An earthquake is the sudden release of stored energy; most earthquakes occur along a fracture within the earth, called a fault. The shaking caused by this sudden shift is often very small, but occasionally large earthquakes produce very strong ground shaking. It is this strong shaking and its consequences – ground failure, landslides, liquefaction – that damages buildings and structures and upsets the regional economy.
Washington, especially the Puget Sound basin, has a history of frequent earthquakes. More than 1,000 earthquakes occur in the state each year. A dozen or more are strong enough that people feel ground shaking; occasionally, earthquakes cause damage. Large earthquakes in 1946 (magnitude 5.8), 1949 (magnitude 7.1) and 1965 (magnitude 6.5) killed 15 people and caused more than $200 million (1984 dollars) in damage throughout several counties. The state experienced at least 20 damaging events in the last 125 years.
The Nisqually earthquake on February 28, 2001, was a deep, magnitude 6.8 earthquake 10 miles northeast of Olympia. One person died of a heart attack, more than 700 people were injured, and various estimates place damage at between $1 billion and $4 billion; exact figures are not available, as insurance claims information is not available.
The earthquake threat in Washington is not uniform. While most earthquakes occur in Western Washington, some damaging events, such as the 1872 magnitude 6.8 (est.) quake, do occur east of the Cascades. Geologic evidence documents prehistoric magnitude 8 to 9.5 earthquakes along the outer coast, and events of magnitude 7 or greater along shallow crustal faults in the urban areas of Puget Sound.
Washington’s earthquake hazards reflect its tectonic setting. The Pacific Northwest is at a convergent continental margin, the collision boundary between two tectonic plates of the earth’s crust. The Cascadia subduction zone, the fault boundary between the North America plate and the Juan de Fuca plate, lies offshore from northern California to southern British Columbia. The two plates are converging at a rate of about 2 inches per year. In addition, the northward-moving Pacific plate is pushing the Juan de Fuca plate north, causing complex seismic strain to accumulate. The abrupt release of this slowly accumulated strain causes earthquakes.
Scientific Earthquake Information
The Geology Division of the Washington State Department of Natural Resources (DNR) conducts geologic hazards mapping across the state and works to identify our earthquake threats. In addition, the United States Geological Survey works closely with DNR to provide the most accurate, credible, and up-to-date scientific earthquake information to the public and emergency management community. Their work forms the basis for the implementation of seismic provisions and standards in building codes and other infrastructure protection standards. For additional information about the earthquake hazards in Washington, see the links below:
- Geological Hazards (DNR)
- Earthquakes in Washington (DNR)
- Geological Mapping of Washington (DNR)
- Washington Earthquake Information (USGS)
- Earthquake Hazards Program (USGS)
- Seismology and Tectonics (UW)
- Advanced National Seismic System (ANSS)
- Pacific Northwest Seismic Network (PNSN)
- Earthquakes in Washington State (EMD) (PDF)
Building Codes in Washington State
The International Code Council (ICC) is a membership association dedicated to building safety and fire prevention. ICC develops the codes and standards used to construct residential and commercial buildings, including seismic provisions for homes, schools, offices, etc. The International Codes, or I-Codes, published by ICC, provide minimum safeguards for people at home, at school and in the workplace. The I-Codes are a complete set of comprehensive, coordinated building safety and fire prevention codes and benefit public safety as well as support the industry’s need for one set of codes without regional limitations.
The State Building Code Council (SBCC) was created to provide independent analysis and objective advice to the legislature and the Governor’s Office on state building code issues. The SBCC establishes the minimum building, mechanical, fire, plumbing and energy code requirements necessary to promote the health, safety and welfare of the people of the state of Washington by reviewing, developing and adopting the state building code. For additional information about building codes used in Washington State, see the links below:
Washington State Emergency Management and the Washington State Seismic Safety Committee have been working on personal, neighborhood, school, and business earthquake preparedness for several decades. This effort includes the use nationally acclaimed programs like Map Your Neighborhood and Prepare in a Year, which were developed by WA EMD.
Most recently, through funding assistance from FEMA, Washington State Emergency Management, the Office of the Superintendant of Public Instruction, the Department of Natural Resources and volunteer structural engineers and building officials are conducting a pilot project to evaluate a method of evaluating school seismic safety in Walla Walla and Aberdeen. This project is expected to be completed by the end of the year.
The Washington State Seismic Safety Committee is beginning a 2-3-year effort entitled “The Resilient Washington State” Initiative. This project seeks to examine earthquake threats to the state and local communities, identify transparent performance measures to gauge our progress, and recommend policies in order to achieve resilience after an earthquake. It is based on a similar effort in the City of San Francisco. For additional information about the state’s emergency management earthquake programs and current projects, see the links below:
- Interactive Earthquake Scenario Catalog (DNR)
- Seattle Fault Study (EERI)
- The Seattle Fault (2 Minute Geology) (Video)
- The Resilient Washington State Final Report (PDF)
- Washington State Emergency Management Council
- Washington State Seismic Safety Committee
- Earthquake Hazards Reduction Program (FEMA)
- National Earthquake Hazards Reduction Program (NEHRP)
Washington uses trust land revenue for state school construction grants that are matched to local school district bond issues. This system generated $19 billion in school construction funds since 1993. The money financed new school construction and major building upgrades – all of which was built to the seismic safety standards in effect at the time of construction.
For additional information about the state’s common school construction program, see the links below:
- School Seismic Safety Project (DNR)
- Office of Superintendant of Public Instruction (OSPI)
- School Funding and Trust Beneficiaries (DNR)
- Washington Trust Lands and Education Funding (Lincoln Institute) (PDF)
- Basic Emergency Planning for Schools (EMD)
- School Emergency Procedure Templates
- Earthquake and Tsunami School Resource Guide 2012 (PDF)
Unit 1: Earthquakes
Unit 2: Understanding WA Earthquake Sources
- Unit 3: Defining Tsunamis
Unit 4: Pacific-Wide Tsunamis
Unit 5: Tsunami Warning System in WA
Unit 6: Earthquake and Tsunami Preparedness
- Unit 7: Learning Activities
References: Glossary, References, About Authors
- The Seattle Fault (2 Minute Geology) (Video)
One of the state’s top priorities since the 2001 Nisqually Earthquake has been the upgrade and strengthening of our transportation infrastructure. Major elements of the program are the replacement of Seattle’s Alaskan Way Viaduct currently estimated to cost $3.1 billion and the construction of a new Lake Washington 520 bridge currently estimated to cost about $4.2 billion. The state also has done complete or partial retrofits of 386 Central Puget Sound bridges in a program that will complete retrofits of another 495 bridges by 2015. For additional information about the state’s bridge retrofit program and other transportation system upgrades, see the links below:
- Seismic Retrofit Program (DOT)
- Alaskan Way Viaduct and Seawall Replacement (DOT)
- Alaskan Way Viaduct Closure System (DOT)
- SR 520 Replacement Program (DOT)
- Ferry Terminal Seismic Retrofit (DOT)
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