After a 4.8-magnitude earthquake shook the densely populated New York City metropolitan area on Friday morning, questions arose about how common seismic events are elsewhere.
Earthquakes along the East Coast are a mystery compared to those along the West Coast, which sits on a tectonic plate boundary, unlike the West Coast, according to the U.S. Geological Survey.
Seismic activity isn't as common in the Midwest, either. However, the region isn't immune to earthquakes.
In January, the USGS released the latest National Seismic Hazard Model, showing where damaging earthquakes would most likely occur. As it unveiled the map, the agency revealed a research team determined nearly 75% of the U.S. could experience potentially damaging earthquakes and intense ground shaking.
California and Alaska are at the highest risk of seismic activity, followed by portions of several states, including Illinois.
While the chances of a strong earthquake are relatively low in most of Illinois, a small portion of the state is on par with California and Alaska in the highest risk category.
That's because a sliver of southern Illinois sits 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.
Local
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 zone that reaches into Illinois.
Stretching 150 miles long, the New Madrid zone extends into portions of seven states: Illinois, Missouri, Arkansas, Kentucky, Mississippi, Indiana and Tennessee.
Feeling out of the loop? We'll catch you up on the Chicago news you need to know. Sign up for the weekly Chicago Catch-Up newsletter here.
Hundreds of small earthquakes occur there every year, however, 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 generated some of the largest earthquakes in U.S. history. Three earthquakes struck between 1811-1812, destroying several settlements along the Mississippi River and spurring a series of aftershocks that lasted for months. Scientists have estimated the intensity of the earthquakes as between 8.3 and 8.7 on the Richter Scale, according to the Iowa Geological Survey.
The northern point of the New Madrid Seismic Zone sits in Cairo, which is one of just a few Illinois communities situated within its boundaries.
A damaging quake there could strike other nearby cities, which like Cairo, are at a 50 to 75% chance of a slight damaging earthquake occuring within 100 years, according to the USGS. Among those cities are Carbondale and Harrisburg.
Not too far away, communities along the Wabash Valley Seismic Zone, like Mount Carmel and Onley, fall in the 25 to 50% range.
While the risk there is lower compared to Carbondale, it's still higher than the rest of Illinois. A wide swath of the state, encompassing Springfield, Champaign and the Chicago area, is at 5-25% risk.
While it's clear Illinois isn't immune to earthquakes, should be expect one soon?
The probability that we see a repeat of earthquakes with a magintude of 7.5-8.0 is anywhere between 7 and 10%. The chance of seeing an earthquake with a magnitude of 6.0 or larger is even greater at 25 to 40%, according to the Illinois Emergency Management Agency.
However, the probability increases as each day goes by.
A catastrophic seismic event on the New Madrid Fault Zone could impact more than 50% of Illinois' population and trigger a national response on a larger scale than any recorded earthquake event in modern U.S. history, IEMA stated.
