HOW DO SHEAR WAVE EVENTS AFFECT NORMAL P‐WAVE RECORDS?*

It has been known since the beginning of reflection seismics that several disturbing events seen in seismic records are caused by waves with S‐wave velocities instead of P‐wave velocity. When using dynamite and recording with vertical geophones these events are primarily caused by converted waves.

On the basis of known P‐ and S‐wave velocities in a certain area a theoretical seismogram is calculated, displaying traveltime as well as energy relation for different wave configurations. By comparison with seismograms recorded in the same area it can be shown that converted wave events can be clearly recognized.

These events can be described theoretically. Thus, either more effective computer programs can be applied to eliminate these disturbing events, or these events can be evaluated to get additional information about specific strata.