Selasa, 11 Agustus 2020

Salton Sea earthquake swarm continues, slightly raises probability of large quake - Press-Enterprise

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Earthquakes are continuing in the area of the Salton Sea in Riverside and Imperial counties, but even so, the U.S. Geological Survey says the probability of a large quake in the region increases only marginally.

The swarm began around 8:30 a.m. Monday, Aug. 10, and, within 24 hours, 26 quakes larger than 2.5 magnitude had been recorded. The largest was 4.6.

On Tuesday, there had been only 10 earthquakes as of about 5 p.m., with the largest, magnitude 3.6 at 4 a.m. The difference between a 4.6 and a 3.6 meant that the potential for the biggest temblor to trigger a large, damaging earthquake was reduced by 10%, said Morgan Page, a research geophysicist with the USGS.

Whereas Monday’s swarm created an 80% chance of continuing earthquakes, with none larger than 5.4, Tuesday’s swarm left a 98% chance of continuing earthquakes with none larger than 5.4. In other words, there was a 2% chance of an earthquake larger than 5.4, Page said.

“The probabilities are still higher than they would be in a typical week,” she added.

The epicenter is under the Salton Sea lakebed in Imperial County, about 8 miles from the southern end of the San Andreas Fault, the USGS said in a news release Monday.

USGS said the area saw similar swarms in 2001, 2009 and 2016. The swarms are caused by the movement of fluid in the Earth’s crust, Page said. The swarms take place in faults that run perpendicular to the San Andreas Fault.

“It’s typical of the way earthquakes operate in this area,” she said.

The USGS said the last earthquake of 7+ on the southernmost section of the San Andreas Fault was more than 300 years ago.

“In a typical week,” a news release said, “there is approximately a 1-in-10,000 chance of a magnitude 7+ earthquake on the southernmost San Andreas Fault. That probability is significantly elevated while swarm activity remains high.”

The swarm prompted Riverside County emergency management officials on Tuesday to remind residents to prepare for earthquakes by creating an emergency kit containing water, food and other essential items that will last three to seven days.

During shaking, people should drop to the ground, cover up and hold on. Drivers should pull to the side of the road and stop — but not under bridges, officials said.

After an earthquake, do not touch or drive over downed electrical lines. And leave areas where natural gas is smelled.

The Link Lonk


August 12, 2020 at 12:42AM
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Salton Sea earthquake swarm continues, slightly raises probability of large quake - Press-Enterprise

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