Asia-Pacific

Big earthquake inevitable in California in 30 yrs

(Xinhua)
Updated: 2011-03-18 09:52

LOS ANGELES  - A big earthquake is expected to hit California sooner or later from now till the next 30 years, but it is unlikely to trigger devastating tsunami similar to what happened in Japan, says a seismologist at California Institute of Technology (Caltech) Seismological Laboratory.

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Kate Hutton, a staff seismologist at Caltech Seismological Laboratory, told Xinhua in an interview Thursday that based on the research by seismologists, a big earthquake will happen in California in the next 30 years. But it is hard to tell when it will happen. It could happen in a year or in 30 years.

Hutton said scientists have not been able to predict earthquakes. No one has predicted the Japan earthquake, and no one can predict when and where the next big earthquake will happen.

According to Hutton, there is no way to predict the earthquake for a short time like weather forecast, but based on long years of research, scientists can make long time predictions.

A landmark study released last August said Southern California is overdue for a major earthquake along the San Andreas fault.

The study was made after several years of research on the geology of the Carrizo Plain area of the San Andreas, which is about 100 miles (160 kilometers) northwest of Los Angeles. It found that earthquakes along the San Andreas fault have occurred far more often than previously believed.

Researchers said for the last 700 years, earthquakes on the southern San Andreas fault have been much more frequent than everyone thought.

The last massive earthquake on that part of the fault occurred in 1857. But researchers found that earthquakes have occurred as often as every 45 to 144 years.

That would make the region overdue for the type of catastrophic quake often referred to as "The Big One."

According to Hutton, "The Big One" could be as strong as eight- magnitude, but she did not believe it would be as big as nine-magnitude.

The seismologist said if the San Andreas fault erupts, it is unlikely to trigger devastating tsunami.

The reason, she explained, is that devastating tsunami in Japan was triggered by a big earthquake under the sea, but "The Big One" as people were talking about in California is an inland earthquake, which is far away from the ocean and would have little chance to trigger devastating tsunami.

Although people have been talking about a big earthquake in California, the real fear came after tsunami caused a nuclear disaster in Japan when reactors at nuclear plant had meltdowns, and the focus is whether big earthquake could trigger tsunami.

"If the full San Andreas fault ruptured it would probably be over eight and maybe close to nine," said Dr. Dimitry Vergun, professor of architecture and building science at the University of Southern California.

The big difference from the situation in Japan is the way the plates will move.

Scientists said the California earthquake would not likely to get a high vertical ground acceleration and movement of the kind that lifted up the ground and the ocean in Japan.

Scientists said the likelihood of a tsunami of the magnitude of the one in Japan is much lower in the US, though one area of major concern continues to be the northern Washington coast.

Meanwhile, former US Geological Survey (USGS) Geologist Jim Berkland predicted that a major earthquake would hit California this month.

Berkland has been known to predict quakes. He predicted that a major earthquake would strike California with a window between March 19th and 26th.

The geologist said that "moon proximity" and fish deaths are signs of massive earthquakes. He has been on Fox News, KFI, and many other networks voicing this warning to everyone that is listening to it. While USGS and other seismologists state that quakes are not predictable, Berkland disagrees.

California currently has two operational nuclear plants. PG&E's Diablo Canyon Power Plant in San Luis Obispo County sits near several fault lines, including the San Andreas. It's designed to withstand a 7.5-magnitude earthquake.

The San Onofre Nuclear Generating Station in San Diego County, run by Southern California Edison, isn't as close to active faults and is designed to withstand just a 7.0-magnitude quake.

Statistics show that since 1812, the California coast has had 14 tsunamis with wave heights higher than three feet; six of these were destructive. The Channel Islands were hit by a big tsunami in the early 1800s. The worst tsunami resulted from the 1964 Alaskan earthquake and caused 12 deaths and at least 17 million dollars in damages in northern California.

The 1992 Cape Mendocino earthquake produced a one-foot tsunami that reached Humboldt Bay about 20 minutes after the shaking. Although not damaging, this tsunami demonstrated that locally generated tsunamis can reach coastline quickly.

According to California State Geologist John Parrish, California, unlike Japan, does not have a subduction zone - a fault where one plate slides under another in an earthquake - off its coast. The thrusting motion under the sea was what generated the 40-foot tsunami seen in Japan.

But Southern California could see a significant tsunami caused either by a large earthquake off Alaska or by undersea landslides spurred by smaller earthquakes off California. Northern California is at greater risk because of the Cascadia subduction zone, which runs along the Pacific Northwest coast.

Quakes off Alaska and the Pacific Northwest could create 15-foot waves in Southern California and 25-foot tsunamis in the northern part of the state, according to Parrish.