Travel times and station corrections for P waves at teleseismic distances

Approximately 3300 shallow focus earthquakes and 1000 seismic stations have been used in a study of P wave travel times and station residuals, including azimuthal effects. The events were selected from a catalog containing 160,000 earthquakes, and those having uniform distance and azimuthal coverage were systematically relocated and used to refine P wave travel times and station corrections. Station corrections are provided for 994 seismic stations. The station corrections involve three terms: the static effect and two cosine terms with appropriate phase shifts. They exhibit general consistency over broad geographic areas and, where coverage is dense, often show abrupt changes from one geological province to another. The cos 2θ terms appear to be due to upper mantle anisotropy, and they correlate with the stress direction in the crust.