Six Earthquakes 2.5 – 4.4 in Last Week in Midwest, South
The last seven days have seen a major increase in the number and magnitude of earthquakes in the Midwest.
What does it mean for Michigan?
The activity has all been part of the New Madrid Seismic Zone.
The USGS says the closest to Michigan was a 2.5 earthquake in Pinckneyville, Illinois on Dec. 9. The biggest of the recent quakes was a 4.4 in Decatur, Tennessee on Dec. 12.
The New Madrid Seismic zone is a serious threat for a future, major earthquake, but it is not a threat to Michigan.
Michigan does see some earthquakes: 3.4 outside of Detroit in April 2018, 2.6 near Detroit in July 2017, 3.3 near Battle Creek in June 2015 and a 4.2 near Galesburg in May of 2015, but the earthquakes we see in Michigan are not attributed to the same seismic zone or fault line. Michigan also will see an occasional mining explosion register on the Richter scale, including this one of 2.7 on June 2016.
The New Madrid Seismic Zone covers parts of eight states: Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and Tennessee.
The earthquakes over the last week haven't caused major damage, but they have renewed concern of the potential for a future quake and a reminder of the area's history of large quakes.
Beginning in 1811, the New Madrid Seismic Zone had three earthquakes in less than two months registering 7.5, 7.3 and 7.5. The USGS says, "The area of strong shaking associated with these shocks is two to three times as large as that of the 1964 Alaska earthquake (9.2) and 10 times as large as that of the 1906 San Francisco earthquake."
In total, the New Madrid earthquakes of 1811-1812 were a series of over 2,000 seismic events that took place over five months. The University of Kentucky says, "Scientific analysis of the region indicates that large, damaging earthquakes, from magnitude 7 to 8, occur on a timescale of 500 years to a few thousand years."
The University of Illinois did a study ten years ago (you can read all 936 pages of it here) of the potential impact a major quake in the New Madrid Seismic Zone could have today. The results could be catastrophic. Thousands of people killed or injured and billions of dollars of damages. Tennessee is among the areas that could be hit the hardest.
One area of further concern is building codes in the seismic areas. Some areas are well-prepared for a major quake, but many are not. FEMA says, "Despite the significant risk, many communities (in the seismic zone) have not taken sufficient earthquake protection, in particular, adoption and enforcement of building codes."
The New Madrid Seismic Zone is expected to have more major earthquakes. We do not know if those earthquakes will happen in days, years or centuries from today, but the earthquakes we have in Michigan are not part of this system.