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The main goal of this review is to emphasize the emerging role of the scientific community of applied geophysics in supporting actions for urban planning. We analyse the new scenario related to the global urbanization process and its impact on environmental sustainability and resilience to natural disasters of urban areas. A selected list of case-studies concerning the application of geophysical methods for the subsurface exploration in historical cities of Italy and megacities located in Asia and south America are described and discussed. The analysis clearly demonstrates that the geophysical surveys are assuming a great relevance to manage the underground urban environment and to adopt new strategies for the mitigation of geological risks. The sensor synergy strategy, the novel algorithms for the tomographic imaging and the capability to explore the subsoil with a multi-resolution approach are the key of success of the urban geophysics. Finally, the innovative aspects of the CLARA project funded by MIUR for promoting the integration of the remote and groundbased technologies for surface and subsurface imaging in urban areas are presented and discussed. [ABSTRACT FROM AUTHOR]

In the framework of S3 project "Short term earthquake forecasting" supported by Department of Civil Protection (DPC) and National Institute of Geophysics and Volcanology (INGV), a magnetotelluric (MT) station was installed in the Pollino area (southern Italy) during September 2012 by the Institute of Methodologies for Environmental Analysis (IMAA-CNR, Italy) in order to investigate possible correlation between electromagnetic signals and seismicity. For the last two years Pollino area has been characterized by swarm-type seismicity, culminating with the earthquake occurred on October 25, 2012 of magnitude MW=5.0. After the mainshock, the INGV installed a seismic station close to the MT station. In this paper, we focus the analysis on the largest event (ML=3.6) recorded during the colocated electromagnetic and seismic experiment. We applied time-frequency misfit criteria based on the continuous Morlet wavelet transform to compare the electric and seismic homologous components: this analysis confirms an overall good waveform similarity between the signals, but also some interesting differences in amplitude for frequencies above 1 Hz in correspondence of the arrival of particular seismic phases that need further investigations. [ABSTRACT FROM AUTHOR]

Abstract: In the context of in-situ geophysical methods the Electrical Resistivity Tomography (ERT) is widely used for the near-surface exploration of landslide areas characterized by a complex geological setting. Over the last decade the technological improvements in field-data acquisition systems and the development of novel algorithms for tomographic inversion have made this technique more suitable for studying landslide areas, with a particular attention to the rotational, translational and earth-flow slides. This paper aims to present a review of the main results obtained by applying ERT for the investigation of a wide spectrum of landslide phenomena which affected various geological formations and occurred in different geographic areas. In particular, significant and representative results obtained by applying 2D and 3D ERT are analyzed highlighting the advantages and drawbacks of this geophysical technique. Finally, recent applications of the time-lapse ERT (tl-ERT) for landslide investigation and the future scientific challenges to be faced are presented and discussed. [Copyright &y& Elsevier]

Abstract: A high resolution geophysical survey was carried out in the archaeological site of Rossano di Vaglio (Basilicata Region, Southern Italy), where an important ancient sanctuary is located. It was built during the IV century B.C. and devoted to the goddess Mephitis. The sanctuary rises in an area affected by a multiple and retrogressive rototraslational landslide, historically and presently subject to reactivation. The main objective of this work was the identification of buried structures of archaeological interest in an area designated by the Archaeological Superintendence of the Basilicata Region. The study was performed by means of the use of high resolution geophysical surveys. In particular, we made use of the joint application of three highly sensitive and non-invasive geophysical techniques, namely the Geoelectrical, the Magnetic and the Ground Probing Radar (GPR) methodologies. In such a way, we obtained two important results: first, we provided the archaeologists with information about the limits of the areas to be excavated; second, we could verify in real time the reliability of the geophysical results. The experimental results showed four main magnetic anomalies in the area of study, in agreement with the GPR results obtained for the same target. Finally, a partial excavation test of the investigated area revealed a buried building structure, located in correspondence of an anomaly identified by means of the geophysical prospecting. [Copyright &y& Elsevier]

Abstract: A geoelectrical monitoring activity has been carried out to improve the geological and hydrogeological knowledge about the Varco d''Izzo landslide (Potenza, Basilicata, Southern Apennine, Italy), an active rotational–translational slide evolved in earth-flow. In this work we have focused on the Self-Potential (SP) method by applying three different SP measuring techniques and combining modern technologies for data acquisition and new methods for tomographic inversion. A SP map and three static SP tomographies have been carried out to better analyse the groundwater circulation system and to better reconstruct the geometry of the landslide body. In the accumulation zone, which is the area more exposed to the geomorphological activity, a new SP measuring strategy has been applied. This strategy, based on time-continuous 2D SP tomographies, helps identify water flow changes in subsurface by studying the time series of SP tomographic images. The analysis of time-dependent changes of water infiltration in near surface is the key to better understand the hydrogeological processes underlying the ground instability phenomena. The time-lapse analysis of tomographic images has allowed us not only to investigate the correlation between the temporal changes of SP signals and rainfall events, but also to quantify the range of these changes. The modification of the distribution of the SP source accumulation zones is associated with the dynamics of the groundwater flows. These preliminary results allow us to consider the SP tomographic method as a tool for geophysical monitoring of landslide areas and encourage to develop new measuring systems for near-real time applications. [Copyright &y& Elsevier]

The first high-resolution images of the fault-controlled High Agri Valley Basin obtained with the electrical resistivity tomography are presented. The Agri Valley is one of the more complex components of the Quaternary fault network of the Apennine chain. The geometry of the pre-Quaternary bedrock, the location and dip of the master fault and the tectonic evolution of the basin are still a subject of debate. Therefore, deep electrical resistivity tomography integrated with stratigraphic analyses has been carried out to improve knowledge of the geological setting of the basin. The high-resolution electrical images allow us to reconstruct the complex geometry of the basin. The electrical imaging highlights the irregular shape of the basin, which is bordered by shallow faults and filled with Pleistocene alluvial deposits. In longitudinal cross-section, the basin appears as a mosaic of fault-bounded blocks forming three different depocenters separated by intrabasinal highs. In transverse cross-section, the basin is an irregular graben, locally asymmetric to the northeast, and with secondary grabens due to antithetic faults. [Copyright &y& Elsevier]

Geoelectrical prospecting techniques have been applied in the study of the Varco d''Izzo landslide, one of the most interesting of its type. It is characterized by a rototranslational movement in the early stage and successively has undergone earthflow-type movement, which still continues today. This landslide is located in the Southern Apennine area near the city of Potenza (Italy). In particular, electrical resistivity tomographies (ERT) and self-potential surveys (SP) have been carried out by combining modern technologies for data acquisition and new methods for data inversion. The high resolution of the electrical tomographic images helped us to accurately describe the geometry of this landslide body. Joint interpretation of geophysical, geological and geomorphological data allowed us to identify the sliding surface, estimate the thickness of the mobilized material and describe the main patterns of the subsurface fluid flows in Varco d''Izzo landslide. [Copyright &y& Elsevier]

The Electrical Resistivity Tomographic method has been applied for mapping active faults and to estimate the subsurface resistivity patterns of the High Agri Valley basin (Southern Italy). The study area is a complex Quaternary fault network of the Apennine chain and its geometry, the location and dip of the master fault and the tectonic evolution are still controversial. The electrical imaging highlights the asymmetrical shape of the basin, bordered by shallow-depth active faults and filled by Pleistocene alluvial deposits. The results of geoelectrical survey allow us to improve the basic knowledge regarding the geological and seismological setting of the High Agri valley. Furthermore, our findings have great relevance in defining the geophysical monitoring strategy in this seismic active zone where is operating a geoelectrical network to detect self-potential signals possible correlated with local earthquakes. The mapping of the resistivity subsurface patterns discloses the way to better locate the geoelectrical measuring stations in the investigated area. [Copyright &y& Elsevier]

This study concerns with an integrated geophysical approach for the detection and spatial-temporal characterization of the water infiltration into the Monte Cotugno dam embankment. This strategic civil infrastructure is the largest rock-fill dam in Europe and represents the nodal point of the water system feeding the Basilicata, Puglia and Calabria regions (southern Italy). Here, we propose an approach based on the combination of geophysical techniques as Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) with Thermal-InfraRed mapping (TIR) and geotechnical in-situ measurements. Such an approach was applied for the diagnosis of the Monte Cotugno dam with the aim both to gain information about the geometry of visible micro-fractures in the dam coverage and have a rapid mapping of the dam inner areas affected by water infiltration phenomena. The sensing methods were deployed in a cascade modality, where the Thermal-InfraRed (TIR) method was used for surveying the dam along the overall length in order to achieve information about the dam coverage status. In particular, TIR analysis allowed us to identify five areas affected by significant fractures and coating detachment. Afterwards, GPR surveys were performed on the sloping side of the dam by investigating few areas among those identified by TIR analysis. In this way, it was possible to get indications whether the water infiltration affected the deeper parts of the dam. Lastly, Electrical Resistivity Tomography (ERT) method was applied in order to detect deeper inner areas affected by water leakages. Finally, a joint interpretation of the three sensing methods was confirmed by shallow boreholes (< 20 m) drilled over the dam crown, which have evidenced the presence of localised water leakages in the dam. In conclusion, the results are encouraging and the integrated use of non-invasive sensing techniques can be considered an effective tool for the diagnosis and short- and long-term monitoring of critical infrastructures as the Monte Cotugno dam. [ABSTRACT FROM AUTHOR]

The Pertusillo reservoir, located in the High Agri Valley (southern Italy), represents an example of a site affected by continued reservoir-induced seismicity. Although it has been shown that annual fluctuation can be considered the main forcing of the induced seismicity in this area, an investigation of the relationships between the seismicity and some water level parameters of the Pertusillo reservoir carried out in this paper. The aim is to understand, apart from the annual fluctuation, if one or more of these parameters play a dominant role in inducing seismicity year after year SW of the reservoir. The findings of this study suggest that the exceedance of water levels over the previous maxima did not trigger any historical earthquake. In addition, the daily water level rate and the duration for which the maximum water level is maintained do not play any significant role in inducing seismicity. The maximum amplitude of water level change in a hydrological cycle as low as 8 m appears to be large enough to trigger the seismicity SW of the Pertusillo reservoir, whereas higher maximum amplitudes of water level in a hydrological cycle seem not to increase the seismicity rate. Furthermore, it is shown that a long-lasting increase of the water level may lead to induced earthquakes with larger magnitude. Finally, it is demonstrated that the geology of the area SW of the reservoir may provide favourable conditions for the water level fluctuations to induce seismicity in that region, whereas a different geology to the NE of the reservoir is the cause of negligible pore pressure increase. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a micro-optical wall pressure sensor concept based on the optical modes of dielectric resonators. The sensing element is a spherical micro-resonator with a diameter of a few hundred micrometers. A latex membrane that is flush mounted on the wall transmits the normal pressure to the sensing element. Changes in the wall pressure perturb the sphere's morphology, leading to a shift in the optical modes. The wall pressure is measured by monitoring the shifts in the optical modes. Prototype sensors with polydimethylsiloxane micro-spheres are tested in a steady two-dimensional channel flow and in a plane wave acoustic tube. Results indicate sensor resolutions of ∼20 mPa and bandwidth of up to 2 kHz. [ABSTRACT FROM AUTHOR]

The remediation of polluted soils by heavy metals concerns wide areas of the planet, and the electrokinetic remediation (EKR) is an alternative method to the traditional ones. Moreover, in the current technologies this technique requests high power levels, with consequent security and cost problems. To enhance the process it is possible to use hydro-silica layers properties: these layers allow to move the heavy metals, if the electrical field is applied for a long time (T > 24 hours). Previous experiences showed that a sinusoidal waveform can improve the efficiency of the process up to 70%. In this paper we show the results of the EKR experiments carried out with two different electric fields: linear and radial. The electric field was controlled both as gradient and waveform (positive sinusoidal and DC). We worked with saturated sands polluted by Cr(VI). The process was monitored and calibrated using sets of voltage electrodes, chemical analysis and complex electrical resistivity of selected sand samples. The EKR process moved the 69% of Cr(VI) applying a linear electric field, while it moved the 34% of Cr(VI), applying a radial electric field. We also observed that the local electric resistivity is an efficient and economic index of the process, and the behaviour of the resistivity versus voltage let us presume that a positive ramp up signal, with a period of 12 hours, should be more effective than the positive sinusoidal one. Moreover, these experiments show that the process electrodeposits the heavy metal on to the surface of the high current electrode, consequently the polarity inversion of the applied electric field can clean this electrode and restore his "storage capacity". [ABSTRACT FROM AUTHOR]

Summary: In this study, the feasibility of the resistivity method for the study of the spatial and temporal soil moisture variations in the Vallaccia catchment (central Italy), covering an area of about 56km2, was investigated. Correlation and regression analyses were performed over a 1year data set of simultaneous soil electrical resistivity and soil moisture measurements, acquired in eight different sites with a Resistivimeter Syscal Junior and a portable Time Domain Reflectometer (TDR), respectively. Measurements acquired in-time by continuous Frequency Domain Reflectometer (FDR) sensors were also used and compared with simultaneous resistivity measurements. The statistical analyses were conducted not only for the whole data set, but also separately for each sampling day, for each sampling site and considering spatially averaged data. Results showed a good correlation between resistivity and soil moisture measurements, revealing the capability of resistivity measurements to infer soil moisture spatial and temporal variability with a root mean square error equal, on average, to 4.4% vol/vol. In comparison with TDR, the resistivity method gives information integrated on a greater volume of soil and the measurements are easier and quicker to be carried out. Therefore, this method can be considered as an alternative tool to be employed for qualitative and quantitative soil moisture monitoring in small to medium catchments. [ABSTRACT FROM AUTHOR]

Nowadays, dam safety management is gaining great importance since it affects in a crucial way the monitoring and improvement of risky reservoirs, but this topic is very challenging since the dam safety requires long-term and time-continuous monitoring. In this framework, the exploitation of conventional geotechnical investigation methods often requires invasive actions in the inner of the structure to be investigated (destructiveness) and only provides punctual information for small volumes. On the contrary, the application of noninvasive sensing techniques makes it possible to investigate higher volumes without affecting the structure. In this paper we describe the application of GPR for the monitoring and diagnostics of one of the largest dams in the Basilicata region (Southern Italy). The investigation aims at detecting and localizing underground sandstone banks that are potential ways of flow of water below the dam. The manageability and the noninvasiveness of GPR have resulted in particularly suitable for this kind of application because the versatility of this geophysical method allows to investigate large areas with a good spatial resolution giving the possibility to detect the presence of inhomogeneities in the subsoil below the dam. [ABSTRACT FROM AUTHOR]

Abstract: The Carlo''s V Castle, located in Crotone Town, on the Ionian coast of the Calabria Region (Italy), date back to the 13th century d.C. (Fig. 1). During its long life, the building changed several owners and sustained the damages and the consequent reconstructions due to the innumerable naval battles. Moreover, the castle suffered the action of the earthquakes which always afflict the region. With the principal aim of detecting the location, depth and geometry of the rests of destroyed structures, a systematic Ground Penetrating Radar (GPR) survey was carried out in the area inside the boundary walls. The results are sixty-two one-meter-spaced, filtered and migrated radargrams arranged in four 3D data-sets. From each data-set, the most significant time-slice was extracted. To reduce the ambiguity in the GPR data interpretation, additional geophysical techniques, such as Magnetic (M), and Electrical Resistivity Tomography (ERT), were carried out with a partial superimposition with the GPR data. A comparison and a joint interpretation amongst different geophysical data pointed out some very remarkable features associated to buried remains and possible buried cannonballs. With the secondary aim to check the presence of an old military walkway linking two bastions a GPR profile was carried out on the sea side boundary wall. The GPR results are in agreement with an ERT survey carried out on the same profile and consistent with the presence of an underground passage. [Copyright &y& Elsevier]

Abstract: Most of Basilicata region in the southern Italian Apennines is characterized by landslides often developing in clayey–marly formations. Many events have been triggered by extreme rainfall or snowmelt. The most important happened (on February–March 2005) at Bosco Piccolo 5 km far from Potenza. This landslide developed subsequently to rapid snowmelt occurred during alternating short periods of high temperatures and intense and continuous snowfalls. This complex landslide affected 4 ha of surface and reached a maximum depth of 20 m inducing damage and collapse of about 80% of the buildings in the village. An integrated multidisciplinary approach has been adopted to study the landslide. A multitemporal aerial photo interpretation and detailed geomorphological surveys have been carried out. Combined Electrical Resistivity Tomography (ERT) and Self-Potential (SP) measurements have been performed and calibrated with boreholes stratigraphy. Such an integrated approach allowed us to partially reconstruct the geometry of the investigated body and to evaluate the effectiveness of drainage system planned for the area. [Copyright &y& Elsevier]

Abstract: We have jointly applied microwave remote sensing imaging and ground-based geophysical methodologies for investigating ground deformation. In particular, the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique referred to as Small BAseline Subset (SBAS) algorithm and the Electrical Resistivity Tomography (ERT) method have been applied. The former is a tool for investigating large areas, allowing us to detect deformation phenomena and to analyse their spatial patterns and temporal evolution; the latter permits us to reconstruct, with high spatial resolution, the geometry of near-surface geological structures and to estimate the electrical resistivity of outcropping terrains. The starting point of our analysis has been a DInSAR survey carried out on an area of about 400 km2 centred around the town of Potenza (Basilicata region, Italy), for which SAR data acquired by the ERS-1/2 sensors in the time interval 1992–2000 were available. The DInSAR analysis allowed us to detect an unknown ground deformation effect which involves the urban area of Satriano di Lucania, located close to Potenza. An on-site ERT survey was then carried out in order to characterize in detail the physical properties of the terrains involved in the main deformation pattern detected via the DInSAR processing. The integration of the DInSAR and ERT measurements permitted us to investigate areas where the deformation have space-variant characteristics and allowed us to formulate a hypothesis on the origin of the detected displacement processes that, although not fully conclusive, is consistent with the overall DInSAR and ERT analysis. [Copyright &y& Elsevier]

We reveal the existence of clustering properties in the temporal distribution of the earthquakes observed in a seismic active area of Southern Apennine Chain (Italy) by means of quantitatively fractal tools (Fano Factor and Allan Factor). Data consist in a sequence of seismic events instrumentally recorded during the period 1983–1995 in the Irpinia-Basilicata Region (Southern Italy), in which in past and recent years, many destructive events occurred. The analysis of the Fano and Allan Factors shows that the sequence of the occurrence times of events with magnitude Mth≥2.5 is characterized by a scale-invariant behavior from the time scale τ∼5 · 10[sup 3] s with a scaling coefficient α∼0.3. By gradually increasing the threshold magnitude up to Mth=3.1, the value of the scaling coefficient monotonically decreases, pointing out a falling-off in the correlation strength. Although the increasing of the threshold magnitude seems to act as a randomizing filter which removes clustered structures, no firm sign of Poissonian, memoryless behavior is detectable in our analysis. [ABSTRACT FROM AUTHOR]