Live in the Seattle area long enough and you’ll experience an earthquake. Most earthquakes in the Northwest are minor; some you may not even feel. However, others, like the 2001 Nisqually Earthquake, are impactful enough to feel and cause notable damage. It is crucial to understand that the Seattle-Tacoma area holds the potential for large, destructive quakes!
The Puget Sound Region is intertwined with multiple fault lines and is located near the Cascadia Subduction Zone, where the Juan de Fuca and North American tectonic plates converge. 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’s a question of when Seattle will face a major earthquake, not if.
Types of Earthquakes in the Puget Sound
Depending on their depth and the type of fault, earthquakes can vary from minor tremors to significant quakes. The Puget Sound can experience three principal types of earthquakes: shallow, deep, and subduction. Shallow earthquakes occur between 0 and 30 kilometers from the surface, while deep earthquakes take place between 35 and 70 kilometers.
Subduction earthquakes occur along the Cascadia Subduction Zone, located off the Washington Coast. Subduction refers to the process where one tectonic plate moves beneath another. These quakes are primarily responsible for creating tsunamis and can reach high magnitudes. Subduction zones, including Cascadia, have the capability to generate megathrust earthquakes, which can be devastating if they occur in densely populated areas. For instance, the 2011 Tohoku earthquake in Japan happened along a similar subduction zone.
Seattle Earthquake History
The Puget Sound area frequently endures minor earthquakes, often unnoticed and without causing damage. Nonetheless, several significant earthquakes have been recorded over the past centuries due to their high magnitudes and the destruction they caused.
February 28, 2001: The Nisqually Earthquake, registering at 6.8 magnitude, was centered south in Nisqually but caused structural damage as far as Seattle.
April 29, 1965: A 6.5 magnitude deep earthquake in the southern Sound area was felt as far away as Montana and British Columbia, resulting in thousands of chimney collapses across the Puget Sound.
April 13, 1949: A 7.0 magnitude quake centered near Olympia led to eight fatalities, significant property damage, and a large mudslide in Tacoma.
February 14, 1946: A 6.3 magnitude deep earthquake affected much of the Puget Sound, causing severe damage in Seattle.
June 23, 1946: A 7.3 magnitude quake centered in the Strait of Georgia caused noticeable damage in Seattle and was felt from Bellingham to Olympia.
1872: Centered near Lake Chelan, this earthquake is believed to have been significant, although the area lacked extensive manmade structures. Most accounts highlight incidents of landslides and ground fissures.
January 26, 1700: The last-known megathrust earthquake near Seattle occurred in 1700. Evidence of a massive tsunami that may have even impacted Japan, along with the destruction of forests, assists scientists in dating this quake.
Around 900 AD: It’s estimated that a 7.4 magnitude quake hit the Seattle area around this time. Local legends and geological evidence support this occurrence.
