GNGTS 2016 - Atti del 35° Convegno Nazionale

348 GNGTS 2016 S essione 2.2 Seismic microzonation of the Accumoli municipality (Rieti, Italy) after the August 24th earthquake: preliminary considerations C. Comina 1 , M. Della Seta 2 , C. Esposito 2 , L. Falconi 3 , S. Foti 4 , L. M. Giannini 2 , S. Hailemikael 3 , L. Lenti 5 , G. Martini 3 , S. Martino 2 , A. Paciello 3 , F. Passeri 4 , M. Proposito 3 , C. Puglisi 3 , S. Rivellino 2 , R.W. Romeo 6 , L. Sambuelli 4 , G. Scarascia Mugnozza 2 , L. V. Socco 4 , F. Troiani 2 , C. Varone 2 , V. Verrubbi 3 1 Dipartimento di Scienze della Terra, Università degli Studi di Torino, Italy 2 Dpt. Earth Sciences and Research Center for the Geological Risks (CERI) of the University «Sapienza», Rome, Italy 3 Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), R.C. Rome-Casaccia and Frascati, Italy 4 Politecnico di Torino, Italy 5 Université Paris-Est LCPC/Institut Français des Sciences et Technologies des Transports, de l’Aménagement et des Réseaux (IFSTTAR)/ Departement GERS, Champs sur Marne, France 6 Department of Earth Sciences, Life and Environment, University “Carlo Bo”, Urbino, Italy OnAugust 24, 2016, at 01:36 UTC a M L =6.0 earthquake struck central Italy with its epicenter between the villages of Accumoli and Amatrice and a hypocentral depth less than 10 km. The mainshock was characterized by a macroseismic field with a maximum felt intensity higher than VIII MCS and a maximum recorded PGAof 0.433 g (Amatrice station E-Wcomponent; ReLuis- INGV Workgroup 2016). The source fault failure generated a seismic sequence characterized by thousands of aftershocks. ��� ����������� ��������� ����������� �� � ����� ������� ����� �� The seismogenic structure corresponds to a fault segment which is part of the Mt. Gorzano extensional fault system. The latter is NNW-SSE oriented and extends for about 25 km between the towns of Norcia and Amatrice. The estimated width is about 11 km and the depth is about 11 km (INGV ���������� ������ ����� ��� ��������� �� ��� Workgroup, 2016). Since the beginning of the seismic sequence, the INGV National Seismic Network recorded and localized more than 5000 earthquakes within the above mentioned areas: 158 earthquakes characterized by magnitude in the range 3.0 – 4.0; 15 events in the range 4.0 – 5.0; 1 event characterized by a magnitude > 5.0 (Mw 5.3 on August 24 at 02:33 UTC close to Norcia town; EMERGEO Workgroup, 2016). Furthermore, since the first hours after the mainshock, the Research Centre for the Geological Risks (CERI) of the Sapienza University of Rome operated in the field to update the Italian Catalogue of Earthquake-Induced Ground Failures (CEDIT). Such a catalogue stores data about ground effects induced by earthquakes with an epicentral intensity of at least 8 on the MCS scale, which occurred from 1000 AD (Martino et al. , this volume). TheNationalCivil ProtectionDepartment (DPC) asked toallUniversities andResearch Institutes involved in the Center for Seismic Microzonation and its applications (CentroMS) to perform Seismic Microzonation studies in municipalities �������� �� � ������������ ��������� � � ���� affected by a macroseismic intensity ≥ 7 MCS. In detail, the Department of Earth Sciences of Rome University “Sapienza”, ENEA, Polytechnic University of Turin and Department of Earth Sciences, Life and Environment, University of Urbino formed a Working-Group focusing on the Seismic Microzonation study in the municipality of Accumoli. The main goal requested by DPC was the in-depth analysis and improvement of available Level 1 of Seismic Microzonation as to identify possible stratigraphic or topographic 1D- 2D amplification effects and areas prone to landslides or debris coverage instabilities. Afterwards, Level 3 of Seismic Microzonation in Accumoli and selected hamlets will be performed as to plan the post-emergency reconstruction of the sites destroyed by the earthquake. We here present the preliminary results about the Accumoli municipality, which is located in central Apennines and in particular in the northern portion of a NW-SE oriented extensional basin structure; it is bounded by the Laga Mts. to the E and by the Sibillini Mts. to the W. The eastern portion of this area is characterized by the outcrop of a succession of calcareous, marly- calcareous, to marly units (Upper Trias - Miocene p.p.), while in the central and western sectors Miocene siliciclastic turbiditic deposits (Messinian in age) widely crop out (Pierantoni et al. , 2013). The Miocene turbitidic terrains belong to the basal arenaceous, arenaceous-pelitic and pelitic-arenaceous members of the “Monti Della Laga Formation” (Cacciuni et al. , 1995). The area of Accumuli lies in the upstream portion of the Tronto River basin, whose trunk-valley here