Quake swarm sparks study

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

The 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.

The swarm has been going on for about two years and is particularly active, Hauksson said. There were previous 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 that’s home to the Cahuilla Band of Mission Indians. There have been more than 6,000 earthquakes greater than magnitude 0.3 since mid-2016, said 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 swarm was in the vicinity of the San Andreas fault — California’s longest — scientists had a higher level of concern that 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.