Synthetic seismograms for marine sediments and determination of porosity and permeability

We present numerical simulations of vertical seismic profiles (VSPs) of marine sediments. The theoretical seismograms, which are computed for vertically incident waves in flat layered poroelastic media, include the effects of dispersion and attenuation predicted by Biot theory. According to Biot theory, fast and slow compressional waves are excited and there is mode conversion at the interfaces. We include this effect in the calculation of reflection and transmission coefficients as an energy-loss mechanism through the slow compressional waves. Finally, we examine the spectral ratio method for determining porosity and permeability from synthetic seismogram data. Analytical expressions for the velocity and specific attenuation are found based on the weak-frame approximation. Once the frequency-dependent velocity and specific attenuation are calculated, the porosity and permeability of marine sediments can be determined by using the proposed weak-frame approximations. Spectral ratio calculations on synthetic examples show that Biot's theory incorporated in the VSP method can be used to determine the porosity and permeability of marine sediments.