How Close are the Edges of a Closed Fracture?

A laboratory experiment is peresented where the theory of amplitude reflection tuning in thin beds is tested. The results show a very good agreement with the theory previsio

Magnetic, electrical, and GPR waterborne surveys of moraine deposits beneath a lake: A case history from Turin, Italy

Bathymetry and bottom sediment types of inland water basins provide meaningful information to estimate water reserves and possible connections between surface and groundwater. Waterborne geophysical surveys can be used to obtain several independent physical parameters to study the sediments. We explored the possibilities of retrieving information on both shallow and deep geological structures beneath a morainic lake by means of waterborne nonseismic methods. In this respect, we discuss simultaneous magnetic, electrical, and groundpenetrating radar (GPR) waterborne surveys on the Candia morainic lake in northerly Turin (Italy).We used waterborne GPR to obtain information on the bottom sediment and the bathymetry needed to constrain the magnetic and electrical inversions. We obtained a map of the total magnetic field (TMF) over the lake from which we computed a 2D constrained compact magnetic inversion for selected profiles, along with a laterally constrained inversion for one electrical profile. The magnetic survey detected some deep anomalous bodies within the subbottom moraine. The electrical profiles gave information on the more superficial layer of bottom sediments. We identify where the coarse morainic material outcrops from the bottom finer sediments from a correspondence between high GPR reflectivity, resistivity, and magnetic anomalie

Geoelectrical measurements for agricultural canal seepage detection

The protection of water resources is a current problem at a global scale, especially in regions where this resource is poorly available. In this respect there is an increased pressure on water managers to improve water use efficiency. The use of geophysical tests as a tool for managing the efficiency of irrigation networks is well documented in literature since they have an high potential for canal seepage identification and quantification. In this respect, the present study is focused on the use of electrical resistivity methods on some sample canals of the Piedmont Region network. The results obtained have underlined the usefulness of geophysical methods in detecting local anomalies in the lining, potentially related to seepage losses, by means of waterborne CVES and in imaging the passage of saline tracer tests plumes, to be used for a quantification of the seepage losses, using cross-flow high-speed ERT

A preliminary test on the feasibility of locating an iron restoration pin in a statue by measuring the TMF anomaly with a triaxial MEMS magnetometer

We made a model of a “restored arm” with a bioclastite cylindrical sample (height= 18 cm; diameter=10 cm) in which an iron pin (length= 9 cm; diameter= 5 mm) was inserted out of the sample axis and obliquely (Figure 2a). A rotating platform surrounded by a graduated scale allowed us to rotate the sample in step of 10°. A sliding beam was used to move vertically the magnetometer so that, combining the two movements, the sample was scanned along horizontal circles 1 cm apart along its height (Figure 2 b) . At each measuring point we recorded 50 times at 50 Sample/s the three magnetic components (Vertical, Radial and Tangent) with the height and the angle. At each point mean, standard deviation and standard deviation of the mean over the 50 readings were calculated and the means were then taken as raw data. With this experimental setup, aimed to perform a preliminary test of the effectiveness of the sensor, the pin rotated within the sample and was always south of the sensor, therefore we did not get the reconstruction of the magnetic field around the sample as it would be in an acquisition, for example, around a statue arm

Discharge measurement with salt dilution method in irrigation canals: direct sampling and geophysical controls

An important starting point for designing management improvements, particularly in irrigation areas, is to record the baseline state of the water resources, including the amount of discharge from canals. In this respect discharge measurements by means of the salt dilution method is a traditional and well-documented technique. However, this methodology can be strongly influenced by the natural streaming characteristics of the canal (e.g. laminar vs. turbulent flow) and accurate precautions must be considered in the choice of both the measuring section and the length of the measuring reach of the canal which can affect the plume shape. The knowledge of plume distribution in the measuring cross-section is of primary importance for a correct location of sampling points aimed in obtaining a reliable measurement. To obtain this, geophysical imaging of an NaCl plume from a slug-injection salt dilution test has been performed within this paper by means of cross-flow fast electric resistivity tomography (FERT) in a real case history. Direct sampling of the same plume has been also performed with a multisampling optimization technique to obtain an average value over the measuring section by means of contemporarily sampling water in nine points. Results show that a correct visualization of the passage of the salt plume is possible by means of geophysical controls and that this can potentially help in the correct location of sampling points

Study of riverine deposits using electromagnetic methods at a low induction number

We conducted electromagnetic EM profiles along the Po River in Turin, Italy. The aim of this activity was to verify the applicability of low-induction-number EM multifrequency soundings carried out from a boat in riverine surveys and to determine whether this technique, which is cheaper than aircarried surveys, could be used effectively to define the typology of sediments and to estimate the stratigraphy below a riverbed. We used a GEM-2 handheld broadband EM sensor operating with six frequencies to survey the investigated area. Ground-penetrating radar GPR, a conductivity meter, and a time-domain reflectometer were used to estimate the bathymetry and to measure the EM properties of the water.A global positioning system, working in real-time kinematic mode, tracked the route of the boat with centimetric accuracy. We analyzed the induction number, the depth of investigation DOI, and the sensitivity of our experimental setup by forward modeling — varying the water depth, frequency, and bottom-sediment resistivity. The simulations optimized the choice of the frequencies that could be used reliably for the interpretation. The 3406-Hz signal had a DOI in the Po River water 27 m of 2.5 m and provided sediment resistivities higher than 100 m.We applied a bathymetric correction to the conductivity data using the water depths obtained from the GPR data.We plotted amap of the river bottom resistivity and compared this map to the results of a direct sediment sampling campaign. The resistivity values 120–240 m were compatible with the saturated gravel and pebbles in a sandy matrix, which resulted from direct sampling and with the known geology

Three-Dimensional (3D) Modelling and Optimization for Multipurpose Analysis and Representation of Ancient Statues

The technological advances that have developed in the field of threedimensional (3D) survey and modelling allow us to digitally and accurately preserve many significant heritage assets that are at risk. With regard to museum assets, extensive digitalization projects aim at achieving multilingual digital libraries accessible to everyone. A first trend is geared to the use of 3D models for further specialized studies, acquiring and processing virtual detailed copies as close as possible to the shape and contents of the real one. On the other hand, many museums look today for more interactive and immersive exhibitions, which involve the visitors’ emotions, and this has contributed to the increase in the use of virtual reality and 3D models in museums installations. In this paper, we present two case studies that belong to these scenarios. Multisensor surveys have been applied to some archeological statues preserved in two museums for multipurpose analyses and representation: a UTI test, which required high detailed data about the geometry of the object, and a communicative application, which needed instead a high level of model optimization, poor geometry, but very good representation that was achieved through remeshing tools and normal maps

Geophysical methods to support correct water sampling locations for salt dilution gauging

To improve water management design, particularly in irrigation areas, it is important to evaluate the baseline state of the water resources, including canal discharge. Salt dilution gauging is a traditional and well-documented technique in this respect. The complete mixing of salt used for dilution gauging is required; this condition is difficult to test or verify and, if not fulfilled, is the largest source of uncertainty in the discharge calculation. In this paper, a geophysical technique (FERT, fast electrical resistivity tomography) is proposed for imaging the distribution of the salt plume used for dilution gauging at every point along a sampling cross section. With this imaging, complete mixing can be verified. If the mixing is not complete, the image created by FERT can also provide a possible guidance for selecting water-sampling locations in the sampling cross section. A water multi-sampling system prototype aimed to potentially take into account concentration variability is also proposed and tested. The results reported in the paper show that FERT provides a three-dimensional image of the dissolved salt plume and that this can potentially help in the selection of water sampling points