Minor Earthquake North of Mount St. Helens Tuesday Afternoon
Did you feel it? A few Washington residents did Tuesday afternoon. A magnitude 3.2 earthquake stuck just before 5pm local time Tuesday afternoon. The earthquake struck at a distance of 11.8 km below the surface and lasted a short 13 seconds.
While this earthquake was minor, did you know a large fault line stretches over 600 miles just off the coast of Washington? This fault line is called the Cascadia Subduction Zone (CSZ). It stretches from Northern Vancouver Island to Cape Mendocino in northern California.
Because of the great length of the fault, the Cascadia Subduction Zone is capable of producing very large earthquakes if rupture occurs along its entire length. However, evidence indicates that great earthquakes may have occurred sporadically at least seven times in the last 3,500 years, suggesting a return time of about 500 years. So while the next great earthquake is still some time away, evidence shows that the next rupture of the Cascadia Subduction Zone is anticipated to be capable of causing widespread destruction throughout the Pacific Northwest.
One of the largest recorded earthquakes in Washington state history, was measured at a magnitude of 6.8 and lasted approximately 45 seconds. The epicenter of the earthquake was Anderson Island, about 11 miles northeast of Olympia.