Some believe the quake would have registered around 7.7 had anyone back then had a seismograph handy. Others say the tremor was the equivalent of 32 megatons of dynamite
or roughly 2,500 times more powerful than the Hiroshima atomic bomb. Nearly all scientists agree, though, that the earthquake was one of the most powerful (if not the
most powerful) to strike America since European settlement.
And that first tremor (strong enough to jostle people out of bed as far away as New York City) was just the beginning. Five hours later the first aftershock, an estimated 7.0 magnitude quake, sent more shock waves across the nation. Another quake, estimated at 7.5 on the Richter scale, struck on January 23, 1812. A final aftershock on February 7 (estimated to be the same magnitude of the original earthquake) destroyed the town of New Madrid and knocked down homes in St. Louis.
Witnesses to the quakes reported that the tremors caused the Mississippi River to "rise like a great loaf of bread" with waves from the vibrations making it appear as though the water was running north.
Some geologists maintain that the New Madrid fault line in southeastern Missouri is long overdue for another series of earthquakes
, measuring between 6 and 6.5 on the Richther scale. As recently as March 2010 the New Madrid fault produced a 3.7 magnitude earthquake that could be felt as far away as Alton, Illinois.
Seismologists don't know for sure the magnitude of the earthquake that rocked Missouri at around 2:15 a.m. December 16.