GNGTS 2018 - 37° Convegno Nazionale

98 GNGTS 2018 S essione 1.1 Ferrari G., Guidoboni E., Mariotti D., Comastri A., Tarabusi G., Sgattoni G., Valensise G.; 2018: Il numero delle vittime dei forti terremoti storici in Italia: oltre 30 anni di ricerche sintetizzati nel CFTI5Med , in questo volume. Guidoboni E., Ferrari G., Mariotti D., Comastri A., Tarabusi G., Sgattoni G., Valensise G.; 2018: CFTI5Med, Catalogo dei Forti Terremoti in Italia (461 a.C.-1997) e nell’area Mediterranea (760 a.C.-1500). Istituto Nazionale di Geofisica e Vulcanologia (INGV). http://storing.ingv.it/cfti/cfti5/ Rovida A., Locati M., Antonucci A., Camassi R. (a cura di). Archivio Storico Macrosismico Italiano (ASMI). Istituto Nazionale di Geofisica e Vulcanologia. https://emidius.mi.ingv.it/ASMI/ 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 Sgattoni G., Tarabusi G., Ferrari G., Guidoboni E., Mariotti D., Comastri A., Ciuccarelli C., Bianchi M. G., Valensise G., 2018: Il futuro del Catalogo dei Forti Terremoti in Italia: dal nuovo portale CFTILab verso il CFTI6Med , in questo volume. DETECTING CRUSTAL VELOCITY CHANGES DURING THE 2016-2017 CENTRAL ITALY SEISMIC SEQUENCE WITH AMBIENT NOISE MONITORING G. Soldati 1 , L. Zaccarelli 2 , L. Faenza 3 1 Istituto Nazionale di Geofisica e Vulcanologia, sezione di Roma1, Roma, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, sezione di Bologna, Bologna, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia, sezione ONT, Roma, Italy The 2016-2017 Central Italy seismic sequence. Starting from August 2016, Central Italy has been hit by a sequence of earthquakes that activates a 80-km normal-fault system. The sequence has been characterized by three main phases: the August 24, Mw6 mainshock, with epicenter close to Amatrice town, located in the middle part of the region interested by the whole sequence; the October 26 Mw 5.9 and October 30 Mw 6.5 earthquakes, between the towns of Norcia and Visso, about 15 km north of the first event, and finally the four earthquakes with 5.0 ≤ Ml ≤ 5.5 which occurred in the southernmost segment of the activated area on January 18, 2017. The mainshocks showed NW-SE striking normal faults, lateral extension of 15-20 km, and confined within the upper 10-12 km of the crust (Marchetti et al. , 2017; Michele et al. , 2016). This sequence fills the gap on the Apenninic chain between the 1997 Colfiorito and the 2009 L’Aquila earthquakes. The whole set of high-angle normal faults is bounded below by a gently east dipping 2–3 km thick layer in which small events plus a series of larger extensional aftershocks (~ Mw 4) occurred, as seen in Chiaraluce at el. (2017) that analyzed the spatio- temporal evolution of seismicity from January 1 to November 29, 2016 for a total of nearly 26,000 earthquakes. From the analysis of the spatio-temporal distribution of the earthquake occurred in the area during the year before the beginning of the sequence, it is not possible to identify any conventional foreshock activity on the main fault plane (Michele et al. , 2016 and Marzorati et al. , 2016). Soon after the first event on August 24, the aftershock activity started covering a 30-km long sector. This first mainshock occurred closed to the village of Accumuli, while the largest aftershock with Mw 5.4, occurred only one hour later, and was located further north, close to the city of Norcia. For at least 10 days the sequence was very active with a series of earthquakes with magnitude larger than 4.0, causing devastation in the village of Amatrice (Chiaraluce at al. , 2017). The second part of the sequence started on October 26 with two large events (Mw 5.4 and 5.9) nearby Ussita and Visso, and the activation of another 20-km long segment in the northwest