The Ste. Genevieve Fault Zone crosses the northeast flank of the Ozark Dome in southeastern Missouri and extreme southern Illinois. The surface trace of faulting trends southeast and is approximately 120 miles (190 km) long. Major displacements are as much as 3,000 feet (900 m) downward to the northeast along a sharp monoclinal flexural, which is cut by one or more high-angle reverse faults. Smaller high-angle normal and reverse faults are found on both sides of the main zone. At both ends the Ste. Genevieve Fault Zone dies out into a monocline. Two periods of faulting occurred. The first was in late Middle Devonian time, and the second ran from latest Mississippian through early Pennsylvanian time, with possible minor post-Pennsylvanian movement. No displacements of Quaternary sediments have been detected, but small earthquakes occur from time to time along the Ste. Genevieve Fault Zone. Many faults in the zone appear capable of slipping under the current stress regime of east-northeast to west-southwest horizontal compression. It is concluded that the zone may continue to experience small earth movements, but catastrophic quakes similar to those at New Madrid in 1811 to 12 are unlikely.
Illinois State Geological Survey
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- Geological Faults;