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March 24, 2021

8 More Millimeters

While [the Mission Creek strand of the san Andreas fault] was long believed to have a slip rate of around 14 millimeters per year, the paper, published in Science Advances, argues that it's actually around 22 millimeters..

Part Of The San Andreas Fault Is Moving Way Faster Than We Previously Thought

Updated March 24, 2021 11:17 AM Published March 24, 2021 11:15 AM

As if the San Andreas fault wasn't concerning enough, research just released today shows that a nearby portion of it is moving much faster than scientists previously thought.

It's called the Mission Creek strand and it runs from around Indio, through Desert Hot Springs and into the San Bernardino Mountains.

While it was long believed to have a slip rate of around 14 millimeters per year, the paper, published in Science Advances, argues that it's actually around 22 millimeters.

"This particular strand of the San Andreas fault has been interpreted to not be very active," said Kimberly Blisniuk, a geochronologist at San Jose State University and lead author on the study. "It's actually very active and is the fastest slipping fault for the San Andreas in Southern California. Therefore it has the highest likelihood of a large magnitude earthquake to occur on it in the future."

A few millimeters might not sound like a lot but when we're talking about massive tectonic plates pushing up against each other, the stress adds up.

"Higher slip rates on faults mean more risk," said Morgan Page, a geophysicist at the U.S. Geological Survey in Pasadena and one of the developers of the Uniform California Earthquake Rupture Forecast. Page was not associated with the recent study. "It means stress is accumulating faster on that fault and you would need basically either more earthquakes or larger earthquakes over centuries to relieve that stress."

All of which means that this particular strand on the San Andreas has a greater risk than was previously understood. How much of an additional risk? It needs to be assessed.

Any infrastructure in that area, like water or gas lines which run over the fault itself, will need to be looked at with a critical eye, given that offsets of as much as 30 feet could occur in the event of a major quake.

"Their study is in a region where the San Andreas fault is quite complex," said Sally McGill, a geology professor at Cal State San Bernardino. "This is a substantial step in improving our understanding of how the Southern San Andreas fault works."

Regardless of what happens on the Mission Creek strand, we know that sizable earthquakes on the San Andreas are possible.

Like... at any moment.

So now is always a good time to get your earthquake kit ready.

Filed under Coachella Valley,Desert Hot Springs,Science | permalink | March 24, 2021 at 01:14 PM

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