Motion on the Surface of a Layered Elastic Half Space Produced by a Buried Dislocation Pulse

In this work solutions are developed for the motions generated in an elastic half space or a half space with a softer layer above it by propagating dislocations on an inclined fault plane. Both dip-slip and strike-slip relative motions have been considered. The dislocations are two-dimensional motions originating in the lower layer. The area over which dislocations are present spreads from a line source as the front of the dislocation propagates on the fault plane. The propagating fault can be stopped suddenly on both sides or on just one side. Surface motions are computed using an extension of the Smirnov-Sobolev method for self-similar solutions. The extension is needed to take care of non-parallel boundaries arising from the inclination of the fault plane to the horizontal. The effect of layering is shown to be extremely important in providing motions at the surface which have the type of II rebound ll that is noted in displacements inferred from strong-motion records of earthquakes. The motions obtained for a single spreading dislocation which suddenly starts and stops is compared with the displacement found from the Pacoima Dam records in the 1971 San Fernando earthquake. The general shape of the motion is seen to . correspond well to the results for a single pulse in a layered solid, whereas the case of no layering cannot produce a similar motion.Office of Naval Research. Department of the Navy: Contract No. N00014-75-C-0164National Science Foundation Contract GK 2429