ST. LOUIS — How often do earthquakes happen in St. Louis? And how do they happen? Here's a look at the data.
Earthquakes are caused by movement along faults in the earth's crust and upper mantle. Seismic activity can be strong and sudden, or so weak that it can't be felt by people.
Note: The video above is from 2021.
St. Louis is in an area of the country designated the "Illinois Basin - Ozark Dome." It is north of the more active New Madrid seismic zone.
The United State Geological Survey tracks all faults on an up-to-date map.
The Illinois Basin - Ozark Dome includes parts of Missouri, Illinois, Indiana, Kentucky and Arkansas.
USGS says irregular but moderately frequent earthquakes can be expected in this region. Moderately damaging earthquakes strike every 10-20 years, with small earthquakes happening once or twice each year.
The largest earthquake recorded in the area happened in 1968. A magnitude 5.4 earthquake damaged southern Illinois. Geologists have evidence of even larger prehistoric earthquakes in the area.
Earthquakes east of the Rockies
Earthquakes near St. Louis have different characteristics than earthquakes along the West Coast.
Earthquakes here can be felt for longer distances. Some earthquakes can be felt as much as ten times farther. Eastern U.S. earthquakes can also cause damage to farther locations from the epicenter.
Earthquakes are less frequent in the Midwest than along active seismic zones of California.
Faults like the San Andreas fault system are well-studied plat boundaries, but less is known about specific faults in the Illinois Basin - Ozark Dome. These faults can be deeply buried. The faults in the region might be yet undetected.
Noises during an earthquake
Shallow earthquakes in St. Louis can produce loud noises that sound like rumbling or even explosions.
These noises are from high-frequency vibrations. During deeper earthquakes, these vibrations do not reach the ground.