Abstract

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 sparse broadband network at monitoring a region located outside of the network, as will be the case in the monitoring of the Comprehensive Test Ban Treaty (CTBT) for low-magnitude seismic events. In addition, we present a case study that is representative of the capabilities of other regional broadband networks. To assess the capability of a sparse network, we compared locations estimated from BDSN phase measurements to a “ground truth” catalog of high-quality earthquake locations derived from data recorded by the Southern California Seismic Network (SCSN). An adaptive grid search location program 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 results indicate that in the regional distance range, it is possible to obtain absolute event locations to within 18 km as is prescribed by the CTBT; however, in the far-regional distance range, the lower signal-to-noise levels precluded the location of the events to within the CTBT objective.

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