Ocean Bottom Hydrodynamic Pressure due to Vertical Seismic Motion

Abstract

Earthquake-induced hydrodynamic pressure on the ocean floor is a key factor in evaluating the surface disturbance and dynamic response of the seabed under the action of a submarine earthquake. An analytical study considering the compressibility of seawater was carried out to obtain the closed-form solution for the hydrodynamic pressure, which depends on water depth, excitation frequency, and seabed characteristics. The commonly used approximate expression for the hydrodynamic pressure, which neglects the compressibility of seawater and is associated with the dynamic displacement of the seabed surface, is presented and compared with the analytical solution. The results reveal that the formulation neglecting the compressibility of overlying seawater could underestimate the hydrodynamic pressure at the ocean bottom and the induced dynamic responses in a poroelastic seabed. Finally, a modified formula for the seismic-induced hydrodynamic pressure at the ocean bottom interface, which is able to consider the compressibility of seawater, is proposed by incorporating the nondimensionalized frequency.