Finite Difference Modelling of Shear Waves

Abstract

The finite difference synthetic seismogram method provides the capability to study compressional and shear wave interaction in range dependent marine models. A study has been carried out of the pressure, vertical displacement, and horizontal displacement of the sound field at the seafloor for the P-SV problem. Compressional, shear and interface waves can be clearly identified in both snapshot and time series formats of the sound field for soft sediments (shear wave velocity = 450m/s). Key features have been identified. 1)The coupled shear head wave in the bottom can drain energy away from the compressional head wave. 2)The evanescently generated shear wave can be quite energetic and will create precursors to the Stoneley wave when there is sub-bottom structure. 3)Backscattered, secondary Stoneley waves are generated when the direct water wave hits a change in slope at the seafloor. 4)Weak backscattered water waves are generated from slope discontinuities in laterally heterogeneous waveguides. 5)At the seafloor, Stoneley waves are most evident on vertical displacement sensors. 6)Below the seafloor, at non-normal offsets, body wave energy is largest on horizontal component sensors.