# Earthquakes

Chapter
Part of the Springer Geophysics book series (SPRINGERGEOPHYS)

## Abstract

Describing earthquake fault motion is indispensable to understanding the mechanism of tsunami generation. Moreover, seismic waves, excited by the fault motion, are analyzed in order to estimate the magnitude and location of earthquakes. The information is used to perform rapid tsunami calculations and predictions. At the same time, we should note that seismic waves sometimes function as noise among tsunami signals. This chapter introduces earthquake seismology, which is closely related to tsunami phenomena, and illustrates a practical method of seismic wave simulation. Section 4.1 explains a mathematical representation of an earthquake fault as a point source in order to quantitatively describe the relation between the fault motion and seismic waves. Section 4.2 explains an empirical scaling law representing the fault size from small to large earthquakes. We also introduce the idea of earthquake stress change (stress drop) as a mechanism behind the scaling law. Section 4.3 illustrates the finite difference method as a practical method of seismic wave simulation. By using this numerical method, we investigate seismic waves, ocean acoustic waves, and the permanent displacement caused by an earthquake. The simulation results can be used in the simulation of tsunami propagation.

## Keywords

Shear dislocation Moment tensor Equivalent body force Scaling law Finite difference method

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