Coseismic Deformation Field and Source Modelling for the August 24, 2016 Amatrice Event from the Inversion of InSAR and GPS Data

On August 24, 2016 a Mw 6.0 earthquake struck the Central Apennines, between the towns of Norcia and Amatrice. The epicentre was located near the village of Accumoli. Twenty hours later the first SAR interferogram was obtained from ALOS-2 data and clearly showed the co-seismic deformation field. In the following days, the InSAR analysis benefited from further data, also from Sentinel-1A and B, and COSMO-SkyMed. All displacement maps showed very similar patterns, with maximum displacement values of 20 cm away from the satellites. We will present the co-seismic deformation measurements and the source model obtained by inverting InSAR and GPS data ( 100 continuous and survey-mode GPS measurements). According to the two-lobe pattern, we modeled the data with two independent fault segments, coming up with very similar geometries and mechanisms. This suggests that the rupture occurred on a single structure, oriented NNW-SSE, dipping W at 45°-55°, extending about 18 km between the towns of Norcia and Amatrice. The slip distribution shows a 1.4 maximum in the north, at 5 km depth, and another large slip concentration ( 1m) in the south at 3 km depth, with an overall "geodetic" magnitude 6.2. We also computed the Coulomb Failure Function (CFF) on six nearby faults, obtained from the DISS Working Group, 2010, database. An increase of the CFF is only visible on two fault planes aligned with the Amatrice fault. These results were repeatedly updated during the emergency, as the new data became available. The information was then summarized in synthetic reports and disseminated to the Italian Civil Protection to support the decision making process. This result was obtained thanks to the free and fast data access procedures made available by initiatives as the CEOS Seismic Pilot, the ALOS 2 scientific AO, the EU Copernicus program.