Patrizio Torrese

In the Vernazza catchment located in Italian Liguria, we studied the activity and hazard of two deep-seated landslides using tree rings. Knowledge of the deep-seated landslide movements in terms of their temporal activation is still scarce in the Vernazza catchment, as well as in similar catchments. To determine the hazard of the studied landslides, we compared the landslide activity for landslides under study with landslides from Poland that activated in 2010. Within the two studied Italian landslides, increased landslide activity occurred at similar times, but the dominant episodes occurred in different years. It means that the information on landslide activity and hazard should be generalised with caution, even within a single catchment. The studied deep-seated landslide activity was significantly higher after the landslide catastrophe in 2011, when many shallow landslides were activated in the studied catchment. The increase in landslide activity in 2011 was accompanied by a substantial transformation of the catchment’s relief. These changes may have resulted in a loss of stability of deep-seated landslides. The landslide activity recorded by trees did not show an increase, unlike what was reported for the Polish landslides. This indicates that there is no high risk of sudden triggering of the studied landslides.

Vineyards cultivated on steep terrains are widespread worldwide and serve as both a dominant landscape feature and the primary economic activity in many regions. These vineyards may face a variety of issues, including shallow slope instabilities, which can be triggered by intense thunderstorms or prolonged periods of heavy rainfall. Shallow landslides can cause significant damage to vineyards, resulting in a loss of soil fertility and biodiversity. It is crucial to characterize the slopes where vineyards are planted to assess potential instability risks and better understand how different inter-row management practices might influence the likelihood of slope failures.The aim of this study is to present a multidisciplinary approach for estimating the susceptibility of shallow slope instabilities in steep terrain vineyards. The method follows several key steps: i) a preliminary characterization of the slope's geological and geomorphological conditions using UAV surveys, soil trenches, and monitoring of soil water content with in-situ probes (TDR, Tensiometers); ii) the slope hydrogeological assessment throughout geophysical approaches such as the Electrical Resistivity Tomography (ERT), iii) the assessment of grapevine root density and reinforcement in inter-rows with different soil management practices (e.g., conventional tillage versus sustainable approaches).This approach was applied to different test sites in the Oltrepò Pavese (northern Italian Apennines), an important Italian wine regions prone to water stress and slope instabilities. The findings of this study can help identify conditions that lead to shallow failures in vineyards on steep terrains and highlight the positive impact of soil management practices, particularly in the context of climate change.This conference abstract is part of the project NODES which has received funding from the MUR – M4C2 1.5 of PNRR funded by the European Union - NextGenerationEU (Grant agreement no. ECS00000036).

In the last years extreme rainfall events and seasonal cumulated rainfall distribution variations occurred, increasing also the arise of slope instabilities, mostly in the more susceptible areas.Heavy rainfall events are one of the main triggering factors in shallow landslides occurrence: therefore, a better understanding of the trigger processes is necessary, also for early warning systems development and improvement. The soil water content of the first 3-5 meters of soil becomes thus an important shallow landslide predisposing factor to monitor. At this purpose, the mainly employed technique for soil moisture monitoring is the in-situ measurement, through different types of soil probes directly installed in the first soil layers. However, despite being a very precise technique, this monitoring technique provides only for a punctual dataset.An integrated method to extend the hydrological characterization from site-specific to a slope scale is presented, combining geotechnical analyses, field data monitoring and geophysical investigations, in particular the electrical resistivity tomography (ERT).Geophysical models of the first subsoil were carried out through different geoelectrical investigations (2D-3D-4D) and were calibrated and interpreted based on soil monitoring data, stratigraphic logs and trenches carried out in the study areas.Estimation of the test sites average bulk permeability was performed through time-lapse 3D-S surveys, carried out by simulating very intense precipitations through manual irrigation, that allowed to determine the resistivity variation from undisturbed to disturbed conditions.Finally, resistivity variations were correlated to soil horizons geotechnical parameters to perform hydrogeological conceptual models of the first soil horizons.This conference abstract is part of the project NODES which has received funding from the MUR – M4C2 1.5 of PNRR funded by the European Union - NextGenerationEU (Grant agreement no. ECS00000036).

Hydrochemical and geophysical methods were used to assess saline paleo-water mass transfer induced by piston flow in the alluvial aquifer of the Oltrepò Pavese plain (northern Italy). The surface aquifer shows salinity contamination from a Tertiary substrate of marine origin, due to mixing of the shallower fresh groundwater with the Po Plain’s deep brines. The study also used continuous monitoring of groundwater electrical conductivity, temperature and piezometric levels. Well logging and geophysical imaging, conducted at different times, revealed that the contamination varies over time, and that the water salinity and the depth of the transition zone (between the surface freshwaters and the deep saline waters) are subject to modifications. This is due to a pressure transfer—and, subsequently, mass transfer−from the groundwater circuits of the nearby Apennine mountains. It suggests that a hydraulic connection exists between the fractured Apennine water circuits and the deeper Mio-Pliocene and Tertiary saline-water circuits found below the plain’s alluvial aquifer. Coinciding with significant recharge episodes that affect Apennine water circuits (prolonged rainfall and snow melt at mid-high altitudes), there is a pressure transfer transmitted along the water circuits in which saline water resides, providing an impulse to rise along the discontinuities and reach the alluvial aquifer. The conceptual model is supported by evidence that wells constructed in correspondence to hydraulically active tectonic discontinuities are affected by the arrival of saline waters with variable delays, while wells sited in sectors not affected by tectonic discontinuities are diluted by ‘fresh’ waters connected to alluvial aquifer recharge.

Shallow landslides triggered by heavy rainfalls are slope instabilities, developed in the most superficial eluvial layers, involving the first 2 m from the ground level. A crucial predisposing factor in shallow landslides occurrence is the soil water content, generally measured trough sensors installed in the first soil layers. However, despite being a very precise approach, this monitoring technique provides for a site-specific dataset. An integrated method to extend the hydrological characterization from site-specific to slope scale is presented, combining geotechnical analyses, field data monitoring, and geophysical investigations, in two experimental test sites located on Italian Apennines. Ten Electrical Resistivity Tomographies (ERT) of the first soil horizons were performed through different array geometries (2D-3D-Time-Lapse), calibrated and interpreted basing on stratigraphic logs, trenches, and monitored soil water content field data. The test sites colluvial covers composition was analyzed and compared to resistivity values to build conceptual hydrogeological models of the deep-water circulation. In addition, two time-lapse (4D) ERT surveys were performed in both test sites simulating very intense precipitations, to determine the resistivity variations at different soil drainage conditions, thus estimating the average bulk permeability. Bulk permeability can be also a useful input parameter for slope stability models, widely employed in engineering practices. This integrated method proved to be very useful for the hydrogeological characterization of the subsoil at slope scale, where it is susceptible to slope instability, improving the knowledge of water circulation, as well as the bulk permeability heterogeneities, which are shallow landslides triggering parameters.

Mud volcanoes are geological structures observed throughout the world that arise from the upwelling of deep fluids along discontinuities in the subsoil. The detection of mud fluid migration pathways can be challenging, even when using Electrical Resistivity Tomography (ERT) as detectability issues may arise from complex geological settings. This paper presents new results from 2D and 3D ERT synthetic modelling for the investigation of the shallow, internal structure of terrestrial mud volcanoes. This study revealed the internal structure of the ‘Cenerone-Pineto’ mud volcano (Central Italy) and provided further clues as to its internal structure. The main results of the study are: the presence of a mud chamber, which represents the last phase of mud accumulation before final emission, not located beneath the crater but laterally offset, as well as the presence of a narrow, shallow feeder channel; these findings represent evidence of a much more complex structure than one would expect. This means that the mud volcano is not supplied with mud fluids directly from below as would be the case with an uprising of deep fluid along a near-vertical open fracture and that the shallow mud fluid reservoir is not correlated to the distribution of any mud volcano observed on the surface. Findings from this study are consistent with the observed structural features already noted in ERT and seismic field data collected at the ‘Cenerone-Pineto’ mud volcano and may be helpful in explaining the mechanisms and processes involved in mud volcanism in similar geological settings.

A pseudo-3D electrical resistivity tomography (ERT) survey has been carried out to detect cavities at the Neolithic/Palaeolithic site of Grotta Scaloria, close to Manfredonia, Apulia, Italy. Scaloria Cave has a rich history of archaeological research of more than 80 years and is one of the most important Neolithic complexes in the Mediterranean. Synthetic data modelling allowed to check the adequacy of the geophysical method and to develop a proper experimental setup at the survey design stage. Indeed, the results of the field data inversion revealed high resistivity anomalies which can be related to cavities and provided a good definition of the main geological structures and boundaries. Moreover, the results suggest that unknown and speleological unexplored cavities are still present at the Scaloria Cave study site. These findings may provide further insights on pseudo-3D ERT applicability, particularly for cavity detection. Furthermore, the approach used in this study yields fruitful information for further archaeological survey design and for the interpretation of ERT investigations targeting similar geological features and structures.

Investigating active tectonics and the structural style of potentially-seismogenic structures at the outer front of active orogenic belts is particularly challenging when the frontal structures are buried and slowly deforming. This is the case of the blind fold-and-thrust belts surrounding the Padanian foreland of Northern Italy and developing across one of the most populated and industrialized Italian territories. In this paper, we focus on the seismogenic role of the Stradella thrust and its possible involvement in the activity of the buried Emilia arc, through a 3D geometric, kinematic, and seismotectonic reconstruction of the overall system. The integrated multi-scale analysis of structural and seismological data, inclusive of new focal mechanisms, highlights two seismological thrust volumes dipping at low-angle southwest-ward, at upper (<12 km) and lower crustal depths (~20-30 km). However, the shallow seismicity only partially illuminates the down-dip prosecution of the Stradella structure. In contrast, the deeper earthquake volume, at the hanging wall of the along-strike southeastward prosecution of the Stradella fault, well highlights the lower crust portion of the Emilia Arc basal thrust.We interpret the above multi-scale data as evidence of ongoing tectonic activity of the outer fronts of the Emilia arc under a regional NNE-directed compressional stress field, with some minor evidence of involvement of the Stradella thrust along the pede-Apennine front. In our 3D reconstruction, both thrust systems are expressions of a thick-skinned deformation that controls earthquake release at different structural depths.

We present new morphostructural and geophysical data to discuss the recent activity of the Broni-Sarmato structure, an 18 km-long outcropping section of the north-verging Stradella thrust, located 50 km south of Milan, along the pede-Apennine compressional front in the rear of the Emilia Arc. An accurate seismic hazard assessment of this structure is necessary due to the presence in the area of widespread housing settlements, industries, lifeline infrastructures and large towns. Along the fault scarp we quantified the offset of recent river deposits by GPS, DTM and drone surveys; the scarp height values range from 6 to 23 m. Respect to previous works, we also better defined the geometry in plan view of the scarp; it is not continuous along the area, being characterized by several left- and right-stepping segments. We also performed new geoelectrical surveys across the scarp that suggest the presence of a wide zone of shallow deformation along the Broni-Sarmato fault trace. These deformations could correspond to fractures that act as preferential flow path for deep saline waters and facilitate the flow towards the surface. Horizontal interruption and vertical dislocation of a shallow, high resistivity layer also revealed by geoelectrical surveys, suggest that the Broni-Sarmato fault possibly produced shallow deformation along vertical and inclined zones. These data, supported by seismic activity, although quite sparse, can be interpreted as evidence of late Pleistocene-Holocene tectonic activity of this section of the Stradella thrust.

The Sirente main crater is a ≈ 130 m wide, in plan view droplet-shaped depression with an elevated rim, surrounded by 30 smaller depressions. It was proposed to be of meteorite impact origin. Given the age of formation in the 3rd to 5th centuries A.D., the inferred catastrophic origin was related to the celestial sign (“Chi Rho”) said to have been seen by Emperor Constantine in 312 A.D. and suggested to have changed the course of both Roman and Christian history. However, the meteoritic origin is not yet confirmed. This paper presents new results from synthetic modelling of Electric Resistivity Tomography field data collected at the Sirente main crater which provide further clues around the controversy of its origin. This study arises from the need to validate the observed structural features which include possible upturned strata (i.e., overturning of strata below impact crater rims) and compaction-fissure-like features below and just outside the crater rim, well-developed “breccia lens”, as well as an ejecta layer, and provide key indicators for objective and quantitative interpretation of the measured resistivity pattern. The results from this study are consistent with the hypothesis of a small impact crater in a low-strength target, with a relatively shallow apparent crater and do not support other proposed mechanisms of formation such as karst, mud volcano or merely anthropogenic origin.