This research is to develop and test methods for resolving the fault plane ambiguity problem, that is, the inability of fault plane solutions from first motions of an earthquake to resolve which of two orthogonal planes was the actual fault surface. The research will be done using locally recorded, broad-band, high dynamic range digital seismograms from the Anza, California, digital seismic array for the Cahuilla earthquake swarm. The broad-band seismic energy of the complete body waves should have some directivity information as a result of the finite source size. Data from portable seismic systems that recorded earthquake swarms between the Elsinore and San Jacinto fault zones will also be analyzed. This research is a component of the National Earthquake Hazard Reduction Program.
