4.4 Quake: Little Effect, Impressive Aftershock

A magnitude 4.4 earthquake that jarred residents in Orange and San Diego counties Thursday morning was centered deep below the ocean, about seven miles southeast of San Clemente Island.

The quake caused no apparent damage or injury, but scientists said they were surprised that one of the three aftershocks was nearly as strong.

Seismologists at Caltech said the fault that produced the 11:04 a.m. quake was probably several miles beneath the ocean and similar to a magnitude 5.4 quake off Oceanside in 1986.

“It’s not unusual for the area to have these small quakes,” said Caltech seismic analyst Nick Scheckel. “We don’t know which fault it occurred on and, because the rocks are . . . miles underneath the ocean, we may never know.”

One of the aftershocks measured 4.2, which scientists said was unusual.

“Typically, the largest aftershock would be a full magnitude less than the main quake, so to have this 4.2 happen about four hours later is a bit strange,” said Doug Given, geophysicist with the U.S. Geological Survey at Caltech.

Those who felt one or more of the tremors came away unfazed.

Barbara Brown, an assistant to Orange County Supervisor Chuck Smith on the fifth floor of the County Hall of Administration in Santa Ana, said the quake fluttered the posters and photographs hanging in her office, but little else. She said she guessed--nearly correctly--that the magnitude was 4.3.

“After sitting in this chair in this office for almost 20 years, I have become experienced at guessing magnitude,” she said.

Constance Downing, who works down the hallway for Supervisor Jim Silva, said she immediately tried phoning her husband to see if he felt it too. “But the call didn’t go through. A voice said, ‘All circuits are busy.’ ”

People on the first floor said they did not feel any rocking.

San Clemente Island, off San Diego County, is the southernmost of the eight Channel Islands and is owned by the Navy.

*

Times staff writer David Reyes contributed to this report.