9614357 Kerr This research involves the development of models for estimating the effects of material variations on the mechanics of earthquake faulting. The objective is to identify characteristics of surface deformations for distinguishing between homogeneous and nonuniform models in order to understand deformation sources at depth in areas where field observations indicate spatial variations in material properties. 3-D analytical and numerical techniques will be developed for calculating elastic fields in nonuniform material to investigate how subsurface variations in elastic moduli influence fault mechanics. Use of these models in simulations of fault behavior will provide more realistic calculations of the slip induced elastic fields, such as the change of the stress state that a slip zone imposes on itself and nearby faults. This research is a component of the National Earthquake Hazard Reduction Program. ***