Answer:
Paleoseismology is the study of ancient rocks and sediments for evidence of seismic events, such as earthquakes and tsunamis, from times before records were kept.The geology of sand blows (sand ejected by water squirting out of the ground due to strong earthquake shaking) created by large earthquakes in the New Madrid seismic zone shows that previous sequences of 1811-1812 size earthquakes occurred around 1450 AD, 900 AD and maybe 300 AD. This is an astonishingly high rate of activity: one large earthquake sequence every 500-1000 years on average.
What do these results mean? One explanation is that large earthquakes occur regularly in the New Madrid seismic Zone. They occurred in the past and will continue to occur in the future. A second explanation is that just because large earthquakes occurred in the past, it does not mean that they will occur in the future. GPS data does not show stress buildup in the faults.