Analysis on the Synthetic Seismograms of Seismic Wave Caused by Low Frequency Sound Source in Shallow Sea with Porous Seabed

Abstract

Elastic wave in the seabed caused by low frequency noise radiated from ship is called ship seismic wave and can be used to identify ship target. In order to obtain the propagation features of ship seismic wave in shallow sea with thick sediment, this paper introduces an algorithm for synthetic seismogram aroused by low frequency point sound source in shallow sea based on Biot’s wave theory for saturated porous media. Numerical calculation of synthetic seismogram at seafloor was carried out at a typical shallow sea environment with thick sediment. According to the results of numerical examples, the time series of seismic wave at seafloor is mostly composed of interface wave and leaky modes. The interface wave can propagate to far distance with small attenuation when the source frequency is very low. When the source frequency increases, the interface wave can no longer propagate to far distance like the leaky modes because the attenuation of sediment increases rapidly with frequency. The porosity and permeability of sediment in shallow sea have some influence on the dispersion characteristic of seismic wave at seafloor.