Synthetic seismograms ofP-waves propagating in solid wedges with free boundaries

A numerical method for the synthesis of seismograms for body wave propagation in solid wedges is presented. The method is based on the superposition of multiple reflections arising from the entrance of a plane primary wave. Therefore the method is restricted to those domains in time-space where no diffracted waves from the wedge axis occur. In spite of this restriction, the dispersion of body waves in wedges can well be studied by this method. Seismograms have been synthesized which show the dispersion of a primary,p-signal propagating in a solid 10°- and a 5°-wedge with free boundaries. For wedge anlges less than 10° the signal from (as distinguished from the wave front) suddently decreases its velocity from that in the infinite medium to about that of the plate wave as the signal approaches the wedge axis. A decrease of the dominant period of the interference signal occurs simultaneously in this transition zone. These observations are concordant with previous seismic model studies [1]. Particle motion diagrams disclose elliptical polarization of the interference signal in the neighboorhood of the wedge axis which changes its sense from prograde to retrograde on passing through the transition zone. This paper has been submitted for publication to Geophysics. It will appear, in Vol. 31 (1966).