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6.23.2005

Experts' Heads Shake After Quakes



Seismologists agree on one thing regarding last week's cluster of tremors: Nobody knows for sure what it portends, if anything.

By Hector Becerra, Times Staff Writer
Were last week's quakes in California connected? Maybe.

Did they relieve pressure on major fault lines? Perhaps, but not much.

Did they make a bigger quake more likely? Possibly.

These are not exactly the answers quake-rattled Californians are looking for.

But the recent temblors involve some of the issues that seismologists most often debate. And the more research they do, the more they sometimes disagree. Even husband and wife seismologists don't see eye to eye.

The quakes — including two felt across Southern California and a 7.2 temblor June 14 off the coast of Eureka that prompted a tsunami warning along the entire West Coast, followed by a 6.7 two days later — didn't cause much damage or injury.

They captured much attention because they came so close together and hit after a period of less-than-normal seismic activity.

One of the first questions Californians had after the series of temblors was whether there was some connection among the quakes.

Lucy Jones, a seismologist with the U.S. Geological Survey, believes that the 5.2 Anza quake June 12 probably triggered the 4.9 Yucaipa quake four days later.

She noted that both quakes were within about 25 miles of each other and occurred on secondary faults — the Anza quake near the San Jacinto fault and the Yucaipa around the San Andreas.

Data have shown that even a modest earthquake can trigger another quake — even at that distance, she said.

One of her colleagues, Jones added, believes that the Yucaipa event might have been an aftershock of the Anza quake.

But Jones' husband, Caltech seismologist Egill Hauksson, is skeptical, arguing that the temblors were too small and too far apart to have been connected

"But as you can see, some people disagree with me," he said with a laugh.

Fellow Caltech seismologist Thomas Heaton also believes that the two quakes may well have been just a coincidence.

There is general agreement that the Southern California quakes were not connected to the ones in Northern California, mainly because of the distance between them.

Another question arising from the quake cluster is whether these temblors make a massive quake more likely.

It has long been held that earthquakes relieve pressure on fault lines, potentially decreasing the threat of a massive quake.

But experts said it was not that simple.

Heaton believes that the quakes last week were too small to significantly reduce stress on major faults.

Comment: One scientist says it's a coincidence(hardly) while others say there could be a connection. These are EXPERTS, apparently, that are disagreeing with each other. The one thing that the scientists agree on is that the risk of a much larger and dangerous quake has not been lessened by the smaller quakes of late.