Landslides are a major threat for population and urban areas. Persistent Scatterer Interferometry (PSI) is a powerful tool for identifying landslides and monitoring their evolution over long periods and has proven to be very useful especially in urban areas, where a sufficient number of PS can be generated. In this study, we applied PS interferometry to investigate the landslide affecting Santo Stefano d’Aveto (Liguria, NW Italy) by integrating classic interferometric techniques with cross-correlation analysis of PS time-series and with geological and geotechnical field information. We used open-source software and packages to process Synthetic Aperture Radar (SAR) images from the Copernicus Sentinel-1A satellite for both ascending and descending orbits over the period 2015–2021 and calculate both the vertical motion and the E-W horizontal displacement. By computing the cross-correlation of the PS time-series, we identified three families of PS with a similarity greater than 0.70. The cross-correlation analysis allowed subdividing the landslide in different sectors, each of which is characterized by a specific type of movement. The geological meaning of this subdivision is still a matter of discussion but it is presumably driven by the geomorphological setting of the area and by the regional tectonics.

<p>Unravelling the tectonic styles that affected the Martian crust is crucial to better understand the evolutionary stages that a rocky planet can experience. Here, we explore the tectonic setting of a key region of Mars, namely the Claritas Fossae (CF). The CF is located in the Highlands to the south-west of the Valles Marineris and is characterized by an elongated system of scarps and troughs, fault sets, and grabens, nearly N-S trending. These morphotectonic features strongly resemble terrestrial grabens (e.g.; Thingvellir in south Iceland) and, for this reason, the CF has been interpreted as a rift-like system (Hauber & Kronberg, 2005).</p><p>In this work we apply a kinematic numerical forward modelling (HCA method; Salvini & Storti, 2004) to reproduce the geometry of the main fault(s) that likely generated the CF in order to better understand the leading tectonic mechanisms. This method allows replicating the superficial morphologies by considering the development of one or multiple faults with given geometry, throw and displacement rate and the relative movement between hanging-wall and foot-wall crustal blocks. It has been successfully used to simulate tectonically controlled morphologies on Earth such as ice buried landscape in the interiors of Antarctica (Cianfarra & Salvini, 2016), a negligible erosional environment considered as a good Martian analogue. In our model, we reproduced the morphology of the central-northern sector of the CF, characterized by an asymmetric valley with a steeper eastern slope and a gently rounded western one, along a topographical profile perpendicular to the strike of the main structure. The eastern valley slope allows locating the upper tip of the fault for the modelling in which we set the crustal thickness (i.e., the bottom of the model) to 70 km (Watters et al., 2007), considered no significant rheological vertical variation and tried different values of initial dip in the range 50°-70° and throw in the range  1000-2000 m. The preliminary results of our modelling show that the topography, including the rounded shape of the western slope, is well replicated by a crustal (listric) normal fault characterized by an initial dip of ca. 60° that gently decrease to ca. 40° and a throw of ca. 1800 m. This allows including the development of the CF in a past extensional tectonic regime of regional relevance. Further modelling on new topographical profiles to the north and to the south respect to the already modelled one will allow better highlighting the 3D shape of the main CF fault and the presence of further secondary but not negligible faults.</p><p>Hauber, E., & Kronberg, P. (2005). The large Thaumasia graben on Mars: Is it a rift?. J. Geoph. Research: Planets</p><p>Salvini, F., & Storti, F. (2004). Active-hinge-folding-related Deformation and its Role in Hydrocarbon Exploration and DevelopmentInsights from HCA Modeling.</p><p>Cianfarra, P., & Salvini, F. (2016). Origin of the adventure subglacial trench linked to Cenozoic extension in the East Antarctic Craton. Tectonophysics</p><p>Watters, T. R., McGovern, P. J., & Irwin Iii , R. P. (2007). Hemispheres apart: The crustal dichotomy on Mars. Annu . Rev. Earth Planet. Sci.</p>

Persistent Scatterer Interferometry (PSI) is one of the most powerful tools for identifying and monitoring areas exposed to surface deformations such as landslides or subsidence. In this work, we propose a new method that we named CAPS (Correlation Analysis on Persistent Scatterers), to extend the capability of PSI in recognizing and characterising areas influenced by complex ground deformations and differential motions. CAPS must be applied to both ascending and descending orbits separately and comprises three major steps: (i) calculating the cross-correlation matrix on detrended PS time-series; (ii) extracting PS pairs with similarity greater than a given threshold; (iii) grouping PS in families by sorting and classification. Thus, in both orbits, PS Families identify groups of PS with similar movements. This allows distinguishing sectors characterised by different displacements over time even in areas with similar LOS (Line of Sight) velocities. As test sites, we considered four different known geological scenarios: two representing landslide environments (Santo Stefano d’Aveto and Arzeno, both in Liguria, NW Italy) and two subsidence environments (Rome and Venice, urban and surrounding areas). This method proved to be versatile, applicable to different geological situations and at different scales of observation, for recognizing both regional and local differential deformations.

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<p>The Claritas Fossae (CF) is a Martian system of scarps and troughs with NNE-SSE elongation that exceeds 1000 km of length and 150 km of width. It develops mainly in Late to Middle Noachian highland units and Hesperian lava flows (Tanaka et al., 2014). It is bounded to the east by the elevated plateau of Syria Planum, Sinai Planum and Solis Planum mostly consisting in late Hesperian volcanic units; and to the west by the relatively topographically lower Daedalia Planum made of the Amazonian-Hesperian volcanic lava flows of Tharsis (Fig 1a).</p> <p><img src="" alt="" width="689" height="627" /></p> <p><em>Figure 1 a<strong>)</strong> Location of the study area. b<strong>) </strong>The study area with its subdivision in the two Sectors A and B and the location of the Western Fault (WF) and the Eastern Fault (EF). </em></p> <p>In this study, we focus on the northernmost part of the CF (Fig 1b) that can be subdivided in two different sectors (Hauber & Kronberg, 2005) on the basis of the characteristics of the main scarps and the valley floor:</p> <ul> <li>Sector A: It is characterised to the north and to the west by a topographically high area etched by numerous depressions up to tens of km long with different orientations, and to the south-east by an asymmetric valley. This valley is bounded to the west by an abrupt scarp, dipping to the east, that exceeds 200 km of length and presents up to 1000 m of elevation change. The eastern slope of the valley is represented by the northernmost part of a scarp here characterised by a maximum elevation change of 300 m and WSW dipping. These steep morphologies suggest a strong tectonic control; the faults responsible for their evolution are hereinafter referred to as the Western Fault (WF) and the Eastern Fault (EF), respectively.</li> <li>Sector B: The western slope of the asymmetric valley is gentler and with lower topographic contrast compared to Sector A lacking the topographic evidence of the WF. On the other side, the southward continuation of the EF presenting topographic changes up to 2000 m describes a steep scarp that strongly suggests its tectonic control.</li> </ul> <p>The aim of this study is to reconstruct the tectonic processes that affected this area in order to gather a better comprehension of the tectonic style(s) that Mars experienced. In this perspective, a multi-scalar approach is of outmost importance. To do so, we conducted two types of analysis:</p> <ul> <li>Structural mapping of the regionally sized faults and fault-related fractures in Sectors A and B (still ongoing);</li> <li>Forward modelling aimed at reproducing the development in depth of the EF in Sector B.</li> </ul> <p>For the structural mapping, we analyse satellite images that were processed to enhance the detectability of tectonic structures. The dataset we used, with different spatial resolution, includes: a) the topographic map of Mars from the Mars Orbiter Laser Altimeter (MOLA DEM and relative colour shade, 200 mppx); b) the Thermal Emission Imaging System dataset that shows the thermo-physical properties of the outcropping lithologies with InfraRed Day and Night acquisitions (THEMIS IRDay/Night, 100 mppx); and c) the Mars Reconnaissance Orbiter Context Camera mosaic (MRO-CTX, 6 mppx), used to explore the crosscutting relationships between the mapped structures. In addition, to better highlight the tectonic structures and to avoid limits and bias related to the use of a single lighting direction (Wise et al., 1985), we produced four shadowed images according to four synthetic lightening conditions (0°, 45°, 90°, 135°).</p> <p>For the modelling of the EF, we consider the regional scale topography of the Martian surface as a reference layer reflecting the crustal tectonic processes. In fact, the erosional processes on Mars have very low rates, and have a negligilble effect in shaping the regional physiography (Klimczak et al., 2018). We used the HCA method (Salvini & Storti, 2004) aimed at reproducing the superficial morphologies by studying the movement of two crustal blocks separated by a fault with a given geometry. We modelled the topography derived from four topographic profiles trending perpendicular to the EF; results show that the activity of a crustal, listric normal fault replicates the topography across the CF.  This crustal  normal fault reaches the base of the crust at 80 km of depth, a value in accordance with literature (Watters et al., 2007). The dip of the fault decreases from about 60 degrees near the surface to about 20 degrees at the boundary between crust and mantle. The fault displacement varies from north to south, reaching a maximum of 2000 m.</p> <p><img src="" alt="" width="746" height="411" /></p> <p><em>Fig. 2 – Sketch of the modelled listric normal EF</em></p> <p>The preliminary results of the structural mapping show that the identified tectonic structures are not randomly distributed. The statistical analysis by frequency distribution of the mapped tectonic structures shows their clustering in four main azimuthal families: i) NNE-SSW; ii) NNW-SSE; iii) ENE-WSW; and iv) WNW-ESE. By analyzing the crosscutting relationships among the mapped structures and the relative ages of the terrains where they develop, we recognized multiple deformation events at different scale, both regional and hemispheric. Furthermore, by comparing the main trend of the found azimuthal families with the expected direction of the structures in a strike-slip regime (Li et al., 2016), we found correspondence with a right lateral strike-slip regime oriented NNW-SSE, similarly to the main scarps of the CF. The ongoing structural mapping and the spatial-azimuthal analysis of the family set will allow us to better constrain the relative chronology of deformation events and to produce a tectonic evolutionary model of the studied region.</p> <p>These preliminary results suggest that the investigated area has been interested by a long-lasting tectonic deformation history made of multiple reactivations of crustal weakness zones. The structural setting of the area is likely related to the contribution of several factors acting also at different scales. At the hemispheric scale we recognized deformations associated to the development/evolution of Tharsis Bulge and of the Tharsis Montes; at the regional scale we recognized tectonic structures related to the evolution of the CF where evidence of strike slip and extensional deformations have been recognized.</p>