Full moment tensor inversion of two Hindu Kush intermediate-depth earthquakes using teleseismic and region waveforms

Rapid and accurate determination of full moment tensors plays an important role in seismic source studies. We developed a joint inversion method for full moment tensors that combines both local and teleseismic waveform data. This method, called "gCAPjoint", which is based on the CAP method, enables time shift for synthetics, thus is more robust to inaccuracies in velocity models. Meantime, this method uses both local full waveforms and teleseismic body waves, thus provides enhanced coverage of azimuth and take-off angles of seismic waves, which are critical in constraining focal mechanism and depth. As a case study, we applied the method to two moderate-size intermediate-depth earthquakes (Mw6.3 and Mw6.6) in Hindu Kush. These two earthquakes share very close centroid locations, but the retrieved moment tensors of them are very different. While one event is essentially a pure double-couple thrust earthquake, the other event shows focal mechanism dominated by CLVD component, which can potentially be attributed to multiple double couple sub-events. Such difference for these two events suggests complex faulting geometries in the source region.