This research is to study the Loma Prieta earthquake using strong ground motion stations and aftershock recordings to (a) map the variability of the fault zone structure along the rupture zone of the Loma Prieta earthquake to locate fault irregularities controlling rupture initiation, termination, and complexities; (b) incorporate known broad regional three dimensional structure in the modeling of the complete set of strong ground motion data within 50 km of the epicenter to determine whether effects of known three dimensional structure can explain any of the observed variations in intensity of ground motion; and (c) derive corrections to rupture models based on the assumption of plane layered structure.