Active faulting and deep-seated gravitational slope deformation in carbonate rocks (central Apennines, Italy): a new "close-up" view

Abstract

Active faulting and deep-seated gravitational slope deformation (DGSD) are common geological hazards in mountain belts worldwide. In the Italian central Apennines, kilometer-thick carbonate sedimentary sequences are cut by major active normal faults that shape the landscape, generating intermontane basins. Geomorphological observations suggest that the DGSDs are commonly located in fault footwalls. We selected five mountain slopes affected by DGSD and exposing the footwall of active seismogenic normal faults exhumed from 2 to 0.5 km depth. Field structural analysis of the slopes shows that DGSDs exploit preexisting surfaces formed both at depth and near the ground surface by tectonic faulting and, locally, by gravitational collapse. Furthermore, the exposure of sharp scarps along mountain slopes in the central Apennines can be enhanced either by surface seismic rupturing or gravitational movements (e.g., DGSD) or by a combination of the two. At the microscale, DGSDs accommodate deformation mechanisms similar to those associated with tectonic faulting. The widespread compaction of micro-grains (e.g., clast indentation), observed in the matrix of both normal faults and DGSD slip zones, is consistent with clast fragmentation, fluid-infiltration, and congruent pressuresolution active at low ambient temperatures (<60°C) and lithostatic pressures (<80 MPa). Although clast comminution is more intense in the slip zones of normal faults because of the larger displacement accommodated, we are not able to find microstructural markers that allow us to uniquely distinguish faults from DGSDs.DEL RIO ET AL.

Slope design in brecciated carbonatite complexes under high-stress regimes

“…The impact of fault characteristics are directly linked to stress heterogeneities created by the interaction between the faults and the mining induced stresses generated during excavation leading to localized high plastic shear strain and high extensional train around the fault (Severin 2017;Stead & Wolter 2015). Del Rio et al (2021) studied that active faulting induces deep-seated gravitational slope deformation (DGSD) leading to slope failure characterized by large volume landslides in mountain belts worldwide. Additionally, Stead & Wolter (2015) demonstrated that structural features, such as folds, bedding planes, faults, and discontinuities commonly affect hydrogeological conditions, a crucial factor in slope stability, acting as either water conduits or aquitards.…”