Do You Know How Many Earthquakes Have Happened In Minnesota + Wisconsin?
Natural disasters happen all over the world. Normally in Minnesota and Wisconsin you'll see blizzards, tornadoes, wildfires, but how often do earthquakes occur?
Earthquakes aren't that common in Minnesota and Wisconsin, but they have happened. According to a geological survey from the University of Minnesota:
Most earthquakes occur when solid rock masses move past one another along fracture planes called faults. To produce movement, stress must build up along a fault plane until it overcomes internal friction and the rocks to either side elastically snap or rebound to relieve the stress.
Minnesota also has one of the lowest occurrence levels of earthquakes throughout the United States. Before I dive into the earthquakes that have happened in the Land of 10,000 Lakes, lets talk about how they are measured.
Earthquakes are measured by magnitude based on the Moment Magnitude Scale. It measures the movement of rock along the fault. Earthquakes are also classified in categories that range from minor to great. The minor earthquakes have a magnitude range from 3.0-3.9, while the great earthquakes have magnitudes large than 8.0. Check out a map from the Science & Engineering Department of the U of M:
As you can see in the map, there are fault lines, rocks of the Midcontinent Rift and you can see all the earthquake epicenters. The first quake dates back to 1860 in Long Prairie, while the most recent was in the small town of Brandon back in 2011. All in all there have been about 20 documented earthquakes throughout Minnesota. Here are the top five biggest based on magnitude and felt area:
- Morris in 1975 (4.6 magnitude, 82,000 felt area)
- Dumont in 1993 (4.1 magnitude, 69,500 felt area)
- Staples in 1973 (4.3 magnitude, 48,000 felt area)
- Granite Falls in 1994 (3.1 magnitude, 11,600 felt area)
- Detroit Lakes in 1939 (3.0-3.9 magnitude, 8,000 felt area)
The closet Minnesota earthquake to Duluth happened in Rush city back in 1979. That was a very small earthquake with a magnitude of .1. Now let's travel across the border and take a look at our friends in Wisconsin.
Wisconsin is an interesting one. There have been many earthquakes around Wisconsin and have been felt in the state according to Wis History. Apparently there is only one documented earthquake in Wisconsin. This happened in 1947 in downtown Milwaukee. with a magnitude of 4, it was strong enough to shake buildings and break windows.
So there you have it. Only about 20 documented in Minnesota and one in America's Dairy Land. If you're interested, you can check out an interactive map of active earthquakes in the US, here.