GNGTS 2017 - 36° Convegno Nazionale

22 GNGTS 2017 S essione 1.1 Coseismic slip of the 2016-2017 Central Italy earthquake sequence from InSAR and GPS data D. Cheloni 1 , D. Cheloni 1 , V. De Novellis 2 , M. Albano 1 , A. Antonioli 1 , M. Anzidei 1 , S. Atzori 1 , A. Avallone 1 , C. Bignami 1 , M. Bonano 2 , S. Calcaterra 3 , R. Castaldo 2 , F. Casu 2 , G. Cecere 1 , C. De Luca 2 , R. Devoti 1 , D. Di Bucci 4 , A. Esposito 1 , A. Galvani 1 , P. Gambino 3 , R. Giuliani 4 , R. Lanari 2 , M. Manunta 2 , M. Manzo 2 , M. Mattone 4 , A. Montuori 1 , A. Pepe 2 , S. Pepe 2 , G. Pezzo 1 , G. Pietrantonio 1 , M. Polcari 1 , F. Riguzzi 1 , S. Salvi 1 , V. Sepe 1 , E. Serpelloni 1 , G. Solaro 2 , S. Stramondo 1 , P. Tizzani 2 , C. Tolomei 1 , E. Trasatti 1 , E. Valerio 5 , I. Zinno 2 , C. Doglioni 1,5 1 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy 2 Istituto per il Rilevamento Elettromagnetico dell’Ambiente-Consiglio Nazionale delle Ricerche, Naples, Italy 3 Istituto Superiore per la Protezione e la Ricerca Ambientale, Rome, Italy 4 Dipartimento della Protezione Civile, Rome, Italy 5 Università degli Studi di Roma “La Sapienza”, Rome, Italy The 2016-2017 central Italy earthquake sequence represent the largest Italian seismic sequence affecting an extensional domain which has been densely observed with modern geodetic and seismological measurements. The seismic sequence started on 24th August 2016 with a Mw 6.1 event that struck the central Apennines between the towns of Amatrice and Norcia, causing extensive damage to the town of Amatrice and several surroundings, and causing about 300 casualties. The main shock was followed by a vigorous aftershock sequence southeast and northwest of the hypocentre, which decreased in frequency and magnitude until the 26th October 2016, when a Mw 5.9 earthquake occurred between Visso and Ussita villages, about 25 km towards NW of the 24th August main shock. After few days, the greatest event of the sequence, an earthquake of magnitude Mw 6.5, nucleated between the previous ruptures below the town of Norcia. Finally, on 18th January 2017 four Mw >5 earthquakes occurred southeast of the previously activated crustal volume, in the Campotosto lake area. Here we use a large dataset of InSAR and GPS measurements to investigate the ground displacements and to infer the fault geometries and the slip distributions of the causative fault segment associated with the greatest events of the 2016-2017 seismic sequence. We used InSAR data acquired by different satellites. In particular, we exploited five interferograms which involve the ALOS-2, the Sentinel-1 and the COSMO-SkyMed sensors to measure the surface displacements relative to the 24th August earthquake, and three interferograms to investigate the ground displacement due to the 26th and 30th October events. As regard the GPS data, the seismic sequence occurred where several continuous and survey-mode GPS networks were operating. In particular, a number of instruments were installed soon after the 24th August earthquake at geodetic benchmarks belonging to the discrete CaGeonet, INGV and IGM networks, and a new INGV permanent station was built at Arquata del Tronto. The ground deformation due to the 24th August event is characterized by two distinct NNW-SSE striking lobes of deformation to the west of the Mt- Gorzano-Mt. Vettore-Mt. Bove alignment, with maximum negative Line-of-Sight (LOS) value of about 20 cm, in agreement with the maximum observed vertical displacement of about 17 cm as depicted by the GPS data. The analysis of the interferograms spanning the October events reveals a subsidence pattern extending for about 35 km along a NNW-SSE direction, with a maximum subsidence of about 90 cm in the Castelluccio area and an uplift of about 15cm in correspondence of Norcia town. Although the GPS measurements related to the October events are limited with respect to the August event, they show a general SW-NE oriented extension across the Mt. Vettore-Mt. Bove fault system, with maximum subsidence of about 25-40 cm and an uplift of about 2-5 cm in the footwall of the main normal fault system. Geodetic data show that the seismic sequence activated four main coseismic asperities belonging to the SW-dipping normal fault system associated with the Mt- Gorzano-Mt. Vettore- Mt. Bove alignment. In particular, the 24th August Mw 6.1 main shock involved two distinct fault segments, the northern part of the Mt. Gorzano fault and the southern part of the Mt.