Abstract

A list of 59 earthquake events felt in North Carolina between 1732 and 1900 has been compiled. It is the most complete such list yet catalogued. Thirty-eight of these events probably had their epicenters within the state or within a few miles of the state line. Much of the activity cannot easily be related to known geologic structures although some of the epicenters fall near the Blue Ridge front and the Brevard zone, near the border faults of the Dan River and Deep River Triassic Basins, and in the Cape Fear Arch region. Magnitudes of the N.C. events were all probably less than 4.5 on the Richter Scale. The maximum intensities experienced were due to the New Madrid, Missouri, earthquakes of 1811–12 and the Charleston, South Carolina, earthquake of 1886. There is a correlation between the growing population of N. C. from 1732 and the number of reported events but the state probably became saturated with respect to seismic detection around 1855 and, hence, the increase in seismic activity after 1870 is probably of genuine geologic origin. Among the most interesting events is the 1874 swarm near Rumbling Bald Mountain in McDowell County when more than 75 earthquakes occurred in two months. Field inspection of the site shows huge relatively recent-looking splits in the mountains there that could have been due to this swarm. The historical record of N. C. is probably not long enough to be a very valid basis for making earthquake risk projections into the future. It may be that the greatest threat to N.C. is large earthquakes outside her borders such as those in the Mississippi Valley and South Carolina. On the otherhand, there is nothing now known that can rule out the possibility that the greatest threat to N.C. is within her own boundaries. This latter possibility becomes a very real and serious concern when one studies the land elevation changes currently in progress in eastern N. C.

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