The U.S. Geological Survey said there was an earthquake in southwest Illinois on Thursday night.
At 6:55 p.m., the earthquake was felt in Clinton County, which is about a mile from Germantown. According to the USGS, it was a 2.8 on the Richter Scale.
This is the second quake of this kind to be felt in southern Illinois in the past month. Two-and-a-half magnitude quakes hit parts of Perry County near Pinckneyville on March 5. In the same area, an earthquake with a magnitude of 3.1 was felt in Washington County, which is about 12 miles southwest of Mount Vernon, on December 16.
Every year, about 1 million earthquakes of the same size happen around the world. Most of the time, people close to the site feel the shaking, but the earthquakes don’t do any damage. The USGS says that the affected area is in the Illinois Basin-Ozark dome region, which is next to the New Madrid earthquake zone.
Parts of Indiana, Kentucky, Illinois, Missouri, and Arkansas are in the Illinois Basin-Ozark dome area, which goes from Indianapolis and St. Louis to Memphis.
The Illinois Emergency Management Agency says that the New Madrid Seismic Zone has about 200 “events” a year, most of which are not noticed. Every year there are tremors of magnitude 2.5 to 3.0, and every 18 months or so there is one of magnitude 4.0 or higher. Every 10 years, there is one of magnitude 5.0 or higher.
The largest earthquakes in U.S. history happened along the New Madrid Fault. In February 1811, there were 8.2- and 7.4-magnitude earthquakes in a row, and in the winter of 1812, there was a run of quakes with magnitudes ranging from 7.0 to 8.6.
Earthquakes are ranked by the U.S. Geological Survey based on how much harm they can do:
2.5 or less: You often can’t feel it.
2.5–5.4: Can be felt a lot, but doesn’t do much damage. Every year, there are about 500,000 around the world.
5.5 to 6.0: Buildings and other structures may get some minor harm. Still, only about 350 of them happen each year, making them more rare.
6.1.6–6.9: The 100 that happen every year may do a lot of damage in places with a lot of people and buildings.
