Far-Field Compressible Ocean Response From Two Opposite Moving Rectangular Seafloor Blocks

Abstract

Acoustic-gravity wave (AGW) and ocean surface wave profiles produced by the simultaneous movement of two adjacent rectangular seafloor blocks of unequal size in opposite directions, imitating a two-fault submarine earthquake, have been analytically studied using linearized water wave theory. Utilizing the Fourier transformation method coupled with the stationary phase approximation, the far-field solutions of the generating surface wave and AGW profiles are deduced. The model is validated with the existing literature. Different expressions of far-field profiles induced by asymmetry of the moving blocks are emphasized. The surface amplitudes and pressure impressions of our two-fault system are found to be higher than those of an equivalent single rectangular moving block. The spectral energy densities (gravitational potential, kinetic, and elastic) are derived and computed. While gravitational potential energy density typically dominates for pure gravity waves, it remains negligible for AGWs, where the kinetic and elastic energies are nearly equally partitioned, reflecting a fundamental energy balance inherent to compressible fluid dynamics. The derived solutions for the potential function generalize the earlier model of a single moving block and provide insight into the wave dynamics generated by more complex multifault seafloor displacements, where the present solution would be crucial for applying the superposition of wave profiles.