Geophysical tomography in engineering geology: an overview

An overview of the tomographic interpretation method in engineering geophysics is presented, considering the two approaches of the deterministic tomography inversion, developed for rock elasticity analysis, and the probability tomography imaging developed in the domain of potential fields methods. The theoretical basis of both approaches is shortly outlined before showing a laboratory and a field application.Comment: 4 pages, 6 figures. Invited lecture at the 7th International Congress of the Brazilian Geophysical Society, Salvador, Bahia, Brazil, 28-31 October 200

Modeling electrical dispersion phenomena in Earth materials

It is illustrated that IP phenomena in rocks can be described using conductivity dispersion models deduced as solutions to a 2nd-order linear differential equation describing the motion of a charged particle immersed in an external electrical field. Five dispersion laws are discussed, namely: the non-resonant positive IP model, which leads to the classical Debye-type dispersion law and by extension to the Cole-Cole model, largely used in current practice; the non-resonant negative IP model, which allows negative chargeability values, known in metals at high frequencies, to be explained as an intrinsic physical property of earth materials in specific field cases; the resonant flat, positive or negative IP models, which can explain the presence of peak effects at specific frequencies superimposed on flat, positive or negative dispersion spectra

On the role of the J-E constitutive relationship in applied geoelectromagnetism

In current applications of the Induced Polarization (IP) method, the Debye and Cole-Cole models are used to study relaxation and dispersion properties of rocks, though it is believed that this type of modelisation is confused and vague, because of the lack of a background physical description. In this paper, we show that the Debye model can physically be deduced as a consequence of the electrodynamic behaviour of a mixture of bound and unbound charged particles immersed in an external electric field. We also clarify that the Cole-Cole model is a synthetic model, which can physically be explained as a continuous distribution of Debye terms

Integration of geophysical datasets by a conjoint probability tomography approach: application to Italian active volcanic areas

We expand the theory of probability tomography to the integration of different geophysical datasets. The aim of the new method is to improve the information quality using a conjoint occurrence probability function addressed to highlight the existence of common sources of anomalies. The new method is tested on gravity, magnetic and self-potential datasets collected in the volcanic area of Mt. Vesuvius (Naples), and on gravity and dipole geoelectrical datasets collected in the volcanic area of Mt. Etna (Sicily). The application demonstrates that, from a probabilistic point of view, the integrated analysis can delineate the signature of some important volcanic targets better than the analysis of the tomographic image of each dataset considered separately

Advanced magnetic visualization of Mt. Vesuvius shallow plumbing system by probability tomography

We show the results of the application of a new magnetic probability tomography imaging method to the aeromagnetic dataset collected by AGIP on Mt. Vesuvius in 1978. A magnetic dipole occurrence probability function is defined in such a way as to contain all information about the whole class of equivalent sources compatible with the original survey dataset. An advanced 3D visual system is also applied for the first time to visualise the spacial pattern of the magnetic dipole occurrence probability function. It is shown that in the case of Vesuvius, the shallow plumbing system is characterised by a high probability of occurrence of a dipole at 2 km of depth b.s.l., nearly directed along the present main earth’s magnetic field. This leads to hypothesize that the top terminal portion of the volcanic apparatus is completely filled with magnetised volcanic material

Examples of application of tensorial resistivity probability tomography to architectonic and archaeological targets

We present the results of the application of the tensor resistivity method to the assessment of the state of conservation of some architectonic features of the S.Giovanni a Carbonara monumental monastery (Naples, Italy) and to the recognition of buried remains in the archaeological site of the roman Port of Claudius at Fiumicino (Rome, Italy). The 3D tomographic approach, based on the concept of resistivity anomaly source occurrence probability, has been used for the analysis of the invariant parameter related to the trace of the determinant of the apparent resistivity tensor

Gd-EOB-DTP-enhanced MRC in the preoperative percutaneous management of intra and extrahepatic biliary leakages: Does it matter?

Postoperative bile leakage is a common complication of abdominal surgical procedures and a precise localization of is important to choose the best management. Many techniques are available to correctly identify bile leaks, including ultrasound (US), computed tomography (CT) or magnetic resonance imaging (MRI), being the latter the best to clearly depict "active" bile leakages. This paper presents the state of the art algorithm in the detection of biliary leakages in order to plan a percutaneous biliary drainage focusing on widely available and safe contrast agent, the Gb-EOB-DPA. We consider its pharmacokinetic properties and impact in biliary imaging explain current debates to optimize image quality. We report common sites of leakage after surgery with special considerations in cirrhotic liver to show what interventional radiologists should look to easily detect bile leaks

Sperimentazione delle metodiche a Potenziali Indotti nella versione a caduta di potenziale - P.I.T.D. - nella prospezione di giacimentologie a solfuri metallici in Sardegna

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