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Officials monitoring SC’s seismic activity after three earthquakes Monday

Published: Oct. 1, 2021 at 2:06 PM EDT|Updated: Oct. 1, 2021 at 8:15 PM EDT
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CHARLESTON, S.C. (WCSC) - Officials at the South Carolina Emergency Management Division are closely monitoring our state’s seismic activity.

Earlier this week, the Summerville and Ladson area experienced three earthquakes in a matter of hours.

Derrec Becker with the state’s Emergency Management Division says the last time we had three earthquakes in about seven hours was back in 2003. And while he says it’s a little unusual to get three in a row, it just proves how seismically active South Carolina is.

“Where these earthquakes occurred is centered sort of near where the largest earthquake ever recorded on the Eastern seaboard occurred, and that was back in August of 1886,” Becker says.

On August 31, 1886, a magnitude 7.3 earthquake hit Charleston. The initial shock lasted nearly one minute. It was felt over 2.5 million square miles from Chicago to Cuba.

“You felt a 3.2,” Becker says about the earthquake that occurred Monday night. “Imagine an earthquake that is exponentially greater than that. That’s what we experienced. That’s why we’re very cautious when we talk about earthquakes.”

SCEMD did a study and looked at what would happen if we got an earthquake of a similar magnitude of what we got in 1886. They found the following:

  • An estimated 45,000 casualties, of which approximately 9,000 (about 20 percent) would be major injuries requiring hospitalization; fatalities would number about 900. A daytime event would cause the highest number of casualties.
  • Nearly 70,000 households, or about 200,000 people, would be displaced, with an estimated 60,000 people requiring short-term shelter.
  • Total economic losses from damage to buildings, direct business interruption losses, and damage to transportation and utility systems would exceed $20 billion. Direct economic losses due to building damages (without the business interruption losses) are estimated to exceed $14 billion. Transportation and utility systems’ direct economic losses would exceed $1 billion.
  • About $10.9 billion in economic losses would occur in the tri-county area of Charleston, Berkeley, and Dorchester. The building damages alone would cause more than $4.2 billion in losses due to direct business interruption in the state. Loss estimates include rental income, business income, wages, and relocation expenses.
  • More than 250 fires would burn, primarily in the tri-county area. The lack of operational firefighting equipment and water due to the earthquake would be a major concern.
  • About 80 percent of urban households in the tri-county area would be deprived of water. It would take weeks, if not months, to restore the water systems to normal operation.
  • Hospitals would likely suffer significant building damage that could result in up to 30 hospitals out of the 108 (about 30 percent) being nonfunctional. • More than 220 schools and more than 160 ­re stations would have significant damage. In addition, extensive damage is expected to the large inventory of relocatable school buildings.
  • Close to 800 bridges would be damaged beyond use, thus hampering recovery efforts.
  • About 63 electric power facilities (51 substations out of 380, and 12 power plants out of 53) would suffer at least moderate damage; about 300,000 households would be without power.
  • More than 36 million tons of debris would be generated.

South Carolina normally experience 10-20 earthquakes a year, about two or three of which we can actually feel.

“We know that some people might be concerned seeing three right in a row is the building up to something major,” Becker says. “Unfortunately, we won’t know until we get a major earthquake and then we can say definitively ‘yes those were building up to this and those were foreshocks.’ If we don’t experience a major earthquake after this, or in the near future, it’s just normal background seismicity.”

Officials say they are about 50/50 the three earthquakes we experienced were just the Earth releasing pressure. We won’t know if it was building toward something greater for another six months to a year or even longer.

Click here to look through SCEMD’s Earthquake Guide which lists how to take cover and how to prepare for an earthquake.

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