Quake damage is slight, but fear is real

Geography helped temper temblor’s effect

By Scott LaFee, UNION-TRIBUNE STAFF WRITER

Originally published April 6, 2010 at 12:03 a.m., updated April 6, 2010 at 12:16 a.m.

Peggy Peattie / Union-Tribune

Brenda Mendez, store employee at the 99 Cent Store in Calexico, restocks items Monday morning. The damage done in Calexico from Sunday's earthquake was mainly along Second Street in the downtown area, where big glass windows were shattered.

Photo by Peggy Peattie - San Diego Union-Tribune

Huge cracks appeared in the streets of Ejido Cucapah Indigena, and water rushed from them, causing flooding. The whole residential area was abandonded.

Sunday’s quakes in Baja California produced seemingly contradictory effects.

They generated some of the most powerful shaking in nearly 20 years in a region with a long history of seismic activity, and the biggest temblor — registering a magnitude of 7.2 — was twice as powerful as the January earthquake in Haiti.

Yet all that geologic disturbance caused relatively little damage, particularly north of the border.

The explanation is a matter of fortunate geography and soil conditions, factors that are likely to significantly determine which areas of San Diego County fare better or worse in future quakes.

The epicenter of the 7.2 temblor was in a rural and sparsely inhabited area surrounding the village of Guadalupe Victoria. The closest major city — Mexicali, with a greater metropolitan population of nearly 1 million — is 38 miles to the north, far away enough that much of the quake’s energy dissipated before reaching there.

“We were lucky the epicenter was in an agricultural region,” said Morgan Page, a geophysicist with the United States Geological Survey. “The quake was strong and shallow, about six miles below the surface. If it had hit closer to a city, it would have been pretty bad.”

AFTER SHOCK REPORTS:

(AP) – May 9th, 2010

SAN DIEGO — A pair of moderate earthquakes and several smaller ones rattled Southern California's San Diego and Imperial counties Sunday as a stream of seismic activity continues a month after a major Easter earthquake ravaged the region. There were no reports of new damage or injuries.

A magnitude-5.0 quake struck at 11:33 a.m. Saturday in the U.S.-Mexico border area about 16 miles southwest of El Centro, near the small farm town of Seeley, according to a report from the U.S. Geological Survey.

A magnitude-4.7 quake hit about 15 minutes later in the same area, and many more followed throughout the day, the largest a magnitude-4.1 at 8:33 p.m.

San Diego County sheriff's Lt. Hank Turner said shaking was felt in downtown San Diego, and the USGS received reports of people far to the north in Riverside County feeling the temblor.

"I sure did feel it," said Lt. Fritz Reber with the police department in Chula Vista, south of San Diego. "I was in the building, sitting in front of the computer, and it shook a little bit. I could hear the ceiling tiles jiggle."

Sheriff's and fire department dispatchers in San Diego and Imperial counties said they received no reports of damage.

Saturday's quakes were among the biggest aftershocks yet following the magnitude-7.2 quake that struck southeast of Mexicali, Mexico, on April 4, killing two people.