At 2.45 pm local time on Tuesday 9 August 2011 the city of Pierre, state capital of South Dakota, was shaken by a small earthquake. Residents reported feeling shaking and hearing several loud booms. According to the United States Geological Survey the quake took place roughly 1 km west of the city, at a depth of about 15.6 km. It measured 3.4 on the Richter Scale. The U.S. Army's Corps of Engineers is conducting a check on the Oahe Dam, 8 km upstream from the city on the Missouri River.
Pierre, South Dakota.
South Dakota is located in the central part of the North American continent, far from any plate margin. It does have some faulting, associated with the uplift of the Rocky Mountains far to the west, which cause the occasional minor earthquake. Earthquakes were recorded in South Dakota in 1872, 1877, 1879, 1895, 1911, 1915, 1928, 1938, 1946, 1961, 1964, 1967, 1975, 1978, 1981, 1982, 1983, 1986, 1987, 1990, 1991, 1993, 1994, 1995, 1996, 1998, 2002, 2003, 2004, 2005, 2006, 2007 and 2010. No major damage or serious injuries have ever been recorded.
See also Earthquakes in the Gulf of California and Earthquakes on Sciency Thoughts Youtube.