Officials with the Evansville/Vanderburgh County Emergency Management Agency in Indiana report that seven earthquakes occurred on Monday morning around the New Madrid fault line.

According to Missouri’s State Emergency Management Agency (SEMA), five earthquakes were detected near Marston, Missouri, while two were recorded near Ridgley, Tennessee. All of the quakes are considered to have a magnitude of 1 or higher.

Michigan Technological University notes that earthquakes with a magnitude of 2.5 or less are usually not felt by people but can be recorded by seismographs. The university states that millions of these small earthquakes occur each year.

The Missouri Department of Natural Resources mentions that Evansville is one of the major cities affected by this seismic zone. Hundreds of small earthquakes happen annually in this area; however, most are too small to be felt by humans and can only be detected by sensitive instruments.

The U.S. Geological Survey (USGS) indicates that the following towns were closest to these earthquakes::

December 9
Marston, MO
Magnitude 2.2
7:30 a.m.
Howardville, MO
Magnitude 1.9
6:25 a.m.
Ridgely, TN
Magnitude 1.8
5:31 a.m.
Howardville, MO
Magnitude 3.0
4:27 a.m.
Howardville, MO
Magnitude 2.1
12:27 a.m.
Matthews, MO
Magnitude 2.2
12:08 a.m.
Hayward, MO
Magnitude 2.0
12:00 a.m.

While the West Coast is well known for its destructive earthquakes, the Mississippi Valley’s New Madrid zone was the most seismically active region east of the Rocky Mountains until 2014, when a sharp spike in Oklahoma earthquakes unseated it, according to the U.S. Geological Survey.

In 1811 and 1812, the seismic area generated numerous earthquakes over a period of months, including three massive quakes that the USGS estimates to have been between magnitude 7 and 8.

The quakes destroyed multiple settlements along the Mississippi River and were reportedly felt as far away as Cincinnati, Ohio; Hartford, Connecticut; Charleston, South Carolina; and New Orleans.