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The compilation and maintenance of experimental databases are of crucial importance in all research fields, allowing for researchers to develop and test new methodologies. In this work, we present a flat-file database of experimental dispersion curves and shear wave velocity profiles, mainly from active surface wave testing, but including also data from passive surface wave testing and invasive methods. The Polito Surface Wave flat-file Database (PSWD) is a gathering of experimental measurements collected within the past 25 years at different Italian sites. Discussion on the database content is reported in this paper to evaluate some statistical properties of surface wave test results. Comparisons with other methods for shear wave velocity measurements are also considered. The main novelty of this work is the homogeneity of the PSWD in terms of processing and interpretation methods. A common processing strategy and a new inversion approach were applied to all the data in the PSWD to guarantee consistency. The PSWD can be useful for further correlation studies and is made available as a reference benchmark for the validation and verification of novel interpretation procedures by other researchers.

The existence of hidden chambers and corridors adjacent to Tutankhamun's tomb (code name KV62) has been long debated. In 2015 it was suggested that these chambers may host the as yet undiscovered burial of Nefertiti. In order to test this hypothesis, two Ground Penetrating Radar (GPR) surveys, conducted in 2015 and 2016 from inside KV62, were carried out, but gave contradictory results. To solve these uncertainties and obtain a more confident and conclusive response, a third GPR survey was conducted by our team in February 2018. The results of this third radar scan are reported in this article. Three GPR systems with multiple frequency bands (from 150 MHz to 3000 MHz) and very dense spatial sampling were adopted. After careful data processing, no evidence of marked discontinuities due to the passage from natural rock to artificial blocking walls were found in the radargrams. It is therefore concluded that there are no hidden chambers immediately adjacent to the Tomb of Tutankhamun.

The joint inversion of multiple data sets encompasses the advantages of different geophysical methods but may yield to conflicting solutions. Global search methods have been recently developed to address the issue of local minima found by derivative-based methods, to analyse the data compatibility and to find the set of trade-off solutions, since they are not unique. In this paper, we examine two evolutionary algorithms to solve the joint inversion of electrical and electromagnetic data. These nature-inspired metaheuristics also adopt the principle of Pareto optimality in order to identify the result among the feasible solutions and then infer the data compatibility. Since the joint inversion is characterized by more than one objective, we implemented the algorithm multi-objective particle swarm optimization (MOPSO) to jointly interpret time-domain electromagnetic data and vertical electrical sounding. We first tested MOPSO on a synthetic model. The performance of MOPSO was directly compared with that of a multi-objective genetic algorithm, the non-dominated sorting genetic algorithm (NSGA-III), which has often been adopted in geophysics. The adoption of MOPSO and NSGA-III enabled avoiding both simplification into a single-objective problem and the use of a weighting factor between the objectives. We tested the two methods on real data sets collected in the northwest of Italy. The results obtained from MOPSO and NSGA-III were highly comparable to each other and largely consistent with literature findings. The MOPSO performed a rigorous selection of the best trade-off solutions and its convergence was faster than NSGA-III. The analysis of the Pareto Front reported data incompatibility, which is very common for real data due to different resolutions, sensitivities and depth of investigations. Notwithstanding this, the multi-objective optimizers provided a complementary interpretation of the data, ensuring significant advantages with respect to the separate optimizations we carried out using the single-objective particle swarm optimization algorithm.

A multi-analytical study was carried out on an ancient Egyptian limestone stele with red figures and hieroglyphs (S. 6145) coming from the village of Deir el-Medina and belonging to the collection of the Museo Egizio (Turin, Italy). With the support of a multidisciplinary team, a project for the preservation and conservation of this stele provided an opportunity to carry out a very detailed study of the object. Petrographic and mineralogical analysis led to the characterization and dating of the limestone, and ultrasonic tests were of great help in shedding light on the state of preservation of the stele, as a preliminary to planning conservation treatment. The chemical nature of the red pigment was investigated by non-invasive spectroscopic analyses. Multispectral imaging and statistical image processing improved the readability of the hieroglyphs, whose preservation ranged from heavily compromised to almost completely invisible, revealing some signs that had previously not been visible.

Carbonate rocks have a widespread diffusion in the Earth crust and are extensively used in cultural heritage and buildings. These rocks can be naturally or anthropically exposed to high temperatures. Consequently, relating physical properties to temperature-induced damage is extremely important. Six sets of compositionally and texturally different carbonate rocks, spanning from limestones and marbles to dolomitic marbles, were analysed in this study. Different physical properties, such as porosity, seismic wave velocities and electrical resistivity, were measured before and after thermal treatments with heating/cooling ranges between 105 and 600°C. Microstructural observations and optical analyses were used to investigate how temperature-induced damage affects the physical measured properties of the different microstructures. This integrated approach allowed to define a generalised relationship between physical properties and thermal-induced damage, by way of an induced damage index valid for a broad suite of carbonate rocks.

A blast-induced liquefaction test was conducted in the surroundings of Mirabello (NE Italy), where extensive liquefaction phenomena were observed after the 2012 Emilia earthquake. This experiment is the first blast-induced liquefaction test carried out in Italy. Several geophysical investigations were performed at the site to define initial soil condition and to evaluate the variations of the geophysical parameters over time. Specifically compressional ( VP) and shear ( VS) wave velocities were measured using both invasive (down-hole) and non-invasive (surface wave) tests. Electric Resistivity Tomography (ERT) tests were also carried out. Tests results before and after the blast-induced liquefaction are here presented and discussed with respect to the observed liquefaction effects. The evolution of measured geophysical parameters suggests that the soil modifications due to blasting ( i.e., changes in porosity and soil structure) can be imaged with the adopted approaches.

A case study on the use of direct and indirect investigations for the effectiveness evaluation of jet-grouting interventions for bridge scour protection is presented. The major concern of this scour countermeasure is that a reliable verification and imaging of the exact dimensions and shape of the grouted elements and their related strength and integrity are difficult to obtain. An integrated cost-effective and slightly invasive approach, by means of indirect surveys, is proposed in this work to limit re-drilling and core sampling of jet columns. Tests are performed on a bridge located in the Province of Cuneo (NW Italy). On site, active fluvial activity was scouring four of the 19 bridge piers and jet-grouting interventions were designed to prevent bridge collapse. A dual approach was consequently applied to evaluate the goodness of jet-grouting treatments: results of direct tests (visual and mechanical characterization of core drillings, with Point Load and Uniaxial Compressive Strength tests) have been compared to indirect investigations (seismic down-hole tests and 2-D cross-hole tomography, laboratory Ultrasonic Pulse Velocity measurements). All the techniques showed potentiality in identifying variations of the jet-grouting properties within the columns. Generally, worsening in jet-grouting properties was coherently identified by a decrease in the seismic velocities and in the mechanical parameters and confirmed by visual inspection of core drillings. Local anomalies and discrepancies between the adopted method were however highlighted and critically discussed as a function of the limitations, disturbances and investigated volumes of each method.

The geologic investigation of water-covered areas is often difficult and inefficient with only the use of traditional surveying techniques (i.e., local drilling and sampling). Waterborne geophysical surveys can offer a valuable alternative to achieve adequate data coverage in a cost-effective way. Two geophysical waterborne methods were combined in this study for the delineation of the submerged subsurface geology along a 5 km stretch of the Po river, within the urban area of Turin. The adopted methods were: continuous vertical electrical sounding (CVES) and ground-penetrating radar (GPR). Special attention was devoted to the accurate geo-referencing of both surveys for combined interpretation. GPR results provide a high-quality representation of the river bed forms, with identification of clear sand dunes in the finer alluvial sediments. CVES resistivity sections enable a deeper characterization, identifying the interface between the shallow alluvial deposits and the deeper low-resistivity marls of the Turin-Hill succession. Our work strengthens the effectiveness of waterborne surveys for geologic prospecting of water-covered and difficult-to-access areas.

Rock glaciers are slowly flowing mixtures of debris and ice occurring in mountains. They can represent a reservoir of water, and melting ice inside them can affect surface water hydrochemistry. Investigating the interactions between rock glaciers and water bodies is therefore necessary to better understand these mechanisms. With this goal, we elucidate the hydrology and structural setting of a rock glacier-marginal pond system, providing new insights into the mechanisms linking active rock glaciers and impounded surface waters. This was achieved through the integration of waterborne geophysical techniques (ground penetrating radar, electrical resistivity tomography and self-potentials) and heat tracing. Results of these surveys showed that rock glacier advance has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. A sub-surface hydrological window connecting the rock glacier to the pond was also detected, where an inflow of cold and mineralised underground waters from the rock glacier was observed. Here, greater water contribution from the rock glacier occurred following intense precipitation events during the ice-free season, with concomitant increasing electrical conductivity values. The outflowing dynamic of the pond is dominated by a sub-surface seepage where a minor fault zone in bedrock was found, characterised by altered and highly-fractured rocks. The applied approach is evaluated here as a suitable technique for investigating logistically-complex hydrological settings which could be possibly transferred to wider scales of investigation.

The characterization of the fracturing state of a potentially unstable rock cliff is a crucial requirement for stability assessments and mitigation purposes. Classical measurements of fracture location and orientation can however be limited by inaccessible rock exposures. The steep topography and high-rise morphology of these cliffs, together with the widespread presence of fractures, can additionally condition the success of geophysical prospecting on these sites. In order to mitigate these limitations, an innovative approach combining non-contact geomechanical measurements, active and passive seismic surveys and 3-D numerical modeling is proposed in this work to characterize the 3-D fracture setting of an unstable rock mass, located in NW Italian Alps (Madonna del Sasso, VB). The 3-D fracture geometry was achieved through a combination of field observations and non-contact geomechanical measurements on oriented pictures of the cliff, resulting from a previous laser-scanning and photogrammetric survey. The estimation of fracture persistence within the rock mass was obtained from surface active seismic surveys. Ambient seismic noise and earthquakes recordings were used to assess the fracture control on the site response. Processing of both datasets highlighted the resonance properties of the unstable rock volume decoupling from the stable massif. A finite-element 3-D model of the site, including all the retrieved fracture information, enabled both validation and interpretation of the field measurements. The integration of these different methodologies, applied for the first time to a complex 3-D prone-to-fall mass, provided consistent information on the internal fracturing conditions, supplying key parameters for future monitoring purposes and mitigation strategies.

Surface waves (SWs) in seismic records can be used to extract local dispersion curves (DCs) along a seismic line. These curves can be used to estimate near-surface S-wave velocity models. If the velocity models are used to compute S-wave static corrections, the required information consists of S-wave time-average velocities that define the one-way time for a given datum plan depth. However, given the wider use of P-wave reflection seismic with respect to S-wave surveys, the estimate of P-wave time-average velocity would be more useful. We therefore focus on the possibility of also extracting time-average P-wave velocity models from SW dispersion data. We start from a known 1D S-wave velocity model along the line, with its relevant DC, and we estimate a wavelength/depth relationship for SWs. We found that this relationship is sensitive to Poisson’s ratio, and we develop a simple method for estimating an “apparent” Poisson’s ratio profile, defined as the Poisson’s ratio value that relates the time-average S-wave velocity to the time-average P-wave velocity. Hence, we transform the time-average S-wave velocity models estimated from the DCs into the time-average P-wave velocity models along the seismic line. We tested the method on synthetic and field data and found that it is possible to retrieve time-average P-wave velocity models with uncertainties mostly less than 10% in laterally varying sites and one-way traveltime for P-waves with less than 5 ms uncertainty with respect to P-wave tomography data. To our knowledge, this is the first method for reliable estimation of P-wave velocity from SW data without any a priori information or additional data.

Recent results within the framework of the collaborative project The Complete Geophysical Survey of the Valley of the Kings (VOK) (Luxor, Egypt) are reported in this article. In October 2018, a team of geomatics and geophysics researchers coordinated by the Polytechnic University of Turin worked side by side in the VOK. Topographic measurements in support of geophysical surveys and the achievement of a very large-scale 3D map of the Eastern VOK were the two main objectives of the geomatics campaign. Innovative 3D metric technologies and methods, based on terrestrial laser scanning (both static and mobile) and close-range photogrammetry were employed by the Geomatics team. The geophysical campaign focused on the acquisition of Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR) and high spatial density Geomagnetic (GM) data. ERT new data around KV62, both inverted in 2D sections and added to the previous ones to perform a new global 3D inversion, confirm the previous results showing both conductive and resistive anomalies that have to be explained. GPR timeslices showed some interesting features in the area in front of the KV2 entrance where GM gradient map also presents localized anomalies. In the area SSW of the KV2 the GM gradient maps evidenced also a large semicircular anomaly which, up to now, has no explanation. The potentialities of using magnetic techniques as a complement to other non-invasive techniques in the search for structures of archeological significance have been explored. The application of modern and innovative methods of 3D metric survey enabled to achieve a complete 3D mapping of what is currently visible in the valley. The integration of 2D/3D mapping data concerning visible elements and hypothetical anomalies, together with the recovering in the same global reference system of underground documentation pertaining to the Theban Mapping Project, prefigure the enhancement of multi-temporal site representation. This strategy enables the fruition development of the already discovered archaeological heritage, using modern criteria of valorization and conservation.

River embankments are linear earth structures, worldwide diffused, commonly used for flood protection. Their integrity and stability are fundamental prerequisites for the protection efficiency they can offer to the increasing frequency and magnitude of extreme flood events associated to changes in climate. Proper characterization and monitoring are essential to verify the construction requirements of newly built structures and to evaluate the durability of aged ones. Considering the linear extent of river embankments, their characterization requires not only local geotechnical investigations but also the application of efficient and economically affordable methods. This is even more essential when the investigations are performed after, or in foresee of, significant flood events, when these structures get stressed and timing of the surveys is crucial. In these conditions, new survey methodologies, with the use of mobile systems, are a main research topic. In this paper the application of a new electric streamer, specifically designed for these aims, is presented. The technical solutions adopted for its construction are described and its application to the characterization of three different river embankments is presented. These case studies were chosen in accordance with the Po River Interregional Agency (AIPO), which is the authority deputed to the safety of flood protection structures in North-West Italy, along the hydrographic network of the Po River. The selected embankments are all earth structures, constructed above the natural alluvial soils, but are characterized by different conditions and challenges. The results obtained with the new system were comparable to standard Electric Resistivity Tomography (ERT) methods. The new system has significant advantages in terms of reducing the survey time, improving the efficiency of the surveys and increasing the data coverage. This resulted in a better definition of potentially dangerous anomalies.

Burial mounds are artificially (or partially artificially) erected hills that cover a monumental tomb, usually in the form of a stone chamber. Different types of burial mounds are distributed worldwide and have built in different archaeologically interesting periods. Use of non destructive geophysical surveys for their study offer the opportunity to image their internal structure and evidence peculiar anomalies that can be later investigated with archaeological excavations, limiting invasiveness. The main innovative part of this work lies on the combined use of Ground Penetrating Radar and Electric Resitivity Tomography over and inside an unexplored burial site in Japan, the Tobiotsuka Kofun, a late Kofun period burial mound, dated approximately late 6th-early 7th century CE and located in the Okayama Prefecture. Effectiveness of the geophysical surveys is demonstrated by the correct imaging of known structures and by the combined evidence of the mound organization, which allowed to draw a reliable initial archaeological interpretation with evidence of several interesting excavation spots. The adopted methodological surveying approach was verified as a valuable choice for investigations in similar archaeological settings.

River embankments are linearly extended earth structures built for river flood protection. Their continuity and uniformity are fundamental prerequisites to ensure and maintain their protection efficiency. Weakness points usually develop in localized areas where geotechnical variability is present in the embankment body or in the underlying subsoil. Given their significant length, and the localized nature of weakness points, the characterization of river embankments cannot rely on local geotechnical investigations but requires the application of efficient and economically affordable methods, able to investigate relevant lengths in a profitable way. This is even more essential when the investigations are conducted near, or in foresee of, significant flood events, when timing of the surveys is essential. In this paper the application of a procedure (W/D procedure) for the seismic characterization of river embankments, specifically designed for surface waves streamer data, is presented. The W/D procedure allows the combined definition of 2D shear (Vs) and compressional (Vp) wave velocity models and can be developed in order to be automated as a fast imaging tool. Its application to the characterization of a test site (Bormida river embankment, Piedmont Region, Italy) is presented. It is also shown that the obtained results are comparable to standard seismic processing approaches with the advantage of reduced survey time and increased efficiency, giving preliminary results directly in the field.

Alpine glaciers are key components of local and regional hydrogeological cycles and real-time indicators of climate change. Volume variations are primary targets of investigation for the understanding of ongoing modifications and the forecast of possible future scenarios. These fluctuations can be traced from time-lapse monitoring of the glacier topography. A detailed reconstruction of the ice bottom morphology is however needed to provide total volume and reliable mass balance estimations. Non-destructive geophysical techniques can support these investigations. With the aim of characterizing ice bottom depth, ground-penetrating radar (GPR) profiles and single-station passive seismic measurements were acquired on the terminal lobes of Belvedere Glacier (NW Italian Alps). The glacier is covered by blocks and debris and its rough topography is rapidly evolving in last years, with opening and relocation of crevasses and diffuse instabilities in the frontal sectors. Despite the challenging working environment, ground-based GPR surveys were performed in the period 2016–2018, using 70-MHz and 40-MHz antennas. The 3D ice bottom morphology was reconstructed for both frontal lobes and a detailed ice thickness map was obtained. GPR results also suggested some information on ice bottom properties. The glacier was found to probably lay on a thick sequence (more than 40 m) of subglacial deposits, rather than on stiff bedrock. Week deeper reflectors were identified only in the frontal portion of the northern lobe. These interfaces may indicate the bedrock presence at a depth of around 80 m from the topographic surface, rapidly deepening upstream. Single-station passive seismic measurements, processed with the horizontal-to-vertical spectral ratio (HVSR) method, pointed out the absence of sharp vertical contrast in acoustic impedance between ice and bottom materials, globally confirming the hypotheses made on GPR results. The obtained results have been compared with previous independent geophysical investigations, performed in 1961 and 1985, with the same aim of ice thickness estimation. The comparison allowed us to validate the results obtained in the different surveys, supply a reference base map for the glacier bottom morphology and potentially study ice thickness variations over time.

Underground Thermal Energy Storage systems have showed to be a useful and increasing technical solution for covering heating and cooling and domestic hot water buildings' demand. Thermal influence of these plants is however not still debated as it deserves and correct monitoring strategies appear to be of major importance both to better understand processes and to highlight their environmental effects into high populated areas. Litho-, hydro- and bio-sphere can indeed be adversely affected by temperature variations induced in the underground by heat storage applications. For this purpose, a geophysical monitoring approach using time-lapse electrical resistivity measurements contemporary to analogical simulations is here tested at laboratory scale. Results of the experiments are reported comparing measured apparent resistivity with direct temperature measurements and numerical simulations of heat propagation. Data presented confirmed that electrical resistivity has powerful relation with temperature variation in monitored media. In addition, they showed that also without performing data inversion valid temperature estimation can be carried out. Post-processing calibration of apparent resistivity data showed to be in acceptable agreement with both temperature measurements and numerical simulations. Simple apparent electrical resistivity variations appear therefore to be a promising, economic, quick and non-invasive tool for mapping thermal modifications induced in the underground by shallow geothermal applications.

Groundwater resource assessment is fundamental for agriculture in arid or semiarid conditions, where precipitations are irregular and scarce. In volcanic islands, groundwater resources are often located at significative depths, thus hindering direct exploration. The application of geophysical techniques is therefore necessary for a preliminary evaluation of water availability and to identify potential drilling points. In this study, Time Domain Electromagnetic Method (TDEM) soundings were used for groundwater prospection in the surroundings of a vineyard on the island of Fogo, Cape Verde. A pseudo-2D profile of ten sounding points was located within the vineyard, and other localized prospections were performed close to known boreholes, for attempting correlations of TDEM evidence with water depth and stratigraphy. The data acquired were interpreted by means of three inversion algorithms to obtain an uncertainty evaluation of the results: the particle-swarm-optimization algorithm, the linearized 1D inversion and the spatially constrained inversion were applied. These methods provided a set of equivalent solutions of the TDEM inverse problem to be evaluated and compared. The inverted models are highly consistent and show little mismatch at greater depths. The main outcome regarding the resistivity distribution in the vineyard subsurface is the evidence of a nearly 150 m-thick conductive region (1–10 Ωm). Information from existent water wells enhanced the hydrogeological interpretation of the profiles and the detection of potential water-saturated formations.

Near-surface sharp lateral variations can be either a target of investigation or an issue for the reconstruction of reliable subsurface models in surface-wave (SW) prospecting. Effective and computationally fast methods are consequently required for detection and location of these shallow heterogeneities. Four SW-based techniques, chosen between available literature methods, are tested for detection and location purposes. All of the techniques are updated for multifold data and then systematically applied on new synthetic and field data. The selected methods are based on computation of the energy, energy decay exponent, attenuation coefficient, and autospectrum. The multifold upgrade is based on the stacking of the computed parameters for single-shot or single-offset records and improves readability and interpretation of the final results. Detection and location capabilities are extensively evaluated on a variety of 2D synthetic models, simulating different target geometries, embedment conditions, and impedance contrasts with respect to the background. The methods are then validated on two field cases: a shallow low-velocity body in a sedimentary sequence and a hard-rock site with two embedded subvertical open fractures. For a quantitative comparison, the horizontal gradients of the four parameters are analyzed to establish uniform criteria for location estimation. All of the methods indicate ability in detecting and locating lateral variations having lower acoustic impedance than the surrounding material, with errors generally comparable or lower than the geophone spacing. More difficulties are encountered in locating targets with higher acoustic impedance than the background, especially in the presence of weak lateral contrasts, high embedment depths, and small dimensions of the object.

Electrical resistivity tomography (ERT) of the area surrounding Tutankhamun's tomb (KV62) in the Valley of the Kings (Luxor, Egypt) reveals the presence of two anomalies located a few meters from Tutankhamun's funerary chamber. The strategy for ERT data acquisition and the adopted methods for data analysis are discussed in detail in this article, together with the possible archaeological significance of the detected anomalies.

The high sedimentological variability of gypsum rocks has the effect that a univocal characterization of this material is not easy to establish. This is particularly true from the geomechanical point of view: when the mechanical properties of gypsum rocks are requested, it is therefore necessary to undertake detailed characterization analyses. Common facies of gypsum was observed in the Upper Miocene evaporitic succession (Messinian Salinity Crisis) within the whole Mediterranean Basin. In this work, mechanical tests were conducted on a site-specific facies, represented by the microcrystalline branching selenite. The tested samples came from the Monferrato area (northwestern Italy). Uniaxial compressive strength (UCS) tests were performed in order to obtain reference mechanical parameters. More rapid and economic point load test (PLT) and ultrasonic pulse velocity (UPV) measurements were additionally performed to verify their applicability as complementary/alternative methods for site characterization. Rock-type specific PLT-UCS and UPV-UCS relationships were established. A wide dispersion of the mechanical parameters was observed due to the heterogeneities of the studied material. Consequently, compositional, textural and microstructural observations on selected samples were performed. Two main material classes were recognized based on average grain size and total gypsum content, underlining the significant influence of the grain sorting on the measured mechanical properties. Keywords: Gypsum, Uniaxial compressive strength (UCS), Point load test (PLT), Mechanical properties, Geological heterogeneity

SUMMARYThe analysis of surface wave dispersion curves (DCs) is widely used for near-surface S-wave velocity (VS) reconstruction. However, a comprehensive characterization of the near-surface requires also the estimation of P-wave velocity (VP). We focus on the estimation of both VS and VP models from surface waves using a direct data transform approach. We estimate a relationship between the wavelength of the fundamental mode of surface waves and the investigation depth and we use it to directly transform the DCs into VS and VP models in laterally varying sites. We apply the workflow to a real data set acquired on a known test site. The accuracy of such reconstruction is validated by a waveform comparison between field data and synthetic data obtained by performing elastic numerical simulations on the estimated VP and VS models. The uncertainties on the estimated velocity models are also computed.

The field-scale microseismic (MS) activity of an unstable rock mass is known to be an important tool to assess damage and cracking processes eventually leading to macroscopic failures. However, MS-event rates alone may not be enough for a complete understanding of the trigger mechanisms of mechanical instabilities. Acoustic Emission (AE) techniques at the laboratory scale can be used to provide complementary information. In this study, we report a MS/AE comparison to assess the stability of a granitic rock mass in the northwestern Italian Alps (Madonna del Sasso). An attempt to bridge the gap between the two different scales of observation, and the different site and laboratory conditions, is undertaken to gain insights on the rock mass behavior as a function of external governing factors. Time- and frequency-domain parameters of the MS/AE waveforms are compared and discussed with this aim. At the field scale, special attention is devoted to the correlation of the MS-event rate with meteorological parameters (air temperature and rainfalls). At the laboratory scale, AE rates, waveforms, and spectral content, recorded under controlled temperature and fluid conditions, are analyzed in order to better constrain the physical mechanisms responsible for the observed field patterns. The factors potentially governing the mechanical instability at the site were retrieved from the integration of the results. Abrupt thermal variations were identified as the main cause of the site microsesimicity, without highlighting irreversible acceleration in the MS-event rate potentially anticipating the rock mass collapse.

Aquifer overexploitation is a common problem in drinking water management. This will become more and more important given the general reduction of water resources. To overcome overexploitation, one of the most adopted solutions is the relocation of extraction wells. To establish the positions of new wells, a precise knowledge of the hydrogeological setting is required. Specific surveys are therefore necessary to obtain information over wide investigation zones. Geophysical methods, particularly electromagnetic and electrical, can be useful with this aim. In the present paper a case history on the combined use of Electric Resistivity Tomography and Time Domain Electromagnetic soundings is reported. Surveys have been performed within the Maggiore and Traversola Valleys, to investigate the uppermost part of the Quaternary deposits, hosting the near surface aquifer. The electromagnetic data have been inverted with a spatially constrained approach by assuming a quasi 1D model of the subsurface. Geophysical surveys allowed for depicting the depth and lateral continuity of the supposed aquifer level in the surveyed area up to a depth of about 200 m and proposing potential positions for well relocation.

The investigation and prediction of geological anomalies in underground quarries is fundamental to ensure safety, efficiency and economic convenience of the exploitation. For these aims, non-destructive geophysical surveys may be an effective alternative approach to classical destructive prospecting techniques (i.e. horizontal drilling), with great advantages particularly in complex geological frameworks and in areas subjected to specific geo-hazards. Ground Penetrating Radar (GPR), for its high resolution, is a suitable technique for underground excavations, particularly for the identification of water bodies, fissures and fractured rocks. The present study is focused on the application of GPR for the prediction of karst structures in underground gypsum quarries. Karst phenomenon is a main risk factor for gypsum orebodies, where large cavities may be intersected by the excavation. The possible filling with clay or pressurized water of these cavities exponentially increases the dangerousness of the phenomenon, due to swelling problems and violent water inrushes. The aim of the present study is to propose, through modelling and field surveys, a description of GPR outputs for principal elements of karst hazard in gypsum bodies, with particular attention to the discrimination of fillings (air, water or clay).

A borehole thermal energy storage living lab was built nearby Torino (Northern Italy). The aim of this living lab is to test the ability of the alluvial deposits of the north-western Po Plain to store the thermal energy collected by solar panels. Monitoring the temperature distribution induced in the underground and the effectiveness of the heat storage in this climatic context is not an easy task. For this purpose, different temperature evolution strategies are compared in this paper: Local temperature measurements, numerical simulations and geophysical surveys. These different approaches were compared during a single day of operation of the living lab. The results of this comparison allowed to underline the effectiveness of time-lapse 3D electric resistivity tomography as a non-invasive and cost-effective qualitative heat monitoring tool. This was obtained even in a test site with unfavorable thermo-hydrogeological conditions and high-level anthropic noise. Moreover, the present study demonstrated that, if properly calibrated with local temperature values, time-lapse 3D electric resistivity tomography also provides a quantitative estimation of the underground temperature.

A Borehole Thermal Energy Storage living lab was built up nearby Torino (Northern Italy). This living lab aims at testing the ability of the alluvial deposits of the north-western Po Plain to store the thermal energy collected by solar thermal panels and the efficiency of energy storage systems in this climatic context. Different monitoring approaches have been tested and analyzed since the start of the thermal injection in April 2014. Underground temperature monitoring is constantly undertaken by means of several temperature sensors located along the borehole heat exchangers and within the hydraulic circuit. Nevertheless, this can provide only pointwise information about underground temperature distribution. For this reason, a geophysical approach is proposed in order to image the thermally affected zone (TAZ) caused by the heat injection: surface electrical resistivity measurements were carried out with this purpose. In the present paper, results of time-lapse acquisitions during a heating day are reported with the aim of imaging the thermal plume evolution within the subsoil. Resistivity data, calibrated on local temperature measurements, have shown their potentiality in imaging the heated plume of the system and depicting its evolution throughout the day. Different types of data processing were adopted in order to face issues mainly related to a highly urbanized environment. The use of apparent resistivity proved to be in valid agreement with the results of different inversion approaches. The inversion processes did not significantly improve the qualitative and quantitative TAZ imaging in comparison to the pseudo-sections. This suggested the usefulness of apparent resistivity data alone for a rough monitoring of TAZ in this kind of applications.

In some areas, the estimation of static corrections for land seismic data is a critical step of the processing workflow. It often requires the execution of additional surveys and data analyses. Surface waves (SWs) in seismic records can be processed to extract local dispersion curves (DCs) that can be used to estimate near-surface S-wave velocity models. Here we focus on the direct estimation of time-average S-wave velocity models from SW DCs without the need to invert the data. Time-average velocity directly provides the value of one-way time, given a datum plan depth. The method requires the knowledge of one 1D S-wave velocity model along the seismic line, together with the relevant DC, to estimate a relationship between SW wavelength and investigation depth on the time-average velocity model. This wavelength/depth relationship is then used to estimate all the other time-average S-wave velocity models along the line directly from the DCs by means of a data transformation. This approach removes the need for extensive data inversion and provides a simple method suitable for industrial workflows. We tested the method on synthetic and field data and found that it is possible to retrieve the time-average velocity models with uncertainties less than 10% in sites with laterally varying velocities. The error on one-way times at various depths of the datum plan retrieved by the time-average velocity models is mostly less than 5 ms for synthetic and field data.

Quick clay is a water-saturated formation originally formed through flocculation and deposition in a marine to brackish environment. It is subsequently leached to low salinity by freshwater flow. If its strength decreases, then the flocculated structure collapses leading to landslides of varying destructiveness. Leaching can result in a reduction of the undisturbed shear strength of these clays and suggestions exist that a reduction in shear wave velocities is also possible. Integration of SH seismic reflection and Love-wave dispersion data was undertaken, in an area near the Gota River in southwest Sweden, to evaluate the potential of shear wave velocity imaging for detecting quick clays. Seismic reflection processing evidenced several geologically interesting interfaces related to the probable presence of quick clays (locally confirmed by boreholes) and sand-gravelly layers strongly contributing to water circulation within them. Dispersion data were extracted with a Gaussian windowing approach and inverted with a laterally constrained inversion using a priori information from the seismic reflection imaging. The inversion of dispersion curves has evidenced the presence of a low velocity layer (lvl, with a velocity reduction of ca. 30 per cent) probably associable to quick clays. This velocity reduction is enough to produce detectable phase-velocity differences in the field data and to achieve a better velocity resolution if compared to reflection seismic velocity analyses. The proposed approach has the potential of a comprehensive determination of the shear wave velocity distribution in the shallow subsurface. A sensitivity analysis of Love-wave dispersion data is also presented underlining that, despite limited dispersion of the data set and the velocity-reducing effect of quick-clay leaching, the proposed interpretation procedure arises as a valuable approach in quick clay and other lvl identification.

Hazard mitigation from rockfalls and landslides is a priority in densely populated areas. A proper characterization of the inner structure of the rock mass is key to the comprehension of the mechanisms enhancing the slope instabilities. To this aim multi-scale geophysical methods can provide a novel and valuable tool for a high-resolution imaging of the internal structure of the rock mass and unique constraints on the physical state of the medium. We present here a cross-hole seismic tomography survey coupled with laboratory ultrasonic velocity measurements and physical properties determination on rock samples to characterize the damaged and potentially unstable granitic cliff of Madonna del Sasso (NW Italy). Results allowed to obtain: i) a lithological interpretation of the velocity field obtained at the site, ii) a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granite (weathering and anisotropy) of the cliff. The multi-scale approach adopted within this study revealed to be crucial for the imaging at depth of the main fractures affecting the cliff (site-scale seismic tests) and for the understanding of the variations in the seismic velocity between altered and intact rock (laboratory-scale tests); similar approaches can be potentially used in further microseismic monitoring studies.