Cascadia Subduction Zone Earthquakes by Cascadia Region Earthquake ...

Since the start of European settlement in the late 19th century, the population of the Pacific Northwest has grown into the millions, and the region is currently experiencing one of the largest population booms in the country. It wasn’t until 20th century researchers compared these records with coastal geology that the source of this tsunami was identified: a magnitude-9.0 earthquake on the Cascadia subduction zone (Atwater et al., 2005 Satake et al., 2003 Ludwin et al., 2005). Magistrate records from Eastern Japan and Native American oral histories from the Pacific Northwest do, however, suggest a large wave of water swept through these regions around this time. We therefore do not have direct measurements of how large the earthquake was. The 1700 quake occurred two centuries before seismometers were invented and widely installed. The risk is particularly high in the Puget Sound, where major population centers are growing directly in harm’s way. Credit: USGSĪ repeat of the 1700 earthquake today would cause extensive damage throughout the Pacific Northwest. Red shading indicates areas of possible slip on the fault during a magnitude-9.0 earthquake. The Cascadia subduction zone sits just offshore of the Pacific Northwest. The region’s last major earthquake was in 1700, when an approximate magnitude-9.0 earthquake ruptured the full length of the fault, which extends from off the coast of Northern California to Vancouver Island in Canada. The interface of the two plates is the Cascadia subduction zone, a fault that has generated magnitude-8.0+ earthquakes over intervals spanning many centuries. Here, the Juan de Fuca tectonic plate is jammed beneath the North American plate at a rate of a few centimeters per year. However, an enormous threat lurks just off the coast of the Pacific Northwest. Should another occur today, the region’s cities would feel intense shaking - some more than others.Ĭitation: Stone, I., 2020, Five Puget Sound cities likely to feel strong shaking in a megaquake, Temblor, Īlthough Washington State’s Puget Sound has been shaken every few decades, damage in the region’s largest cities, including Seattle, Tacoma and Olympia, has only ever been modest. candidate, University of Washington has experienced major earthquakes in the past.

Cascadia Subduction Zone Earthquakes by Cascadia Region Earthquake ...