Originally created 02/04/05

Seismic devices record tremors



In the back yard of an Evans neighborhood, a gray device resembling an ice chest was attached by a wire to a one-foot-diameter cylinder resembling a large orange Thermos.

The cylinder was wedged into the ground to decipher ground vibrations, and the equipment was juiced up with two car batteries.

Those devices, which might have seemed like a nifty science project, have now been recovered from their test site and results show that all those reporting shakes in Columbia County recently were right.

Officials say there was at least one aftershock Jan. 25 after three minor earthquakes hit the county Jan. 18.

The aftershock didn't register on the Richter scale, but Pam Tucker, the county's emergency services director, said the Savannah River Site seismic device showed an aftershock did occur for at least seven seconds.

"It's been very educational, I think, for the citizens," she said about the findings.

The most recent report of activity in the area of eastern Columbia County near the Savannah River occurred at about 1 p.m. Monday. Mrs. Tucker said some residents in the area reported hearing yet another rumble. The device placed in the county was unable to pick up that shake, Mrs. Tucker said, because recent colder temperatures caused the monitoring device's batteries to lose power earlier than anticipated.

The three confirmed earthquakes in the county were registered on Jan. 18 at 2.5, 2.3 and 2.0 on the Richter scale. The next Saturday and Sunday, more rumblings were felt, causing officials to wonder whether aftershocks were occurring and to have the equipment placed out in the area.

Since the three earthquakes occurred, Don Stevenson, a seismologist at SRS, said on Tuesday that nothing major had been recorded by the closest monitoring station, which is about 50 miles away from the Columbia County site in question.

Mr. Stevenson said he finds it somewhat surprising that people are still feeling vibrations, but he said small aftershocks were possible.

"People are feeling something," he said.

And even though at least one aftershock has occurred, Mr. Stevenson said that doesn't signal a buildup to another earthquake.

"The general rule is that it's not building up but just readjusting," he said. "The little pops that follow are just things readjusting from the bigger one."

Reach Preston Sparks at 868-1222, ext. 115, or preston.sparks@augustachronicle.com.