Don’t be rattled — get ready

Rubble litters Cumberland and East Bay streets on Sept. 1, 1886, after a devastating quake struck Charleston. A fault line runs through Summerville, and seismologists say the Charleston area is at high risk for a damaging temblor within the next half-century.

Every couple of months, Lowcountry residents are reminded that the underground rock layer that supports everything is not all that stable.

Houses shake. Some people report hearing a boom.

The fault line that causes these minor tremors runs through Summerville, but the entire Lowcountry is equally at risk.

It’s the same fault line that caused the massive earthquake that devastated the whole Charleston area on Sept. 1, 1886. The earthquake was centered near Summerville across the Ashley River from Middleton Place, according to the U.S. Geological Survey. But it shook the entire East Coast.

Students are reminded of the possibility that another temblor could happen at any time each year during a drill in which they drop to the floor, crawl under desks or tables and hold on for several minutes.

It’s called The Great Southeast Shake Out, and it’s set this year for 10:15 a.m. Oct. 15. The idea is for people to remember to “Drop, Cover, Hold” when they feel an earthquake. Experts say getting under a desk or table is safer than running around risking a fall or getting hit by something.

Students at Harbor View Elementary School on James Island go through the drill with earthquake sound effects rumbling over the public-address system, said Principal Laura Latto, who will be participating for the third year.

“Students get excited knowing they’re part of something everybody else is doing,” she said.

Jane Edwards Elementary School on Edisto Island is also participating for the third year. Principal Susan Miles said she sees no problems with students getting out of control because they’re already used to drills for hurricanes, tornadoes and fires.

“We tell them it’s important for them to be Level 1 (no talking) in case one of the adults needs to give them information to be safe,” she said.

The Charleston County School District sent out tweets earlier this week encouraging more schools to sign up and will start a major push Friday. More information is at shakeout.org/southeast.

Seismologists say Charleston is at high risk for a damaging earthquake within the next 50 years. As a result, the school district in the past few years has rebuilt several schools that might have put students at risk during a magnitude-5 quake.

But nobody can say when that might happen.

“Unfortunately, there is no known reliable way of predicting when a large earthquake will occur,” said Steven Jaumé, an associate professor of geology at the College of Charleston who is with the college’s S.C. Earthquake Education and Preparedness program. “Many methods have been tried and all have fallen short.”

Other scientists agree.

“Neither the USGS nor any other scientists have ever predicted a major earthquake,” the Geological Survey says on its website. “They do not know how, and they do not expect to know how any time in the foreseeable future.”

The most recent tremor near Charleston was recorded at 11:24 p.m. Aug. 23. The small quake registered at magnitude 2.1, which was strong enough that several Summerville residents said they could feel the house shake.

The Geological Survey has a map that shows the epicenter of tremors down to the street level. The center of the last quake was on Lark Street, which is south of East 3rd North Street and east of the Berlin G. Myers Parkway.

People generally don’t feel tremors below 2.0. People are much more likely to notice a tremor while they’re sitting down eating supper than in the middle of the work day, Jaumé said,

People who report a boom during a tremor are likely hearing it from the house moving rather than the ground itself, he said.

An increase in small tremors is no indication that a bigger quake is imminent, but a shaking house is a good reminder of the possibility.

The strongest quake near Charleston recently was a magnitude 3.6. It was reported at 8:42 a.m. Dec. 16, 2008. Its center was near Interstate 26 just south of Jedburg Road.

“That one got a lot of people’s attention,” Jaumé said. “We got a lot of phone calls on it.”

In the past two years, 17 tremors have been recorded in the Charleston area, including eight that were strong enough to feel, according to the U.S. Geological Survey.

Reach Dave Munday at 937-5553.