Southeastern Section - 64th Annual Meeting (19–20 March 2015)

Paper No. 11
Presentation Time: 11:40 AM


BOCKHOLT, Blaine M. and LANGSTON, Charles A., University of Memphis, Center for Earthquake Research and Information, 3890 Central Ave, Memphis, TN 38152,

Seismic waveforms from the Eastern Tennessee Seismic Network are corrected to the nominal Wood-Anderson torsion seismometer to obtain a total of 11905 maximum trace amplitudes from 690 events seen on 50 different horizontal components to determine a local-magnitude scale for the Eastern Tennessee Seismic Zone (ETSZ). The distance-correction function –log10(A0) = 0.538(r/17)-0.0002516(r-17) + 2.0, where A0 is the maximum amplitude measured in millimeters and r is the hypocentral distance measured in kilometers, better agrees with reported moment magnitudes for larger events in the ETSZ. Using the normal 100 km distance for ML normalization severely over estimates ML at distances greater than 17 km suggesting unusually low distance attenuation at local and near-regional distances from the ETSZ. Wood-Anderson response reported by the International Association of Seismology and Physics of the Earth’s Interior to the nominal response shows no significant difference in the distance-dependent factor for the log A0 term although the revised response consistently yields ML values that are 0.1 lower than those found using the nominal response. b-values estimates are obtained showing that the b-value for the currently reported duration magnitude is lower than the b-values obtained using the newly calculated ML scale. The relationship between ML and MD can be expressed as ML = 0.68093MD + 0.64603. The catalog of events used in this study is seen to be complete for ML greater than 1.3.