GNGTS 2015 - Atti del 34° Convegno Nazionale

In the short-term (tens to hundreds of years), the above kinematic/tectonic context mainly develops during and just after major decoupling earthquakes. When a strong shock occurs at the inner extensional boundary of the MS wedge that block accelerates, increasing its belt- parallel push on the ELA. This indentation may cause the seismic activaction of the L’Aquila or Fucino sinistral transtensional fault systems, located at the western edge of the ELA. The sudden acceleration of ELA stresses in turn the RMU and TE wedges in the northernApennines, favouring further seismotectonic activity. The proposed tectonic context is compatible with the spatio-temporal distribution of major earthquakes that occurred during the main seismic crises developed in that belt since 1300 (Mantovani et al. , 2010, 2012). � �������� ����������� ��� ��� ������ �� ��� ����� ����������� A possible explanation for the timing of the major earthquakes Fig. 1 – Tentative reconstruction of the main morphological elements (ridges and basins) in the northern Apennines since the Pliocene (after Viti et al ., 2015). A) Pliocene. The red lines identify the main ridges in the RMU and TE wedges: CA Catenaia Alps, CA-FE-SP Catria-Fema-Spoleto, FR-SU-MA Frontano-Subasio-Martani, FV-PE-NA- SB Favalto-Peglia-Narni-Sabini, GM Giovi-Morello, LUA Luna Alps, PA Pistoia Apennines, PRM Pratomagno, SA Serra Alps, SBA San Benedetto Alps, SV-SI-TE S.Vicino-Sibillini-Terminillo. The blue line indicates the Albano-Chianti-Rapolano-Cetona (ACRC) ridge. The violet lines indicate the metamorphic ridge (taken as the inner limit of our reconstruction): AA ApuaneAlps, MA Montalcino-Amiata, PM Pisano Mt., TM Toscana metamorphic belt. The blue zones identify the main basins: Ch Chiana, EP Elsa-Pesa, Ga Garfagnana, LT Lower Tiber, Lu Lunigiana, LV Lower Valdarno, Ra Radicofani, Si Siena, UV Upper Valdarno. LA Lazio-Abruzzi platform, LAT Latina fault system. B) Early-Middle Pleistocene. RMB Roman Magmatic Body. C) Upper Pleistocene. New basins: Ca Casentino, Gu Gubbio, Mu Mugello, PF Pistoia-Firenze, To Topino, UT Upper Tiber. Segments of the previous ACRC ridge: AL Albano, CE Cetona, CH Chianti, RAP Rapolano. Fu-VR Fucino-Val Roveto fault system. D) Present. Aq L’Aquila fault system, GS Gran Sasso arc, LAU Laga units. See text for explanations. 134 GNGTS 2015 S essione 1.2