Moment-tensor inversions for local earthquakes using surface waves recorded at TERRAscope

Abstract

We have developed a method to determine moment tensors for local earthquakes using short period (10 to 50 sec) surface waves recorded at TERRAscope stations. To correct for the substantial lateral variations in crustal structure, we applied phase corrections to the data using a regionalized phase-velocity model. We have determined moment tensors for over 180 events in the last 3 yr in southern California for magnitudes as small as 3.2 and as large as 6.5. The results are consistent with those obtained from first-motion data as well as other waveform inversions. When continuous data telemetry from the stations becomes available this method can yield moment tensors for earthquakes in southern California and adjacent regions within minutes after the occurrence of an event. Our results confirm the relation log M_o (seismic moment) ∝ 1.5M_L (local magnitude) obtained by an earlier study.