Radiation from a strike-slip fault

Abstract

Huygens' principle for elastodynamics has been applied to the problem of the radiation resulting from the introduction of a tear fault of finite length into an otherwise homogeneous medium. The fault has the following properties: (1) it is a surface across which the normal stresses vanish; (2) it has a rectangular shape with one dimension increasing at a constant rate in the direction of faulting; (3) the times of initiation and termination of the fault are both finite. The relative displacement on opposite sides of the fault is prescribed to be a step function of time. This configuration may be imaged in the earth's surface by symmetry, so that the problem is reducible to that of a propagating strike-slip fault of finite length in an infinite elastic medium. The observed events are the P and S waves from the two ends of the fault. Simplified “first motion” responses are computed and compared with solutions derived from the usual theory of force couples.