Simulation of three-component seismic motions at seafloor using onshore earthquake recordings

Abstract

This paper proposes a simulation method of three-component seafloor seismic motions using onshore earthquake recordings. Firstly, a pair of onshore and seafloor motions recorded during one earthquake is selected; the onshore recordings are employed as the predefined motions in the simulation of seafloor motions. The ground motion transfer functions of the sites beneath the onshore and seafloor stations are calculated based on the one-dimensional wave propagation theory. The base rock power spectral density function is estimated by dividing the PSD functions of the onshore motion with the onshore site transfer functions. The seismic motions at seafloor site are simulated using the base rock PSD functions and the offshore site transfer functions, which takes the influence of seawater layer and water saturation into consideration. The recorded seafloor motion is used to validate the characteristics of the simulated seafloor motions. Comparison results show that the vertical-to-horizontal spectral ratios of the simulated seafloor motions are compatible with those of the actual seafloor records.