Primo rapporto di sintesi sul terremoto di amatrice ml 6.0 del 24 agosto 2016 (italia centrale)

Abstract

Abstract On August 24, 2016, at 03:36 (local time) a ML 6.0 earthquake (Mw 6.0) struck an extensive portion of the Central Apennines between the towns of Norcia and Amatrice. The epicenter was located near the town of Accumoli. The area was struck by several earthquakes in historical times (1627, 1639, 1672, 1703; http://emidius.mi.ingv.it/CPTI15-DBMI15/). The preliminary observations (seismological, geodetic and geological) collected in the area affected by the Amatrice earthquake sequence and the available scientific knowledge of the area allow to elaborate a first interpretative framework of the ongoing seismic sequence. The seismogenic structure is oriented NNW-SSE and extends about 25-30 km between the towns of Norcia and Amatrice with a width of about 10-12 km and a depth of 10-12 km. This seismogenic volume is characterized by a complex tectonic setting. The August 24, 2016 (ML 6.0) main shock likely ruptured a SW dipping, NNW-SSE trending fault segment. The coseismic rupture started near the town of Accumoli and appears to have spread bilaterally towards Amatrice to S-SE and toward Norcia to N-NW. Preliminary fault slip inversion suggests two patches of co-seismic deformation located NW and SE of the hypocenter. It is still unclear whether there is fault continuity between the two patches that generated the ML 6.0 main shock, namely whether rupture occurred on a single fault segment, or on two different segments separated by the Olevano-Antrodoco structural discontinuity. The seismicity of the seismic volume in the NW sector (i.e., between Accumoli and Norcia) is dispersed suggesting the activation of different fault segments after the main shock of August 24. In particular, the trend of the replicas shows the activation of the Monte Vector fault segment and of different structures antithetical dipping towards NE.