Alarms aren't going off in South Carolina after the U.S. Geological Survey updated its earthquake hazard maps for the first time since 2008, but the Charleston area is considered a high risk spot for future temblors.
"It looks fairly familiar," said Steve Jaume, seismologist at the College of Charleston. "We are the bull's-eye on the East Coast, and we were on the last one too."
The maps show the most current understanding of where earthquakes will occur, how often they will occur, and how hard the ground will likely shake. They increase the risk in about half of the United States.
The report does not take into consideration seismic activity associated with human activities such as fracking because injection-induced earthquakes may not behave like natural earthquakes. Scientists plan to focus on them in the future, according to the report.
The report "is vital because you can't plan for earthquakes if you don't know what you are planning for," said Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project. "Our nation's population and exposure to large earthquakes has grown tremendously in recent years. The cost of inaction in planning for future earthquakes and other natural disasters can be very high."
In the latest maps, the Charleston area is at high risk for a damaging earthquake within 50 years. While all states have some potential for earthquakes, 42 have a reasonable chance of one, and South Carolina, as one of 16 states that have had a magnitude 6 or greater quake, is at a "relatively high likelihood."
"They have slightly increased the estimates of earthquake hazards near us," said Erin Beutel, earthquake expert at the College of Charleston and director of the state Earthquake Education and Preparedness Program. The map also shifts the risk a tad south toward Savannah, Ga., lowering the risk in the Myrtle Beach area.
The increased risk comes from more and updated information available to those who make the maps.
"We are just getting a better definition of the risk," Jaume said. "It's always been there, we just didn't always know about it."
In general, the East has the potential for larger and more damaging earthquakes than previous maps indicated. Scientists learned a lot following the magnitude 5.8 earthquake that struck Virginia in 2011, which was among the largest earthquakes on the East Coast in the last century.
"One of the things that makes Charleston stand out on a map like this is not just the 1886 earthquake, which was a good bit bigger than the one in Virginia in 2011, but we also have geological evidence of repeated earthquakes every few hundred years," Jaume said.
Seismographs didn't exist when Charleston was hit by the 1886 earthquake, which was estimated to be more than a magnitude 7.
"It didn't leave a big scar on the ground, so by necessity we have to be a little more uncertain," Jaume said.
Local faults - known as the Middleton Place-Summerville Seismic Zone - are covered with a kilometers-thick layer of sand and sentiment, stopping quakes from reaching the earth's surface, unlike the San Andreas fault, which is so close to the surface it can been seen in aerial photos.
"We know they are down there, but exactly which ones are moving at what rate is kind of diffused by all the gunk," Beutel said.
While the new information should not make anyone go running from the area, it will be used to determine insurance rates, and improve emergency preparedness plans and building codes, officials said.
"The report doesn't really change anything about how we should deal with earthquakes," Beutel said. "It's good because it will help reinforce what people are already doing. Basically, people should keep their hurricane kit ready all year round."
If a strong earthquake hits, one thing to remember is to fight the instinct to get outside.
"In a First World country, we are not as worried about the buildings collapsing," Beutel said. "Most people are killed by falling stuff, so you just want to be under something to protect the head and body. You are more likely to be injured if you move more than 10 feet from your original position."
Charleston County Emergency Preparedness Director Cathy Holmes said the area is "as ready as we can ever be. It's kind of like, when they predict the number of hurricanes, we don't focus on how many we might have, we just focus on the fact that we could have one and we get as prepared as we can. Same with an earthquake."
The information could affect insurance rates. Most companies offer earthquake coverage as an optional separate rider on policies.
"Updated maps are always helpful to insurers when studying rates," said Chris Hackett of the Property Casualty Insurers Association of America. "It's important for homeowners to consider the risk, and there is certainly a risk in the Charleston area. It's worth it for your own peace of mind and to protect what probably is your most valuable asset, your home."
While insurers don't see any dramatic rate increases from the new map, one immediate effect could be changes in building codes to address the risk.
Charleston showed it is proactive after the last report was released. In 2010 the Charleston County School District shuttered and rebuilt four buildings on the peninsula it deemed unsafe for children in the event of a magnitude 5.0 quake.
"We will have new buildings better able to handle earthquakes, so when we have the next one, the level of damage will go down a lot," Jaume said. "We can't stop them from occurring, but we can make them less dangerous."
To view the full report, visit usgs.gov.
Reach Brenda Rindge at 937-5713 or @brindge on Twitter.
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