Classical Description of Earthquake Sources

Abstract

It is widely accepted that a shallow earthquake is shear faulting on a finite fault on which the rupture spreads with a finite velocity. Mathematically, an earthquake source is represented by a displacement discontinuity vector $\vec D$ across the fault plane Σ. For a shear fault $\vec D$ is perpendicular to the normal vector $\vec n$ of the fault plane. The orientation of $\vec D$ is specified in seismology by fault strike ø, dip angle δ and slip angle (rake) λ. Figure 1–1 schematically illustrates the definition of these earthquake fault parameters.