There were 4 earthquakes in central Nebraska on April 9th and 10th, according to the USGS. The first one, with a magnitude of 3.3 shook near Arnold, Nebraska Monday morning, at 4:33.
The next quake held off until Tuesday morning, starting at 6:41, hitting with a magnitude of 3.7. Just over 10 minutes later, a weaker 2.5 magnitude earthquake struck nearby. Later in the morning, a 3.3 magnitude earthquake hit in the same general area at 10:49.
All 4 earthquakes were about 5 km under the ground, according to USGS data. Each one was considered weak. While people reported feeling the shaking, no damage was reported.
You can see Tuesday morning's 3.1 earthquake plotted by a seismograph in the image above, courtesy of Earthquake-Report.com.
It's not normal for Nebraska to see so many earthquakes in a week, or even a year. The state averages just one earthquake each year. Since 1931, the state has been shaken by quakes just 45 times. Last year, in 2017, there were none.
The strongest earthquake on record in the state had a magnitude of 4.3, which happened in Grant County, on May 7th, 1978. More recently, an earthquake more comparable to this week's, was a 3.6 in Auburn, Nebraska on December 12th, 2009.