Estimation of surface focusPtravel times

Abstract

An iterative technique was used to locate some 400 earthquakes, estimate corrections to the Jeffreys-Bullen P travel times and estimate azimuthally dependent station adjustments (station corrections). An oversimplified model for the upper 700 km of the mantle was adopted in order to provide a standard for the investigation of regional variations in travel times. In the estimation procedure only data for epicentral distances in the range 20° to 105° were used, and the data were truncated to remove gross errors. The new P travel times are generally 2 to 3 sec less than those given in the Jeffreys-Bullen Tables.