A Grid Search Algorithm to Determine Earthquake Source Parameters. Application to the 1992 Yellow Sea, China, Earthquake

A grid search method has been implemented to determine earthquake focal mechanism and source depth using a set of Green's functions computed for a representative continental crustal structure. The method directly compares observed and synthetic waveforms through a misfit function. selecting as the result the model with the lowest misfit. The method has been tested with synthetic data and with CDSN long period (LH band) observations of the 1992 Yellow Sea earthquake. I obtain a focal mechanism and source depth broadly consistent with that inferred by Nguyen (1994): strike = 19 deg, dip = 90 deg. and rake = 173 deg, depth = 15 km. Variations on the starting crustal model. which was derived from Nguyen and Hsu's (1993) MDJ model. are tested using the new focal mechanism. I find that better overall fits are obtained using higher attenuation throughout the crust and lower seismic velocity in the lower crust.