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by Weatherboy Team Meteorologist - July 1, 2022
South Carolina officials have announced they are working on scheduling a special earthquake meeting as quakes continue to shake the state, rattling nerves across the region. Officials within the town of Elgin announced they are coordinating an event with Kershaw County and state officials to put together a town hall meeting for residents and business owners to discuss the recent earthquake swarm.
Geologists studying the ongoing swarm of earthquakes in Kershaw County believe this may be the longest period of successive earthquake activity in the state’s recorded history. This swarm began December 27, 2021, with a magnitude 3.3 earthquake centered near Elgin, South Carolina. Since then, more than 47 low-magnitude earthquakes have occurred in the Elgin-Lugoff area, with the strongest being a magnitude 3.6 on June 29.
According to USGS, a swarm is a sequence of mostly small earthquakes with no identifiable mainshock. “Swarms are usually short-lived, but they can continue for days, weeks, or sometimes even months,” USGS adds. However, the South Carolina event doesn’t fit the typical definition of a swarm since the first event was substantially larger than the rest.
According to USGS, “aftershocks” are a sequence of earthquakes that happen after a larger mainshock on a fault. “Aftershocks occur near the fault zone where the mainshock rupture occurred and are part of the ‘readjustment process’ after the main slip on the fault,” says USGS. However, aftershocks of a 3.3 magnitude earthquake would only last a few days, not the week plus they have.
According to the South Carolina Emergency Management Division (SCEMD), there are approximately 10-15 earthquakes every year in South Carolina, with most not felt by residents; on average, only 3-5 are felt each year. Most of South Carolina’s earthquakes are located in the Middleton Place-Summerville Seismic Zone. The two most significant historical earthquakes to occur in South Carolina were the 1886 Charleston-Summerville earthquake and the 1913 Union County earthquake. The 1886 earthquake in Charleston was the most damaging earthquake to ever occur in the eastern United States; it was also the most destructive earthquake in the U.S. during the 19th century. South Carolina has experienced thousands of earthquakes like these throughout the state’s history, according to State Geologist Scott Howard. What makes these unique is the length of time over which they are occurring. “These earthquakes are now the longest running series of earthquakes in recent history,” Howard said. “Unlike earthquake swarms occurring elsewhere in the country, these have been low in magnitude and haven’t posed a hazard to people, fortunately.”
“The Piedmont Fault System is made up of several smaller fault lines that stretch across the middle of South Carolina.” explained Dr. Steven C. Jaume’ with the College of Charleston’s Department of Geology and Environmental Geosciences Department, “The first earthquake on December 27 appears to be the one that started this swarm in Kershaw County. When an earthquake occurs in a region where there hasn’t been much activity over a long period of time, we can expect similar earthquakes to occur in that general area for the foreseeable future.”
According to SCEMD, both Juame’ and Howard have confirmed there isn’t a man-made cause behind these quakes. There are no mining or fracking operations around that would trigger all of the shaking experienced in South Carolina.
While USGS doesn’t think a larger earthquake is imminent, state officials are urging caution to residents, informing them of how they can be prepare for future earthquakes, including major ones. “We know our state was at the center of major earthquakes in the past. We all need to be prepared for the possibility of a large-scale earthquake, however unlikely the possibility may be,” SCEMD Director Kim Stenson said, “Check your insurance policies, conduct a home hazard hunt and practice Drop, Cover, Hold On. Those are all things you can do right now to make sure you’re prepared for earthquakes.”
Experts are concerned that a large scale earthquake will strike at some point of the future and bring about significant damage and loss of life. While more than 100 years have passed since the last large earthquake, a 2001 study titled “Comprehensive Seismic Risk and Vulnerability Study for the State of South Carolina” confirmed the state is extremely vulnerable to earthquake activity. The study, based on scientific research, provided information about the likely effects of earthquakes on the current population and on modern-day structures and systems, including roadways, bridges, homes, commercial and government buildings, schools, hospitals and water and sewer facilities.
The last major earthquake event unfolded in Charleston in 1886. That earthquake claimed 60 lives and produced more than $186 million dollars (in 2022 dollars) in damage. Both numbers are remarkable considering how small the population in the southeast was at that time. In addition to damaging more than 2,000 buildings throughout the southeast, that quake, estimated to be a magnitude 7.3 event, was strong enough to be felt as far away as Chicago, Illinois, Boston, Massachusetts, and New Orleans, Louisiana. Kershaw County is distributing a South Carolina Earthquake Guide to residents online; they share these safety tips for people throughout the state: