Swarm of earthquakes east of Temecula sparks interest from scientists

Scientists are studying a prolific swarm of small earthquakes that recently generated a magnitude 4.4 earthquake about 20 miles east of Temecula.

The seismic swarm is not considered likely to be a foreshadowing of a large, damaging earthquake. The cluster of quakes is not particularly close to any major faults — it’s about halfway between the Elsinore and San Jacinto faults, said Caltech seismologist Egill Hauksson.

If the swarm did generate an earthquake, “it could be a magnitude 5. But anything bigger is highly unlikely,” Hauksson said.

This earthquake swarm has been going on for about two years and is particularly active, Hauksson said. There were previous seismic swarms in the area in the 1980s, but they were not followed by bigger events on other faults.

The swarm has been given a name — the Cahuilla swarm, as it’s on the western edge of the reservation home to the Cahuilla Band of Mission Indians. There have been more than 6,000 earthquakes greater than magnitude 0.3 since the middle of 2016, according to the Southern California Seismic Network.

“This is a fascinating sequence from a scientific point of view, but it has almost no immediate hazards implications,” the seismic network report said.

The earthquakes appear to be in an aftershock mode, but the tremors are moving to the southeast, and it’s possible that more quake activity could occur.

This earthquake swarm is seen as less of a risk than one that occurred about two years ago under the Salton Sea. Because that seismic swarm was in the vicinity of the San Andreas fault — California’s longest — scientists had a higher level of concern it could awaken the big fault that is capable of producing the state’s most powerful earthquake. That swarm, however, did not result in a big, damaging earthquake.

While half of all large quakes are preceded by smaller foreshocks, the other half are not. California could easily experience a huge quake without any hint of earlier, smaller seismic activity.

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