Earthquake Ground Motion Modeling. I: Deterministic Point Source

Abstract

A model for earthquake ground motion is developed using principles of geophysics and stochastics in a sequence of two papers. In the first paper, the earth is idealized as being composed of horizontally stratified layers, with uniform physical properties for each layer. The seismic source is modeled as a concentrated seismic moment located within one of the layers. The partial differential equations for the seismic motion in each layer are solved using a Fourier finite‐Hankel transformation approach, and solutions in terms of state vectors of displacements and forces are converted to wave vectors composed of up‐going and down‐going waves. Transmission and reflection matrices are obtained for each layer, for each layer‐to‐layer interface, and for the free ground‐surface boundary to characterize their roles in transmitting and reflecting a wave motion. The use of these matrices allows the numerical calculation to be channeled in the directions of wave propagation, resulting in better numerical accuracy. An example is included for illustration.