A swarm of earthquakes rattled South Carolina and appeared to be getting more powerful. About 30 quakes have hit the state this year, and geologists are stumped about what’s causing “earthquake swarms” similar to those felt in Southern California.
Two earthquakes hit Elgin, South Carolina, on Wednesday. The first was a magnitude 3.5, and the second 3.6, according to data from the United States Geological Survey. A 3.4 magnitude earthquake hit the state days before, while a stronger 3.9 rattled parts of the Georgia-South Carolina border on June 18.
Wednesday’s earthquakes were the strongest since a magnitude of 4.1 struck the state in 2014.
South Carolina’s Emergency Management Division shared a video of Wendy Bohon, an earthquake geologist at the Incorporated Research Institutions for Seismology in Washington D.C., who said about 30 quakes struck in the year’s first half. She said the swarm of quakes is different than others because “there is no mainshock, or a larger earthquake that happens first then there are lots of smaller earthquakes that happen afterward … in this case, the swam of quakes are happening a few every week without a large shock.”
The emergency agency also tweeted the state does have several fault systems and is “one of the most seismically active states on the East Coast.” However, some geologists are puzzled at why so many swarms are happening.