Prepared in cooperation with the State of Washington Military Department Emergency 

Management Division 

Population and Business Exposure to Twenty Scenario 

Earthquakes in the State of Washington 

Open-File Report 2011-1016

U.S. Department of the Interior 

U.S. Geological Survey 

Population and Business Exposure to Twenty Scenario 

Earthquakes in the State of Washington 

By Nathan Wood and Jamie Ratliff 

Prepared in cooperation with the State of Washington Military Department Emergency 

Management Division 

Open-File Report 2011-1016

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

KEN SALAZAR, Secretary 

U.S. Geological Survey 

Marcia K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia 2011

For product and ordering information: 

World Wide Web: http://www.usgs.gov/pubprod 

Telephone: 1-888-ASK-USGS 

For more information on the USGS—the Federal source for science about the Earth, 

its natural and living resources, natural hazards, and the environment: 

World Wide Web: http://www.usgs.gov 

Telephone: 1-888-ASK-USGS 

Suggested citation: 

Wood, N., and Ratliff, J., 2011, Population and business exposure to twenty scenario earthquakes in the State of 

Washington: U.S. Geological Survey Open-File Report 2011-1016, 13 p.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report. 
v 

Contents 

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

Methods ......................................................................................................................................................................... 2

Results ........................................................................................................................................................................... 4

Acknowledgments ........................................................................................................................................................ 13

References Cited ......................................................................................................................................................... 13

Figures 

Figure 1. Study area map of scenario earthquakes in Washington (fault locations and extents generalized from 

U.S. Geological Survey, 2010, and Washington State Department of Natural Resources, 2010).......... 2

Figure 2. Residential population exposure to scenario earthquakes in Washington. ............................................ 6

Figure 3. Exposure of occupied housing units to scenario earthquakes in Washington. ....................................... 7

Figure 4. Increase in residential population exposure to earthquakes, 1990 to 2000, in Washington. .................. 9

Figure 5. Business exposure to scenario earthquakes in Washington. ............................................................... 10

Figure 6. Employee exposure to scenario earthquakes in Washington. ............................................................. 12

Tables 

Table 1. Modified Mercalli Intensity (MMI) classes, including relations to peak-ground-acceleration values 

(Wald and others, 1999) and impact descriptions (abridged from U.S. Geological Survey, 1989). ........ 3

Table 2. Residential population exposure to scenario earthquakes in Washington. ............................................ 5

Table 3. Exposure of occupied housing units to scenario earthquakes in Washington. ....................................... 7

Table 4. Increase in residential population exposure to earthquakes, 1990 to 2000, in Washington. .................. 8

Table 5. Business exposure to scenario earthquakes in Washington. ............................................................... 10

Table 6. Employee exposure to scenario earthquakes in Washington. ............................................................. 11
Population and Business Exposure to Twenty Scenario 

Earthquakes in the State of Washington 

By Nathan Wood and Jamie Ratliff 

Introduction 

This report documents the results of an initial analysis of population and business exposure to 

scenario earthquakes in Washington. This analysis was conducted to support the U.S. Geological 

Survey (USGS) Pacific Northwest Multi-Hazards Demonstration Project (MHDP) and an ongoing 

collaboration between the State of Washington Emergency Management Division (WEMD) and the 

USGS on earthquake hazards and vulnerability topics. This report was developed to help WEMD meet 

internal planning needs. A subsequent report will provide analysis to the community level. 

The objective of this project was to use scenario ground-motion hazard maps to estimate 

population and business exposure to twenty Washington earthquakes. In consultation with the USGS 

Earthquake Hazards Program and the Washington Division of Geology and Natural Resources, the 

twenty scenario earthquakes were selected by WEMD (fig. 1). Hazard maps were then produced by the 

USGS and placed in the USGS ShakeMap archive (U.S. Geological Survey, 2010). The scenario 

earthquakes and their moment magnitudes for this study are: 

Boulder Creek Fault M 6.8; 

Canyon River-Price Lake Fault M 7.4; 

Cascadia subduction zone megathrust M 9.0;

Cascadia subduction zone megathrust (northern section) M 8.3; 

Chelan Fault M 7.2; 

Cle Elum-Wallula deformed zone M 6.8; 

Devils Mountain Fault M 7.1; 

Devils Mountain Fault (western section) M 7.4; 

Hite Fault M 6.8; 

Little River Fault (Lake Creek) M 6.8; 

Toppenish Ridge Fault (Mill Creek) M 7.1; 

Mount Saint Helens deformed zone M 7.0; 

Nisqually intraslab zone M 7.2; 

Saddle Mountain Fault M 7.35; 

Sea-Tac intraslab zone M 7.2; 

Seattle Fault M 7.2; 

Spokane blind fault M 5.5; 

Southern Whidbey Island Fault (SWIF) zone M 7.4; 

Southern Whidbey Island Fault (SWIF) zone (southeastern section) M 7.2; and 

Tacoma Fault M 7.1. 
2 

Figure 1. Study area map of scenario earthquakes in Washington (fault locations and extents generalized from 

U.S. Geological Survey, 2010, and Washington State Department of Natural Resources, 2010).

Methods 

To describe population and business exposure to scenario earthquakes, geographic-informationsystem (GIS) tools were used to integrate publicly available hazard and socioeconomic data. 

Earthquake-hazard zones were delineated using GIS polygons that represent peak-ground-acceleration 

(PGA) values from the USGS ShakeMap archive (U.S. Geological Survey, 2010). PGA values were 

translated and represented by Modified Mercalli Intensity (MMI) classes. MMI describes the severity of 

an earthquake in terms of its effect on humans and structures. We used MMI classes instead of PGA 

values at WEMD’s request because MMI classes are more easily understood by emergency managers 

than PGA values. Table 1 summarizes the relation between PGA values and MMI classes, as well as 

providing a description of societal impacts at each MMI level. 
3 

Table 1. Modified Mercalli Intensity (MMI) classes, including relations to peak-ground-acceleration values (Wald 

and others, 1999) and impact descriptions (abridged from U.S. Geological Survey, 1989). 

Modified Mercalli 

Intensity

Peak Ground 

Acceleration (PGA) Description of Societal Impact

I < 0.0017 g Not felt except by a very few under especially favorable conditions

II 0.0017 – 0.014 g

Felt only by a few persons at rest, especially on upper floors of 

buildings

III 0.0017 – 0.014 g

Felt quite noticeably by persons indoors, especially on upper floors of 

buildings. Many people do not recognize it as an earthquake. Standing 

motor cars may rock slightly. Vibrations similar to the passing of a 

truck. Duration estimated.

IV 0.014 – 0.039 g

Felt indoors by many, outdoors by few during the day. At night, some 

awakened. Dishes, windows, doors disturbed; walls make cracking 

sound. Sensation like heavy truck striking building. Standing motor cars 

rocked noticeably

V 0.039 – 0.092 g

Felt by nearly everyone; many awakened. Some dishes, windows 

broken. Unstable objects overturned. Pendulum clocks may stop

VI 0.092 – 0.18 g

Felt by all, many frightened. Some heavy furniture moved; a few 

instances of fallen plaster. Damage slight

VII 0.18 – 0.34 g

Damage negligible in buildings of good design and construction; slight 

to moderate in well-built ordinary structures; considerable damage in 

poorly built or badly designed structures; some chimneys broken. 

VIII 0.34 – 0.65 g

Damage slight in specially designed structures; considerable damage in 

ordinary substantial buildings with partial collapse. Damage great in 

poorly built structures. Fall of chimneys, factory stacks, columns, 

monuments, walls. Heavy furniture overturned

IX 0.65 – 1.24 g

Damage considerable in specially designed structures; well-designed 

frame structures thrown out of plumb. Damage great in substantial 

buildings, with partial collapse. Buildings shifted off foundations

X > 1.24 g

Some well-built wooden structures destroyed; most masonry and frame 

structures destroyed with foundations. Rails bent.
4 

Societal-asset calculations focus on the number of residents and businesses in the various 

earthquake-hazard zones. These assets are determined because U.S. jurisdictions are encouraged to 

collect similar data as they develop State and local mitigation plans (Federal Emergency Management 

Agency, 2001), a requirement to qualify for funds under the U.S. Hazard Mitigation Grant Program in 

accordance with the Disaster Mitigation Act of 2000, Public Law 106-390. Data used in this analysis 

include: 

Population—based on block-level population counts (GIS polygons) compiled for the 1990 and 

2000 U.S. Census (U.S. Census Bureau, 2009) that identifies total residents and occupied housing 

units; and 

Business—based on the 2010 infoUSA Employer Database, a proprietary business database (GIS 

point file) that identifies location of businesses, number of employees, total sales volume, and the 

North American Industry Classification System (NAICS) code (infoUSA, 2010). 

Before analysis, geospatial data were transformed to share the same datum (North American 

Datum of 1983, High Accuracy Reference Network, State Plane, Washington, South, FIPS 4602 Feet) 

and projection (Lambert Conformal Conic), thereby conforming to existing GIS data from the State of 

Washington’s GIS database. Spatial analysis of vector data (for example, population polygons and 

business points) focused on determining whether or not points and polygons are inside earthquakehazard zones. Slivers of population polygons that overlap earthquake-hazard zones were taken into 

account during analysis, and final values were adjusted proportionately.

In the tables and stacked bar-graphs, we have chosen to summarize resident, employee, housing 

unit, and business counts only for MMI V and above. In discussion with WEMD staff, we agreed that 

peak-ground-acceleration values at MMI V represent the beginning of significant earthquake-related 

impacts and damages. Calculations at lower MMI levels are likely to be less useful to emergency 

managers and therefore were not performed. 

The results summarized in this report should be considered first approximations of population 

and business exposure and not exhaustive inventories. The ShakeMap geospatial layers we received had 

explicit spatial boundaries. Therefore, certain MMI zones, especially lower classes (MMI V for many 

scenarios, as well as MMI VI for the SWIF southeastern scenario), were clipped at study-area 

boundaries and do not represent the entire area likely to experience a certain level of ground shaking. 

Finally, this assessment of population and business exposure to earthquake hazards is based on scenario 

earthquakes and ground-shaking models. The results are not definitive loss estimates and are designed 

solely to help local and State emergency managers in their earthquake preparedness and planning 

efforts. 

Results 

Data presented in this initial report were generated to provide information for the WEMD staff. 

A subsequent report will build on this initial analysis with results tailored to individual communities and 

counties that could be impacted by the various scenario earthquakes. Preliminary results are presented in 

both tables and graphs to satisfy various needs of emergency managers. Results reported here include 

the number of residents, occupied housing units, businesses, and employees in the areas affected by the 

various MMI classes related to the twenty earthquake scenarios. We also calculate the change in 

residential exposure to earthquake hazards between 1990 and 2000. 
5 

On the basis of the 2000 Census, there are millions of Washington residents living in areas prone 

to significant ground shaking (table 2; fig. 2). The earthquake scenario with the highest number of 

residents in earthquake-hazard zones (MMI V and greater) is a Cascadia subduction zone (CSZ) 

megathrust earthquake. More than 5 million people are living in zones prone to MMI V and above 

ground shaking for earthquakes along the entire CSZ (M 9.0) and also for just the northern section of the 

CSZ (M 8.0). 

Although CSZ earthquakes represent the highest overall residential exposure in Washington, a M

7.4 earthquake within the Southern Whidbey Island Fault (SWIF) zone could expose the highest number 

of residents (more than 137,000) to the greatest ground shaking (MMI IX) projected for the State. A M

7.1 earthquake on the Tacoma Fault could also expose a significant number of residents (approximately 

62,000) to MMI IX ground shaking. Earthquake scenarios for the CSZ are not projected to expose any 

populations in the State of Washington to MMI IX ground shaking. 

Table 2. Residential population exposure to scenario earthquakes in Washington. 

Earthquake scenario Exposed residential population in 2000, organized by MMI class

V VI VII VIII IX TOTALS

Boulder Creek M 6.8 528,183 136,908 13,857 3,463 321 682,732

Canyon River M 7.4 2,901,320 791,490 39,459 2,861 116 3,735,245

Cascadia M 9.0 780,400 989,190 3,482,525 109,738 0 5,361,853

Cascadia (northern section) M 8.3 3,415,432 1,674,719 207,926 8,901 0 5,306,978

Chelan M 7.2 124,342 49,019 71,190 10,078 167 254,796

Cle Elum M 6.8 1,575,609 149,362 38,234 401 17 1,763,623

Devils Mountain M 7.1 2,394,711 397,411 107,617 45,873 2,164 2,947,777

Devils Mountain (western section) M 7.4 2,161,370 572,988 118,136 98,997 720 2,952,211

Hite M 6.8 139,232 3,235 23,537 29,266 0 195,269

Lake Creek M 6.8 3,682,057 16,370 18,110 32,770 1,726 3,751,033

Mill Creek M 7.1 322,549 157,650 69,938 3,147 20 553,304

Mt St Helens Zone M 7.0 1,284,015 100,031 5,532 1,203 0 1,390,781

Nisqually M 7.2 47,061 1,448,439 2,262,156 0 0 3,757,656

Saddle Mountain M 7.35 197,958 426,628 47,245 13,363 255 685,449

SeaTac M 7.2 52,207 445,927 3,305,549 0 0 3,803,683

Seattle M 7.2 355,105 1,441,297 1,103,800 1,035,911 0 3,936,113

Spokane M 5.5 126,124 136,667 181,365 0 0 444,156

SWIF M 7.4 1,270,495 1,221,859 1,070,349 403,838 137,848 4,104,389

SWIF (southeastern section) M 7.2 1,203,827 1,576,691 906,266 249,304 0 3,936,088

Tacoma M 7.1 799,104 1,477,240 1,097,000 406,773 61,915 3,842,031
6 

Figure 2. Residential population exposure to scenario earthquakes in Washington. 

The exposure of occupied housing units, not surprisingly, follows the trends in residential 

exposure (table 3; fig. 3). Exposure of occupied housing units to MMI V to IX ground-shaking classes 

ranges from approximately 68,000 for a M 6.8 Hite Fault earthquake to more than 2 million for a CSZ 

earthquake. Earthquakes related to the SWIF (M 7.4) and the Tacoma Fault (M 7.1) would expose the 

greatest number of occupied housing units to the greatest ground-shaking potential (more than 51,000 

and 23,000 housing units, respectively, to MMI IX shaking). 
7 

Table 3. Exposure of occupied housing units to scenario earthquakes in Washington. 

Earthquake scenario Exposed occupied housing units in 2000, organized by MMI class

V VI VII VIII IX TOTALS

Boulder Creek M 6.8 203,804 52,679 4,671 1,179 118 262,451

Canyon River M 7.4 1,135,578 318,863 14,552 1,357 58 1,470,408

Cascadia M 9.0 275,627 361,110 1,384,118 43,002 0 2,063,857

Cascadia (northern section) M 8.3 1,328,325 628,800 81,135 4,161 0 2,042,421

Chelan M 7.2 45,657 18,038 26,224 3,593 72 93,585

Cle Elum M 6.8 586,065 53,299 14,721 152 8 654,246

Devils Mountain M 7.1 965,101 151,125 39,312 16,634 829 1,173,001

Devils Mountain (western section) M 7.4 872,284 220,586 44,277 37,108 312 1,174,567

Hite M 6.8 47,909 1,063 9,022 10,202 0 68,195

Lake Creek M 6.8 1,447,013 7,254 8,365 13,965 661 1,477,258

Mill Creek M 7.1 114,445 56,711 19,425 796 5 191,383

Mt St Helens Zone M 7.0 478,782 37,980 2,184 493 0 519,439

Nisqually M 7.2 17,926 565,224 893,998 0 0 1,477,148

Saddle Mountain M 7.35 72,425 146,633 16,426 3,469 75 239,028

SeaTac M 7.2 21,147 170,133 1,301,711 0 0 1,492,991

Seattle M 7.2 138,222 542,087 432,342 431,866 0 1,544,516

Spokane M 5.5 44,778 52,120 76,451 0 0 173,349

SWIF M 7.4 479,709 479,095 448,132 151,450 51,672 1,610,059

SWIF (southeastern section) M 7.2 455,320 632,095 358,475 98,615 0 1,544,506

Tacoma M 7.1 305,286 592,176 432,761 154,974 23,696 1,508,892

Figure 3. Exposure of occupied housing units to scenario earthquakes in Washington. 
8 

Between 1990 and 2000, the exposure of residential populations has increased across the State of 

Washington (table 4; fig. 4). The greatest increases were related to CSZ earthquakes. Although 

residential exposure has increased between 1990 and 2000, a comparison of figures 2 and 4 suggests 

that increases in residential exposure are not unique to any one earthquake scenario and that population 

across the State of Washington increased fairly uniformly. 

Table 4. Increase in residential population exposure to earthquakes, 1990 to 2000, in Washington. 

Earthquake scenario Increase in residential exposure to earthquakes, 1990 to 2000, by MMI class

V VI VII VIII IX TOTALS

Boulder Creek M 6.8 119,702 31,139 2,071 2,243 119 155,274

Canyon River M 7.4 458,958 124,235 8,319 595 65 592,173

Cascadia M 9.0 145,145 272,080 528,423 9,021 0 954,668

Cascadia (northern section) M 8.3 576,409 348,586 21,282 1,352 0 947,629

Chelan M 7.2 25,259 10,951 14,056 1,679 36 51,981

Cle Elum M 6.8 301,478 23,447 6,989 35 4 331,953

Devils Mountain M 7.1 357,674 95,674 24,896 11,774 638 490,657

Devils Mountain (western section) M 7.4 295,434 146,687 30,720 16,981 56 489,878

Hite M 6.8 25,220 1,031 2,481 2,580 0 31,311

Lake Creek M 6.8 596,939 4,032 3,943 2,721 512 608,147

Mill Creek M 7.1 72,297 24,200 10,103 318 12 106,929

Mt St Helens Zone M 7.0 265,128 15,290 640 78 0 281,136

Nisqually M 7.2 6,443 243,153 349,527 0 0 599,123

Saddle Mountain M 7.35 34,798 80,269 9,688 5,342 74 130,172

SeaTac M 7.2 4,166 99,380 519,388 0 0 622,934

Seattle M 7.2 59,233 293,715 163,643 130,761 0 647,351

Spokane M 5.5 27,416 26,080 10,072 0 0 63,568

SWIF M 7.4 237,609 183,914 151,993 76,315 40,101 689,933

SWIF (southeastern section) M 7.2 204,025 243,189 144,804 55,332 0 647,350

Tacoma M 7.1 173,728 217,415 149,156 75,034 8,795 624,128
9 

Figure 4. Increase in residential population exposure to earthquakes, 1990 to 2000, in Washington. 

The exposure of businesses to MMI V to IX ground-shaking classes ranges from approximately 

6,500 for a M 6.8 Hite Fault earthquake to more than 200,000 for a CSZ earthquake (table 5; fig. 5). 

This analysis of business exposure does not differentiate between small businesses with only a few 

employees and large corporations with thousands of employees. A subsequent analysis of employee 

exposure accounts for variations in business size. 

An earthquake related to the Seattle Fault (M 7.2) would likely have the greatest impact to 

business communities, as it could expose more than 55,000 businesses to MMI VIII ground shaking. 

Earthquake scenarios for the SWIF (M 7.4) and Tacoma Fault (M 7.1) would expose several thousands 

of businesses to MMI IX ground shaking (3,827 and 1,486, respectively) but would have significantly 

lower numbers of businesses in MMI VIII classes (14,339 and 14,950 businesses, respectively) than a 

Seattle M 7.2 earthquake scenario. In general, scenario earthquakes associated with the Seattle, SWIF, 

and Tacoma faults likely represent the greatest threats to businesses of the twenty scenarios in this 

study. 
10

Table 5. Business exposure to scenario earthquakes in Washington. 

Earthquake scenario Exposed businesses in 2010, organized by MMI class

V VI VII VIII IX TOTALS

Boulder Creek M 6.8 20,529 6,507 341 50 8 27,435

Canyon River M 7.4 105,931 44,614 1,275 47 1 151,868

Cascadia M 9.0 26,841 33,629 146,947 3,467 0 210,884

Cascadia (northern section) M 8.3 142,043 59,683 7,587 199 0 209,512

Chelan M 7.2 4,529 1,692 3,077 168 1 9,467

Cle Elum M 6.8 57,498 5,633 1,776 14 0 64,921

Devils Mountain M 7.1 104,685 15,583 3,624 2,321 49 126,262

Devils Mountain (western section) M 7.4 95,457 22,350 4,264 4,226 27 126,324

Hite M 6.8 4,268 70 779 1,450 0 6,567

Lake Creek M 6.8 152,171 1,130 1,100 1,759 30 156,190

Mill Creek M 7.1 11,531 6,199 1,414 43 0 19,187

Mt St Helens Zone M 7.0 44,323 4,129 99 8 0 48,559

Nisqually M 7.2 880 51,918 98,587 0 0 151,385

Saddle Mountain M 7.35 6,948 15,710 1,830 223 5 24,716

SeaTac M 7.2 1,631 15,657 136,628 0 0 153,916

Seattle M 7.2 12,531 51,830 39,569 55,907 0 159,837

Spokane M 5.5 3,620 5,137 9,516 0 0 18,273

SWIF M 7.4 43,698 53,917 52,249 14,339 3,827 168,030

SWIF (southeastern section) M 7.2 42,863 73,945 34,264 8,765 0 159,837

Tacoma M 7.1 26,797 61,129 50,819 14,950 1,486 155,181

Figure 5. Business exposure to scenario earthquakes in Washington. 
11

The exposure of employees to MMI V to IX ground-shaking classes ranges from approximately 

68,000 for a M 6.8 Hite Fault earthquake to more than 2.2 million for a CSZ earthquake (table 6; fig. 6). 

An earthquake related to the Seattle Fault (M 7.2) would likely have the greatest impact to business 

communities, as it could expose more than 678,000 employees to MMI VIII ground shaking. Again, 

earthquake scenarios for the SWIF (M 7.4) and Tacoma Fault (M 7.1) would expose significant numbers 

of employees to MMI IX ground shaking (42,737 and 9,567, respectively) but would have significantly 

lower numbers than a Seattle scenario in MMI VIII classes (both approximately one-third of Seattle 

Fault estimates). 

Table 6. Employee exposure to scenario earthquakes in Washington. 

Earthquake scenario Number of Employees (2010), organized by MMI class

V VI VII VIII IX TOTALS

Boulder Creek M 6.8 188,657 66,923 2,564 202 18 258,364

Canyon River M 7.4 1,112,577 575,656 9,616 253 30 1,698,132

Cascadia M 9.0 291,546 297,972 1,662,116 27,755 0 2,279,389

Cascadia (northern section) M 8.3 1,549,172 651,810 68,419 789 0 2,270,190

Chelan M 7.2 46,788 13,648 33,358 1,674 1 95,469

Cle Elum M 6.8 657,580 62,266 11,567 52 0 731,465

Devils Mountain M 7.1 1,161,231 153,138 34,050 22,547 233 1,371,199

Devils Mountain (western section) M 7.4 1,077,903 221,021 36,928 36,942 70 1,372,864

Hite M 6.8 46,683 2,386 5,314 13,839 0 68,222

Lake Creek M 6.8 1,717,686 6,729 6,018 15,114 136 1,745,683

Mill Creek M 7.1 134,814 66,648 18,388 659 0 220,509

Mt St Helens Zone M 7.0 460,550 38,141 512 73 0 499,276

Nisqually M 7.2 4,369 531,130 1,155,059 0 0 1,690,558

Saddle Mountain M 7.35 64,699 195,056 15,340 2,499 47 277,641

SeaTac M 7.2 14,375 132,619 1,562,848 0 0 1,709,842

Seattle M 7.2 101,488 564,679 417,017 678,087 0 1,761,271

Spokane M 5.5 35,044 50,967 124,568 0 0 210,579

SWIF M 7.4 448,337 628,400 574,810 143,361 42,737 1,837,645

SWIF (southeastern section) M 7.2 464,566 877,856 333,159 85,690 0 1,761,271

Tacoma M 7.1 245,299 655,844 618,869 191,380 9,567 1,720,959
12

Figure 6. Employee exposure to scenario earthquakes in Washington. 
13

Acknowledgments 

This report was supported by funds from the USGS Earthquake Hazards Program (EHP) and the 

USGS Geographic Analysis and Monitoring Program. We thank John Schelling of the State of 

Washington Emergency Management Division (WEMD) for his support of this project. We also thank 

WEMD and the USGS EHP for providing funds for the acquisition of the proprietary economic dataset. 

We thank John Schelling, Mara Tongue (USGS Western Geographic Science Center), and Craig 

Weaver (Pacific Northwest Coordinator, USGS EHP) for their insightful reviews of earlier versions of 

the report. 

References Cited 

Federal Emergency Management Agency, 2001, State and local mitigation planning how-to guide 

No. 2—Understanding your risks: Federal Emergency Management Agency no. 386-2, last accessed 

August 21, 2007, at http://www.fema.gov/library/viewRecord.do?id=1880. 

InfoUSA, 2010, Employer database: online dataset, last accessed December 14, 2010, at 

http://www.infousagov.com/employer.asp. 

U.S. Census Bureau, 2009, Census 2000: Census 2000 Gateway, last accessed December 14, 2010, at 

http://www.census.gov/main/www/cen2000.html. 

U.S. Geological Survey, 1989, The severity of an earthquake: U.S. Geological Survey General Interest 

Publication, 15 p.

U.S. Geological Survey, 2010, ShakeMap Archive: last accessed December 14, 2010, at 

http://earthquake.usgs.gov/earthquakes/shakemap/list.php?x=1&n=global. 

Wald, D., Quitoriano, V., Heaton, T., and Kanamori, H., 1999, Relationships between peak ground 

acceleration, peak ground velocity, and Modified Mercalli Intensity in California: Earthquake Spectra, 

v. 15 no. 3, p. 557–564.

Washington State Department of Natural Resources, 2010, Seismogenic features, Washington State 

Department of Natural Resources, Division of Geology and Earth Resources, last accessed January 

21, 2011, at http://www.dnr.wa.gov/ResearchScience/Topics/GeosciencesData/Pages/gis_data.aspx.