Evaluation of Hypocenter Location Techniques with Applications to Southern Utah: Regional Earthquake Distributions and Seismicity of Geothermal Areas

摘要

Three techniques for the computation of earthquake hypocenter locations were compared through empirical results of synthetic test cases utilizing four different computer programs. The three approaches: (1) the single event method, (2) the master event method, and (3) the joint hypocenter determination method, were analyzed with respect to their application to regional (epicenter-to-station distances from 10 to 500 km) and local (epicentral distances from 0 to 70 km) seismic network recording situations. It was found that the joint hypocenter technique can significantly correct for inadequacies in assumed velocity models by simultaneous computation of station adjustments. Earthquakes located using the joint hypocenter technique are located more precisely with respect to each other. The joint epicenter location technique was then applied to relocations of epicenters in southern Utah below 40 exp 0 N latitude with the intent of resolving some spatial relationships of epicenter occurrence on this regional scale. Earthquakes in Utah occur in a diffuse zone 150 km to 200 km wide that coincides with the physiographic boundary of the Colorado Plateau. Swarm activity is prevalent where the zone changes from a north-south to a southwest orientation, but except for a cluster northwest of Cedar City, the only major alignments of epicenters are north-south. (ERA citation 06:016733)