Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the V S,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical Electronic supplementary material The online version of this article

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Monitoring the temporal evolution of resonance frequencies and velocity changes detected from ambient seismic noise recordings can help in recognizing reversible and irreversible modifications within unstable rock volumes. With this aim, the long-term ambient seismic noise data set acquired at the potentially unstable cliff of Madonna delSasso (NW Italian Alps) was analysed in this study, using both spectral analysis and cross-correlation techniques. Noise results were integrated and compared with direct displacement measurements and meteorological data, to understand the long-term evolution of the cliff. No irreversible modifications in the stability of the site were detected over the monitored period. Conversely, daily and seasonal air temperature fluctuations were found to control resonance frequency values, amplitudes and directivities and to induce reversible velocity changes within the fractured rock mass. The immediate modification in the noise parameters due to temperature fluctuations was interpreted as the result of rock mass thermal expansion and contraction, inducing variations in the contact stiffness along the fractures isolating two unstable compartments. Differences with previous case studies were highlighted in the long-term evolution of noise spectral amplitudes and directivities, due to the complex 3-D fracture setting of the site and to the combined effects of the two unstable compartments.

Extensive waterborne Continuous Vertical Electrical Soundings survey.Laterally Constrained Inversion for the identification of the lakebed sediments.Groundwater recharge area, reconstruction of lake basin genesis.

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. Copyright © 2017 John Wiley & Sons, Ltd.

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The reliability of surface wave tests for the evaluation of V S,30 in seismic site characterization is assessed with respect to both uncertainty and accuracy. The discussion of uncertainty is mainly focused on the implications of solution nonuniqueness in inverse problems; only the inversion uncertainty is considered within this work, omitting other possible sources like non trivial geological settings (e.g. lateral variations) or the influence of different processing procedures. A Monte Carlo approach has been used to select, through a statistical test, a set of shear wave velocity models that can be considered equivalent with respect to fitting the experimental dispersion curve according to the information content (dispersion velocities and frequency range) and the experimental uncertainties. This set of equivalent solutions is then used to evaluate the uncertainty in the determination of V S,30. Moreover, comparisons between the results obtained by surface wave tests and invasive seismic methods are reported to assess the accuracy of V S,30 evaluation using surface wave methods. It is shown that, given an adequate investigation depth, the solution non uniqueness is not a major concern and that the results are in most situations comparable with the ones of invasive tests providing an accurate estimate of V S,30 , even with simplified approaches.

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 noncontact 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 noncontact 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 data sets 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.