Strongest earthquake in nearly 20 years shakes Northern California: What is the Cascadia Subduction Zone?

7.0 quake off CA coast could trigger another major one

FOX 35 Storm Team Meteorologist Noah Bergren joined FOX 35 News+ to talk about the major earthquake off the coast of California on Thursday, the numerous aftershocks that followed, and why the tectonic activity could lead to another major earthquake in the coming days.

ORLANDO, Fla. - An earthquake struck off the northern California coast on Tuesday, marking the strongest in the region in nearly two decades. The 6.5-magnitude quake occurred at 1:44 p.m. EST (10:44 a.m. PST), approximately 35 miles offshore.

While the event triggered a rare tsunami warning for over 4 million people along the West Coast, no destructive waves materialized, according to officials.

The quake serves as a reminder of the long-term seismic risks posed by the Cascadia Subduction Zone, a less-publicized but potentially catastrophic fault system that extends from Northern California to British Columbia.

"Often you only hear about the San Andreas Fault in movies or on the internet, but the real, much less common, bigger threat every few 100 years is from a 9-plus magnitude quake from the Cascadia Subduction Zone," explained FOX 35 Meteorologist Noah Bergren.

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The Cascadia Subduction Zone is capable of generating "megathrust" earthquakes with magnitudes of 9.0 or higher.

Such an event, which last occurred over 300 years ago, could trigger a tsunami reaching heights of 75 to 100 feet and impact regions as far away as Japan. FEMA estimates a Cascadia megathrust quake could result in tens of billions of dollars in damage and potentially 10,000 fatalities.

Tuesday's earthquake occurred near the Mendocino Fault Zone, where the Pacific, North American, and Juan de Fuca plates converge. Geologists note this region is seismically active, but today’s event underscores the broader risks of living near tectonic plate boundaries.

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