P. M. Barone

Comparison of GPR and unilateral NMR for water content measurements in a laboratory scale experiment

Several factors affect antenna-soil coupling in a Ground Penetrating Radar (GPR) survey, like surface roughness, lithology, lateral heterogeneities, vegetation, antenna height from the surface and water content. Among them, lithology and water content have a direct effect on the bulk electromagnetic nproperties of the material under investigation. It has been recently pointed out that the wavelet of the early-time portion of a radar signal is correlated to the shallow subsurface dielectric properties of a material. This result indicates that some information on such properties can be directly extracted from the analysis of GPR early-time traces. In the present paper, we use the early-time GPR signal, in terms of average envelope amplitude computed on the first half-cycle, to map the near-surface (few centimetres) lateral distribution of dielectric parameters, induced by changing the shallow water content on a concrete slab. This controlled experiment was specifically designed to study the effect of water content variations on antenna-material coupling, minimizing the influence of both surface roughness and heterogeneity. nThe quantitative control of the water in the shallow portion of the slab is performed by using a portable unilateral Nuclear Magnetic Resonance (NMR) sensor, which is able to determine the water content in the material on the basis of the measured proton density. The results show a matching pattern of the physical parameters measured with the two different techniques and a very high degree of linear correlation (r = 0.97) between the radar early-time signal average amplitude and the intensity of the NMR signal, which is proportional to the proton density, i.e., to the water content. This experiment suggests that the early-time approach could be used as a fast and high- spatial resolution tool for qualitatively mapping water content lateral variations in a porous material at shallow depth, using a ground-coupled single-offset antenna configuration and that a quantitative evaluation of the moisture content would require a calibration procedure.

An evaluation of the early-time GPR amplitude technique for electrical conductivity monitoring

In the present paper we use the recently-proposed early-time GPR (Ground Penetrating Radar) amplitude technique with the aim of detecting the variations of electric conductivity in a porous material having a uniform permittivity. A specific laboratory setup has been realised to evaluate the sensitivity of the early-time amplitudes to the variations of the subsurface salt concentration (i.e., conductivity). To assess the capacity of the early-time amplitude to follow the electrical conductivity changes, we compare the early-time results acquired using the envelope of the first part of GPR signals with the concurrent conductivity measured with TDR (Time Domain Reflectometry). The GPR survey has been carried out using a bistatic radar unit (Sensors & Software, Inc) operating at 1 GHz. Further useful information has been derived by suitably implementing a full-wave numerical modelling, able to accurately analyse the features of the waves detected by the GPR with flexible parameterization. Our results indicate that the near-surface electromagnetic properties of the material can be directly extracted from the GPR early-time amplitude technique. In particular, both experimental and numerical data show a very high correlation coefficient between the radar signal amplitude and the TDR-derived electrical conductivities.

Forensic Geophysics: how GPR could help police investigations

Police regularly use GPR to uncover buried caches of drugs, money, weapons as well as locate unmarked graves. GPRs versatility and sensitivity to buried objects has lead to an ever widening use in forensics. While GPR does not deliver the fantasy results portrayed on some TV shows, GPR can provide powerful insight to forensics specialists needing to conduct non-destructively detailed subsurface site investigations.

GPR application to the structural control of historical buildings: two case studies in Rome, Italy2009-06

Preservation of historical buildings requires particular care, as any intervention must not alter or damage nthe style, structure or contents of the edifice. In order to properly plan the restoration of a building, non-destructive techniques can be used extensively to detect structural elements and weaknesses. Ground-penetrating radar (GPR) is particularly well adapted to this type of work, as the method is non-invasive, rapid and provides high-resolution images of contrasting subsurface materials. nIn the present work we show the successful application of the GPR technique to the investigation of two historical buildings that differ in age, structure and geometry. nThe first case is the GPR detection of fractures and internal lesions in the architrave of the Porticus Octaviae, a partially restored Roman building. The second case uses GPR in the important Zuccari Palace to determine the internal structure above vaulted ceilings that host a series of 16 th century frescos. Both buildings are located in downtown Rome, Italy. nThese examples show that GPR can give detailed, non-invasive data that describe the state of conservation of historical buildings. In particular, this technique can produce fundamental information nfor the restorers (e.g., location, dimension and geometry of the structural lesions) that will help them develop the best possible protection plan, retrieving quantitative information about the location nand the dimension of the lesions as well as the thickness of the different layers.

Applications of GPR to archaeology and geology: the example of the regio III in Pompeii (Naples, Italy)

GPR investigations has been collected in Pompeii, in an area of the regio III not yet fully excavated. In this area, as in many other parts of this roman city, large portions of archaeological features are still buried under thick volcanic deposits. The radar survey has been conducted on the top of a long scarp parallel to Nola Street. This site was chosen because some remains are well visible on the front of the scarp, so they can be use to calibrate the radar sections. The results allowed us to reconstruct the subsurface structure of the area, and to locate the main roman ruins buried in the volcanic deposits. Moreover, the analyses of the radar sections highlighted the geometry of the volcanic deposits overlain the roman ruins, and made possible the correlation between the shallow geological stratigraphy and the reflectors sequence shown in the radargrams.

Ground-Penetrating Radar technique to investigate historic eruptions on the Mt. Etna volcano (Sicily, Italy)

In the present paper we demonstrate the capability of different remote sensing techniques to reconstruct the evolutionary history of the lava flows on the Mt. Etna volcano. A preliminary approach to the sites, based on aerial photogrammetry, DEM, and topographic analyses, supports an intense GPR (Ground Penetrating Radar) survey in several sites with different stratigraphical characteristics. The GPR measurements are performed with a bistatic system equipped with both 500 and 1000 MHz antennas. The use of different polarizations (TE, TM, Cross-Tx, and Cross-Rx) allow to extract subsurface features information having 3D geological structure reconstruction, electromagnetic nature information and properties of buried reflectors. This preliminary study highlights how the GPR technique provides, non-destructively, useful data to study the mechanisms of emplacement and the correlated hazard. Furthermore, if an inactive lava tubes can only be detected after the collapse of their vault, the use of GPR, on the contrary, could help to locate buried undamaged lava tubes and to measure their dimensions, providing useful structural information. Lava tubes, also, strongly influences the development of lava fields and the hazard connected with them, because they keep the lava thermally isolated causing a propagation longer than it would have done in an open channel. Additionally, the combined use of different remote sensing techniques can be useful to better estimate the thickness of the lava fields, giving precious data about the nature of the flow. Finally, the results highlight the importance of this combined approach to evaluate different physical parameters at the same time.

Integrated GPR and unilateral NMR approach to estimate water content in a porous material

In the present paper we combined two different non-destructive techniques to detect the water content spatial variation in a porous material. The main goal of this work was to verify the ability of radar “early time” signals, using the proton density values measured with the unilateral NMR (Nuclear Magnetic Resonance) technique, in order to detect the spatial distribution of water in the subsurface of a concrete slab. This site was chosen because it was the best compromise between an uniform, porous and slow drainage material and the antenna-coupling, affected only by the surface permittivity variations due to the change in water content. The GPR (Ground Penetrating Radar) survey has been conducted using a bistatic radar unit (Sensors & Software, Inc) operating at 1000 MHz; on the other hand, NMR data were collected using portable unilateral NMR operating at 16.3 MHz. The results obtained in this paper confirm that the “early time” radar signal and the NMR response can be applied to estimate some physical properties of both natural and man-made materials. In fact, the data show a matching pattern of the water distribution in the shallow part of the slab measured by GPR and NMR, and a very high correlation coefficient between the radar signal amplitude and the NMR signal integral. Finally, the results highlight the importance of this new combined approach to evaluate different physical parameters at the same time.

P6.18 Pisa Syndrome in Parkinson's disease: EMG features disclose two different underlying pathophysiological mechanisms

highlighted the contribution of the cerebellum in its pathophysiology. Cerebellum is involved in the temporal organization of rhythmic finger movements. Specifically, lateral cerebellum seems to be implicated in the process of synchronization of paced digital movements at a given movement rate. Objective: Aim of the present study was to demonstrate kinematic abnormalities of paced digital movements in task specific focal hand dystonia (FHD). Methods: We studied 10 patients with FHD and 10 healthy controls, all right-handed. Each subject underwent kinematic analysis of finger movements, using a sensor-engineered glove, while subjects performed a finger opposition motor task. Recording were obtained from the affected and the unaffected hand of patients and the right and left hand of controls evaluating the following parameters: touch duration (TD) and inter tapping interval (ITI) during opposition movements of the index (Finger Tapping-FT) and of all the four fingers against the thumb (sequential finger movements, SEQ). These tasks were repeated at 1 and 3 Hz speed in a metronome-paced condition, with the eyes closed. Results: TD was significantly prolonged and ITI was significantly shortened in both the affected and the unaffected hand of FHD patients compared to the right and left hand of control subjects. This abnormality was evident for both SEQ movements at 1 and 3 Hz speed and for FT movements at 1 Hz speed. Conclusions: Patients with focal hand dystonia display bilateral kinematical abnormalities in simple and sequential finger movements. These alterations likely reflect the role of the cerebellum in modulating the temporal organization of movements. Our results, showing a bilateral impairment of rhythmic finger movements in FHD, support the role of cerebellum in the pathophysiology of the disease.

A GPR Investigation in Pompeii (Neaples, Italy) - The Archaeological Area of Nola Gate

The scope of the present work was to test the performance of Ground Penetrating Radar in the volcanic sediments, and to use this technique to investigate the archaeological ruins of one of the most important archaeological and geological sites in the world, Pompeii. The preliminary results demonstrate that the GPR technique is particularly suitable in this type of volcanic terrain. In fact, the survey conducted on the archaeological area of Nola Gate has produced good results both in term of signal penetration and vertical resolution. In particular, the radar data clearly shows a series of reflectors that match well with contacts observed in the geological section, as well as hyperbolic events related to man-made structures.