COLOSSEO · Seismogenic COmpression in southern Italy? – High-resolution topography (Lidar) and mOrphotectonic analySis to test the active nature of the Southern ApenninE Outer Thrust Front

Seismogenic COmpression in southern Italy? – High-resolution topography (Lidar) and mOrphotectonic analySis to test the active nature of the Southern ApenninE Outer Thrust Front

Earthquakes are a major natural hazard in Italy [1]. The bulk of the seismic energy is released along the Apennine belt’s topographic high, where most of the historical- [2] and recent instrumental seismicity [3] nucleates. However, in the last 50 years, moderately energetic sequences (4.0≤Mw≤6.0) with compressional/transpressive sense of motion [4] have unexpectedly occurred also along the external sectors of the Apenninic chain. Geological, seismic, and morphotectonic evidence of ongoing shortening is reported along the northern- and central Apenninic Outer Front (NAOF and CAOF, respectively), along the Sicilian outer front of the Maghrebian chain and along the Calabrian Arc. On the other hand, orogenic activity along the NW-SE trending Southern Apennines Outer Front (SAOF) is well documented only until the Lower- and part of the Middle Pleistocene (~0.7 Ma) [5, 6]. Nearly 23% of the Italian population is concentrated in southern Italy (https://demo.istat.it). The cost of human losses consequent to earthquakes in Italy (in the last fifteen years) dramatically pointed out the significant vulnerability of the territory [7, 8] even if exposed to moderate magnitude events. This implies a pressing need to fill a gap of understanding on the seismic potential of SAOF, the latter representing about 1/3 of the Apennine outer compressional front. The COLOSSEO project aims to detect evidence of Late Quaternary (post-125 ka) shortening along the SAOF and document the geometry of possible seismogenic faults. The research strategy envisages a multidisciplinary approach adequate to the peculiar geological-tectonic setting, the SAOF being buried under the Plio-Quaternary foredeep successions [9] and not strongly indicative of recent activity. Tectonic structures belonging to the front are difficult to investigate even because of the low deformation rates (<2 mm/y). The exploited methodology includes a) analysis of High-Resolution Topography data (e.g. lidar data) to capture fault zone structure and/or offsets; b) assess relative rock uplift rate across the landscape using geomorphic indices from topographic- and fluvial network analysis; c) regional scale field geology; d) seismotectonic analysis exploiting available instrumental seismicity, focal mechanisms and geodetic data. [1] Gruppo di Lavoro MPS, 2004. http://zonesismiche.mi.ingv.it/; [2] Rovida et al., 2019. https://doi.org/10.13127/CPTI/CPTI15.2; [3] Chiarabba et al., 2016. https://doi.org/10.1111/ter.12233; [4] Montone & Mariucci., 2016. DOI: 10.4401/ag-7235; [5] Patacca, E. and Scandone P. (2004). In: Special Volume of the Italian Geological Society for the IGC 32, 93-129, Florence (2004);[6] Vezzani et al. (2010). DOI: 10.1130/2010.2469; [7] M. Dolce (2004). Seismic safety of schools in Italy. In: Keeping schools safe in earthquakes, Organisation for Economic Co-operation and Development, Paris (OECD, 2004); [8] Ceci et al., 2010. https://doi.org/10.1016/j.engstruct.2009.12.023. [9] CNR, 1992, Structural Model of Italy, Quaderni de La Ricerca Scientifica, 114, sheet 4, scale 1:500,000, S.E.L.CA., Firenze

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