On Sunday (5/31), a series of earthquakes hit the Oregon Coast. The magnitudes of the seven ranged between 5.9 and 3.9, all too small to trigger a tsunami. Each earthquake was located nearly 300 miles west of Coos Bay, Oregon and had a relatively shallow depth of approximately 6 miles. A USGS seismologist discussed the physical irrelevancies between this earthquake event and the potential Cascadia Subduction event that has occurred in the past and is currently building up pressure (see the figure below (https://pnsn.org/outreach/earthquakesources/csz)). Due to the distance away from the coast, these recent earthquakes were located outside of the Cascadia subduction zone, which stretches from North Vancouver Island to Cape Mendocino, California. To access the news story on the recent Oregon earthquakes, click here.
Great subduction zone earthquakes are the largest in the world, and the only source zones that can produce earthquake events greater than M8.5
(https://pnsn.org/outreach/earthquakesources/csz). The last event of this magnitude in Northwest was in 1700, and have returned at irregular intervals of hundreds of years. A 13-year study published by Oregon State University, concluded that there is a 40% chance of a major earthquake in the Coos Bay, Oregon region in the next 50 years
(http://oregonstate.edu/ua/ncs/archives/2012/jul/13-year-cascadia-study-complete-–-and-earthquake-risk-looms-large). The image to the right produced by a seismologist from San Diego State University, illustrates a simulation of a Cascadia Subduction M9 earthquake event (https://pnsn.org/outreach/earthquakesources/csz).
In order to prepare for a major earthquake, there are a number of sources that provide guidelines, helpful tips and assistance: