Why Humboldt is vulnerable to earthquakes

By Shawn Hubler, The New York Times, December 21, 2022

“The most seismically active stretch of the state, scientists say, lies around Cape Mendocino in Humboldt County, where the westernmost tip of the Pacific coastline curves out into the ocean. There, under roiling blue waves, three tectonic plates meet, grinding and heaving. The Mendocino Triple Junction, as the configuration is known, generates an average of 80 earthquakes of magnitude 3.0 or greater each year.

“On [December 20] … that immense junction again shifted, jolting Humboldt County awake with a 6.4 magnitude temblor. 

“California’s MyShake early warning earthquake app, a statewide alert that the lab helped develop, issued its largest heads-up since the state debuted it in 2019.

[The New York Times spoke with Richard Allen, director of the University of California, Berkeley’s Seismology Lab. Excerpts from their conversation follow.]

“[How is the North Coast’s] Mendocino Triple Junction different?

“Three plates join at the Mendocino Triple Junction, and it creates a real mess of faults mashing and colliding.

“So more plates mean more motion?

“Right. It’s a much more complicated geometry of faults, along with more motion to be accommodated, and that leads to more events.

“Is the area getting more active or less active?

“People always ask that. It’s neither. We have a magnitude 6.5 earthquake in this region about once a decade.”

Read the full article here.  (~4 min.)

Colin Atagi in the Santa Rosa Press Democrat provides on-the-ground coverage of the recovery in Humboldt County. Read his reporting here.

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