Cascadia Subduction Zone is a 620-mile fault that runs from Northern California to Vancouver Island in Canada. This fault has produced 9.0 – 9.2 earthquakes in the past, due to the fact that the entire fault slips all at once, causing 5-minute earthquakes, aftershocks and tsunami’s following. The last significant earthquake was January 26, 1700, with estimated magnitude of 9.0.

Orally transmitted legends from the Olympic Peninsula area tell of epic battle between a Thunderbird and Whale. Other tribes, including Huu-ay-aht, Makah, Hoh, Quileute, Yurok and Duwamish have told stories of earthquakes and saltwater floods. The date of the last “full rip” has been estimated by as January 26, 1701, based upon Native American Stories and a large tsunami that hit Japan on that date, presumed to be from last major full-rip earthquake (when the entire 620-mile fault movement simultaneously.) 3/4 of the time, intervals longer than 323 years resulted in Full-Rips. In 2025, we are in year 325 since the last Full-Rip episode. (Source, Surviving Cascadia Likelihood of a 9.0 – Surviving Cascadia Over the last 10,000 years, the earthquakes have occurred every 300 – 1000 years. There is a 1:3 chance of a Full Rip earthquake in the next 50 years.

There are several other notorious faults in our region, Darrington – Devils Mountain Fault, Skipjack Island Fault, and many more.

Track recent Earthquakes in the San Juan Islands here

Recommended Lecture: Nick Zenter, Central Washington University “Great Earthquakes of the Pacific Northwest”

Recommended Reading: