GNGTS 2014 - Atti del 33° Convegno Nazionale

Seismogenetic mechanism in the Tuscany-Umbria Apennines M. Viti 1 , N. Cenni 2 , D. Babbucci 1 , E. Mantovani 1 ,M. Baglione 3 , V. D’Intinosante 3 1 Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente, Università di Siena, Italy 2 Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Italy 3 Ufficio Prevenzione Sismica, Regione Toscana, Firenze, Italy Introduction. The Tuscany-UmbriaApennines host major seismic zones that have generated several strong earthquakes. In this note we discuss the geodynamic/tectonic setting which may be responsible for the generation of the main fault systems and their present activity. The analysis of a huge amount of information in the central Mediterranean area (e.g., Mantovani et al. , 2006, 2009, 2014a; Viti et al. , 2006, 2011) suggests that since the early/ middle Pleistocene the outer part of this belt, stressed by the Adriatic plate, has undergone a belt parallel shortening, mainly accommodated by uplift and lateral extrusion of orogenic wedges at the expense of the Adriatic domain. Such belt sector is constituted by the Molise-Sannio (MS) wedge in the southern Apennines, the eastern sector of the Lazio-Abruzzi carbonate platform (ELA) in the central Apennines, and the Romagna-Marche-Umbria (RMU) and Toscana-Emilia (TE) wedges, in the northern Apennines (Fig. 1). The escaping material only involves the sedimentary cover, decoupled from its crustal basement at seismogenic depth (of the order of 6-10 km) by mechanically weak lithological horizons, such as Late Triassic evaporitic layers (e.g., Finetti et al. , 2005; Mirabella et al. , 2008; Cenni et al. , 2012). Fig. 1 – Post-early Pleistocene tectonic scheme of the eastern sector of the Apennine belt, reported on the Carta Tettonica d’Italia (after Cenni et al ., 2012, modified). The outward escape of the coloured wedges accommodates the belt-parallel shortening of the outer sector of the Apennine chain in the framework of the large scale geodynamics proposed by Mantovani et al., (2009). White arrows indicate the kinematics of Adria and the Apennine wedges. 1,2,3) Main extensional, shear and compressional features. AVT=Alta Valtiberina, Be = Benevento, ELA= Eastern Lazio- Abruzzi platform, Ga=Garfagnana trough, GS= Gran Sasso Arc, Ir=Irpinia, La= Laga units, Lu= Lunigiana trough, MS = Molise-Sannio wedge, Mt=Matese, Mu=Mugello trough, No-Cf-GT-Gu=Norcia-Colfiorito-Gualdo Tadino- Gubbio faults system, OA=Olevano-Antrodoco transpressional front, RDFS=Supposed decoupling fault system in the Romagna Apennines, RMU=Romagna-Marche-Umbria wedge, SV=Sangro-Volturno thrust zone, TE=Toscana- Emilia wedge. 182 GNGTS 2014 S essione 1.2