what when and where was the largest earthquake recorded in minnesota over the past 50 years
1975 Morris earthquake The 1975 Morris earthquake occurred in western Minnesota on July 9 at 14:54:15 UTC, or 9:54Â a.m.[2] The strongest instrumentally recorded rupture in the history of the state, it registered at magnitude 4.6 Mn and had a maximum Mercalli intensity of VI (Strong). It was the first earthquake to be recorded on any seismic instrument in the state since 1917. Tremors were felt over much of Minnesota, northern Iowa, and the eastern Dakotas.