Local Risk

New Madrid Fault

The New Madrid Fault System extends 120 miles southward from the area of Charleston, MO and Cairo, IL, through New Madrid, following Interstate 55 to Marked Tree, AR. It crosses five state lines and cuts across the Mississippi River in three places and the Ohio River in two places.

While we dont typically feel a lot of earthquakes, the fault line is very active with more than 200 measured events a year (1.0 on the Richter Scale).  Some tremors are that are large enough to be felt (2.5 – 3.0 on the Richter scale) also happen annually. According the USGS, every 18 months the fault releases a shock of 4.0 or more, capable of local minor damage.

Types of quakes

A damaging earthquake would be 6.0 or greater.  These typically occur every 80 years – the last one was in 1895. The results would cause serious damage to schools and masonry buildings from Memphis to St Louis.

A major earthquake would be 7.5 or greater.  these types of quakes typically happen every 200- 300 years – the last one in 1812. There is a 25% chance by 2040. An event like this size would be felt throughout half the United States and damage 20 states or more.

The Great Madrid Earthquake of 1811-1812

This event lasted five months and consisted of multiple earthquakes (five were 8.0 or more in magnitude) and 2000 aftershocks from 1811 to 1812. It was the largest burst of seismic energy east of the Rocky Mountains in the history of the United States and was several times larger than the San Francisco quake of 1906. There was enormous damage in Kentucky, Ohio, Illinois, Arkansas, Indiana and Mississippi.

Wabash Valley Seismic Zone

The Wabash Valley Seismic Zone is located in Southeastern Illinois and Southwestern Indiana and it is capable of producing ‘New Madrid’ size earthquake events. Since the discovery of this seismic zone, earthquake awareness and preparedness have increased. Residents are seeing that moderate sized earthquakes are not just occurring to the south, but occur right at home and can affect Illinois, Indiana, and Kentucky.

On April 18, 2008, a 5.4 magnitude earthquake struck near Mt. Carmel, Illinois. This quake was felt in at least 16 states, by more than 40,000 people, according to the USGS. Fortunately, there were no serious injuries or fatalities, but non-structural damage was reported in the states of Illinois, Indiana, & Kentucky.