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Titel Implementation of a new picking procedure in the Antelope software
VerfasserIn Lara Tiberi, Giovanni Costa, Daniele Spallarossa
Konferenz EGU General Assembly 2014
Medientyp Artikel
Sprache Englisch
Digitales Dokument PDF
Erschienen In: GRA - Volume 16 (2014)
Datensatznummer 250089420
Publikation (Nr.) Volltext-Dokument vorhandenEGU/EGU2014-3622.pdf
 
Zusammenfassung
Automatic estimates of earthquake parameters continues to be of considerable interest to the seismological community. In this study we present a new automatic procedure for a quasi real-time location of events. This procedure is a combination of the solid and tested Antelope sotfware with a new picking procedure, the AutoPicker (DipTeRiS, University of Genova). Antelope picking procedure consists on: a) Prefiltering into different frequency pass bands; b) Run STA/LTA detectors in one or more channels of the waveform data; c) Associate event locations by searching over one or more spatial grids for a candidate hypocenter that produces theoretical time moveout (P and S) to each station that most closely matches the observations. The main characteristics of the AutoPicker picking algorithm are: a) Pre-filtering and envelope calculation to prearrange the onset; b) Preliminary detection of P onset using the AIC based picker; c) P validation, Signal Variance/Noise Variance analysis sample by sample; d) Preliminary earthquake location; e) Detection of S onset adopting the AIC based picker; f) S/N analysis, S validation; g) Earthquake location. We have applied these two automatic procedures to the Emilia sequence occurred in May-June 2012. In this comparison the distribution of the differences between the manual and the two automatic P-onset are comparable. The average values of P differences are similar, but we have to point out that the AutoPicker procedure gives a st.deviation value lower than the Antelope ones and most important it picks the 16% of phases more than the other algoritm. For S-phases the AutoPicker algorithm picks 178 phases with a mean value of 0.09 sec, instead of the 16s of Antelope with a mean value of 3.75 sec. For more than 90% events the epicentral differences of AutoPicker is less than 5 kms, instead of the Antelope differences which are less than 10 kms. For the depth differences the mean values and the distributions of the two procedures are quite similar, even if Antelope locates only 38 of the 44 events studied, despite of the 43 of the AutoPicker. So AutoPicker finds more and preciser phases than Antelope both P- (16% more) and mainly S-phases(90% more); but Orbassoc process in Antelope, is able to correctly associate the detections and to find the right location. So in this work we illustrate the implementation of the AutoPicker picking procedure in Antelope software. In the final configuration the AutoPicker is used to rilevate the P- and S- phases, and then these P- and S- onset are associated through the use of the Antelope associator and localizator.