| Abstract |
Seismic activity in the West Bohemia/Vogtland area expresses itself in the form fast event sequences with majority of earthquake swarm-type character. Thousands of events are recorded during each sequence whose efficient processing requires automation of the procedure. Recently processing of the WEBNET data has been automated using the PEPiN picker and locator, which provides P and S-wave arrival time picks and preliminary location and magnitude determination; the automatic picks are then approved by human interpretor in routine processing. The error of automatic picks ranges within few first samples, which is expressed also in the rather low location residual with median of about 0.05 s. In order to avoid the necessity of manual inspection we further enhance the accuracy of the automatically measured arrival times by measuring delay times within pairs of events using the waveform cross-correlations method. We cross-correlate the P and S-wave time windows that are derived from the automatic arrival time picks. The resulting delay times are, along with the automatic catalog picks, used as an input for hypoDD relocation software package. To limit the computation time we crosscorrelate only waveforms of the event pairs with similar locations, which is accomplished by clustering the events using the ph2dt code. |