New Madrid Seismic Zone
The New Madrid Seismic Zone, located in southeastern Missouri, was once the most active seismic area in the United States east of the Rocky Mountains. In 1811 and 1812, five quakes measuring magnitude 8 or higher reportedly shook the area with a force 10 times stronger than that of the famous 1906 San Francisco earthquake, caused by a breakage in the San Andreas.
Since the New Madrid Zone has witnessed seismic events of this magnitude every 250 years or so, scientists have predicted that another will come in the next half-century. Recently, however, movement along the fault lines has slowed considerably, leading some geologists to speculate that the zone might be shutting down.