Surface-wave studies of some South Carolina earthquakes

Abstract Long-period surface waves generated by three South Carolina earthquakes are used to infer focal mechanisms and seismic moments of the events. The 3 February 1972 Bowman, South Carolina, earthquake is found to be shallow and to require an almost strike-slip focal mechanism with pressure axes trending northeast-southwest. The 22 November 1974 Charleston, South Carolina, earthquake was smaller and was recorded by only three long-period WWSSN stations. For this earthquake, only an estimate of the seismic moment and focal depth were possible. The focal mechanism of the 2 August 1974 Clarkhill reservoir earthquake indicated motion on a northwest striking almost vertical dip-slip fault. In order to specify preferred motions on the nodal planes, full waveform modeling of the long-period traces at ATL was necessary. The results are not without ambiguity, but represent the best estimates of source parameters for these earthquakes.