Regional and far-regional earthquake locations and source parameters usingsparse broadband networks: A test on the ridgecrest sequence

Events of the 1995 Ridgecrest, California, earthquake sequence were located and source parameters were estimated using data recorded by the broadband, high-dynamic-range instrumentation of the Berkeley Digital Seismic Network (BDSN). The purpose of this study is to investigate the capability of a sp arse broadband network at monitoring a region located outside of the networ k, as will be the case in the monitoring of the Comprehensive Test Ban Trea ty (CTBT) for low-magnitude seismic events. In addition, we present a case study that is representative of the capabilities of other regional broadban d networks. To assess the capability of a sparse network, we compared locat ions estimated from BDSN phase measurements to a "ground truth" catalog of high-quality earthquake locations derived from data recorded by the Souther n California Seismic Network (SCSN). An adaptive grid search location progr am that utilizes the timing and azimuth of multiple-phase picks from one or more stations was used to determine the importance of the different types of data on absolute event locations. Sparse subnets of BDSN stations in the distance ranges from 250 to 500 km and 500 to 800 km were used. The result s indicate that in the regional distance range, it is possible to obtain ab solute event locations to within 18 km as is prescribed by the CTBT; howeve r, in the far-regional distance range, the lower signal-to-noise levels pre cluded the location of the events to within the CTBT objective.