Earthquakes Affecting St. Louis, MO

Intensity is a measure of shaking based on the damage to human-made structures and the perception of the shaking by those who felt it. One of the earliest intensity scales was developed by engineer Jared Brooks who recorded the intensity of shaking in Louisville, Kentucky cause by shocks in New Madrid earthquake sequence.

Today we use the Modified Mercalli Intensity scale, a twelve level measure of the intensity of ground movement. The first three levels are not generally perceived by many people, but by intensity IV, almost everyone feels the jolt. The level of damage increases with successive intensities: An intensity level of VII can produce considerable damage to poorly built structures; regions that experience an intensity level of VIII or higher experience considerable damage to structures not prepared for earthquakes; a level of XII indicates total destruction.