Live in the Seattle area long enough and you will experience an earthquake. Most earthquakes in the Northwest are minor. Some you may not even feel them. Others, like the 2001 Nisqually Earthquake, are large enough to feel and cause some damage. But make no mistake: the Seattle-Tacoma area has the potential for large, destructive earthquakes!
The Puget Sound region is traversed by fault lines and zones and is also near the Cascadia subduction zone, where the Juan de Fuca and North American tectonic plates meet. According to the Washington State Department of Natural Resources, more than 1,000 earthquakes occur in Washington State each year! Living in such a seismically active area, it is not a question of whether Seattle has a major earthquake, but when.
Types of earthquakes in the Puget Sound
Depending on how deep an earthquake is and the type of fault in which it occurs, earthquakes can be minor or major, near the surface or deep in the ground. The Puget Sound has the potential to experience three different types of earthquakes: shallow, deep, and subduction. Shallow and deep earthquakes are exactly what they sound like: shallow earthquakes occur between 0 and 30 km from the surface; Deep earthquakes occur between 35 and 70 km from the surface.
Subduction earthquakes in our region occur along the Cascadia subduction zone off the coast of Washington. Subduction is when a plate moves under another plate and these are the tremors largely responsible for tsunamis and large magnitudes. Subduction zones (including Cascadia) are capable of producing so-called megathrust earthquakes, which are enormously powerful and destructive if they occur in a populated area. The 2011 Tohoku earthquake in Japan occurred along a subduction zone similar to the Cascadia subduction zone.
Seattle earthquake history
The Puget Sound area is often subject to small earthquakes that most people do not even feel and that do not cause any damage. In the last hundreds of years, some earthquakes have made history due to their greater magnitude and damage that remained in their wake.
February 28, 2001: The 6.8 magnitude Nisqually earthquake was centered south on Nisqually, but caused some structural damage in Seattle.
April 29, 1965 – A magnitude 6.5 earthquake in the southern Sound area was felt as far away as Montana and British Columbia, and knocked down thousands of smokestacks in Puget Sound.
April 13, 1949 – A 7.0 earthquake was centered near Olympia and caused eight deaths, extensive property damage in Olympia, and a large landslide in Tacoma.
February 14, 1946 – A 6.3 magnitude earthquake, a deep earthquake shook most of the Puget Sound and caused major damage in Seattle.
June 23, 1946 – A 7.3 magnitude earthquake struck the Straits of Georgia and caused some damage in Seattle. The earthquake was felt from Bellingham to Olympia.
1872: Centered near Lake Chelan, this earthquake is estimated to have been large, but there were few man-made structures in its path. Most of the reports focus on landslides and cracks in the ground.
January 26, 1700 – The last known megathrust earthquake near Seattle was in 1700. Evidence of a massive tsunami (which may have even affected Japan) and the destruction of forests helps scientists date this earthquake.
Around 900 AD: A 7.4 magnitude earthquake is estimated to hit the Seattle area in about 900. Local legends and geology help confirm this earthquake.
