Odd 3.6 magnitude earthquake shakes north-central Illinois

STANDARD, Ill. — A 3.6-magnitude earthquake shook north-central Illinois early Wednesday morning. The quake, which the USGS recorded at 4:41 a.m., was at a depth of 2.8 miles just south of the Illinois River.

The USGS lists that area as a stable continental region, and earthquakes are unusual here. It may have been the result of faulting bedrock.

The earthquake was fairly large, at 3.6 on the Richter scale. Because of its location, it would have been felt for around 60 miles from the epicenter.

There have been other earthquakes in this region, as well as larger ones in Illinois. There was an earthquake near the same location in 1972 that measured between four and five on the Richter scale, according to the New York Times. A 5.0 quake shook southeastern Illinois in 1987, causing minor damage.

The largest Illinois earthquake happened on November 9, 1968 and measured 5.4 on the Richter scale. And caused significant damage, toppling chimneys hundreds of miles away in Chicago. It happened far away from today’s quake in Hamilton County, along the border with Indiana. A 2.7-magnitude earthquake happened near there around two months ago. A 2.6 earthquake struck between St. Louis and Hamilton County just two weeks ago.

The Illinois Department of Natural Resources says that serious damage from earthquakes happens every 70 to 90 years. Devastating earthquakes are rare in the Midwest, happening every 700 to 1200 years.

One of the most active seismic zones in the US is located in southern Missouri’s boot heel along the borders of Arkansas, Illinois, and Tennessee. It is called the New Madrid Seismic Zone and small earthquakes radiate from there on a near-daily basis. Some of the largest earthquakes ever recorded in the US happened there between 1811 and 1812 and could be felt as far away as New York City. The largest one of them was magnitude 8.8 and had the Mississippi River running backwards, cracks opening up in the ground, smog, and sand boils.

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