GNGTS 2019 - Atti del 38° Convegno Nazionale

64 GNGTS 2019 S essione 1.1 member of the continuum between NFs and DSGD) and cuts the < 500 m thick Medium Pleistocene in-age conglomerates. 5. Santilli (Venere) Fault (Vf) (length~10 km, slip rate ~0.4-0.5 mm/yr) vs. Colle Cerese (CC) DGSD . The latter is a minor fault at the footwall of the Santilli Fault and reactivated as DGSD. Similar host rocks: shallow-water wackestone carbonates; 6. Serrone (SE) DGSD. Minor anthitetic fault at the footwall of the Gioia dei Marsi Fault and reactivated as DGSD. This ~500 m long scarp cuts Cretaceous rudstones. The field work consisted in the collection of structural data (bedding, faults, fractures, veins, etc.) and geological mapping at 1:500 scale by exploiting aerial photos and drone images as topographic maps. Eighteen slip surfaces and slip zones from 14 main scarps were investigated with the SEM CamScan MX3000 (resolution 200-300 nm) installed at the Dipartimento di Geoscienze (Padua, Italy) and with the FESEM Merlin Zeiss (resolution 1-2 nm) installed at CERTEMA (Grosseto, Italy). Results and discussion. Here below the main results from the field work and microstructural investigations conducted on the four selected cases underlined above so far: Field structural data. Alto di Cacchia («end-member» DGSD). The scarp (main slip surface) is steeply dipping (~70 o ) and is discontinuous and undulated along strike and cuts sub-horizontal conglomerate strata. About one hundred joints and secondary slip surfaces were measured in the footwall and hangingwall of the main slip surface. Most of the joints are sub- vertical and opened (from 1 to 10 cm) (Fig. 2). According to the Mohr-Coulomb-Griffith’s failure envelope, such a fracture distribution is consistent with low confining pressures at the time of joint formation and slip. Valle Force Fault (minor fault bordering a small intra-mountain basin). The scarp (main slip surface) dips on average ~45 o . The over 200 fractures and minor faults measured along the Fig. 1 - Deep-Seated Gravitational Slope Deformations (DGSDs) and Normal Faults (NFs) in the Italian Central Apennines. a) Map of the DGSDs (white in color), Normal Faults (NFs, red in color) and minor faults bordering intra- mountain basins (yellow in color). Yellow stars are the sampling sites of the studied fault rocks. The selected cases are in the blue boxes (see also list and acronyms in main text). b) Example of the case of study Venere Fault (Vf) vs. Colle Cerese (CC) DGSD. Sharp slip surfaces are present in both the Vf and in the CC.