The Italian Seismic Bulletin: strategies, revised pickings and locations of the central Italy seismic sequence

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Alessandro Marchetti
Maria Grazia Ciaccio
Anna Nardi
Andrea Bono
Francesco Mariano Mele
Lucia Margheriti
Antonio Rossi
Patrizia Battelli
Cinzia Melorio
Barbara Castello
Valentino Lauciani
Michele Berardi
Corrado Castellano
Luca Arcoraci
Giulio Lozzi
Alexia Battelli
Corrado Thermes
Nicola Pagliuca
Giorgio Modica
Arianna Lisi
Luca Pizzino
Paola Baccheschi
Stefano Pintore
Matteo Quintiliani
Alfonso Mandiello
Carlo Marcocci
Massimo Fares
Daniele Cheloni
Alberto Frepoli
Diana Latorre
Anna Maria Lombardi
Milena Moretti
Marina Pastori
Massimiliano Vallocchia
Aladino Govoni
Laura Scognamiglio
Alberto Basili
Alberto Michelini
Salvatore Mazza


The central Italy seismic sequence, started with the Mw = 6.0 Amatrice earthquake on August 24th 2016, is the first significant one after the Italian Seismic Bulletin (BSI) changed its analysis strategies in 2015. These new strategies consist on the release of the BSI every four months, the review of the events with ML ≥ 1.5 and the priority on the review of events with ML ≥ 3.5. Furthermore, in the last year we improved the bulletin tools and made possible the analysis of all the stations whose data are stored in the European Integrated Data Archive (EIDA). The new procedures and software utilities allowed, during the first month of 2016 emergency, to integrate, in the Bulletin, the temporary stations installed by the emergency group SISMIKO, both in real–time transmission and in stand-alone recording. In the early days of the sequence many of the BSI analysts were engaged in the monitoring room shifts, nevertheless at the end of August all events occurred in those days with ML ≥ 4 were analyzed; the largest event recovered and localized is a ML = 4.5 event immediately following the main shock. In September 2016, 83 events with ML ≥ 3.5 were analyzed and re-checked, the number of pickings greatly improved. The focal mechanism of the main shock was evaluated using first motion polarities, and compared with the available Time Domain Moment Tensors and Regional Centroid Moment Tensor. The first eight hours of the day on August 24th, the most critical for the INGV surveillance room, were carefully analyzed: the number of located events increased from 133 to 408. The magnitude of completeness, after the analysis of the BSI, has dropped significantly from about 3.5 to 2.7. The mainshock focal mechanism and the relative locations of the first 8 hours’ aftershocks give clues on the initial fault activation. The seismic sequence in November 2016 is still ongoing; it included a mainshock of Mw = 6.5 on October 30th and 3 events of magnitude greater than 5.0 one on August 24th and two on October 26th.

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Marchetti, A., Ciaccio, M. G., Nardi, A., Bono, A., Mele, F. M., Margheriti, L., Rossi, A., Battelli, P., Melorio, C., Castello, B., Lauciani, V., Berardi, M., Castellano, C., Arcoraci, L., Lozzi, G., Battelli, A., Thermes, C., Pagliuca, N., Modica, G., Lisi, A., Pizzino, L., Baccheschi, P., Pintore, S., Quintiliani, M., Mandiello, A., Marcocci, C., Fares, M., Cheloni, D., Frepoli, A., Latorre, D., Lombardi, A. M., Moretti, M., Pastori, M., Vallocchia, M., Govoni, A., Scognamiglio, L., Basili, A., Michelini, A. and Mazza, S. (2016) “The Italian Seismic Bulletin: strategies, revised pickings and locations of the central Italy seismic sequence”, Annals of Geophysics, 59. doi: 10.4401/ag-7169.

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