The US Geological Survey announced a small earthquake shook South Dakota for the second time in just a month. According to the USGS, an earthquake hit about six miles north of Tyndall in Bon Homme Count y, at about 8:55 a.m. Monday. It registered at a 3.1 on the Richter Scale, which is just above the 3.0 mark on the scale where earthquakes can be felt by people. This comes less than a month after a 3.2 magnitude earthquake near Bowdle and Hosmer. According to historical data, South Dakota generally experience one earthquake per year on average.