Kern County Aftershocks May Last a Year, Scientists Say

As more aftershocks rattled on Monday, scientists from Caltech and the U.S. Geological Survey warned that the earthquake sequence in the desert north of Ridgecrest has not exhausted itself and could last as long as a year.

Sunday’s magnitude 5.2 temblor was the third quake in the moderately strong magnitude 5 range since the sequence began with a 5.4 quake on Aug. 17.

The strongest of Monday’s quakes measured magnitude 4.3 at 2:52 a.m. and 4.1 at 12:57 a.m. Seismologists at Caltech reported a total of 350 aftershocks since Sunday’s 5.2.

The strongest jolt of the overall series was a 5.8 on Sept. 20, and through Monday there have been more than 8,000 shocks concentrated in an unpopulated part of the China Lake Naval Air Weapons Station, about 10 miles north of the Kern County town of Ridgecrest.

Damage has been minor and only one injury was reported in the town of 28,000, which is about 100 miles north of Los Angeles.

Caltech seismologist Egill Hauksson predicted Monday that more quakes will occur in the months ahead.

“I think this is not all over with,” he said. “The sequence continues. It’s kind of irregular, but what we see is a definite zone of activity. The 5.2 was within a couple of kilometers of the 5.8.”

Hauksson added that in the welter of faults in the region, some are capable of producing a quake more powerful than magnitude 6, and he said such a quake would be strongly felt--if not damaging--in the Los Angeles metropolitan area.

But, he noted, scientists do not have enough information to be able to predict that such a larger quake will occur.

Jim Mori, the scientist in charge of the Pasadena field station of the U.S. Geological Survey, said, “In the past, these quake swarms have gone on for anywhere from a few months to about a year. But this is the largest series of swarms in the area in some time.

“Any time you get a lot of quakes happening, there’s an increased chance of a large one,” he said.

Mori said the Geological Survey will continue to monitor the quakes through a portable seismographic station--one of five in Southern California--that was moved to the area in September.

The Ridgecrest quakes are occurring in what is known as an Eastern California shear zone that was also involved in the Landers-Big Bear quakes of 1992 and the magnitude 8.0 quake at Lone Pine in the Owens Valley in 1872.

Some scientists believe this zone may mark an eventual shift east over many thousands of years of the tectonic plate boundary between the North American and Pacific plates from the San Andreas Fault to beyond the Sierra Nevada Mountains.