## 1 Introduction  
The characterization of geometrical features and spatial arrangement of any mechanical discontinuity in rock mass, including both primary-secondary foliations and fractures, hereafter referred to as a fracture network, is relevant in different areas of the geosciences (e.g., structural and geomechanical analysis, studies for geoengineering projects, and georesource exploitation). This is because geometrical features of any mechanical discontinuities (e.g., orientation, spacing, length, and shape) and their topological relationships control many of the physical properties of rock masses (e.g., [1; 2; 3]). Numerous studies describe that during deformation events, the geometric development of fractures and their relative abundance expressed as density (fracture number per unit length or unit area) and intensity (fracture length per unit area or unit volume) can be controlled by lithology and mechanical stratigraphy as well as structural position (e.g., [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]). An increase in fracturing and relative complexity is typically observed within the damage zone of faults due to nucleation, propagation, and offset accommodation of the different brittle structures that are related to the faulting mechanism (e.g., [17; 18; 19; 20; 21; 22; 23; 24; 25; 26]). Among the different areas of application, the characterization of the fracture network and its variability in the rock masses are relevant in the analysis of landslide phenomena. Characterization of fracture networks is important for landslide susceptibility analysis, because slope stability is influenced by the location and orientation of discontinuity (such as faults, bedding, foliation). The interaction of these surfaces in the rock masses influences the production of disaggregated and loose rock material that is potentially involved in a landslide [27]. In landslide susceptibility analysis aimed at identifying potential landslide areas at the basin scale, fault traces obtained from geological maps and/or lineaments extracted from remote sensing analyses are usually used to characterize the regional discontinuity network in terms of density and intensity data [28]. The degree of fracturing is usually included in the attributes of geological formations and/or considered to be homogeneously distributed along main faults as a regular buffer zone. In the landslide susceptibility studies that our group is carrying out in the Susa Valley (Italian Western Alps), we defined an index of fracture intensity (with five classes of values from weak to intense) for pre-Quaternary bedrock outcrops (identified from aerial photographs), considering mapped faults and lineament traces defined by remote survey (corroborated by traditional scan line surveys) and a strength classification of the bedrock lithologies [29; 30]. The interaction of the degree of fracturing with other predisposing factors (bedrock lithology, unconsolidated Quaternary deposits, slope inclination, and hydrographic network) was considered using the Rock Engineering System (RES) [31] methodology to define a debris flow susceptibility index at the basin scale. As part of our research, given the importance of fracturing as a predisposing factor for landslides, we selected a few areas to characterize how bedrock fracturing at the outcrop scale may vary at major faults compared with their adjacent sectors and attempt a quantitative comparison of the abundance of fractures related to fault damage zones compared with a background value of the rock masses. For this scope, we considered faults reported in geological maps at a 1:50.000 scale [32; 33], cross-cutting different bedrock lithologies and running in areas with different areal extents of bedrock outcrops (due to the occurrence of Quaternary deposits).