Seismic Scenarios

Predicted earthquake shaking intensity distribution for a M9.0 Cascadia subduction zone earthquake event.

Seismic scenarios demonstrate possible earthquake events that could strike Washington state. There are 20 seismic scenarios presented here that Washingtonians should be aware of. No matter where you live in Washington, you could be impacted by a future earthquake. These scenarios can help you plan and prepare for earthquake hazards.

Note that these seismic scenarios were previously available for viewing and download on the Geologic Information Portal. They have now been moved to this webpage along with information to help you understand the data better. The Cascadia subduction zone, Seattle, and Tacoma seismic scenarios are still available for viewing on the Portal under the 'Earthquakes' tab in the table of contents.

What is a seismic scenario

What it is

A seismic scenario represents one realization of a potential future earthquake by assuming a particular magnitude, location, and fault-rupture geometry, and estimating shaking using a variety of strategies.

These scenarios represent reasonable estimates of the earthquake hazards in Washington State, and are to be used for planning. Organizations, local government, emergency managers, and individuals are best served by conducting training exercises based on realistic earthquake situations—ones similar to those they are most likely to face.

How it’s created

All scenarios are based on ShakeMap, developed by the U.S. Geological Survey. ShakeMap maps the predicted intensity of earthquake shaking based on the earthquake characteristics and geologic properties.

The scenarios also include information based on Hazus, developed by the Federal Emergency Management Agency to help planners estimate potential losses from earthquakes, floods, tsunamis, and hurricanes. Hazus estimates the amount of physical damage and economic losses based on ShakeMap. Hazus correlates the zones of higher or lower shaking to possible building and infrastructure damage.

Components of a seismic scenario

Injuries and fatalities

Injuries and casualties are calculated at the census tract level, and aggregated to the county level. Estimates were based upon the 2000 United States Census.

The injuries and fatalities shown in this layer are those directly related to damage caused by earthquake shaking. Casualties from induced hazard events—such as fire following earthquake, hazardous materials releases, and inundations (tsunamis, dam failures, levee failures, and seiches)—are NOT included in this estimation.

HAZUS-MH MR4 classifies injuries according to the following severity level:

  • Severity 1: Injuries requiring basic medical aid that could be administered by paraprofessionals. These types of injuries would require bandages or observation. Some examples are: a sprain, a severe cut requiring stitches, a minor burn (first degree or second degree on a small part of the body), or a bump on the head without loss of consciousness. Injuries of lesser severity that could be self treated are not estimated by HAZUS.
  • Severity 2: Injuries requiring a greater degree of medical care and use of medical technology such as x-rays or surgery, but not expected to progress to a life threatening status. Some examples are third degree burns or second degree burns over large parts of the body, a bump on the head that causes loss of consciousness, fractured bone, dehydration or exposure.
  • Severity 3: Injuries that pose an immediate life threatening condition if not treated adequately and expeditiously. Some examples are: uncontrolled bleeding, punctured organ, other internal injuries, spinal column injuries, or crush syndrome.
  • Severity 4: Instantaneously killed or mortally injured.

Injuries and fatalities are estimated for three times of day:

  • Earthquake striking at 2:00 a.m. (night time scenario)
  • Earthquake striking at 2:00 p.m. (day time scenario)
  • Earthquake striking at 5:00 p.m. (commute time scenario)

Damaged buildings

Following an earthquake, inspectors typically inspect buildings for safety using the ATC-20 Procedures for Postearthquake Safety Evaluation of Buildings. Green, yellow and red placards are placed on inspected buildings.

The meaning of the color designation is as follows:

  • Green Tagged Buildings: Inspected, no apparent structural hazards found. Lawful occupancy permitted.
  • Yellow Tagged Buildings: Restricted use. The structure has been inspected and found to have damage, described on the placard. Written placard instructions indicate restrictions to entry, occupancy, and lawful use.
  • Red Tagged Buildings: Unsafe. The structure has been inspected and been found to be seriously damaged and unsafe to occupy. (Note that a red placard does not indicate that demolition is ordered. The structure may be repairable.)

Injuries and fatalities are estimated for three times of day:

  • Earthquake striking at 2:00 a.m. (night time scenario)
  • Earthquake striking at 2:00 p.m. (day time scenario)
  • Earthquake striking at 5:00 p.m. (commute time scenario)

Debris in 1,000 tons

According to HAZUS-MH MR4, very little has been done in the area of estimating debris from earthquakes. HAZUS adopts an empirical approach to estimate two different types of debris. The first is debris that falls in large pieces, such as steel members or reinforced concrete elements. These require special treatment to break into smaller pieces before they are hauled away. The second type of debris is smaller and more easily moved with bulldozers and other machinery and tools. This includes brick, wood, glass, building contents, and other materials.

Given the damage states for structural and nonstructural components, debris estimates are based on observations of damage that has occurred in past earthquakes. No debris estimates are made for bridges or other lifelines.

Displaced households

Earthquakes can cause loss of function or habitability of buildings that contain housing units, resulting in approximately predictable numbers of displaced households. These households may need alternative short-term shelter, provided by family, friends, renting apartments or houses, or public shelters provided by relief organizations such as the Red Cross, Salvation Army, and others.

In HAZUS-MH MR4, loss of habitability is calculated directly from damage to the residential occupancy inventory, and from loss of water and power. The methodology for calculating short term shelter requirements recognizes that only a portion of those displaced from their homes will seek public shelter, and some will seek shelter even though their residence may have no or insignificant damage.

Households may also be displaced as a result of fire following earthquake, inundation (or the threat of inundation) due to dam failure, and by significant hazardous waste releases. This Hazus module does not specifically deal with these issues, but an approximate estimate of displacement due to fire or inundation can be obtained by multiplying the residential inventory in affected census tracts by the areas of fire damage or inundation derived from those modules. The hazardous materials module is confined to identifying locations of hazardous materials and no methodology for calculations of damage or loss is provided.

If the particular characteristics of the study region give the user cause for concern about the possibility of housing loss from fire, dam failure, or hazardous materials, it would be advisable to initiate specific studies directed towards the problem.

Building economic loss in $1,000

Using estimates of damage to infrastructure, HAZUS-MH MR4 provides estimates of the structural and nonstructural repair costs caused by building damage and the associated loss of building contents and business inventory. Building damage can also cause additional losses by restricting the building’s ability to function properly. To account for this, business interruption and rental income losses are estimated. Direct building economic loss estimates are provided in 1994 dollars.

The economic loss estimates shown in this layer are limited to those losses that can be directly derived from building and infrastructure damage, and that lend themselves to ready conversion from damage to dollars. The real socio/economic picture is much more complex: economic impacts may have major societal effects on individuals or discrete population groups, and there may be social impacts that ultimately manifest themselves in economic consequences.

Building economic loss estimates are broken down into the following categories:

  • Building economic loss: Building economic loss is divided into structural and nonstructural loss. Replacement costs are based on 2003 estimates and may underestimate current replacement costs.
  • Building content loss: Building contents are defined as furniture, equipment that is not integral with the structure, computers, and other supplies. Contents do not include inventory or nonstructural components such as lighting, ceilings, mechanical and electrical equipment, and other fixtures. HAZUS assumes that a percentage of building contents cannot be retrieved at moderate, extensive, and complete structural damage states (5%, 25%, and 50%).
  • Business inventory loss: Business inventories vary considerably with occupancy. HAZUS assumes that business inventory for each occupancy class is based on annual sales. Furthermore, it assumes losses to business inventory most likely occurs from stacks of inventory falling over, objects falling off shelves, or from water damage when piping breaks.
  • Relocation loss: Relocation costs may be incurred when a building or portions of the building are unusable while repairs are being made. In the HAZUS estimate of relocation loss, only the disruption costs of shifting and transferring to a new space and the rental of temporary space is estimated.
  • Rental income loss: Rental income losses are the product of floor area, rental rates per square foot, and the expected days of loss of function for each damage state. Rental income losses include residential, commercial and industrial properties. It is assumed that a renter will pay full rent if the property is in the damage state none or slight. Thus rental income losses are calculated only for damage moderate or greater.
  • Wage losses: Income losses occur when building damage disrupts economic activity. Income losses are the product of floor area, income realized per square foot and the expected days of loss of function for each damage state.

Households without water – Day 1

The default inventory in HAZUS-MH MR4 contains estimate of potable water pipelines aggregated at the census tract level. This pipeline data was developed using the US Census TIGER street file datasets. By default, HAZUS-MH MR4 assumes eighty (80) percent of the pipes are brittle. The remaining pipes are assumed to be ductile.

HAZUS-MH MR4 calculates expected number of leaks and breaks per census tract and a simplified evaluation of the potable water system network performance (i.e. number of households without water).

Shaking intensity (MMI value)

The Modified Mercalli Intensity (MMI) scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake on the earth’s surface, humans, objects in nature, and the building environment. The scale ranges from 1 (not felt) to 12 (total destruction), often expressed as Roman numerals I through XII.

Following is a detailed description of MMI shaking intensity levels:

  • MMI 4: Vibration felt like passing of heavy trucks. Stopped cars rock. Hanging objects swing. Windows, dishes, doors rattle. Glasses clink. In the upper range of IV, wooden walls and frames creak.
  • MMI 5: Pictures move. Felt outdoors. Sleepers wakened. Liquids disturbed, some spilled. Small unstable objects displaced or upset. Doors swing. Pictures move. Pendulum clocks stop.
  • MMI 6: Objects fall. Felt by all. People walk unsteadily. Many frightened. Windows crack. Dishes, glassware, knickknacks, and books fall off shelves. Pictures off walls. Furniture moved or overturned. Weak plaster, adobe buildings, and some poorly built masonry buildings cracked. Trees and bushes shake visibly.
  • MMI 7: Nonstructural damage. Difficult to stand or walk. Noticed by drivers of cars. Furniture broken. Damage to poorly built masonry buildings. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles, cornices, unbraced parapets, and porches. Some cracks in better masonry buildings. Waves on ponds.
  • MMI 8: Moderate damage. Steering of cars affected. Extensive damage to unreinforced masonry buildings, including partial collapse. Fall of some masonry walls. Twisting, falling of chimneys and monuments. Wood-frame houses moved on foundations if not bolted; loose partition walls thrown out. Tree branches broken.

List of scenarios for download

Limitations of use

The Washington State Earthquake Hazards Scenario Catalog contains loss estimates for a suite of earthquake scenarios. These scenarios were selected to represent reasonable estimates of the most serious earthquake hazards everywhere in Washington as a basis for planning. In most cases, these scenarios are realistic and have undergone rigorous peer review. Some of these scenarios, however, are hypothetical or speculative, and the recurrence interval, or average time between earthquakes, varies from a few tens of years to a few tens of thousands of years; however, all scenarios are consistent with data included the USGS National Seismic Hazard Map.

The loss estimates were produced by Hazus-MH, which is a regional loss estimation tool produced by the Federal Emergency Management Agency (FEMA) and the National Institute of Standards and Technology (NIST). Results are most accurate when aggregated on a county or regional scale. Modeled results depend on accurate inventories. The more complete the inventories, the more accurate the results. Because of their complexity, it is more difficult to estimate losses to lifelines (utility and transportation) than buildings. These data are not a substitute for site-specific investigations assessing the level of risk for an area. They cannot be used to determine the earthquake hazard at a specific locality. Such a determination requires a site-specific geotechnical investigation performed by a qualified practitioner.

The Washington State Earthquake Hazards Scenario Catalog is the result of a collaborative effort by the Washington State Department of Natural Resources (WADNR), the Washington Military Department Emergency Management Division (EMD), Western Washington University (WWU), Huxley College of the Environment, Federal Emergency Management Agency (FEMA), US Geological Survey (USGS) and URS Corporation.

For more information about Hazus-MH, visit the Hazus-MH web page.

Download the data

Click on the map images below to download data for that scenario. The download is a zip file containing a geodatabase and supporting information about the data. You will need GIS software such as Esri ArcGIS or QGIS to view the geodatabase. Click the words 'Download Summary Report' below each map image to download a PDF summary of the results of the modeling for a given scenario.

Click here to download all the scenarios at once. Note that this is a very large zip file (370 MB) and could take some time to download.

Boulder Creek

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Canyon River

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Cascadia North

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Cle Elum

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Devils Mountain

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Devils Mountain West

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Lake Creek Boundary Creek

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Mill Creek

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Mount St. Helens

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Saddle Mountains

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Southern Whidbey Island

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