Quake aftershocks are moving toward dangerous faults

LOS ANGELES — Aftershocks of the magnitude 7.1 earthquake near Ridgecrest have been creeping into areas close to two major earthquake faults, a development that is generating interest and some concern among seismologists over whether it could trigger another huge temblor.

Both faults are capable of producing new earthquakes of magnitude 7 or greater. The U.S. Geological Survey says the chance of an earthquake of magnitude 7 or greater from the July 5 earthquake is 1 in 300 — “possible, but with a low probability.”

Some aftershocks have rumbled northwest of the Searles Valley earthquake, approaching the Owens Valley Fault. That fault triggered an earthquake of perhaps magnitude 7.8 or 7.9 in 1872, one of the largest in California’s modern record.

Felt as far away as Los Angeles and Sacramento, the 1872 earthquake killed 27 people — 1 out of every 10 people in the mining camp of Lone Pine — and destroyed 52 of 59 houses there.

The Ridgecrest aftershocks have also headed southeast toward the Garlock fault, a lesserknown fault capable of producing an earthquake of magnitude 8 or more.

The fault along the northern edge of the Mojave Desert can send shaking south and west into Bakersfield and Ventura and Los Angeles counties.

“Those are places we would be more concerned,” U.S. Geological Survey research geophysicist Morgan Page said. “Little earthquakes are telling us where big earthquakes are more likely.”

No one can predict exactly when and where the next big earthquake will occur in California. Some quakes can trigger seismic activity on nearby faults, but it’s not a given.

Perhaps the most famous example of triggered earthquakes in California occurred in 1992.

An April 22 magnitude 6.1 earthquake in Joshua Tree National Park began a quake sequence that migrated north in the coming months.

Then on June 28, an earthquake 63 times stronger ruptured — the magnitude 7.3 Landers earthquake with an epicenter more than 25 miles northeast of Palm Springs. A sleeping 3year-old toddler died after being struck by a collapsing chimney during a sleepover.

Three hours later, a magnitude 6.3 quake struck about 20 miles west, just a few miles away from Big Bear.

“We always worry when seismicity picks up very close to a major fault or if it’s at the end of a major fault — whether it’ll push it enough to start a major rupture,” California Institute of Technology seismologist Egill Hauksson said.

Sometimes fears of seismic triggering don’t materialize.

The Easter Sunday magnitude 7.2 quake of 2010 directed tectonic stress toward Southern California from Mexico.