Assessing Location Capability With Ground Truth Events: The Dead Sea and South Africa Regions

摘要

We are combining locally derived ground truth (GT) information with analyses of regionally recorded waveform data to derive path corrections to global network stations for earthquakes and explosions in the Dead Sea and South Africa regions. Our strategy is to determine locations that are quality GT5 or better for events using 'local' information, and then to treat these locations as known, fixed hypocenters in a regional joint hypocenter determination (JHD) inversion for the path corrections. We are using arrival time picks from all available waveform data from global network stations in the inversion for path corrections. For the Dead Sea region, we are using data from 53 earthquakes and the 3 Dead Sea calibration explosions to derive local 1-D velocity models and station corrections for about 70 seismic network stations within Israel and Jordan, using JHD. The explosions are treated as sources with known (fixed) location and origin time in the JHD inversion. The resulting locations for the earthquakes are constrained quite well, with estimated 95% confidence regions ranging from 1 to 3 km in both epicenter and depth. Thus, we feel confident in treating these earthquakes as GT5 events. The next step is to use a smaller group of events with data available at regional and teleseismic distances as 'master events' with fixed locations in a regional JHD solution for path corrections to global network stations. We also investigate the use of 'surrogate' stations to interpolate path corrections at IMS stations without observations. For South Africa, we have obtained ground-truth information on mining-induced earthquakes from the seismology investigators (T. Jordan and D. James) who operated the PASSCAL South African craton broadband experiment. We identified 14 events having regional and teleseismic waveforms that could be used for location calibration purposes, and we were provided with locations (including depths) determined from mine records for these events. As in the.