After a magnitude 4.8 earthquake shook New York City’s densely populated metropolitan area Friday morning, questions arose about the frequency of seismic events elsewhere.
Earthquakes along the East Coast are a mystery compared to those on the West Coast, which sits on the edge of a tectonic plate unlike the West Coast, according to the U.S. Geological Survey.
Seismic activity is also not as common in the Midwest. However, the region is not immune to earthquakes.
In January, the USGS released the latest national seismic hazard model, showing where devastating earthquakes would most likely occur. In unveiling the map, the agency revealed that a research team had determined that nearly 75 percent of the United States could experience potentially damaging earthquakes and intense ground shaking.
California and Alaska are most at risk for seismic activity, followed by parts of several states, including Illinois.
Although the chances of a strong earthquake are relatively low across most of Illinois, a small portion of the state is tied with California and Alaska in the highest risk category.
Indeed, part of southern Illinois lies on two major seismic zones, the smaller of which is the Wabash Valley Seismic Zone. The state’s largest earthquake in recent years occurred there, registering a magnitude of 5.4 and injuring two people in April 2008.
Until 2014, following a dramatic increase in earthquake rates in Oklahoma, the most seismically active area east of the Rocky Mountains was in the New Madrid Seismic Zone, the largest area extending to Illinois.
Stretching 150 miles in length, the New Madrid area spans seven states: Illinois, Missouri, Arkansas, Kentucky, Mississippi, Indiana, and Tennessee.
Hundreds of small earthquakes occur there each year, but most are too small to be felt by humans and can only be detected by sensitive instruments, according to the Missouri Department of National Resources.
The seismic zone has generated some of the largest earthquakes in U.S. history. Three earthquakes struck between 1811 and 1812, destroying several settlements along the Mississippi River and causing a series of aftershocks that lasted for months. Scientists estimated the intensity of the earthquakes between 8.3 and 8.7 on the Richter scale, according to the Iowa Geological Survey.
The northern tip of the New Madrid Seismic Zone is in Cairo, which is one of the few communities in Illinois located within its borders.
A devastating earthquake could strike other nearby cities, which like Cairo, have a 50 to 75 percent chance of a mild, destructive earthquake occurring within 100 years, according to the USGS. Among these cities are Carbondale and Harrisburg.
Not far away, communities along the Wabash Valley seismic zone, like Mount Carmel and Onley, fall between 25 and 50 percent.
Although the risk there is lower than Carbondale, it is still higher than the rest of Illinois. A large portion of the state, encompassing Springfield, Champaign and the Chicago area, is at 5 to 25 percent risk.
While it is clear that Illinois is not immune to earthquakes, should we expect one soon?
The chance that we will see a repeat of earthquakes with a magnitude of 7.5 to 8.0 is between 7 and 10 percent. The chance of seeing an earthquake with a magnitude of 6.0 or greater is even higher, at 25 to 40 percent, according to the Illinois Emergency Management Agency.
However, the probability increases as the days pass.
A catastrophic seismic event on the New Madrid Fault Zone could affect more than 50% of Illinois’ population and trigger a national response on a larger scale than any seismic event recorded in modern state history -United, said IEMA.
NBC Chicago
