Earthquake Felt By Many in Weird Part of Illinois Saturday Night

Well, this was certainly a new place for an earthquake in Illinois where earthquakes don't normally happen and definitely aren't normally felt. It happened late Saturday night according to the USGS.

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I heard a few people online talking about a shaking in eastern Illinois, so I decided to investigate. Sure enough the USGS is reporting there was a 2.5 magnitude earthquake located very near New Salem, Illinois.

For the record, 4:11 UTC translates into around 11:11 pm Saturday, September 9, 2023 Illinois time. As you can see from the USGS graphic, there were almost immediately a handful of people that reported feeling it.

Saturday night's quake happened in an area that is on the fringe area between the Wabash Valley Seismic Zone and the New Madrid Fault. There is some interesting earthquake history in this part of Illinois. According to Wikipedia, there was a very significant 5.3 magnitude quake in Illinois on November 9, 1968. It was felt in 23 different states and even shook the Gateway Arch in St. Louis. Damage was even reported in south-central Iowa.

Is this a foreshock of an even bigger quake yet to happen?

That's very unlikely, but there's no way to know for sure. Wikipedia says that "scientists determined that a 90% probability existed of a magnitude 6–7 earthquake occurring in the New Madrid area during the next 50 years.". By the way, that study happened in 2005, 18 years ago.

For the record, the Wabash Valley Seismic Zone appears to have been responsible for an earthquake of greater than 7.0 at some time in its history. Scientists estimate there is normally only one earthquake in this part of Illinois every year that's large enough to be felt. Looks like 2023 has now had one of those quakes in the Land of Lincoln.