Diffractions due to P and SV waves on irregular bathymetries

Diffractions of P and SV waves on irregular bathymetries are studied using the indirect boundary element method. This allows us to evaluate the complete displacement field by the superposition of a free field plus a diffracted one. Six elemental bathymetries are analyzed in the frequency domain and normalized displacement spectra are obtained. Hence, synthetic seismograms are generated in order to get a better perspective on the effects caused by the bathymetries. Results in the frequency domain suggest that the absolute value of normalized displacement is amplified almost four times in a sinusoidal bathymetry for incoming P-waves. For the incidence of SV-waves on a semi-circular bathymetry, the amplification reaches a value of five times. Moreover, several kinds of materials for the semi-circular bathymetry are used for comparison purposes, these are: sandstone, limestone and granite. Results for these materials reveal that sandstone produces an amplification of almost 3.5 times an incident P-wave. Therefore, seismic amplifications should be taken into account when marine foundations or pipelines are designed.