Frequency sensitive moment tensor inversion for light to moderate magnitude earthquakes in eastern Africa

摘要

We provide a procedure for the routine determination of moment tensors from earthquakes with magnitudes as low as M-W 4.4 using data recorded by only a few permanent seismic stations at regional to teleseismic distances. Waveforms are inverted for automatically determined frequency pass-bands that depend on source-receiver locations as well as the earthquake magnitude. Inversion results are stable against small variations in the frequency band and provide low data variances, i. e., a good fit between observed and modelled waveform traces. The total frequency band used for our procedure ranges from 10 mHz to 29 mHz ( periods of 35 s to 100 s). This enables us to determine focal mechanisms for earthquakes that were not derived previously by routine procedures of CMT or other agencies. As a case study, we determine focal mechanism solutions of 38 light to moderate magnitude earthquakes in eastern Africa between 1995 and 2002.