Earthquake history of Montana

Montana is one of the most seismically active States in the Union. Since 1925, the State has experienced five shocks that reached intensity VIII or greater (Modified Mercalli Scale). During the same interval hundreds of less severe tremors were felt within the State. Montana's earthquake activity is concentrated mostly in the mountainous western third of the State which lies within a seismic zone that also includes southeastern Idaho, western Wyoming, and central Utah.