Powerful 6.5M Earthquake Detected Off The Coast Of California


Robin Andrews

Science & Policy Writer

The epicenter of the 6.5m quake. USGS

A 6.5M earthquake has just struck off the coast of California at 6:50am local time.

As reported by the United States Geological Survey (USGS), it occurred at a depth of 12.1 kilometers (7.5 miles) beneath the waves no more than 160 kilometers (100 miles) west of the town of Eureka.


At present, there are no reports of damage or injuries to anyone along the western seaboard, and no tsunami warning was issued. The quake did not generate any violent shaking or ground movement of any significant kind on land, although many coastal residents could feel it.

Aftershocks will be expected with a quake of this magnitude, but the threat has, for now, passed.

Any seismic activity around the infamous San Andreas Fault is likely to cause a bit of a stir in the media, but the data coming in so far suggests that nothing major will happen along that particular fault network anytime soon. The risk of the “big one” likely remains unchanged, although as we’ve previously reported, this risk is still fairly high and is increasing day by day.

This new quake appears to have taken place on the Mendocino Fracture Zone (MFZ), a strike-slip fault where two pieces of a larger tectonic plate are grinding past each other. This movement is similar to how the North American Plate is grinding up against the Pacific Plate along the San Andreas Fault, but the MFZ is far smaller.


Clearly, a high amount of stress had built up within the MFZ, and it had jutted suddenly forwards, unleashing it in the form of an earthquake. As the fault segments were sliding past each other, but not over or under each other, a tsunami would almost certainly have not been generated.

The MFZ is connected to the San Andreas Fault, however, and this tremor may have transmitted some of its stress towards the 1,300-kilometer-long (800-mile) behemoth. This would only serve to hasten the pace in which part of it – or perhaps all of it – will rupture.

So far, the USGS estimates that there is a 1-in-3 chance that a 7.5M quake along the San Andreas Fault will hit Los Angeles within the next 30 years. They also calculated that there is a 99 percent chance a 6.7M quake will take place.

Make no mistake – it’s coming. This new quake, if anything, has likely only made things ever so slightly worse.


Image in text: The regional tectonics. This new quake took place on the Mendocino Fracture Zone, at the bottom of the image. NASA


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  • California,

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  • tsunami warning,

  • Mendocino Fracture Zone