Some windows rattled and the ground shook a bit, but there was no damage reported when a small earthquake rumbled near Summerville on Thursday afternoon.
The National Earthquake Information Center confirmed the area felt a magnitude 2.5 quake. That’s the smallest magnitude that can generally be felt by humans. The next morning, the U.S. Geological Survey reported a second small quake near Ladson. It was the fifth reported quake in the Summerville area in less than a month
College of Charleston Geology professor Dr. Steven Jaume says residents should not be alarmed. “Earthquakes tend to occur fairly randomly, so you have times when they occur more frequently like now. We also found times back in 1998 when there were like seven earthquakes in a month. So we get these little bursts but then it will go quiet for several months.”
Jaume says the small earthquakes are useful because as they are tracked over time, they reveal where the faults are in a particular area.
“We produce simulations of larger earthquakes based on those faults are and its helps emergency management folks. we can predict what sort of ground motions in different parts of the Lowcountry we can expect for the earthquakes on the different faults and look at what those potential impacts are. Emergency management planning folks use that information to make their preparations.”
Insurance companies also use such data, along with other information, to calculate earthquake insurance rates.
Jaume says frequent small earthquakes does not mean that a major quake will soon follow. Charleston’s last major earthquake was an estimated 7.3 magnitude quake in 1886. Jaume says researchers have studied “liquefaction pools”… or craters of saturated sand… that form during major earthquakes. He said they indicate that these strong quakes do not occur in the Lowcountry very often.
“By finding organic material that fell into these craters following the earthquakes we can roughly date when those occurred; and It looks like it tends to be from 300 to 800 years apart are the approximate times of how often these bigger earthquakes that cause all the liquefaction occur.”