GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.1 87 pressoché totale. Una riflessione su questo aspetto diventa necessaria se portata sul piano della comparazione tra terremoti recenti e storici, inevitabilmente basata su dati macrosismici, e sulle implicazioni relative alla parametrizzazione degli eventi soprattutto in termini di magnitudo. Bibliografia Azzaro R., Stucchi M.; 2000. The evaluation of the effects of earthquake sequences in the light of the EM-98 intensity scale . In: Papers and memoranda from the first workshop of the ESC working group “Historical seismology”, V. Castelli and G. Monachesi (Eds.), (1-5 September 1999, Macerata, Italy), 48-53. Azzaro R., Tertulliani A., Bernardini F., Camassi R., Del Mese S., Ercolani E., Graziani L., Locati M., Maramai A., Pessina V., Rossi A., RovidaA., Albini P., Arcoraci L., Berardi M., Bignami C., Brizuela B., Castellano C., Castelli V., D’amico S., D’amico V., Fodarella A., Leschiutta I., Piscini A., Sbarra M.; 2016. The 24 August Amatrice 2016 earthquake: macroseismic survey in the damage area and EMS intensity assessment . Ann. Geophys., 59, 8, doi: 10.4401/ag-7203 Grunthal G., (Ed.); 1998. European Macroseismic Scale 1998 (EMS-98). European Seismological Commission, Subcommission on Engineering Seismology, Working Group Macroseismic Scales. Conseil de l’Europe, Cahiers du Centre Européen de Géodynamique et de Séismologie, 15, Luxembourg, 99 pp. Gruppo di Lavoro INGV sul terremoto di Amatrice (2016). Secondo rapporto di sintesi sul Terremoto di Amatrice Ml 6.0 del 24 Agosto 2016 (Italia Centrale) , Internal Report INGV, doi: 10.5281/zenodo.154400 Rovida A., Locati M., Camassi R., Lolli B., Gasperini P. (eds); 2016. CPTI15, the 2015 version of the Parametric Catalogue of Italian Earthquakes . Istituto Nazionale di Geofisica e Vulcanologia. doi :http://doi.org/10.6092/ INGV.IT -CPTI15. Longer aftershocks duration in extensional tectonic settings E. Valerio 1,* , P. Tizzani 2 , E. Carminati 1 , C. Doglioni 1,3 1 Department of Earth Sciences, Sapienza University of Rome, Italy 2 National Research Council (CNR), Istituto per il Rilevamento Elettromagnetico dell’Ambiente (IREA), Napoli, Italy 3 National Institute of Geophysics and Volcanology (INGV), Roma, Italy Every day, moderate to large magnitude earthquakes release seismic energy stored within the Earth’s crust. This energy is accumulated for tens or thousands of years, during the interseismic phase, and released instantaneously (i.e., seconds) through an earthquake (i.e., the mainshock) during the co-seismic phase (e.g., Kanamori and Bordsky, 2004). After the mainshock, the energy release continues (for months to years) during the post-seismic phase with aftershocks generally characterized by magnitudes smaller than the mainshock. Few studies were dedicated to the control of tectonic setting on the duration of aftershock sequences, although a better understanding of aftershocks decay with time is fundamental to better constrain seismic hazard during ongoing seismic sequences by predicting their duration. Typically, seismological observations indicate that, within a seismic sequence, the aftershocks decay in time follows the Omori-Utsu law (e.g., Omori, 1894; Utsu, 1961) and depends on several parameters peculiar of each seismogenic region, such as the tectonic setting (i.e., extensional, strike-slip, contractional regimes), stress changes along fault, structural heterogeneities, crustal rheology. However, the geological and seismotectonic parameters that control the aftershocks decay during seismic sequences are still unclear (e.g., Utsu and Ogata, 1995). In this work, we focus on the tectonic setting control on the aftershocks decay within seismic sequences. In particular, using data from international catalogues and proposing and comparing two different methods, we analysed the aftershocks sequences following five extensional settings earthquakes and five contractional settings earthquakes. In particular, we show that within extensional tectonic settings the average duration of aftershock sequences is longer and the number of events is larger than in contractional tectonic settings. We propose an interpretation of these different behaviours in terms of different type of energy involved during earthquake nucleation processes.