9614448 Xie This research is for collaborative research between Columbia and Texas A&M Universities on the failure processes in the New Madrid Seismic Zone (NMSZ) of the Central U.S. through characterization of microearthquake clustering. Earlier analysis is to be extended to clustered events throughout the NMSZ. Most clusters are located near the kink in the central segment, or near the junctions of that segment with other major segments. The spatial/temporal clusters occur over a range of depths of 4 to 9 km, display both strike and reverse slip focal mechanisms, and are located both near and away from the segment junctions and the kink. The goal is to provide the best physical model for the clustering and give additional insight into 1) the relation of the static stress drops of the larger ruptures to focal depths, focal mechanisms, and locations near or away from the junctions, 2) the mode of interactions among major fault segments in the NMSZ, such as triggering of ruptures by seismic or aseismic preslip along intersecting fault segments, and 3) the role of fluid involvement in faulting processes. This research is a component of the National Earthquake Hazard Reduction Program. ***
