Monday, Nov. 02, 2009

Even medium S.C. quake would be costly

CHARLESTON -- People talk about "the big one," but recent studies show smaller earthquakes along the coast could cause billions of dollars in damage.

That's the conclusion of recent computer model studies at the College of Charleston. One of the studies looked at the damage from a moderate earthquake near Summerville, where the 1886 quake struck.

"It might be worse than what you would expect," said Norm Levine, College of Charleston associate geology professor who works with the college's S.C. Earthquake Education and Preparedness Program, and led the studies with students. "Something normally considered moderate could do damage. We really do have an issue here. Let's see what we can do to protect against it."

The 7.3 magnitude earthquake in 1886 killed 100 people and destroyed or damaged most of the buildings in Charleston and Summerville. But moderate quakes occur here, and not so rarely.

Two 3.6 temblors and one 3.2 temblor have rattled Summerville since December 2008. As recently as 2002, a 4.4 magnitude quake erupted in the ocean off Kiawah Island. Summerville had two 4.1 quakes in the 1990s. They didn't do much more than shake nerves. But a 5 magnitude quake would be 10 times stronger, and some 800 of them occur across the globe every year.

Moderate quakes are a great concern to emergency managers, said Cathy Haynes, Charleston County Emergency Preparedness director. "The biggest thing in my mind would be the uncertainty. With the big one, we're going to know the building is falling down. In a moderate quake we may not know. The damage might not be visible to the naked eye -- buildings, bridges, any infrastructure."

One study looked at the impact of a 5.3 quake in the same spot as the 1886 quake, under the Ashley River near Middleton Place. The other study looked at the impact of a 5.5 magnitude quake in the same spot 17 miles offshore as the 4.4 quake in 2002.

The 5.3 magnitude quake could cause nearly $9 billion in damage and economic losses in Charleston County alone, the models estimated.

Most of the damage from the offshore quake would be confined to areas east of or near U.S. 17. But with either quake "there would be a few casualties, but nothing major in terms of fatalities," Levine said.