Washingtonians can join them today by registering for the 2017 Great Washington ShakeOut. Participating is a great way for your family or organization to be prepared to survive and recover quickly from big earthquakes– wherever you live, work, or travel. Learn tips on how to get 2 Weeks Ready and craft your own emergency kits here. ShakeOut is also a major activity of America’s PrepareAthon!
Start here to be included in the 2017 Washington ShakeOut!
The Pacific Coast of Washington is at risk from tsunamis. These destructive waves can be caused by coastal or submarine landslides or volcanism, but they are most commonly caused by large submarine earthquakes.
Tsunamis are generated when these geologic events cause large, rapid movements in the sea floor that displace the water column above. That swift change creates a series of high-energy waves that radiate outward like pond ripples. Offshore tsunamis would strike the adjacent shorelines within minutes and also cross the ocean at speeds as great as 600 miles per hour to strike distant shores. In 1946, a tsunami was initiated by an earthquake in the Aleutian Islands of Alaska; in less than 5 hours, it reached Hawaii with waves as high as 55 feet and killed 173 people.
Tsunami waves can continue for hours. The first wave can be followed by others a few minutes or a few hours later, and the later waves are commonly larger. Washington Emergency Management Tsunami Program
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.
Earthquakes at Washington Military Department Emergency Management Division.
In Washington, earthquakes and landslides are the most likely sources of a tsunami.
The Pacific Rim countries have a history of damaging tsunamis caused by both distant and local earthquakes. Earthquakes have caused 98% of the world’s tsunamis with over 73% of these being observed along the Pacific “Ring of Fire”. For this reason, communities in low-lying coastal areas around the Pacific Rim are among the most at risk to tsunami damages generated from both local and distant sources that can strike within minutes to many hours.
Washington State Earthquake Scenario Catalog (Washington State Department of Natural Resources)
DNR Interactive Geology Portal (Washington State Department of Natural Resources)
The Seattle Fault – Beneath Largest City in the Pacific Northwest (2 minute Geology, from HUGEfloods.com Youtube Channel)
Tsunami inundation maps (Washington State Department of Natural Resources)
Tsunami Evacuation Zones (Washington State Department of Natural Resources)
Recent Earthquakes Map (Pacific Northwest Seismic Network)
Earthquakes in Washington (United States Geological Survey)