Moment tensor inversions and dipping slabs


Moment tensor inversions were performed on synthetic teleseismic P and SH body wave data for two plausible orientations of intermediate depth earthquakes located in a slab. A ray method was used to generate the synthetic P and SH data for dipping slab models. Plane layered Green's functions were assumed in the inversions even though the synthetic data contained the effect of slab dip. This was done to simulate the typical situation where horizontal plane layers are assumed in mechanism studies. The inversion of data from an oblique‐slip source, for dipping slabs up to 45°, gave the assumed double couple source. When the initial mechanism was a near vertical dip‐slip type, results from the inversion showed significant departures from the assumed mechanism. A surprising result was that even though the presence of a dipping slab can occasionally distort the radiation pattern enough to yield fictitious source orientations, amplitudes and polarities were satisfactorily explained within typical variations seen in real data. Thus, the non‐double couple terms in the moment tensor can compensate for the perturbing effects of slab dip. Copyright 1982 by the American Geophysical Union.

Publication Title

Geophysical Research Letters