P And S at distances smaller than 25°

Abstract

A study was made of the P‐ and S‐phases of three European earthquakes as recorded at distances up to about 25°. One of the earthquakes occurred at a depth of about 275 km. It was well recorded at distances around 20° where the P‐ and S‐curves were found to bend gradually and have only one branch. There is therefore, no abrupt change of velocity at the 20° discontinuity. The second earthquake studied was shallow; the third one probably had its focus at the base of the crust. The behavior of P and S was explained on the assumption of the existence of a “soft,” low‐velocity layer at some depth below the Mohorovicic discontinuity.