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Jun 14

Written by:
6/14/2013 10:07 AM 

If you have even been curious about the potential impact of all those various earthquakes that geologists have identified – and see which might have the largest impact for a general region like Vashon Island (i.e., parcel level damage estimates are NOT supported!), then check out the State Seismic Hazards Catalog.

While many reports have previously quantified potential impacts from a variety of potential quakes, these 20 new scenarios are the first systemic analysis of potential casualties and damage.

These scenarios also use a new version of HAZUS-MH modeling software – recently updated with new geographic data and now incorporating liquefaction modeling.

Hosted by the Washington State Department of Natural Resources (DNT), the scenarios describe the potential impacts on communities and their infrastructure — from homes to utilities — from large earthquakes on 20 major earthquake faults across the state.

Tacoma Fault Scenario

For instance the Tacoma fault (running right under Vashon actually) could unleash a magnitude 7.1 quake which might then displace some 12,000 households with more than 6,000 people injured throughout the region. The orange image above shows the King County specific damage possible, while the table below shows the entire potential damage to the entire region.

A summary and detailed report of this scenario are available. From the summary comes the following list of potential damage to the entire region:

TACOMA FAULT SCENARIO EARTHQUAKE End-to-end length of fault (kilometers) 68 Magnitude (M) of scenario earthquake 7.1 Number of counties impacted 16 Total injuries (*severity 1, 2, 3, 4) at 2:00 PM 6,070 Total number of buildings extensively damaged 4,457 Total number of buildings completely damaged 15,410 Income losses in millions $1,847 Displaced households 11,576 People requiring shelter (individuals) 7,146 Capital stock losses in millions $8,654 Debris total in millions of tons 2.95 Truckloads of debris (25 tons per truckload) 117,960 People without power (Day 1) 87,675 People without potable water (Day 1) 193,544 Table 1. Summary of significant losses in the M7.1 Tacoma fault earthquake scenario. Among the counties most likely to be affected are Grays Harbor, Jefferson, King, Kitsap, Mason, Pierce, and Thurston. *Injury severity levels: 1—requires medical attention, but not hospitalization; 2—not life-threatening, but does require hospitalization; 3—hospitalization required; may be life-threatening if not treated promptly; 4—victims are killed by the earthquake

 

Building Damage Estimates for the Tacoma Fault Scenario HAZUS runs estimate that about 84,296 buildings will be at least moderately damaged. This is over 4.00 % of the total number of buildings in the region. There are an estimated 4,457 buildings that will be damaged beyond repair. The definition of the ‘damage states’ is provided in Volume 1: Chapter 5 of the HAZUS technical manual. Table 3 above summaries the expected damage by general occupancy for the buildings in the region. Table 4 summaries the expected damage by general building type.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The State Seismic Hazards Catalog is intended to help citizens, businesses, and safety officials plan for better resilience to and recovery from a major earthquake.

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 effects from these and other earthquakes may vary significantly from what is depicted.
 
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.

Local Press Coverage:

• http://seattletimes.com/html/localnews/2021019310_quakescenariosxml.html
• www.seattlepi.com/local/article/Just-how-devastating-will-earthquakes-be-in-4532382.php