Single-station location of seismic events: a review and a plea for more research

Traveltime-based location methods are ineffective for locating regional sei smic events which are recorded by few stations; however, the Comprehensive Test Ban Treaty (CTBT) makes it imperative that we monitor sparsely observe d events. This paper reviews the current status of single-station location (SSL) methods-the location of seismic events using records from one three-c omponent broadband digital station. We argue here that SSL methods may ulti mately provide the most effective and economical means for monitoring small -magnitude (M similar to 3) seismic events over most of the earth. Potentia lly, station-event distance and focal depth may be determined accurately by utilizing broadband three-component data and matching observed and synthet ic waveforms; station-event azimuth is determinable from the polarization o f the P-wave arrival and P coda. However, more research is required before SSL methods become a practical alternative to traveltime-based methods. Cur rently, the most significant problem is that regional seismograms are stron gly dependent on regional crustal structure. Thus, future research efforts should focus both on determining appropriate crustal models in specific reg ions, and also on improved methods for dealing with regional variations in crustal structure. A second important problem concerns location errors; wit h SSL they may involve 180 degrees errors in station-event azimuth or other highly non-Gaussian 'blunders'. (C) 1999 Elsevier Science B.V. All rights reserved.