Strong Quake Predicted to Hit Desert by Sept. 5

A team of scientists that predicts that a quake with a magnitude of 6.4 or greater will occur somewhere in the Southern California desert by Sept. 5 has received a qualified endorsement from a state earthquake council.

The California Earthquake Prediction Evaluation Council, a group of eight scientists selected by the state Office of Emergency Services, said it considers the new prediction by the UCLA team to be “a legitimate approach in earthquake prediction research.”

Still, the council pointed out in a report to the state that “the physical basis for the prediction ... has not been substantiated.”

The UCLA team, headed by Vladimir Keilis-Borok, has generated interest in its prediction after it successfully forecast -- although with wide parameters in place and time -- the magnitude-6.5 San Simeon quake of Dec. 22, as well as an 8.1 quake last year off Japan’s Hokkaido island.

Based on its analysis, the team claims that a quake will occur somewhere within a 12,000-square-mile area east of L.A. by early September.

The large geographic area within the prediction zone -- including a large portion of the Mojave Desert, the Coachella Valley, the Imperial Valley and eastern San Diego County -- led the council to conclude “that the results do not at this time warrant any special public policy actions in California.” Such actions, when taken, could include warnings to the public or alerts issued to utilities to help them prevent disruptions in service.

Lucy Jones, scientist-in-charge of the U.S. Geological Survey’s Pasadena office and a member of both the prediction council and the state Seismic Safety Commission, pointed out Tuesday that the prediction zone includes both the epicenters of the 7.3 Landers earthquake of 1992 and the 7.1 Hector Mine earthquake of 1999.

The zone is so seismically active that the council noted in its report that the chances of an earthquake of at least magnitude 6.4 occurring randomly in the area sometime before the Sept. 5 deadline is about 10%.

Nonetheless, Jones and Ned Field, a Geological Survey colleague, have worked up nine scenarios for the predicted quake, mapping out where it might occur.

Some of the scenarios, which Jones released Tuesday, indicate the predicted quake could cause damage in Palm Springs, San Bernardino, or both.

The UCLA team bases its predictions on long chains of small earthquakes recorded in the area.

“In the vicinity of each such chain,” Keilis-Borok recently explained, “we look backward and see its history over the preceding years -- whether our candidate [for an earthquake] was preceded by certain seismicity patterns. If yes, we accept the candidate as a short-term precursor and start a nine-month alarm.”

In the San Simeon case, the team issued a prediction in June that a strong quake would occur somewhere between Fort Bragg in Mendocino County and Cambria in San Luis Obispo County. The actual quake occurred near the southern end of this 310-mile stretch six months later.