Earthquakes are continuing in the area of California’s Salton Sea, and the U.S. Geological Survey says the event “significantly” raises the probability of a large quake in the region.
The swarm began around 8:30 a.m. Monday, and, within 24 hours, 26 quakes larger than 2.5 magnitude had been recorded. The largest has been 4.6.
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.
It said the area saw similar swarms in 2001, 2009 and 2016.
The USGS release detailed three scenarios for the following week:
- Scenario One (about 80% chance): Earthquakes continue but none will be larger than magnitude 5.4, and the rate will decrease over the course of the week.
- Scenario Two (about 19% chance): An earthquake of magnitude 5.5 to 6.9 could occur within the next seven days.
- Scenario Three (about 1% chance): An earthquake of magnitude 7 or higher could occur within the next seven days.
The agency 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,” it 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.”