Best practice in earthquake location using broadband three-component seismic waveform data

We present an earthquake location algorithm, the Broadband Waveform Regiona l Earthquake Location Program (BW_RELP), which utilizes phase onset times a nd wave azimuths recorded by three-component broadband seismic stations and an adaptive migrating grid search algorithm to find the global minimum in an arbitrary normed misfit parameter. The performance of BW_RELP is demonst rated using regional (300-800 km distant) broadband recordings to locate ev ents in the 1995 Ridgecrest, California earthquake sequence. The purpose of this study is to introduce the BW_RELP algorithm in detail and to expand o n the previous paper by Dreger et al. (BSSA, 88, 1353-1362, 1998), using on e Berkeley Digital Seismic Network (EDSN) station (YBH) and two USNSN stati ons (ELK and MNV) which span 300-800 km in distance and 55 degrees in azimu th, to further investigate the capability of a sparse broadband network of three-component stations at monitoring a region located outside of the netw ork, as will be the case in the monitoring of the Comprehensive Test-Ban-Tr eaty (CTBT) for low magnitude seismic events. We assess the capability of t his sparse three-station broadband network and we compare locations estimat ed from phase onse: time and wave azimuth measurements to a ground-truth ca talog of high-quality earthquake locations derived from data recorded by th e Southern California Seismic Network (SCSN). The results indicate that in the regional distance range it is possible, when an appropriate calibration event is available, to obtain absolute event locations to within 18 km as is prescribed by the CTBT.