What do the hundreds of earthquakes swarming Southern California near the Salton Sea mean for the chances of a major quake?
The quake swarm, which began about 4 p.m. Wednesday, continued overnight and into Thursday morning with hundreds of small quakes, the U.S. Geological Survey reports.
Most of the tremors are below 3.0 magnitude, but a few earthquakes registering over 4.5 magnitude have been recorded, the USGS reports. The agency had recorded at least 240 quakes by Wednesday night.
“Quakes make other quakes more likely, but only nearby,” seismologist Lucy Jones wrote on Twitter Wednesday night. “The only faults nearby are small. In other words, there is no scientific reason to predict a big quake in another location today.”
The quake swarms “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 says. Previous swarms in the area happened in 1981 and 2012.
“Past swarms have remained active for 1 to 20 days, with an average duration of about a week,” the USGS reported.
The swarm most likely will continue for several days, possibly including quakes up to 5.4 magnitude. A less likely scenario includes a possible quake of up to 6.9 magnitude.
And there’s a very slim chance of a quake of 7.0 magnitude or higher, but only in the Salton Sea area, not along one of the major California fault lines, the USGS said.
“While this is a very small probability, if such an earthquake were to occur, it would have serious impacts on communities nearby and would be followed by aftershocks that would increase the number of smaller earthquakes per day,” the USGS said.
An #earthquake swarm has kicked off southwest of the #SaltonSea today, producing 240 earthquakes as of 8pm Pacific. The largest earlier this evening was M4.9.
So what does this mean? We’ve put together some scenarios to explain what could happen next. https://t.co/wMzKa8FKQM pic.twitter.com/ow9r7J5FH4
— USGS Earthquakes (@USGS_Quakes) October 1, 2020
”One of the largest swarms we have had in the Imperial Valley — and it is historically the most active swarms in SoCal,” Jones wrote on Twitter.
Magnitude measures the energy released at the source of the earthquake, the U.S. Geological Survey says. It replaces the old Richter scale.
Quakes between 2.5 and 5.4 magnitude are often felt but rarely cause much damage, according to Michigan Tech.