Study of phase and group velocities in a dipping layer overlying an elastic medium using theoretical seismograms.

Abstract

Theoretical displacement seismograms are computed for the study of group and phase velocities of Love type surface waves in a dipping layer overlying an elastic body using the solution derived in a previous paper by the present authors. The result does not show that the group velocity in a dipping structure corresponds to the theoretical group velocity of horizontal structure having the thickness equal to an arithmetic average of depths between the source and receiver. The Sato's formula is found to explain the group velocity obtained by the analysis of theoretical seismograms for the short period waves in the cases of dip angles smaller than 2.0°, his formula being derived under the assumption that the phase velocity depends only upon the thickness at an observation station. The analyzed phase velocity agrees well with the phase velocity for horizontal layer with the thickness at an observation point for the short period waves when the dip angle is small.