BERTRAND, Mo. — An earthquake shook the ground in southern Illinois and Missouri early Friday morning, but experts believe residents did not feel it.
The United States Geological Survey confirmed that a 1.7 magnitude earthquake struck near Bertrand, Missouri, south of Cape Girardeau, around 2 a.m. Friday. The earthquake struck an estimated four and a half miles underground.
The earthquake also occurred in the New Madrid Seismic Zone, a network of faults or fractures between two blocks of rock that runs up and down the Mississippi River Valley and has been seismically active for centuries. The zone has also recently become the focus of unfounded apocalyptic conspiracy theories.
According to the USGS, Friday morning’s earthquake was not a “felt” earthquake, or one that people felt. The size of an earthquake is determined by its “magnitude,” which is the amount of energy released at its source, and its “intensity,” which is the effects of shaking on people and buildings. In contrast to magnitude, the intensity of an earthquake can vary greatly from place to place.
Intensity values are usually higher near the epicenter of an earthquake and decrease as one moves away from it.
“Typically, people report feeling earthquakes larger than about magnitude 3.0,” USGS officials stated on the survey website. “The magnitude, location, and depth of an earthquake, and overlying soil conditions determine how widely and strongly any particular event can be felt.”
Even if they did not feel the earthquake, USGS officials recommend that people who were close to it report it on their “Did You Feel It?” website. Responses fill in the gaps between instruments that record shaking, allowing for more complete earthquake assessments.
