THE SEISMIC HAZARD FROM MAJOR EARTHQUAKES IN THE CENTRAL AND EASTERN UNITED STATES

While earthquake hazard arises from all earthquakes above about magnitude 5, major earthquakes (those of magnitude 7 or above) contribute the most to the hazard since their effects can be so devastating. In the Central and Eastern US (CEUS), it is difficult to ascertain where and how often major earthquakes are likely to occur because of their low rates of occurrence and our poor understanding of seismogenic structures. Evidence is accumulating that major earthquakes might be generated more frequently and on more geologic structures or faults in the CEUS and nearby Canada than previously believed. Several major earthquake sequences in the New Madrid seismic zone over the past two millenia and recurrent M7 earthquakes near Charleston, SC have been documented . Less widely recognized but nevertheless significant earthquakes took place at Charlevoix, Quebec, in 1663 and perhaps in central New Hampshire in 1638. Geologic evidence has been uncovered of major prehistoric earthquakes in Holocene time on the Meers Fault in Oklahoma, in the Wabash Valley region, and in the St. Louis area. Given the past earthquake history, people in the CEUS should not discount the possibility of one or more M7+ earthquakes affecting the CEUS sometime during the 21st century.