Wabash Valley seismic zone

The Wabash Valley seismic zone consists largely of vertically oriented ("normal") faults deeply buried under layers of sediment.

Although the tectonics of the region are not fully understood and are the subject of ongoing research, these faults are thought by some to be associated with a branch of the New Madrid aulacogen, an old rift zone where the lithosphere actively began to pull apart at perhaps two separate times in the distant past.

Present-day GPS measurements show that the region deforms at about 1–2 mm per year with compression along the Wabash Valley fault zone and extension in southwestern Indiana.

This zone has been proven to have had earthquakes for the last 20,000 years, with geologic evidence that they may have been as strong as 7.0–7.5 or greater on the Richter scale.

[4] According to the United States Geological Survey, lesser earthquakes occur relatively frequently, but those at a magnitude less than 3.5 or so are usually not felt.