Expert: L.A.'s quake a 'small sample' of one to come

Expert: L.A.'s quake a 'small sample' of one to come

LOS ANGELES, California (CNN) -- The magnitude 5.4 earthquake in Southern California on Tuesday caused no serious damage or injuries, but experts say it's a reminder that the "Big One" could happen at any time.

"This earthquake reminds us to be prepared," California Gov. Arnold Schwarzenegger said. "We were very fortunate that there were no serious injuries or property damage."

California has a 99 percent chance of experiencing a major earthquake within the next 30 years, according to a report by state and federal agencies.

Tuesday's quake in the Los Angeles metropolitan area "is a sample, a small sample," said Kate Hutton, a seismologist at the California Institute of Technology.

"This is somewhere between small and moderate." She said there is a 5 percent chance the quake could be a precursor to a larger earthquake. After 24 hours, she said, that chance will drop to 1 percent.

"Every earthquake relieves some stress," Hutton said. "It's usually only a drop in the ocean. In other words, the amount of stress released by this earthquake is minuscule compared to the amount that's built up and is building up for the Big One when it happens some day in the future." Watch Hutton say Tuesday's quake was a sign of bigger ones to come »

And when will that be?

"From a geologist's point of view, the answer has to be soon," she said. "But geologists are used to thinking on millions of years and thousands of years time scale, so I don't think that gives any useful information for people, except be prepared at any time because it could happen at any time."

A magnitude 5.4 quake is considered by the U.S. Geological Survey to be moderate, which can cause slight damage to buildings and other structures. So far this year, the United States has had 39 moderate earthquakes between magnitude 5.0 and 5.9. Globally, that number is 790.

The last moderate quake to strike California was a magnitude 5.4 in April in the northern part of the state. A magnitude 4.4 struck the greater Los Angeles area in August 2007.

There is a 99 percent chance of California experiencing a quake of magnitude 6.7 or larger within the next 30 years, according to the Uniform California Earthquake Rupture Forecast, sponsored by the U.S. Geological Survey, the California Geological Survey and the Southern California Earthquake Center in a report published in Science Daily in April.

Schwarzenegger said he believes the state is "as prepared as anyone can be. We have continuous discussions about that. We are fanatics about emergencies and to be ready."

The largest earthquake in recent years in California was a magnitude 7.1 in 1999, Hutton said. But it was centered in the desert, near Twentynine Palms, in a sparsely populated area.

Tuesday's quake struck about 11:42 a.m., according to the USGS. Its epicenter was about 2 miles southwest of Chino Hills and about 5 miles southeast of Diamond Bar.

More than 30 aftershocks were recorded. Hutton said the largest was a magnitude 3.6.

Los Angeles police said a downtown hotel sustained some structural damage, but no one was injured and the building was not evacuated. There were some unconfirmed reports of minor injuries.

Despite the absence of serious damage or injuries, some Los Angeles-area residents were left rattled. The quake was felt as far south as San Diego, and the USGS said it received reports of light shaking as far north as Rosamond, California, about 55 miles north-northeast of Los Angeles.

Reports from those who felt the quake poured into CNN.

"My house was like a fun house. Everything was moving," said Danny Casler, 28, of Huntington Beach. He said he was sleeping when his house began shaking, and some things fell in the living room. He ran out of the house in his boxer shorts.

Lawyer Kevin Crisp said he was on the phone with his partner, who burst out, "Big quake!" Crisp said he felt it about five seconds later. "This was very impressive. Long and very uniform. Really had the building going." He said doors were swinging on the hinges and bottles of wine were rolling back and forth on his shelf.

"It just started with a really strong jolt," Wendy Criner said. "I ran and got my daughters from different rooms, and we squatted in the living room. I did have stuff fall off the shelf, some books in my daughters' room and some things in the kitchen."

The quake knocked out a ground radar system at Los Angeles International Airport, but that did not interfere with operations, according to the Federal Aviation Administration. Tiles fell from the ceiling in one terminal as water flowed from a burst pipe.

The calculation of the quake's magnitude fluctuated as seismologists reviewed the data. Initially classified as a magnitude 5.8, the quake's intensity was reduced to a 5.6 and then to a 5.4. Because the earthquake magnitude scale is exponential, a 5.8 magnitude quake is four to five times more intense than a 5.4.

Two nuclear plants are in the vicinity of the quake's epicenter near Chino Hills, according to the Nuclear Regulatory Commission. The closest to the epicenter is in San Onofre, 50 miles south, but an NRC spokesman said, "this is well below the threshold for any conceivable damage to the plants."

Still, the quake jolted the nerves of many Californians.

"I've lived in California, I've lived through several of them," Margot Wagner of Santa Barbara told CNN. "It's always a little unnerving."

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