Centroid moment tensor catalogue using a 3D continental scale Earth model: Application to earthquakes in Papua New Guinea and the Solomon Islands
Abstract
Although both earthquake mechanism and 3D Earth structure contribute to the seismic wavefield, the latter is usually assumed to be layered in source studies, which may limit the quality of the source estimate. To overcome this limitation, we implement a method that takes advantage of a 3D heterogeneous Earth model, recently developed for the Australasian region. We calculate centroid moment tensors (CMTs) for earthquakes in Papua New Guinea (PNG) and the Solomon Islands. Our method is based on a library of Green's functions for each sourcestation pair for selected Geoscience Australia and Global Seismic Network stations in the region, and distributed on a 3D grid covering the seismicity down to 50 km depth. For the calculation of Green's functions, we utilize a spectralelement method for the solution of the seismic wave equation. Seismic moment tensors were calculated using least squares inversion, and the 3D location of the centroid is found by grid search. Through several synthetic tests, we confirm a tradeoff between the location and the correct input moment tensor components when using a 1D Earth model to invert synthetics produced in a 3D heterogeneous Earth. Our CMT catalogue for PNG in comparison to the global CMT shows a meaningful increase in the doublecouple percentage (up to 70%). Another significant difference that we observe is in the mechanism of events with depth shallower then 15 km and M_{w} < 6, which contributes to accurate tectonic interpretation of the region.
 Publication:

Journal of Geophysical Research (Solid Earth)
 Pub Date:
 July 2017
 DOI:
 10.1002/2017JB014230
 Bibcode:
 2017JGRB..122.5517H
 Keywords:

 centroid moment tensor;
 reciprocity theorem;
 3D Earth structure;
 doublecouple percentage of moment tensor;
 Papua New Guinea;
 Solomon Islands