Hundreds of earthquakes have rattled an area about 100 miles east of San Diego just southeast of the Salton Sea since Wednesday afternoon, suggesting more activity will shake the region over the next week including a quake up to a 5.4 magnitude, the U.S. Geological Survey said.
As many as 240 tremors – most registering a magnitude of 3.0 or lower – had been detected as of 11 p.m. EDT Wednesday evening in and around the town of Westmoreland, with the largest recording a 4.9 magnitude at about 8:30 p.m. EDT. The San Andreas fault runs through the area.
“One way to consider these forecasts is that there is always a risk of a larger earthquake on any given day,” the USGS said in a Twitter post. “This swarm activity and our associated forecast communicate how much the risk has been elevated, and we update them as time goes on, posted online at this link.”
“This earthquake and the associated swarm are located in an area of diffuse seismic activity between the San Andreas fault in the north and the Imperial fault to the south,” the USGS added in a release.
The same area has seen earthquake swarms before, the USGS said, notably in 1981 and again in 2012.
It gave a 90% likelihood of continued activity over the next seven days, “which could cause localized damage, particularly in weak structures.”
The USGS said there was a 10% chance of an earthquake of up to 6.9 magnitude, a scenario which it said followed the 1981 swarm.
The least likely, a one in 300 chance, was the possibility of an earthquake of 7.0 or higher.
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