Abstract
A method of simultaneously estimating hypocenter parameters, station corrections, and velocity parameters has been developed for a velocity model with an arbitrary dipping layer boundary. The seismic ray is traced two-dimensionally by defining an equivalent ray path in a flat-layered velocity model for each combination of source and receiver. The partial derivatives of the travel time with respect to the perturbations in the hypocenter parameters and velocity model parameters are found to be expressed in analytical forms. These advantages are utilized in developing a time-saving computational procedure for the simultaneous estimation. The computer program coded according to the above procedure is tested for an artificial data set. The arrival-time data are stably inverted for true hypocenters and a true velocity model. Thus, it is concluded that the method works well, at least for an ideal data set. The present method may be used in estimating the gross image of the lateral variation in the crust of the velocity structure.
