Full waveform moment tensor inversion by reciprocal finite difference Green's function

  • Okamoto Taro
    Department of Earth and Planetary Sciences, Tokyo Institute of Technology

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Abstract

We study two important aspects of the waveform moment tensor inversion for the shallow earthquakes in the subduction region: the effect of the intense lateral inhomogeneity in the structure, and the strategy to invert the waveform data for the focal mechanisms. For the first aspect, using a “forward” finite difference modeling, we demonstrate that the effect of the inhomogeneity is quite large on the surface waves with a period of about 20s, and the current knowledge on the subduction region structure is practically effective in reproducing the characteristics in the observed waveforms. For the second aspect, we develop a “reciprocal” moment tensor inversion method that can generate the Green's functions for a large quantity of source locations (19, 200 in this study) in a realistic inhomogeneous structure by only three finite difference calculations per a single station. The inversion with a grid search scheme result in a reasonable source location, moment tensor and fit of the waveforms using data from only two stations. The constraint on the epicenter in the “transverse” direction is found to be somewhat weak in the case of single-station inversions, but the two-station inversion improves the constraint.

Journal

  • Earth, Planets and Space

    Earth, Planets and Space 54 (6), 715-720, 2002

    Society of Geomagnetism and Earth, Planetary and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

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