Dispersion in oceanic crust during earthquake preparation

Dispersion of Stoneley waves is studied in a sedimentary layer of ocean bottom resting over basaltic solid half space[ Sedimentary layer is assumed a transversely isotropic poroelastic medium[ Lower!most solid half!space is assumed to be embedded with vertically aligned saturated micro!cracks and behaves transversely isotropic to wave propagation[ Frequency equation is obtained in the form of determinantal equation[ Role of phase angle is eliminated by expressing slowness of waves in terms of phase velocity and elastic constants[ Numerical solutions for phase velocity and group velocity are obtained for a particular model[ Calculations are made for di}erent depths of ocean and sediments[ E}ect of thickness and density of cracks on these velocities are observed[ Special cases are discussed which represent the absence of ocean and sediments\ in the model considered[ Changes in dispersion are discussed during the stress accumulation in an earthquake preparation region