . . . . . . . . . . . . . . . 23

4.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.2 Priority Areas . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.3 Inferences About Past Tsunamis . . . . . . . . . . . . . . . . 23

4.4 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 24

Tsunami source modeling . . . . . . . . . . . . . . . . . . 24

Science improvement . . . . . . . . . . . . . . . . . . . . . 24

5. Seattle-Duwamish Waterfront Inundation .......... 24

5.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.2 Priority Areas . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5.3 Event Description . . . . . . . . . . . . . . . . . . . . . . . . 25

Source specification . . . . . . . . . . . . . . . . . . . . . . 25

Model results . . . . . . . . . . . . . . . . . . . . . . . . . 26

Model limitations . . . . . . . . . . . . . . . . . . . . . . . 28

Source uncertainty and sensitivity . . . . . . . . . . . . . . 28

5.4 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 29

Science improvement . . . . . . . . . . . . . . . . . . . . . 29

6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 29

Addendum: Seismic Surface Wave Forcing of Water Waves and

Seiches (by H. O. Mofjeld) . . . . . . . . . . . . . . . . . . . 34

Appendix A: Workshop Participants . . . . . . . . . . . . . . . . . 35
iv Contents

List of Figures

1 (a) Schematic of fault zone locations in the Puget Sound region,

(b) Vertical deformation for an M 9.1 Cascadia earthquake. (c) Pacific Northwest peak ground acceleration with 2% probability of exceedance in 50 years. ........................... 6

2 Locations of major river deltas in Puget Sound. . . . . . . . . . . . . 11

3 Potential landslide zones. . . . . . . . . . . . . . . . . . . . . . . . . 13

4 (a) Distribution of landslides in Lake Washington classified by type,

(b) Submarine landslides in Lake Washington classified by age,

(c) Geologic map of Lake Sammamish. . . . . . . . . . . . . . . . . . 14

5 Seattle-Duwamish waterfront inundation modeling products. . . . . . 27

List of Tables

2.1 Fault parameters used in making the 2002 version of the USGS National Seismic Hazard Map ....................... 9

3.1 Historic delta landslide. . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.2 Subaerial landslide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.3 Worst-case delta failure. . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.4 Submarine landslide. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.5 Dimensions of selected large landslides in Puget Sound. . . . . . . . 22

5.1 Sub-fault parameters for magnitude 7.3 and 7.6 Seattle Fault earthquake models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.2 Vertical deformation values for field estimates and the M 7.3 and M

7.6 Seattle Fault models. . . . . . . . . . . . . . . . . . . . . . . . . . 26
Puget Sound Tsunami Sources—2002 Workshop Report v

Puget Sound Tsunami Sources Workshop History

This workshop was jointly sponsored by NOAA’s Center for Tsunami Inundation Mapping Efforts (TIME), the U.S. Geological Survey, the Washington

State Military Department Emergency Management Division (WAEMD),

and the Washington State Department of Natural Resources (WADNR).

The Workshop Organizing Committee consisted of:

George Crawford WA State Emergency Management Division

Frank Gonz ́alez (Chair) NOAA TIME Center

Mark Holmes U. Washington

Hal Mofjeld NOAA TIME Center

Brian Sherrod U.S. Geological Survey

Vasily Titov NOAA TIME Center

Angie Venturato NOAA TIME Center

Tim Walsh WA State Dept. Natural Resources

Craig Weaver U.S. Geological Survey

This committee held a planning meeting on 24 April 2002. On 9 May, an

informational e-mail was distributed to 35 individuals, inviting their participation and soliciting pre-workshop scientific contributions for the workshop

web site. The web site served to stimulate and facilitate pre-workshop e-mail

discussion and to provide resource material for the subsequent workshop activities. Twenty-three attendees participated in the workshop, held on 10

June 2002 at NOAA’s Pacific Marine Environmental Laboratory in Seattle,

Washington. The full list of invitees and the pre-workshop contributions are

posted on the workshop web site at http://www.pmel.noaa.gov/tsunami/

time/PS source wkshp/. The full list of workshop participants is provided

in Appendix A.

At the workshop, the following sub-groups were formed to concentrate

on specific source issues:

Earthquake Sources: A. Frankel, C. Garrison-Laney, T. Jovanelly,

B. Sherrod, C. Weaver, J. Whisler

Delta Failure and Landslide Sources: J. Gardener, M. Holmes, R. Karlin,

R. Kayen, S. Palmer, H. Shipman, T. Walsh, H. Yeh

Paleotsunami Field Evidence: B. Atwater, B. Jaffe, H. Mofjeld, V. Titov

The remaining participants were specialists in tsunami modeling and emergency management, and they participated in each sub-group as needed.

Subsequently, the following individuals served as lead contributors to

individual sections of the report: Gonz ́alez (Sections 0 and 1), Sherrod,

Atwater, and Frankel (Section 2), Palmer, Holmes, and Karlin (Section 3),

Jaffe and Atwater (Section 4), Titov, Mofjeld, Gonz ́alez, and Venturato

(Section 5). In June 2002, a first rough draft was distributed via e-mail list

PugetSources@pmel.noaa.gov to all workshop invitees and participants for

their review. The manuscript went through several rounds of revision and

review before completion in June 2003.

Puget Sound Tsunami Sources—2002 Workshop Report

Workshop Report Committee:

Frank I. Gonz ́alez, compiler, with contributions from Brian L. Sherrod, Brian F. Atwater,

Arthur P. Frankel, Stephen P. Palmer, Mark L. Holmes, Robert E. Karlin, Bruce E. Jaffe,

Vasily V. Titov, Harold O. Mofjeld, and Angie J. Venturato

Executive Summary

Potential tsunami sources in Puget Sound were reviewed by a 23-person

panel of geoscientists, oceanographers, and emergency managers who participated in a 1-day workshop. Their goal was to lay scientific groundwork

for hazard assessment in coastal areas threatened by tsunamis and, in so

doing, assist emergency managers that seek to comply with the spirit of the

Washington State Growth Management Act, which instructs officials to seek

out and consider the “best available science.” The panelists recommended

that tsunami modelers focus on several kinds of sources, and they also recommended improvements in source identification and modeling.

Tsunami Modeling Recommendations

 Earthquakes on the Seattle fault zone, the Tacoma and South Whidbey

Island faults, and other structures that generate tsunamis by tectonically raising or lowering the floor of Puget Sound, consistent with best

estimates that may include fault parameters used in the USGS National Seismic Hazard Map (Table 2.1 or updates) and paleoseismic

estimates of land-level change.

 Delta slope failures of the Puyallup, Duwamish, and Snohomish River

deltas, with parameters based on the 1894 Commencement Bay event

(Table 3.1) and a scaled-down 1964 Valdez event (Table 3.3).

 Submarine landslides associated with Quaternary faults (not deltas),

with parameters based on currently unpublished seismic profiling data

and maps (Table 3.4).

 Subaerial landslides, with parameters based on the 1949 Tacoma Narrows landslide (Table 3.2).

 Tsunami modelers should develop these source scenarios in close collaboration with geoscience experts on earthquakes, slope stability, and

paleotsunami evidence in Puget Sound.

Science Improvement Recommendations

 Use LIDAR data to update deformation estimates for A.D. 900 Seattle

Fault earthquake and for other fault ruptures.
2 F. Gonz ́alez et al.

 Do additional fieldwork to document coastal deformation and constrain

the eastern end of the Tacoma Fault.

 Expand the existing program of slope instability mapping to increase

the geographical coverage and improve the quality of submarine and

subaerial landslide assessments, including the acquisition of multibeam

bathymetry and sediment cores.

 Improve estimates of wave height and water velocity of prehistoric and

recent tsunamis through combined use of sedimentology and inundation modeling.

 Do additional fieldwork to check for tsunami deposits at Lynch Cove,

Lake Washington, Lake Sammamish, and other Puget Sound area sites.

 Make and update summary maps that incorporate all available field

evidence for tsunami deposits, coseismic deformation, and submarine

and subaerial landslides.

 Develop methods to assess the sensitivity of coastal areas to tsunami inundation, based on multiple simulations that reflect the possible range

of variations in the source parameters.

 Hold yearly workshops to review the best available scientific information and develop updated recommendations for tsunami inundation

mapping in Washington State.
Puget Sound Tsunami Sources—2002 Workshop Report 3

1. Introduction

Future Puget Sound tsunamis are guaranteed by a combination of setting and

history. The inland waters and lakes of the Puget Sound lowland cross active faults and contain records of earthquakes and landslides. From geologic

and historical evidence, it is known that some of these events have generated tsunamis. A workshop on 23 January 2001 concluded that “Tsunamis

and landslides in the greater Puget Sound region pose significant hazards

that must be included in local and regional emergency response and development plans” (Crawford et al., 2001). That workshop was organized

by the Washington State Military Department Emergency Management Division (WAEMD), the National Oceanic and Atmospheric Administration

(NOAA), and the U.S. Geological Survey (USGS), all partners of the U.S.

National Tsunami Hazard Mitigation Program (Bernard, 2001).

A major goal of the national tsunami program is to develop tsunami

inundation maps for all U.S. coastal communities at risk (Gonz ́alez et al.,

2001). In 2002, NOAA’s Center for Tsunami Inundation Mapping Efforts

(TIME) made initial simulations of Seattle-Duwamish waterfront inundation

by a tsunami generated by an M 7.3 Seattle Fault earthquake scenario. In

2003, the TIME Center plans to begin numerical simulations and mapping

of tsunami inundation in the Puget Sound lowland. Such simulations are

intended to help state, county, and municipal officials develop emergency

management tools, including evacuation maps, response plans, educational

material, and outreach and mitigation programs. The inundation maps are

expected to evolve as emergency managers apply them and as researchers

revise their scientific basis.

In Washington, this effort provides the basis for community development of a mitigation plan that is in compliance with the Washington State

Growth Management Act, under which coastal areas threatened by tsunamis

are designated as critical areas (Washington State Office of Community Development, 2002). In 1995, a section was added to the Growth Management

Act that requires counties and cities to include the “...best available science when developing policies and development regulations to protect the

functions and values of critical areas...” and encourages state officials to

“...consult with a qualified scientific expert or team of qualified scientific experts to identify scientific information, determine the best available science,

and assess its applicability to the relevant critical areas” (Washington State

Legislature, 1995).

In the spirit of complying with these requirements, a Puget Sound

Tsunami Sources Workshop was organized by NOAA’s TIME Center, the

USGS, WAEMD, and Washington Department of Natural Resources

(WADNR). This workshop had two specific objectives:

1. Develop quantitative descriptions of potential sources for inundation

modeling to assess Puget Sound tsunami hazards.

2. Develop recommendations for improving the scientific basis for source

specification and tsunami source modeling.
4 F. Gonz ́alez et al.

The 1-day workshop was held on 10 June 2002 at NOAA’s Pacific Marine Environmental Laboratory in Seattle, Washington. The 23 participants

included scientists with specialties in earthquakes, landslides, delta failures,

paleotsunami field evidence, tsunami modeling, and emergency management

(Appendix A). Strawman source scenarios, reports, and other relevant reference materials were contributed by invitees prior to the workshop. These

were made available on the workshop web site, at http://www.pmel.noaa.

gov/tsunami/time/PS source wkshp/ .

The workshop consisted of whole-group discussions and sub-group sessions. First, an open discussion of earthquake, delta failure, and landslide

scenarios was held; participants then divided into three sub-groups. Two

sub-groups concentrated on developing quantitative descriptions of potential

tsunami sources—the first dealt with earthquake uplift and subsidence, the

second with slope failures. The third sub-group dealt with geologic records

of past tsunamis and their triggers. Finally, an example was presented of a

recent tsunami inundation modeling study for the Seattle-Duwamish waterfront area.

2. Earthquake Sources

2.1 Background

Earthquakes at Puget Sound occur along faults in three tectonic settings:

within the subducted oceanic plate (Juan de Fuca plate) at depth beneath

Puget Sound, within the overriding continental plate (North America plate),

and at the boundary fault between those plates.

For each of these sources, the largest earthquakes recur at poorly known,

probably irregular, intervals. On average, the intervals are on the order of

decades for the Juan de Fuca plate, millennia for the best-known of the

upper-plate faults (the Seattle Fault), and centuries for the plate boundary

(http://www.ess.washington.edu/SEIS/PNSN/INFO GENERAL/eqhazards.

html).

Although few earthquakes result in tsunamis at Puget Sound, each of the

three earthquake sources has demonstrated its capability of generating such

waves. A landslide that set off a tsunami in Tacoma Narrows occurred a

few days after the 1949 earthquake in the Juan de Fuca plate (Noson et al.,

1988). The earthquake of ca. A.D. 900 on the Seattle fault caused uplift

that triggered a tsunami in central Puget Sound and also caused landslidegenerated waves in Lake Washington (Atwater and Moore, 1992). Tsunamis

from plate-boundary earthquakes probably account for several sand sheets

on northwestern Whidbey Island (Williams and Hutchinson, 2000) and at

Discovery Bay (Williams et al., 2002).

2.2 Priority Areas

The workshop focused on coseismic uplift and subsidence along three fault

zones as sources for tsunamis in the Puget Sound region—the Seattle Fault,
Puget Sound Tsunami Sources—2002 Workshop Report 5

Tacoma Fault, and South Whidbey Island Fault. Also discussed was coseismic subsidence 1100 years ago near Olympia (Sherrod, 2001), and the

Cascadia Subduction Zone (CSZ) as a likely source for tsunamis at northwestern Whidbey Island (Williams and Hutchinson, 2000) and Discovery

Bay (Williams et al., 2002). Puget Sound probably has additional tectonic sources of tsunamis, particularly vertical displacement along faults

beneath the Sound near the latitude of the Strait of Juan de Fuca (Johnson,

2001). These structures, along with rapidly changing views of the Seattle

and Tacoma faults, will need reassessment in future workshops.

Maps in Fig. 1 summarize several aspects of the region’s earthquake

hazards. Figure 1a schematically summarizes the general location of some

known fault zones at Puget Sound. This map includes deformation contours for a worst-case event—the modeled crustal deformation pattern for

an M 7.3 Seattle Fault earthquake discussed in section 5.0, below. Figure 1b

presents the modeled deformation pattern for an M 9.1 earthquake on the

CSZ. Figure 1c provides estimates of peak ground acceleration that might be

experienced in the Puget Lowlands area with a 2% probability of exceedance

in 50 years (Frankel et al., 1996).

Seattle Fault

Tsunami generation models for the Seattle Fault Zone depend on a complicated geometry that was being reassessed as this report was written and

revised. This reassessment may produce large changes in fault parameter

estimates, in which case the tsunami source models presented in Table 5.1

may require modification.

Previously, the Seattle Fault Zone was inferred to have roots in a widespread, nearly horizontal detachment fault tens of kilometers beneath much

of Puget Sound (Pratt et al., 1997). It was also mapped as containing multiple near-surface strands that are rooted in a master reverse fault (Johnson

et al., 1999; Blakely et al., 2002). More recently, this master fault has been

considered largely disconnected from near-surface strands. Instead, much

like a well-studied reverse fault in Japan (Ishiyama et al., 2002), the master

fault may terminate kilometers below the surface, and the master fault may

deform rocks above it much like the blade of a snowplow. These various

interpretations provide many ways of suddenly raising or lowering the floor

of Puget Sound—the deformation that would generate a tsunami.

The main mapped strands of the Seattle Fault Zone, from north to south,

have been called the Frontal fault, the Blakely Harbor fault, and the Orchard

Point fault (Johnson et al., 1999; Blakely et al., 2002). The Frontal fault

projects to the surface about 3.5 km north of Restoration Point and may

dip steeply to the south (Brocher et al., 2001; Calvert and Fisher, 2001; ten

Brink et al., 2002).

A late Holocene earthquake, with a magnitude (M) of 7 or more occurred

on the Seattle Fault Zone about 1100 years ago (Bucknam et al., 1992). This

earthquake, probably between A.D. 900 and 930 (Atwater, 1999), generated

a tsunami known from deposits at West Point (in Seattle), Cultus Bay (at

the south end of Whidbey Island), and the Snohomish River delta near
6 F. Gonz ́alez et al. South Whidbey Fault Zone Utsalady Fault Zone Swantown Discovery Bay Shine Snohomish River Delta Cultus Bay15 0 15 Km Lynch Cove Dumas Bay Hat Island Seattle Fault Zone Olympia Fault Zone Source area of a magnitude 9.1 Cascadia earthquake. This type of earthquake probably accounts for tsunami deposits found at Swantown and Discovery Bay. Contours indicate vertical crustal deformation in meters.”

0

1

3

5

-1

Burley

Gorst

Earthquakes

Tsunami Evidence

Published geologic tsunami deposit

Candidate geologic tsunami deposit seen in reconnaissance

Native American Stories

(a)

(b)

>2

>2

>2

Oakland

Bay

Little Skookum

Inlet

1

~1 Nisqually Delta,

McAllister Creek,

Red Salmon Creek

(c)

Peak Ground Acceleration with 2% probability of

exceedance in 50 years (after Frankel, et al.,1996)

200100

80

604030

2010

6

0

%g

150

9070

50453525

15

842

Map (a) is based on discussions held during the Puget Sound Tsunami Sources

workshop held in Seattle, Washington on 10 June 2002, and on subsequentreviews and discussion by workshop participants. Contributing institutionsincluded Kent State University, National Oceanic and Atmospheric Administration(NOAA), University of Nevada, University of Washington, U.S. GeologicalSurvey (USGS), and Washington Division of Geology and Earth Resources. Theworkshop was organized by NOAA’s Center for Tsunami Inundation MappingEfforts (TIME), the USGS, Washington’s Department of Natural Resources (WADNR)and Washington’s Emergency Management Division (WAEMD).

124° 122° 120° 118° 116°W

46°

48°N

Published co-seismic Vertical Deformation Estimates

(Color-coded for Tsunami Evidence)

Uplift of n metersSubsidence of n meters

~1-3

West

Point

Tacoma

Fault Zone

Winslow

Restoration

Point

7

Fault ZonesVertical deformation for Mw 7.3 Seattle Fault

n

n

Figure 1: (a) Schematic of fault zone locations in the Puget Sound region, with vertical deformation contours for an Mw 7.3 Seattle Fault. Inset (b)Vertical deformation for an M 9.1 Cascadia earthquake. (c) Pacific Northwest peak ground acceleration with 2% probability of exceedance in 50 years(from Frankel et al., 1996).
Puget Sound Tsunami Sources—2002 Workshop Report 7

Everett (Atwater and Moore, 1992; Bourgeois and Johnson, 2001). The

tsunami probably resulted from 5–7 m of uplift in a band 6 km wide south

of the fault, and secondarily from as much as 1 m of subsidence to the north.

This uplift and subsidence displaced large volumes of water in Puget Sound,

whether or not fault rupture extended upward to the floor of the sound.

A south-facing scarp within the Seattle Fault Zone, identified by airborne laser mapping, crosses Bainbridge Island about 2 km north-northwest

of Restoration Point (Bucknam et al., 1999). Stratigraphy and structure

exposed in trenches excavated across the scarp show a postglacial history of

folding and faulting from multiple earthquakes, with the most recent event

occurring about 1100 years ago (Nelson et al., 1999; 2002). A full-length

report on the trench results was nearing completion as this workshop report

was being written.

A north-facing scarp within the Seattle Fault Zone, near the west shore

of Lake Sammamish, was recently trenched by Sherrod (2002). He found

evidence for one postglacial surface rupture and dated it to the past 13,000

calendar years.

Tacoma Fault

Like the Seattle Fault Zone, the Tacoma Fault separates an area of coseismic

uplift from an area of coseismic subsidence (Brocher et al., 2001). The

documented examples of these land-level changes date to about 1100 years

ago (Bucknam et al., 1992). Though much remains to be learned about its

extent and shape, the Tacoma Fault is evident from gravity and aeromagnetic

anomalies, seismic tomography, and seismic-reflection lines. The fault likely

runs westward and northwestward from Tacoma across much of the Puget

Lowland (Fig. 1a). Seismic tomography implies at least 6 km of post-Eocene

uplift to the north relative to basinal sedimentary rocks to the south.

Uplift to the north of the fault and subsidence to the south occurred

most recently in A.D. 800–1200, not necessarily in a single year (Sherrod

et al., 2002). To the northwest at Lynch Cove, tide flats rose as much as

3 m between A.D. 870–990. Uplift 16 km to the east at Burley, accompanied

there by liquefaction and a tsunami, allowed woody shrubs to invade former

tideflats in A.D. 770–1000. Shells in tideflat mud at North Bay record uplift

loosely dated to the past 3000 years. Fossil foraminifera from Dumas Bay

limit the eastward extent of uplift north of the fault, for they show that

a brackish marsh remained in the intertidal zone throughout the last 2000

years. However, trees at Wollochet Bay, on the south side of the fault,

subsided into the intertidal zone. A single radiocarbon age implies that this

subsidence occurred A.D. 980–1190, in which case the subsidence postdates

uplift at Lynch Cove and Burley by 30–270 years.

The age range of this uplift on the north side of the Tacoma Fault includes

times of coseismic uplift and subsidence at many sites around Puget Sound.

As noted above, an earthquake raised shorelines along the Seattle Fault

Zone in A.D. 900–930; moreover, several shores of southern Puget Sound

subsided A.D. 860–940. Therefore, the uplift north of the Tacoma Fault

either coincided with a single large event in A.D. 900–930, or it represents a
8 F. Gonz ́alez et al.

separate earthquake of about that age. However, the subsidence at Wollochet

Bay implies either coseismic or aseismic deformation after A.D. 900–930.

South Whidbey Island Fault

The South Whidbey Island Fault is one of several that splay eastward from

the Strait of Juan de Fuca and appear to displace postglacial deposits (Wagner and Tomson, 1987). It has been mapped as a transpressional deformation

zone that crosses Admiralty Inlet and southern Whidbey Island (Johnson,

1996; 2001). This zone separates pre-Tertiary rocks to the northeast from

Eocene volcanic and sedimentary rocks to the southwest. The highest Tertiary rocks have as much as 420 m of relief across the fault, either from

vertical tectonic movement (Johnson, 1996) or from subglacial erosion. An

earthquake on the South Whidbey Island Fault might produce both vertical

and horizontal displacement of the floor of Puget Sound.

Compared with the Seattle and Tacoma structures, the South Whidbey

Island Fault may have produced little vertical displacement in the Holocene.

The evidence reported thus far comes from northern Whidbey Island, where

two sites (Crockett and Hancock Lakes) appear to differ by about 2 m in

relative sea-level change about 3000 years ago. The inferred difference is

tentative because it has been reported only in abstract and because it has

been inferred from differences in the radiocarbon age of intertidal deposits

at similar elevation (Kelsey and Sherrod, 2001).

2.3 Event Descriptions

Table 2.1 provides fault parameter estimates for the Seattle and South Whidbey Island Fault Zones as used by the USGS National Seismic Hazard Mapping Project (Frankel et al., 2002). Because of lively research and debate

about the structure and Holocene history of these faults, the tabulated parameters represent a recent consensus that is already out of date. The lack

of estimates for the Tacoma Fault reflects an early stage of research into the

Holocene history of this structure.

2.4 Recommendations

Tsunami Source Modeling

 Seattle Fault: Incorporate the most current fault and earthquake parameters provided by active researchers and the USGS National Seismic Hazard Mapping Project.

 South Whidbey Island Fault: Incorporate the most current fault and

earthquake parameters provided by active researchers and the USGS

National Seismic Hazard Mapping Project.
Puget Sound Tsunami Sources—2002 Workshop Report 9

Table 2.1: Fault parameters used in making the 2002 version of the USGS National Seismic Hazard Map

(Frankel et al., 2002, http://geohazards.cr.usgs.gov/eq/faults/fsrpage21.html#washington). End

points listed in the table should not be interpreted as a straight line fault trace; they correspond to the two

ends of a more complex fault trace that is not detailed here (Art Frankel, personal communication). T, the

recurrence time for earthquakes of magnitude M, is especially uncertain. In the characteristic earthquake

model, a fault produces earthquakes of one size only (of M 7 in the case of the Seattle and south Whidbey

Island faults) at the indicated recurrence interval. In the truncated Gutenberg-Richter model, the fault

produces earthquakes in a certain size range (greater than M 6.5, in this case) at the indicated recurrence

interval. The 2002 hazard map gives the two models equal weight (Frankel et al., 2002, p. 11).

Truncated

Characteristic- Gutenbergearthquake Richter

model model

Fault Slip Rate End Points Length Width Dip T T

Zone (m/1000 yr) (deg., lat., long.) (km) (km) (deg) (yr) M (yr) M

Seattle 0.5 47.6, −121.9 71 21 45 5000 7 1000 ≥6.5

47.6, −122.9

Tacoma TBD TBD 50 TBD TBD TBD TBD TBD TBD

S. Whidbey 0.6 47.9, −122.3 63 17 60 3000 7 1000 ≥6.5

Island 48.2, −123.0

Science Improvement

 Seattle Fault: Use high-resolution topography from LIDAR, verified

by field work, to update estimates of crustal deformation for A.D. 900

event.

 Tacoma Fault: Study surface ruptures and shoreline changes that can

be associated with the fault.

3. Delta Failure and Landslide Sources

3.1 Background

The working group identified three distinct landslide situations that could

result in a significant tsunami affecting local communities bordering Puget

Sound: submarine landslides on delta fronts, submarine slides elsewhere in

the Sound, and slides from adjacent uplands.

Submarine landslides can originate on the delta slopes of major rivers

flowing into the Sound, in particular the Nisqually, Puyallup, Duwamish,

and Snohomish rivers. In 1894 a large submarine landslide occurred on the

Puyallup River delta in Commencement Bay, resulting in two deaths and

the destruction of the Northern Pacific freight docks and other port facilities

(Stephen Palmer, unpublished data; Gardner et al., 2001). A smaller submarine landslide in 1943 destroyed jetties along the mouth of the Puyallup

River (University of Washington, Department of Oceanography, 1953). In

addition to these Puget Sound examples, larger submarine landslides have
10 F. Gonz ́alez et al.

occurred on river deltas in British Columbia and Alaska. Some of these slides

were triggered by large earthquakes, and others resulted simply from river

delta evolution, including oversteepening of the delta front. The submarine

landslides resulting from the 1964 Alaska earthquake resulted in more than

50 deaths and the near-total destruction of three port communities: Valdez,

Seward, and Whittier (Wilson and Torum, 1972; Spaeth and Berkman, 1972;

Lander, 1988). At Valdez, large tsunamis were generated by a number of

submarine slides, including a massive slide off the Lowe River delta that included the Valdez waterfront and the shore north of town; docks, canneries,

the boat harbor, and many boats were totally destroyed, oil tanks were set

on fire, and 31 died. At Seward, the earthquake triggered slides on the Resurrection River fan delta, causing a large stretch of waterfront to slide into

Resurrection Bay; the slide and the resultant tsunami destroyed almost the

entire economic foundation of the community and caused 11 deaths. Whittier suffered 13 fatalities, destruction of docks, oil tank farms, and railroad

facilities, due to the earthquake and tsunami waves evidently generated by

delta failures. Known historical Puget Sound delta failures, all far smaller

than these Alaskan examples, are shown in Fig. 2, as are the locations of

major river deltas.

Additional landslides originate on steep submarine slopes that are not

part of a delta. Unpublished seismic profiling data and mapping presented

by members of the working group (Robert Karlin and Mark Holmes) indicate

that large submarine landslides have occurred on submarine slopes in Puget

Sound, Lake Washington, and Lake Sammamish that are not associated

with large river deltas, but that appear proximal to a number of Quaternary

faults that cross the Sound (Karlin et al., 2002). Large prehistoric landslides

have been identified on continental shelves and slopes off Europe, Africa, and

North and South America (Moore, 1978). Most have been identified through

seismic profiling and sediment coring on the continental margins. In addition, some submarine slope failures, such as the Grand Banks landslide of

1929, have occurred during historical times. This landslide caused a tsunami

that resulted in the loss of 27 lives in southern Newfoundland (Heezen and

Ewing, 1952; Heezen and Drake, 1964; Hasagawa and Kanamori, 1987). The

1929 slide apparently consisted of multiple slumps of many sizes (Piper et al.,

1999). In 1998, a large submarine landslide is suspected of contributing to

a Papua New Guinea tsunami that caused more than 2200 fatalities (Titov

and Gonz ́alez, 2001).

Subaerial landslides that fall into Puget Sound with sufficient volume and

velocity, and at the appropriate tidal conditions, can generate large water

waves. Such a tsunami was generated by a landslide at the Tacoma Narrows

that occurred three days after the 1949 Ms 7.1 Olympia earthquake. The

landslide occurred on the steep bluff bordering The Narrows, and the fall of

the slide debris into the water caused the tsunami (Chleborad, 1994). Native

American oral tradition suggests that a large subaerial landslide at Camano

Head created a water wave that drowned many people on Hat (Gedney)

Island (Shipman, 2001). Because the story does not include ground shaking,

this landslide was not necessarily associated with an earthquake. Figures 3
Puget Sound Tsunami Sources—2002 Workshop Report 11 Swantown Discovery Bay Shine Cultus Bay 15 0 15 Km Lynch Cove Dumas Bay Burley Delta Failures Tsunami Evidence Historic Delta Failure Published geologic tsunami deposit Candidate geologic tsunami deposit seen in reconnaissance Native American Stories West Point Winslow River Deltas Skagit Delta Stillaguamish Delta Snohomish Delta Duwamish Delta Puyallup Delta Nisqually Delta Skokomish Delta Probabilistic shaking hazard contours1 5040 60 50 60

1Acceleration in percent of gravity. Peak ground acceleration with 2%

 probability of exceedance in 50 years. Frankel, et al. 1997. Seismic60

hazard maps for the conterminous United States, U.S. GeologicalSurvey Open-File Report 97-131.

60

Gorst

Hat

Island

Snohomish

River Delta

This map is based on discussions held during the Puget Sound Tsunami Sourcesworkshop held in Seattle, Washington on 10 June 2002, and on subsequentreviews and discussion by workshop participants. Contributing institutionsincluded Kent State University, National Oceanic and Atmospheric Administration(NOAA), University of Nevada, University of Washington, U.S. GeologicalSurvey (USGS), and Washington Division of Geology and Earth Resources. Theworkshop was organized by NOAA’s Center for Tsunami Inundation MappingEfforts (TIME), the USGS, Washington’s Department of Natural Resources (WADNR)and Washington’s Emergency Management Division (WAEMD).

1894 and1943

Figure 2: Locations of major river deltas in Puget Sound, including two historic failures of the Puyallup River delta that occurred in 1894 and 1943,and locations for which evidence of past tsunamis exists. Also presented are contours of peak ground acceleration with 2% probability of exceedancein 50 years (Frankel et al., 1997).
12 F. Gonz ́alez et al.

and 4 summarize information on both submarine and subaerial landslides

discussed at the workshop.

3.2 Priority Areas

Several hypotheses may aid in setting priorities for modeling tsunamis from

landslide sources.

River delta failures

Deltas of the Puyallup, Duwamish, and Snohomish Rivers probably pose

more of a landslide hazard than do other Puget Sound deltas, as shown by

historical submarine landslides on the Puyallup River delta, the proximity

of these three deltas to major port facilities, and stability analysis of the

Duwamish River delta slope (Kayen et al., 1999).

Non-deltaic submarine landslides

Away from deltas, submarine areas most susceptible to landsliding may be

in the vicinity of faults having Quaternary displacement. This inference is

based on preliminary mapping of Puget Sound (Fig. 3), Lake Washington,

and Lake Sammamish submarine landslides (Fig. 4) by Karlin and Holmes.

Subaerial landslides

Landslides as large as the 1949 Tacoma Narrows failure are the subaerial

slides most likely to cause tsunamis in Puget Sound. The two major geological parameters that control the generation of a water wave from subaerial

landslides are the volume of the slide mass, and the motion of the mass as

it reaches the water body. Some very large prehistoric landslides have been

mapped along Puget Sound bluffs; when reactivated, these deep-seated landslides tend to be very slow moving (inches per day), and would not appear

to be capable of generating a tsunami.

3.3 Scenarios

As further guidance for tsunami modeling, landslides at Puget Sound can be

envisioned in several scenarios: landslides with historical precedent in Puget

Sound, credible “worst case” landslides based on analogies with other places,

and submarine slides not associated with river deltas.

Historical precedent scenarios

The first kind of scenario is based on tsunamigenic Puget Sound landslides

such as the 1894 Commencement Bay delta failure and the 1949 Tacoma

Narrows subaerial landslide. The geometry of each is well defined from field

observations, and summaries of the estimated parameters are provided in

Tables 3.1 and 3.2.

Scenario landslides based on local historical precedent offer the great advantage of having dimensions and effects like those known to have occurred
Puget Sound Tsunami Sources—2002 Workshop Report 13 Swantown Discovery Bay Shine 15 0 15 Km Lynch Cove Burley Landslides Tsunami Evidence Potential landslide zones of concern identified at workshop Large submarine landslides Steep coastal topography Published geologic tsunami deposit Candidate geologic tsunami deposit seen in reconnaissance Native American Stories

1

50

40

60

50

60

1 

60

Unpublished data. See text.

60

Gorst

This map is based on discussions held during the Puget Sound Tsunami Sourcesworkshop held in Seattle, Washington on 10 June 2002, and on subsequentreviews and discussion by workshop participants. Contributing institutionsincluded Kent State University, National Oceanic and Atmospheric Administration(NOAA), University of Nevada, University of Washington, U.S. GeologicalSurvey (USGS), and Washington Division of Geology and Earth Resources. Theworkshop was organized by NOAA’s Center for Tsunami Inundation MappingEfforts (TIME), the USGS, Washington’s Department of Natural Resources (WADNR)and Washington’s Emergency Management Division (WAEMD).

Hat

Island

Subaerial landslides

Probabilistic shaking hazard contours1Deep coastal water

Steep topography near deep water

Winslow

Alki

Three TreePoint

Maury Island

1949 Tacoma Narrows

Camano Head

Mukilteo Cultus

Bay

1 Acceleration in percent of gravity. Peak ground acceleration with 2%

 probability of exceedance in 50 years. Frankel, et al. 1997. Seismichazard maps for the conterminous United States, U.S. Geological

Survey Open-File Report 97-131.

Dumas

 Bay

West Pt

Snohomish

River Delta

Figure 3: Potential landslide zones, including the location of the 1949 Tacoma Narrows slide and unpublished field data (Karlin and Holmes) forlarge submarine slides. Also presented are contours of peak ground acceleration with 2% probability of exceedance in 50 years (Frankel et al., 1997),

locations for which evidence of past tsunamis exists, and a TIME Center analysis of gridded bathymetric and topographic data to identify sites withsteep coastal topography adjacent to deep coastal water.
14 F. Gonz ́alez et al. (a) (b) (c) Figure 4: (a) Lake Washington subaqueous landslides mapped from high-resolution single channel seismic reflection profiles and swath sidescan imagery, and classified into submerged forests, coherent block slides, debris flows, sand flows, and mixed slumps. (b) Lake Washington subaqueous landslides classified by age. (c) Lake Sammamish geologic map, showing underwater landslides, onland exposures of pre-Frasier geology, and Holocene mass wasting.
Puget Sound Tsunami Sources—2002 Workshop Report 15

at Puget Sound. Well-defined historic landslides that produced observed water waves provide a means for evaluating tsunami models and for estimating

such factors as the velocity of the landslide mass.

Worst-case scenarios

“Worst-case” scenarios for landslides at Puget Sound can be explored by

means of analogy with landslides in similar settings elsewhere. For example,

as a starting hypothesis, tsunami modelers could assume a landslide about

one-third the volume of the 1964 Valdez slide—a giant delta-front failure

triggered by the 1964 Alaska earthquake. This particular worst case could

be modeled as a delta slope, submarine, or subaerial occurrence. In all cases,

however, it probably needs a large earthquake as a trigger. And because the

recurrence of large shallow earthquakes on faults at Puget Sound is poorly

known at best, defining the likelihood for outsize failures will ultimately

depend on better definition of prehistoric earthquake recurrence.

Coulter and Migliaccio (1966) provide the best documentation of the

1964 Valdez submarine landslide. Their Figure 2 shows that Valdez Arm

is a long east-west oriented fjord that terminates at the (former) town of

Valdez, where it is approximately 3 miles (5 km) in width. A large delta

formed by the Lowe and Robe rivers and a large stream flowing from the

Valdez Glacier occupies the east end of the fjord, which was the former

site of the town of Valdez. They report a total landslide volume estimated

at 96 million cubic yards (74 million cubic meters). The delta slopes to a

depth of 600 ft at the bottom of the fjord approximately 2 miles west of

the tide flat. Based on their Plate 2, the total perimeter of the landslide is

approximately 2500 m, and the top to toe distance is about 1200 m; these

dimensions require an average thickness of about 25 m. Consequently, one

possible geometry of a landslide that is only one third the volume of the

Valdez failure would have a width of 1700 m, a thickness of 20 m, and a top

to toe length of 800 m.

Could such a landslide fit into the Puyallup or Duwamish River deltas?

Both Elliott and Commencement Bays are at the head of fjords that have

been significantly filled with sediment during the mid to late Holocene

(Dragovich et al., 1994). Large deltas deposited by the Puyallup and

Duwamish rivers occupy the head of these flooded fjords, similar in setting

to the delta at the head of Valdez Arm. The floor of the fjords in Elliott

and Commencement bays are at a depth of approximately 450 ft, somewhat

shallower than at Valdez.

Because of the shallower depth of the floors of Elliott and Commencement bays, the top to toe distance of the proposed “worst-case” submarine

landslide scenario must be decreased to a distance of 500 m. To accommodate this decrease, the perimeter and thickness of the scenario landslide

can be set to 2000 m and 25 m, respectively. These small changes yield a

landslide volume of 25 million cubic meters, roughly one third of the volume

of the 1964 Valdez failure (Table 3.3).

Commencement Bay is approximately 2.5 miles wide, and similar in

width to Valdez Arm. This is more than sufficiently wide to accommo-
16 F. Gonz ́alez et al.

date the “worst-case” delta failure scenario. The Puyallup River is largely

free flowing with its water and sediment source originating from Mt. Rainier

glaciers. Because of anthropogenic changes to the White/Stuck River channels, sediment supply to the Puyallup delta has significantly increased in

the last 100 years. The history of delta landslides (1894 and 1943) clearly

indicate the potential instability of this location.

Elliott Bay is just a little over 2 km in width, and the “worst-case” scenario delta failure would just fit within the embayment. Because of anthropogenic changes to the White/Stuck River channels and dams on the Green

River, sediment supply to the Duwamish delta has significantly decreased in

the last 100 years. However, the Duwamish delta is situated directly above

the Seattle Fault, and the predicted ground motions from a major earthquake on this fault could easily exceed the ground motion that caused the

1964 delta failure in Valdez. Because of this factor, failure of the entirety of

the Duwamish delta front does not seem far-fetched.

The Snohomish delta appears similar to the Puyallup in width, bathymetric configuration, and sediment supply. From that perspective, it would

easily accommodate the “worst-case” scenario.

What is the likelihood of occurrence of this worst-case scenario? Because

the most likely trigger for the “worst-case” failure of the Duwamish delta is

an M 7 earthquake directly beneath it, on the Seattle Fault, this Duwamish

scenario is subject to large uncertainties in estimating the recurrence intervals for such earthquakes (Section 2.2). In the event of a large earthquake

on the Seattle Fault, the tsunami from tectonic displacement of the floor of

the sound may further destabilize the Duwamish delta when troughs in the

tsunami reduce the water load on the delta front.

The Puyallup delta has a rich history of small and moderate-sized failures, and this represents only a 110-year historic record. If delta failures

behave like other natural phenomena (e.g., floods or earthquakes), then this

short history suggests that the recurrence of an 1894 failure on this delta is

relatively frequent on a geologic timescale. Prediction of the recurrence of

this failure using statistical methods would no doubt yield a recurrence in the

hundreds or few thousands of years, with large uncertainty. This situation is

similar to attempts to assign a recurrence to the Seattle Fault. Although the

historic Puyallup delta failures were non-seismogenic, the “worst-case” event

on the Puyallup delta would likely have a seismic trigger; in this case, the appropriate question would be: “What is the recurrence of major earthquakes

on nearby fault structures, especially the Tacoma Fault?”

The Nisqually delta has a significantly shallower slope, is inherently more

stable than either the Puyallup, Duwamish, or Snohomish deltas, and was

not considered a likely candidate for the modeling study without a more

detailed evaluation. The M 6.8 Nisqually earthquake on 28 February 2001

did not trigger a Nisqually delta failure. It is not surprising that this slope

remained stable in this earthquake as it did in the somewhat larger 1949

Olympia earthquake. Ground shaking in the port area of Tacoma during the

Nisqually earthquake was less than 0.1 g peak ground acceleration and of

short duration; this seismic loading was at or below the threshold necessary

to generate liquefaction in the worst soil conditions. One hallmark of this
Puget Sound Tsunami Sources—2002 Workshop Report 17

earthquake was the paucity of subaerial landslides, likely the result of the

severe drought conditions that preceded the event. However, the slopes

adjacent to the Salmon Beach landslide triggered by the 1949 Olympia event

did fail. If soil moisture conditions were nearer normal, this landslide might

have been large enough to reach the Sound and generate a splash wave as

was generated in 1949.

The Duwamish delta was shaken more strongly than the Puyallup delta

during the Nisqually earthquake, and comparison of pre- and post-earthquake

surveying indicated movement of Harbor Island by a number of inches.

Whether this was the initiation of a delta failure that might have accelerated

if the shaking was significantly stronger and/or longer is speculative. The

Snohomish delta was too far distant from the Nisqually earthquake epicenter

to experience even moderate shaking.

Non-deltaic submarine slide scenarios

Tables 3.4 and 3.5 provide estimates of the dimensions of selected large landslides in Puget Sound, compiled by Robert Karlin, Mark Holmes, and Shane

Smith from high-resolution seismic reflection profiles, sidescan imagery, and

bathymetric data. They tend to be located near Quarternary faults that

cross Puget Sound, Lake Washington, and Lake Sammamish (Figs. 3 and 4).

There are no historical records of these slides, and it is unknown whether

they generated tsunamis.

Lake Washington subaqueous slides are presented in Fig. 4a, classified

into submerged forests, coherent block slides, debris flows, sand flows, and

mixed slumps. Coherent block slides are recognizable in sidescan imagery

as displaced blocks with widths more than about 20 m. Block slides show

coherent, but often deformed bedding in seismic reflection profiles. Submerged forests are large block slides that have upright or fallen trees on

them, with the trees visible on sidescan sonar images. Debris flows show a

strong reflective contrast with normal lake sediment, and may contain small

boulders interspersed with incoherent sediment flows. Such flows are often

found at the toe of block slides, but can occur separately. Sand flows have a

bright signature on sidescan records compared with normal sediment. They

show little structure, except occasional sand waves. Mixed flows are undifferentiated areas with both debris and incoherent sediment flows. Fig. 4b

classifies these slides by age. The seismic reflection profiles show a distinctive

sequence of reflectors within the Holocene lake sediments that can be correlated with stratigraphy known from piston coring (Karlin and Abella, 1992;

1996). The Holocene section consists of ∼1 m of transparent soft sediments

over a clayey silty seismite deposited throughout the lake about 1100 years

ago. The 5–15 cm thick Mazama ash deposited ∼7600 years ago forms a

prominent reflector at 3–5 m sub-bottom depth. A strong acoustic contrast

of the Holocene lake sediments with a hard blue-gray glacial clay at 7–20 m

sub-bottom depths gives a strong, recognizable glacial/ interglacial reflector.

Given the sedimentation rates in the lake and the subbottom depths of the

1100-year silt layer at 1 3 m and the 7600-year Mazama ash at 3–5 m, landslides with sediment cover of 1–3 m probably are from 1100 to 7600 years
18 F. Gonz ́alez et al.

old. Landslides with >5 m sediment covers probably are of early Holocene

age.

Lake Sammamish geology, underwater landslides, onland exposures of

pre-Frasier geology, and Holocene mass wasting are presented in Fig. 4b.

The underwater landslide distribution was determined from high-resolution

seismic reflection profiling and sidescan swath mapping by R. Karlin, M.

Holmes, and T. Pratt. The geology is modified from Minard and Booth

(1988), Booth and Minard (1992) and Yount et al. (1993). Also see Prunier

(1998).

3.4 Recommendations

Tsunami modelers should work closely with geoscientists who have past experience evaluating slope stability in the Puget Sound region, because it is

particularly important for the credibility of the modeling that the source parameters and location of the tsunamigenic landslide are defensible. Two of

the slide parameters listed in Tables 3.1 to 3.4—duration and acceleration—

are essential to the modeling, but values will be difficult or impossible to obtain through field observations. Landslide source locations are not spatially

random, but rather depend on factors that typically make slopes unstable

(steepness of slope, geologic conditions, etc.).

Tsunami source modeling

 Tsunami scenarios should include:

– Delta slope failures of the Puyallup, Duwamish, and Snohomish

Rivers, using scenarios similar to the historical 1894 Commencement Bay event summarized in Table 3.1 and a worst-case scenario

of unsure but likely very rare occurrence, based on a scaled-down

version of the 1964 Valdez submarine landslide as in Table 3.3.

– Submarine landslides due to non-delta slope failures proximal to

known Quaternary faults, including those identified at Alki Point

and Maury Island, using scenarios similar to that summarized in

Table 3.4.

– Subaerial landslides of the size and magnitude of the 1949 Tacoma

Narrows event, summarized in Table 3.2.

Science improvement

 Expand the existing program of slope instability mapping to increase

the geographical coverage and improve the quality of assessments:

– Acquire multi-beam bathymetric data and denser high-resolution

seismic reflection data, first in the areas of potential concern as

shown in Fig. 3, and then for the rest of Puget Sound.

– Collect bottom sediment cores for geological and geotechnical

characterization directed toward submarine slope stability assessment.
Puget Sound Tsunami Sources—2002 Workshop Report 19

 Characterize the geometry, nature, and timing of major submarine

and subaerial landslides to determine their frequency of occurrence,

method(s) of failure, and tsunami generating potential.
20 F. Gonz ́alez et al.

Table 3.1: Historic delta landslide.

Justification: Historic precedent based on the 1894 Commencement Bay landslide

Probability of occurrence: Less than 50% in 50 years (recurrence interval of at least 100 years)

Locations: Puyallup, Duwamish, and Snohomish River deltas

Probable Range of Values

Parameter (MKS Units) Comments

Geometry Length: 400 m Geometry of this landslide well defined

Width: 300 m

Thickness: 20 m

Volume: 2.4 × 106 m3

Slope angle: 15 degrees

Aspect: Parallel to delta slope fall line

Time History Duration: TBD Parameters can be estimated by back

calculation using the 1894 Commencement

Bay slide geometry and reported wave

height.

Distance of slide: TBD

Initial acceleration: TBD

or

Density: TBD Volume, slope, density and sediment type

can provide a rough estimate of initial

acceleration.

Sediment type: TBD

Table 3.2: Subaerial landslide.

Justification: Historical precedent based on the 1949 Tacoma Narrows landslide

Probability of occurrence: Recurrence interval of 50 years or more

Locations: Slope north of Tacoma Narrows Bridge—possibly analogous to other steep bluffs along Puget Sound

Probable Range of Values

Parameter (MKS Units) Comments

Geometry Length: 150 m Geometry of 1949 landslide well defined

Width: 120 m

Thickness: 8 m

Volume: 1.5 × 105 m3

Slope angle: 35 degrees

Aspect: Parallel to delta slope fall line

Time History Duration: 5–10 seconds Slope, volume, density, and sediment type

can provide a rough estimate of impact

acceleration.

Distance of slide: 75 m

Impact acceleration: TBD

or

Density: TBD

Sediment type: TBD
Puget Sound Tsunami Sources—2002 Workshop Report 21

Table 3.3: Worst-case delta failure.

Justification: Based on 1964 Valdez submarine landslide volume, scaled by 1/3.

Probability of occurrence: Unknown if this large a landslide can occur at all throughout the study areas.

If so, the probability is dependent on that of large earthquakes on nearby faults.

Locations: Major river deltas, especially those of the Puyallup, Duwamish, and Snohomish Rivers.

Probable Range of Values

Parameter (MKS Units) Comments

Geometry Length: 500 m Geometry of 1964 landslide well defined, but

Width: 2000 m may not be applicable to Puget Sound

Thickness: 25 m

Volume: 25 × 106 m3

Slope angle: Site dependent

Aspect: Parallel to delta slope fall line?

Time History Duration: TBD Volume, slope, density, and sediment type

can provide a rough estimate of initial

acceleration.

Distance of slide: TBD

Initial acceleration: TBD

or

Density: TBD

Sediment type: TBD

Table 3.4: Submarine landslide.

Justification: Slides indicated by unpublished seismic profiling data and mapping (R. Karlin, M. Holmes).

Tsunami generation potential undetermined. No historic precedent exists.

Probability of occurrence: Unknown

Locations: Proximal to known Quaternary faults that cross Puget Sound, Lake Washington, and Lake

Sammamish (see Figs. 3 and 4 for potential landslide zones).

Probable Range of Values

Parameter (MKS Units) Comments

Geometry Length: 0.5 to 3 km

Width: 0.5 to 5 km

Thickness: 50 to 100 m

Volume: 2.4 × 106 m3 (Maximum value

that constrains specification of

length, width, and thickness)

Slope: Variable

Aspect: Parallel to slope fall line?

Time History Duration: TBD Estimate parameters by back calculation,

using 1894 Commencement Bay slide

geometry and reported wave height.

Distance of slide: TBD

Initial acceleration: TBD

or Volume, slope, density, and sediment type

can provide a rough estimate of initial

acceleration. Density: TBD

Sediment type: TBD
22 F. Gonz ́alez et al.

Table 3.5: Dimensions of selected large landslides in Puget Sound. Table compiled by Robert Karlin

and Shane Smith from high-resolution seismic reflection profiles, sidescan imagery, and bathymetric data.

Volumes were approximated by a wedge of volume (Width × Length × Thickness)/2.

Width Length Thickness Volume

Name (m) (m) (m) (106 m3) Type

Maury Island South 590 1830 60 33 Block slide

Maury Island Mid 300 1330 50 10 Block slide

Maury Island North 1000 2780 50 70 Block slide

Three Tree Point 1750 3390 TBD TBD Three complex slides each with

multiple events

Restoration Point 1000 1050 TBD TBD Block slide, bathymetric expression

Alki Point 1000 2700 5 to 20 for

most recent

debris flow

7 to 27 Deformation zone covered by debris

flow(s), bathymetric expression

Edmonds 1850 2850 120 316 Large block slide, bathymetric

expression

Mukilteo 1400 2750 10–15 20 to 29 Sand flow

Edgewater 1280 2940 5 to >40 for

most recent

slide

10 to >76 Multiple block slides of varying

thickness

Possession Point South 630 1250 60 for most

recent slide

23 Multiple block slides and events

Possession Point Middle 500 1230 75 23 Two or more block slides and

events

Possession Point North 920 1530 75 53 Multiple block slides and events
Puget Sound Tsunami Sources—2002 Workshop Report 23

4. Paleotsunami Field Evidence

4.1 Background

At Puget Sound, tsunami hazards are being identified and quantified by

combining geologic field observations with inundation modeling. Although

earthquakes, landslides, and delta failures have the potential to generate

tsunamis in Puget Sound and nearby lakes, little is known about the frequency and size of tsunamis from these sources. Geologic field evidence

useful in tsunami inundation modeling includes: (1) amount and distribution of coseismic uplift and subsidence, (2) size and location of delta failure

and landslide scarps and deposits, (3) distribution, grain size, and internal

structure of tsunami deposits, (4) microfossils, which are useful in quantifying subsidence and uplift and in identification of tsunami deposits, and (5)

dateable material within deposits that help establish tsunami frequency.

Tsunami deposits are especially valuable because they demonstrate that

Puget Sound tsunamis have occurred in the past, as illustrated by deposits

of the A.D. 900–930 tsunami identified in Seattle, Cultus Bay, and the

Snohomish delta (Atwater and Moore, 1992; Bourgeois and Johnson, 2001;

Koshimura et al., 2002). Deposits can be used for education of the general

public and by emergency managers as solid evidence of a tsunami hazard.

For example, locations of identified tsunami deposits appear on a tsunami

inundation map for the southwest coast of Washington (Walsh et al., 2000).

4.2 Priority Areas

To identify a tsunami deposit is to identify a tsunami hazard, but tsunami

deposits in the Puget Sound area have not been comprehensively identified.

Therefore, the entire Puget Sound area is a priority area for tsunami deposit

research, except for the very few spots where deposits have already been identified. High potential areas should be explored in a reconnaissance mode,

with high priority given to those areas where modeling reasonable source

scenarios suggests large tsunamis. This type of collaboration by modelers

and field geologists will improve definition of areas with tsunami risk. The

area studied should include the shores of Lake Washington because large,

potentially tsunamigenic landslides occurred there 1100 years ago, and because currents from a moderate tsunami in Lake Washington could pose a

hazard to floating bridges.

4.3 Inferences About Past Tsunamis

What happened at Puget Sound during past tsunamis can be learned, to

some extent, from clues in tsunami deposits. Sedimentation models can be

used in conjunction with inundation models to interpret tsunami deposits

found in the Puget Sound area and help estimate tsunami parameters, including inundation distance, runup height, flow depth, and flow velocity; bottom friction estimates, extremely important in inundation modeling, can also

be improved by using velocity estimates from both inundation and tsunami
24 F. Gonz ́alez et al.

sedimentation models (Titov et al., 2001). If deposits can be dated, then

estimates can also be made of tsunami frequency.

4.4 Recommendations

Tsunami source modeling

 Incorporate any available paleotsunami parameter estimates into sitespecific tsunami model development, as a test of accuracy and as a

possible constraint on model input parameters.

Science improvement

 Map tsunami deposits where present at Puget Sound and Lakes Washington and Sammamish.

 Conduct detailed sedimentology, micropaleontology, and age dating

studies at selected tsunami deposit sites.

 Continue the combined use of sedimentation and inundation models to

help improve estimates of paleotsunami parameters.

 Compile geologic evidence for coseismic uplift and subsidence, landslides, delta failures, and tsunami deposits and develop maps of this

evidence to help constrain and test tsunami models.

 Improve quantification of coseismic uplift and subsidence.

5. Seattle-Duwamish Waterfront Inundation

The NOAA Center for Tsunami Inundation Mapping Efforts (TIME) recently modeled tsunami inundation along the Seattle-Duwamish waterfront

(Titov et al., 2003). This modeling provides preliminary estimates of the

flooding that might result from a rare event—a large earthquake on the

Seattle fault. The computed tsunami results entirely from tectonic uplift

and subsidence during the earthquake; not included in the model is deltafront failure, such as discussed in Section 3.

5.1 Background

NOAA’s TIME Center has been conducting numerical model simulations of

Puget Sound tsunamis for the Washington State Emergency Management

Division (WAEMD). The first modeling effort was a relatively coarse-grid

simulation covering most of Puget Sound for a tsunamigenic earthquake

on the Seattle fault (Koshimura et al., 2002). The results of that simulation were one factor considered by the WAEMD in identifying Puget Sound

communities at risk and prioritizing these communities for development of

fine-resolution inundation maps.
Puget Sound Tsunami Sources—2002 Workshop Report 25

5.2 Priority Areas

The coarse-grid Puget Sound simulation suggested that, based on the extreme scenario modeled, a significant tsunami could strike the Seattle-Elliott

Bay area, which is characterized by high population and critical infrastructure, within a few minutes of an earthquake on the nearby Seattle Fault.

Subsequently, the WAEMD funded the NOAA TIME Center to develop inundation map products for the somewhat larger Seattle-Duwamish area.

5.3 Event Description

Source specification

TIME modelers used an M 7.3 earthquake on the Seattle Fault Zone as a

nearly worst-case tsunami generating mechanism. Because the recurrence

intervals for such an earthquake probably span thousands of years, it is

believed that a similar event has a very low probability of occurring in our

lifetimes. The justification for modeling this low, but finite, probability

event as a credible near-worst-case Puget Sound threat is the significant and

growing population and infrastructure that is now at risk.

The model uses assumptions about the dip of the fault plane and the

width and length of fault rupture that are within the broad range of possibilities consistent with reports cited in Section 2.2. For instance, the Brocher

et al. (2001) interpretation suggests dips of ∼60◦ to 80◦ and fault widths of

∼30 km (values not specifically provided in the text, but shown on a figure), while Calvert and Fisher (2001) suggested dip angles of 40◦ to 80◦ (60◦

± 20◦). The slip distribution was constrained, through trial and error, to

match available field estimates of vertical displacement at three sites—Alki

Point, Restoration Point, and West Point—which presumably occurred as

a result of the earthquake in A.D. 900–930. The fault parameters specified

for the simulation are provided in Table 5.1. The comparison of computed

displacement with field estimates is provided in Table 5.2, and the resulting

vertical deformation is illustrated in Fig. 1a, along with the location and

values of the vertical deformation field estimates.

It should be noted that different sets of model parameters can produce

similar fits to the observations. Thus, each of these two models, though

somewhat different, provide a reasonable fit to the observed deformation. In

this case, it made little difference in the inundation model results. It is generally true, however, that professional judgment must be applied to assess the

geophysical credibility of each model. Because of this, and because the geometry and earthquake history of the Seattle fault remain controversial among

Earth scientists, these model parameters need to be reviewed in a separate,

formal workshop, in which experts come together to reach a consensus and

provide official recommendations. Such a workshop, dedicated to tsunami

source specification, is essential to developing site-specific tsunami generation scenarios and the resulting inundation maps. A workshop dedicated

to the systematic assessment of current scientific information by a group

of experts is a traditional way of establishing the best available science for

a particular topic and judging the adequacy of that science to contribute
26 F. Gonz ́alez et al.

Table 5.1: Sub-fault parameters for magnitude 7.3 and 7.6 Seattle Fault earthquake

models. The M 7.3 vertical deformation pattern is shown in Fig. 1a.

M 7.3 M 7.6

Sub-fault Depth Length Width Strike Dip Slip Slip

(west to east) (km) (km) (km) (deg) (deg) (m) (m)

1 0.5 15.2 20 87.9 60 1 3

2 0.5 6.3 20 86.6 60 1 3

3 0.5 8.9 20 96.0 60 12 14

4 0.5 3.2 20 128.8 60 11 10

5 0.5 11.5 20 99.3 60 4 4

6 0.5 14.9 20 81.0 60 1 3

Table 5.2: Vertical deformation values for field estimates and the M 7.3 and M 7.6

Seattle Fault models. See Fig. 1a for the geographical location of the sites.

M 7.3 M 7.6

Field Model Model

Site (m) (m) (m)

Alki Point 4–6.5 3.9 4.0

Restoration Point 7 7.1 7.0

West Point –1 ± 0.5 −1.2 −1.0

meaningfully to issues of concern—public safety and hazard mitigation, for

example.

Accordingly, recommendations below include yearly workshops, because

updating tsunami source specification is an important part of developing

and improving inundation maps. As an example of source refinement, the

Koshimura et al. (2002) model is characterized by a magnitude Mw 7.6 with

uniform slip of 2.8 m on each of six sub-faults composed of a shallow fault

plane dipping 60◦ situated directly above a deeper fault plane with dip of

25◦. A different seismic source model emerges if an earthquake in the range

Mw 7.3–7.6 has sources composed of six sub-faults, each with independently

assigned slip along a single plane that dips 60◦ (Table 5.1). The TIME

model may need revision as patterns of coseismic vertical deformation become clearer from studies of fault geometry (ten Brink et al., 2002) and highresolution topographic maps (http://duff.geology.washington.edu/

data/raster/lidar/surfmap/).

Model results

The model of Titov and Synolakis (1998), also known as the Method of

Splitting Tsunami (MOST) model (Titov and Gonz ́alez, 1997) was used by

TIME modelers to simulate the generation, propagation, and inundation of

tsunamis in the Seattle-Duwamish area. Close communication was maintained during the study with WAEMD and the Washington Department of
Puget Sound Tsunami Sources—2002 Workshop Report 27

Seattle Inundation Modeling

4000 0 4000 m

NOAA TIME Center

Pacific Marine Environmental Laboratory

Seattle, Washington NAT OI NAL OCEANIC AND ATMOSPHERIC ADMINISTRAT OI N

U.S. DEPARTMENT OF CO M MERCE

Figure 5: Seattle-Duwamish waterfront inundation modeling products: (a) crustal deformation in the

Seattle-Duwamish area; (b) zoned maximum inundation depth; (c) zoned maximum current speed. See

text for discussion of selection of ranges for individual zones.

Natural Resources (WADNR) and, upon completion of the study, a suite of

model-derived mapping products were delivered to both agencies in the form

of electronic files and, where appropriate, hard copy representations. The

product suite included an animation of the entire simulation, which is also

available for viewing on the Workshop website (http://www.pmel.noaa.gov/

tsunami/time/PS source wkshp/). Three graphical summary products derived from that simulation are presented in Figs. 5a–c.

Figure 5a presents the computed vertical deformation for the SeattleDuwamish area. The general pattern is one of subsidence as great as 2 m

at Duwamish Head, the north end of Harbor Island, and the entire region

north of these sites, including the Seattle waterfront, and uplift as great as

4 m south of these sites. The decrease in the modeled uplift eastward from

Alki Point may prove inconsistent with uplifted tidal-flat deposits along the

Duwamish River (B.F. Atwater, unpublished data).

Figures 5b and 5c present two fundamental modeling products of primary importance to emergency managers—maximum inundation depth (the

height of water above land) and maximum current speed, respectively. These

products are obtained by monitoring each variable at individual grid points
28 F. Gonz ́alez et al.

and saving the maximum value attained over the course of the entire simulation. Zonation is then performed to produce the maps shown—i.e., the fine

scale details are deliberately suppressed by binning values into zones with

ranges that have physical significance to emergency managers. Thus, for an

average adult, the depth range zones correspond roughly to “up to kneehigh” (Low), “up to head-high” (Medium) and “over the head” (High), and

current speed zones are roughly “up to the speed of a brisk walk” (Low) and

“faster than a brisk walk” (High). For the Seattle-Duwamish waterfront areas, the computed water depths are greater than 2 m and the current speeds

in excess of 2 m/s.

Model limitations

The model has limited ability to simulate tsunami generation and tsunami

effects. The model results express few uncertainties about the fault geometry, the spatial distribution of slip, and the amount of surface rupture

that generate the tsunami. Although the tectonic deformation illustrated in

Fig. 5a is accounted for in the tsunami inundation computations, additional

tsunami sources such as delta failure, submarine and subaerial landslides,

and liquefaction, were not. Nor does the simulation account for hydrodynamic effects on the tsunami wave and currents of smaller scale features and

objects—buildings, automobiles, maritime vessels, large rocks, trees, and the

thousands of shipping containers stored on Harbor Island, for example—that

would, in some cases, become entrained debris that would act as projectiles.

Also ignored are the effects on structures and humans of the tsunami waves

and currents, as well as hazards such as the spreading of flammable liquids.

Source uncertainty and sensitivity studies

There is a fundamental difference in the nature of the seismic hazard maps

and the inundation map presented here. The seismic hazard maps are developed as a weighted probabilistic distribution of earthquake events. In

contrast, the inundation map is deterministic: it is intended to represent

a maximum credible event based on an extreme scenario earthquake that

occurs rarely.

In a deterministic approach, multiple simulations can be conducted to

develop site-specific sensitivity studies. Such studies constrain the possible

range of source parameters—e.g., variations in the magnitude, location, dip,

slip, etc., of earthquake sources—and then perform tsunami inundation simulations that correspond to the source variations. The result is a mapping of

potential source variation into potential tsunami inundation variation that

provides additional insight into the vulnerability of a site. This approach

is routinely used in many other scientific and engineering disciplines and

is frequently referred to as a response study, in which the input to a system is varied systematically and the output is analyzed and interpreted to

characterize the system.

As a very simple example of this approach, an M 7.6 Seattle fault event

was also modeled, subject to the constraint that the resulting deformation
Puget Sound Tsunami Sources—2002 Workshop Report 29

pattern must match the three field observations at least as well as the M 7.3

model. Again, trial and error was used to adjust the fault plane parameters.

The M 7.6 slip values and the resulting deformation values at the three field

sites are listed in Tables 5.1 and 5.2. The M 7.6 model produced a vertical

deformation pattern that was somewhat different, but very similar, to the

pattern produced by the M 7.3 model. As a consequence, the M 7.6 model

produced tsunami inundation values and patterns that were essentially the

same as the M 7.3 event.

5.4 Recommendations

In addition to recommendations in previous sections about tsunami sources,

the following may improve tsunami inundation models and mitigation products derived from them.

Science improvement

 Complete Puget Sound LIDAR coastal bathymetric/topographic surveys.

 Complete Puget Sound swath-beam bathymetric surveys.

 Use Puget Sound LIDAR and swath-beam surveys to develop a system

of improved bathymetric/topographic computational grids.

 Review and assess existing models for sub-aerial and sub-aqueous slides,

and determine the sensitivity of tsunami generation to variations in the

model parameters.

 Review and assess existing methodologies for simulating tsunami effects on and interactions with structures and humans.

 Develop hardware and software technologies for fast, efficient multiple

simulations.

 Develop methods for site-specific, multiple simulation sensitivity studies.

 Develop improved hazard mitigation products based on site-specific

sensitivity studies, in close collaboration with WAEMD and WADNR.

 Conduct yearly workshops to review the best available scientific information and develop recommendations for Washington State inundation

mapping.

6. Acknowledgments

Preparation of this report was sponsored by the National Oceanic and Atmospheric

Administration, the U.S. Geological Survey, the Washington State Natural Resources Division, and the Washington State Military Department Emergency Management Division. Figures were prepared by Karen Birchfield. The final manuscript

was formatted and prepared for publication by Ryan Layne Whitney.
30 F. Gonz ́alez et al.

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Critical Areas. URL http://www.ocd.wa.gov/info/lgd/growth/.

Williams, H., and I. Hutchinson (2000): Stratigraphic and microfossil evidence

for late Holocene tsunamis at Swantown Marsh, Whidbey Island, Washington.

Quatern. Res., 54 , 218–237.

Williams, H., I. Hutchinson, and A. Nelson (2002): Multiple sources for late

Holocene tsunamis at Discovery Bay, Washington State. American Geophysical Union, 2002 fall meeting, abstract S22B-1032.

Wilson, B.W., and A. Torum (1972): Effects of the tsunamis: An engineering

study. In The Great Alaska Earthquake of 1964: Oceanography and Coastal Engineering, Committee on the Alaska Earthquake, National Academy of Sciences,

361–523.

Yount, J.C., J. Minard, and G. Dembroff (1993): Geologic map of surficial deposits

in the Seattle 30 × 60 quadrangle. U.S. Geological Survey Open File Report

93-233, 2 sheets.
34 F. Gonz ́alez et al.

Addendum: Seismic Surface Wave Forcing of

Water Waves and Seiches (by H. O. Mofjeld)

Well after the workshop, the Mw 7.9 Alaska earthquake on 3 November 2002

generated strong seismic surface waves southward that created damaging

water waves in Lake Union (Barberopoulou et al., 2002) and Puget Sound

marinas (A. Qamar and W. Steele, private communication). There is also

evidence that the Seattle sedimentary basin acted to amplify the seismic

surface waves in its vicinity (Barberopoulou et al., 2002). Vertical seismic

wave amplitudes as large as 0.3 m were recorded in the Seattle area.

Strong seismic waves will occur in the Puget Sound region as the result

of earthquakes on local, Cascadia, and even distant fault zones. Therefore,

it is appropriate to include seismic surface waves as potential geophysical

sources of dangerous water waves in Puget Sound.

To fully characterize the seismic surface waves as sources, a database

is needed that contains the probabilities of their amplitudes, frequencies,

and orientations as functions of geographical location. Of particular importance are the horizontal velocities of the ground, since these are the primary

mechanism generating the water waves at the shore (Mofjeld, in preparation). These are needed for the fault zones in the Puget Sound region, the

Cascadia Subduction Zone, and more distant regions such as Alaska. The

orientation is important because the amplitudes of the water waves can be

very sensitive to this parameter.

Also needed are observed and synthetic time series of the seismic surface

waves to drive water response models. The wave periods of greatest interest

are between one to 60 seconds, in terms of generating dangerous waves and

seiches within small bodies of water.

The USGS shake map for the Puget Lowland is an essential step forward in developing this database. At present, it provides peak accelerations

due primarily to earthquakes on the Seattle Fault, South Whidbey Island

Fault, and the Cascadia Subduction Zone. These accelerations need to be

integrated in time in order to give peak horizontal velocities. Deep focus

earthquakes under the Puget Lowland occur on irregular decadal to multidecadal timescales, as observed in the 20th century. While they are less

prone to generate strong seismic surface waves than shallow earthquakes,

they cannot be discounted as potential sources.

References

Barberopoulou, A., K. Creager, A. Qamar, G. Thomas, and W. Steele (2002):

Local amplification of seismic waves from the Mw 7.9 Alaska earthquake and

a damaging seiche in Lake Union, Seattle, Washington. Fall AGU Meeting,

Abstracts.

Mofjeld, H.O., F.I. Gonz ́alez, V.V. Titov, and J.C. Newman: The generation of

seismic seiches and their dependence on seismic wave dispersion and imperfect

boundary reflection. In preparation.
Puget Sound Tsunami Sources—2002 Workshop Report 35

Appendix A: Workshop Participants

Brian F. Atwater

Univ. of Washington

Box 351310

Seattle, WA 98195

Phone: 206.553.2927

Fax: 206.553.8350

E-mail: atwater@usgs.gov

Eddie Bernard

NOAA/PMEL

7600 Sand Point Way NE

Seattle, WA 98115

Phone: 206.526.6800

Fax: 206.526.4576

E-mail: eddie.n.bernard@noaa.gov

George Crawford

Washington State Military Dept.

Emergency Management Div.

Camp Murray, WA 98430-5122

Phone: 253.512.7067

Fax: 253.512.7207

E-mail: g.crawford@emd.wa.gov

David Finlayson

School of Oceanography

University of Washington

Seattle, WA 98195

Phone: 206.543.7229

E-mail: dfinlays@u.washington.edu

Arthur D. Frankel

P.O. Box 25046

Lakewood, CO 80225

Phone: 303.273.8556

Fax: 303.273.8600

E-mail: afrankel@usgs.gov

James V. Gardner

Bldg. 15, McKelvey Building

USGS Mailstop 999

Menlo Park, CA 94025

Phone: 650.329.5469

E-mail: jvgardner@usgs.gov

Carolyn Garrison-Laney

Department of Earth and Space Sciences/USGS

63 Johnson Hall, Box 351310

University of Washington

Seattle, WA 98195-1310

Phone: 206.313.7946 cell

E-mail: cegl@u.washington.edu

Frank I. Gonz ́alez

NOAA/PMEL

7600 Sand Point Way NE

Seattle, WA 98115

Phone: 206.526.6803

Fax: 206.526.6485

E-mail: frank.i.gonzalez@noaa.gov

Mark L. Holmes

Dept. of Oceanography

Univ. of Washington

Box 357940

Seattle, WA 98195

Phone: 206.543.7313

Fax: 206.543.6073

E-mail: mholmes@u.washington.edu

Bruce E. Jaffe

U.S. Geological Survey Pacific Science Center

University of California

Santa Cruz, CA 95064

Phone: 831.459.2824

Fax: 831.427.4748

E-mail: bjaffe@usgs.gov

Tamie Jovanelly

619 Franklin Ave.

Kent, Oh 44240

(Kent State University)

Phone: 330.678.3962

E-mail: tjovanel@kent.edu

Bob Karlin

University of Nevada, Reno

Dept. of Geological Sciences

M/S 172

Reno, NV 89557-0180

Phone: 775.784.1770

E-mail: karlin@mines.unr.edu

Robert E. Kayen

Bldg. 15, McKelvey Building

USGS Mailstop 999M

345 Middlefield Rd.

Menlo Park, CA 94025

Phone: 650.329.4195

Fax: 650.329.5590

E-mail: rkayen@usgs.gov
36 F. Gonz ́alez et al.

Workshop Participants (cont.)

Harold O. Mofjeld

NOAA/PMEL

7600 Sand Point Way NE

Seattle, WA 98115

Phone: 206.526.6819

Fax: 206.526.6485

E-mail: harold.o.mofjeld@noaa.gov

Stephen P. Palmer

Washington State Dept of Natural Resources

Washington Division of Geology and Earth Resources

P.O. Box 47007

Olympia, WA 98504-7007

Phone: 360.902.1437

Fax: 360.902.1785

E-mail: steve.palmer@wadnr.gov

Brian Sherrod

Univ. of Washington

Box 351310

Seattle, WA 98195

Phone: 253.653.8358

206.553.0153 mobil

E-mail: bsherrod@usgs.gov

Hugh M. Shipman

Washington State Dept. of Ecology

3190 – 160th Ave. SE

Bellevue, WA 98008-5452

Phone: 425.649.7095

Fax: 425.649.7098

E-mail: hshi461@ecy.wa.gov

Vasily V. Titov

NOAA/PMEL

7600 Sand Point Way NE

Seattle, WA 98115

Phone: 206.526.5436

Fax: 206.526.6485

E-mail: vasily.titov@noaa.gov

Angie J. Venturato

NOAA/PMEL

7600 Sand Point Way NE

Seattle, WA 98115

Phone: 206.526.6556

Fax: 206.526.6485

E-mail: angie.j.venturato@noaa.gov

Timothy Walsh

Division of Geology & Earth Resources

P.O. Box 47007

Olympia, WA 98504-7007

Phone: 360.902.1432

Fax: 360.902.1785

E-mail: tim.walsh@wadnr.gov

Craig S. Weaver

Univ. of Washington

Dept. of Earth and Space Sciences

Seattle, WA 98195-1310

Phone: 206.553.0627 x

Fax: 206.553.8350

E-mail: craig@geophys.washington.edu

craig@usgs.gov

Jon Whisler

1008 NE 72 St.

Seattle, WA 98115

Phone: 206.336.1639

Fax: 206.524.3543

E-mail: whislerj@u.washington.edu

Harry H. Yeh

Civil and Environmental Engineering

167 Wilcox Hall

Univ. of Washington

Box 352700

Seattle, WA 98195

Phone: 206.685.1024

206.685.8655

Fax: 206.685.3836

E-mail: harryeh@u.washington.edu
U.S. Department of Commerce

National Oceanic and Atmospheric Administration

Pacific Marine Environmental Laboratory

7600 Sand Point Way NE

Seattle, WA 98115