9416318 Unruh This study will analyze the aftershocks of the January 17, 1994 Northridge earthquake to obtain distributed seismogenic deformation and t test existing models of uplift and folding above blind thrust faults. Detailed studies of recent blind thrust earthquakes have shown that significant deformation of the hangingwall of the fault occurs by slip on small faults at a high angle to bedding, and not just by bedding-plane slip as the models imply. Another possible reason for departure from the standard model is that the thrusts beneath the Los Angeles and San Fernando Valleys are rooted in crystalline basement rocks, rather than in sedimentary rocks for which the model was originally developed. The analysis will use patterns of seismic P and T axes to obtain seismogenic strain rates and the rotational component (vorticity), which will then be compared with the model prediction. The results will enhance understanding of deformation associated with blind thrusts, and will be therefore test the ability of the existing models to predict behavior of the crust during blind thrust earthquakes.
