The shakemaps of the Amatrice, M6, earthquake

Abstract

In this paper we describe the performance of the ShakeMap software package (Wald et al., 1999; Worden and Wald, 2016) obtained from the fully automatic procedure to estimate ground motions, based on manually revised location and magnitude, during the main event of the Amatrice sequence with special emphasis to the M6 main shock, that struck central Italy on the 24th August 2016 at 1:36:32 UTC. Our results show that the ShakeMap procedure we developed in the last years, with real-time data exchange among those institutions acquiring strong motion data, produces a reliable and useful description of the ground motion experienced throughout a large region in and around the epicentral area. The prompt availability of the rupture fault model, within three hours after the earthquake occurrence, provided a better description of the level of strong ground motion throughout the affected area. Progressive addition of station data and manual verification of the data insures improvements in the description of the experienced ground motions. In particular, comparison between the MCS (Mercalli-Cancani-Sieberg) intensity shakemaps and preliminary field macroseismic reports show overall agreement within the limitations imposed by the station geometry. Finally the overall spatial pattern of the ground motion of the main shock is consistent with reported rupture directivity toward NW and reduced levels of ground shaking toward SW probably linked to the peculiar source effects of the earthquake.