LOS ANGELES (AFP) – Strong earthquakes along the San Andreas fault in southern California are more frequent than previously thought, so the dreaded “Big One” could be just around the corner, US researchers said Friday in a study.

University of California at Irvine and Arizona State University scientists examined the geological record stretching back 700 years along the fault line 160 kilometers (100 miles) northwest of Los Angeles.

They found that strong earthquakes — between 6.5 and 7.9 magnitude — shook the area every 45-144 years, instead of the previously established 250-400 years.

Since the last big 7.9 magnitude earthquake struck southern California in 1857, or 153 years ago, scientists believe the next “Big One” could happen at any time.

The scientists on Friday provided an abstract of their study, which will be published in full in the September 1 issue of the magazine Geology.

“What we know is for the last 700 years, earthquakes on the southern San Andreas fault have been much more frequent than everyone thought,” said the study’s lead author Sinan Akciz.

“Data presented here contradict previously published reports,” he added.

With 37 million people living in southern California, chiefly in the cities of Los Angeles, San Diego and Anaheim, a major earthquake could kill between 2,000 and 50,000 people and cause billions of dollars in damage, scientists said.

UCI seismologist Lisa Grant Ludwig, the study’s chief investigator, said people in the area should already be taking precautions.

“There are storm clouds gathered on the horizon. Does that mean it’s definitely going to rain? No, but when you have that many clouds, you think, ?I’m going to take my umbrella with me today.? That’s what this research does: It gives us a chance to prepare,” she said.

For individuals, that means having ample water and other supplies on hand, safeguarding possessions in advance, and establishing family emergency plans.

For regulators, Ludwig advocates new policies requiring earthquake risk signs on unsafe buildings and forcing inspectors in home-sale transactions to disclose degrees of risk.

Some things, she added however, remain unpredictable, especially Los Angeles’ troublesome highway grid, which in the best of times gets hopelessly choked in traffic.

Ludwig said the new data “puts the exclamation point” on the need for state residents and policymakers to be prepared.

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Location 32.128°N, 115.303°W
Depth 10 km (6.2 miles) (poorly constrained)
Region BAJA CALIFORNIA, MEXICO
Distances 26 km (16 miles) SW (225°) from Guadalupe Victoria, Baja California, Mexico
60 km (38 miles) SSE (165°) from Mexicali, Baja California, Mexico
62 km (38 miles) SW (233°) from San Luis Río Colorado, Sonora, Mexico
167 km (104 miles) ESE (105°) from Tijuana, Baja California, Mexico

Location Uncertainty horizontal +/- 2.4 km (1.5 miles); depth +/- 31.6 km (19.6 miles)
Parameters Nph= 13, Dmin=70 km, Rmss=0.28 sec, Gp=259°,
M-type=regional moment magnitude (Mw), Version=2
Source California Integrated Seismic Net:
USGS Caltech CGS UCB UCSD UNR

Event ID ci14607652

Magnitude-7.2 quake strikes Baja California

LOS ANGELES (AP) – Damage reports from the U.S.-Mexico border region are growing after a magnitude-7.2 earthquake in Baja California that was felt from Tijuana and Los Angeles to Las Vegas and Phoenix.

The quake struck south of Mexicali, Mexico, at 3:40 p.m. Sunday, but damage also was being reported north of the border.

Calexico Fire Chief Peter Mercado tells KABC-TV in Los Angeles that there is substantial damage in the older section of the southeastern California city. Mercado says there is structural damage and broken windows, leaking gas lines and damage to the water system. But he says no injuries have been reported.

Across the border, a parking structure at the Mexicali city hall has collapsed. Mexicali is a bustling commerce center where trucks carrying goods cross into California.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP’s earlier story is below.

LOS ANGELES (AP) — A powerful earthquake in Baja California rocked the U.S.-Mexico border region Sunday, collapsing a parking structure south of the border and causing power outages in both countries as it sent out seismic waves felt from Los Angeles to Las Vegas and Arizona.

The 7.2-magnitude quake struck at 3:40 p.m. about 19 miles southeast of Mexicali, a bustling commerce center on the Mexican side of the border where trucks carrying goods cross into California. More than 900,000 people live in the greater Mexicali area.

It was the largest earthquake in the region in nearly 18 years and was followed by aftershocks or distant “triggered” earthquakes on both sides of the border, said U.S. Geological Survey seismologist Lucy Jones.

A multistory parking structure collapsed at the Mexicali city hall but no one was injured, said Baja California state Civil Protection Director Alfredo Escobedo.

Other early reports indicated only minor damage, but communication in the region more than 100 miles southeast of Los Angeles is often slow.

“I grabbed my children and said, ‘Let’s go outside, hurry, hurry!’” said Elizabeth Alvarez, 54, who said the quake hit as she was getting ready to leave her house with her children in an eastern Tijuana neighborhood, across the border from San Diego.

Hundreds of people fled Tijuana’s beach fearing a tsunami, said Capt. Juan Manuel Hernandez, chief of aquatic rescue at the Tijuana fire department. Tsunami experts quickly reported that no tsunami was expected along the West Coast, and Hernandez said the beach filled back up with people within an hour.

Tijuana Fire Chief Rafael Carillo said firefighters were rescuing people trapped in an elevator at the Ticuan Hotel in downtown Tijuana, but mostly were responding to reports of fallen cables and minor damage to buildings.

The Crowne Plaza hotel in Mexicali had minor damage — burst pipes and broken windows — but no on was hurt, said receptionist Juan Carlos Fernandez.

“There was a little bit of panic,” Fernandez said. “Wait, it’s trembling again.”

Guests fled their rooms at the Hotel Playa Club in San Felipe, on the Gulf of California, but there was no damage, said receptionist Araceli Marquez.

Seismologists said there have been many earthquakes in the region including many in the magnitude-3.0 range before Sunday’s big shock.

“The last time we had an earthquake this large in either Baja or California was in 1992 with the Landers Earthquake, which was 7.3,” Jones said.

The USGS reported three strong aftershocks within the hour, including a magnitude-5.1 jolt in the Imperial County desert east of San Diego. Magnitude-4.5 and magnitude-4.3 aftershocks were also reported. Another occurred off Malibu.

The 7.2-magnitude quake was felt as far north as Santa Barbara, USGS seismologist Susan Potter said. It was one of the strongest to hit California in recent history. Only one has been stronger — a 7.3 quake that hit Landers, Calif., and left three dead in 1992 — and there were at least two other 7.2-magnitude quakes in the last 20 years.

Seismologists also said a number of small quakes were triggered in a geothermal area in Northern California.

More than 5,000 Southern California Edison customers were affected, mostly with about 30 seconds of flickering lights. Several hundred had longer outages.

In Arizona, 3,369 customers in the Yuma area had a “relatively momentary outage” from the quake, Arizona Public Service Company spokesman Don Wool said.

Only about 70 people were still without service in the rural Gadsden and Summerton areas. But Wool said he expected electricity to be restored there in about two hours.

Clint Norred, a spokesman for the Yuma, Ariz., Police Department, said the quake was very strong there but he’d heard no reports of injuries or major damage.

In the Phoenix area, Jacqueline Land said her king-sized bed in her second-floor apartment felt like a boat gently swaying on the ocean.

“I thought to myself, ‘That can’t be an earthquake. I’m in Arizona,’” the Northern California native said.

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See earthquakes pound San Francisco and pulverize Taiwan.