Simultaneous use of electrostatic quadrupole and GPR in urban context: Investigation of the basement of the Cathedral of Girona (Catalunya, Spain)

Geophysics ◽  
2000 ◽  
Vol 65 (2) ◽  
pp. 526-532 ◽  
Author(s):  
Michel Dabas ◽  
Christian Camerlynck ◽  
Pere Freixas i Camps
Keyword(s):  
A Priori ◽  
Geophysical Methods ◽  
Limited Area ◽  
Urban Context ◽  
Northern Spain ◽  
Geophysical Investigation ◽  
Combined Use ◽  
Priori Information ◽  
Ground Penetrating ◽  
Electrostatic Quadrupole

There is a growing demand for nondestructive geophysical investigation in archaeology, especially in an urban context. This is a result of taking our heritage more seriously than in the past. Since excavations are possible only over a very limited area, any a priori information brought by geophysical methods can help to focus these excavations. The classical geophysical methods used in archaeology (resistivity, magnetism) are not applicable in an urban context with problems of accessibility and inherent electromagnetic noise. The potential of the combined use of ground‐penetrating radar (GPR) and electrostatic (ES) quadrupole data is demonstrated in the investigation of the floor of the cathedral of Girona in northern Spain. A 1.3 × 1.3 m electrostatic quadrupole was towed continuously over a set of parallel profiles to produce a resistivity map for a 20 × 60 m area. A set of resistive anomalies corresponds with known structures (probably graves). The largest observed anomalies appear to be related to foundations of former buildings. A set of 450-MHz GPR profiles were collected and common midpoint (CMP) soundings were performed to convert from time to depth. The time slice centered at 14 ns (at 0.9-m depth) shows anomalies similar to those in the resistivity map. Two different physical properties are measured (electrical resistivity and a reflectivity coefficient that is mainly a function of the contrast in dielectric permittivity); both methods may be sensitive mainly to the water content in the volume under investigation. The improved confidence in an interpretation obtained by combining these two sets of data enables us to infer the location and geometry of the Romanesque building which stood previously on the site of the present cathedral of Girona. Excavations support the interpretation.

scholarly journals Seismic Constrained Gravity Inversion: A Reliable Tool to Improve Geophysical Models Away from Seismic Information

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 467
Author(s):  
Daniele Sampietro ◽  
Martina Capponi
Keyword(s):  
High Resolution ◽  
Gravity Field ◽  
A Priori ◽  
Geophysical Methods ◽  
Real Life ◽  
Gravity Inversion ◽  
Seismic Surveys ◽  
Real Model ◽  
Gravity Fields ◽  
Priori Information

The exploitation of gravity fields in order to retrieve information about subsurface geological structures is sometimes considered a second rank method, in favour of other geophysical methods, such as seismic, able to provide a high resolution detailed picture of the main geological horizons. Within the current work we prove, through a realistic synthetic case study, that the gravity field, thanks to the availability of freely of charge high resolution global models and to the improvements in the gravity inversion methods, can represent a valid and cheap tool to complete and enhance geophysical modelling of the Earth’s crust. Three tests were carried out: In the first one a simple two-layer problem was considered, while in tests two and three we considered two more realistic scenarios in which the availability on the study area of constraints derived from 3D or 2D seismic surveys were simulated. In all the considered test cases, in which we try to simulate real-life scenarios, the gravity field, inverted by means of an advanced Bayesian technique, was able to obtain a final solution closer to the (simulated) real model than the assumed a priori information, typically halving the uncertainties in the geometries of the main geological horizons with respect to the initial model.

scholarly journals Multi-Frequency GPR Microwave Imaging of Sparse Targets through a Multi-Task Bayesian Compressive Sensing Approach

2021 ◽  
Vol 7 (11) ◽  
pp. 247
Author(s):  
Marco Salucci ◽  
Nicola Anselmi
Keyword(s):  
Compressive Sensing ◽  
Quantitative Imaging ◽  
A Priori ◽  
Wide Band ◽  
Frequency Diversity ◽  
A Priori Information ◽  
Spectral Components ◽  
Priori Information ◽  
The One ◽  
Ground Penetrating

An innovative inverse scattering (IS) method is proposed for the quantitative imaging of pixel-sparse scatterers buried within a lossy half-space. On the one hand, such an approach leverages on the wide-band nature of ground penetrating radar (GPR) data by jointly processing the multi-frequency (MF) spectral components of the collected radargrams. On the other hand, it enforces sparsity priors on the problem unknowns to yield regularized solutions of the fully non-linear scattering equations. Towards this end, a multi-task Bayesian compressive sensing (MT-BCS) methodology is adopted and suitably customized to take full advantage of the available frequency diversity and of the a-priori information on the class of imaged targets. Representative results are reported to assess the proposed MF-MT-BCS strategy also in comparison with competitive state-of-the-art alternatives.

Mapping fractures with GPR: A case study from Turtle Mountain

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. B139-B150 ◽  
Author(s):  
Ulrich Theune ◽  
Dean Rokosh ◽  
Mauricio D. Sacchi ◽  
Douglas R. Schmitt
Keyword(s):  
Slope Stability ◽  
Fractured Rock ◽  
A Priori ◽  
Rough Terrain ◽  
Geologic Mapping ◽  
Geologic Hazard ◽  
Bedding Planes ◽  
Priori Information ◽  
Ground Penetrating ◽  
Future Work

Ground-penetrating radar (GPR) surveys were acquired of rocks on the highly fractured summit of Turtle Mountain in Canada. In 1903 a disastrous rock slide occurred at Turtle Mountain and it still poses a geologic hazard. Dips, shapes, and penetration depths of fractures are important parameters in slope-stability analysis. Determination of fracture orientation at Turtle Mountain has been based mostly on areal geologic mapping and, most recently, on data collected from boreholes. The purpose of GPR surveys was to test, confirm, and extend information about fractures and bedding planes. Data acquisition was complicated by the rough terrain; because slopes are steep and uneven. This also complicated analysis of the data. Measurement of in situ velocity — an important value for migration — was impossible. Instead, data were migrated with different velocities and data results were chosen that were considered to be reasonable. Analysis and interpretation of the data, resulted in confirmation and extension of the a priori information on orientations of fractures and bedding planes at Turtle Mountain. Despite the rough terrain and highly fractured rock mass, GPR surveys provide reliable information about the shapes and density of fractures — information important for slope-stability evaluation. The most reliable migration results obtained for velocities were considerably less than the standard velocities recorded for limestone, the dominant lithofacies at Turtle Mountain. We interpret this observation as an indicator of water within the rock. However, thorough investigation of this conclusion remains a project for future work.

scholarly journals A joint thermal and electromagnetic diagnostics approach for the inspection of thick walls

2016 ◽  
Author(s):  
Nicolas Le Touz ◽  
Jean Dumoulin ◽  
Gianluca Gennarelli ◽  
Francesco Soldovieri
Keyword(s):  
Ground Penetrating Radar ◽  
Preliminary Analysis ◽  
A Priori ◽  
Numerical Inversion ◽  
Reconstruction Method ◽  
A Priori Information ◽  
Priori Information ◽  
Ground Penetrating ◽  
Surface Temperature Field ◽  
Evolution With Time

Abstract. In this study, we present a numerical inversion approach to detect and localize inclusions in thick walls under natural solicitations. The approach is based on a preliminary analysis of the surface temperature field evolution with time (for instance acquired by infrared thermography); after, this analysis is improved by taking advantage of a priori information provided by ground penetrating radar reconstructions of the structure under investigation. In this way, it is possible to improve the accuracy of the images achievable with the stand-alone thermal reconstruction method in the case of quasi-periodic natural excitation.

scholarly journals A synthetic study to assess the applicability of full-waveform inversion to infer snow stratigraphy from upward-looking ground-penetrating radar data

Geophysics ◽  
2016 ◽  
Vol 81 (1) ◽  
pp. WA213-WA223 ◽  
Author(s):  
Lino Schmid ◽  
Jürg Schweizer ◽  
John Bradford ◽  
Hansruedi Maurer
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
A Priori ◽  
Waveform Inversion ◽  
Liquid Water Content ◽  
A Priori Information ◽  
Full Waveform ◽  
Snow Stratigraphy ◽  
Priori Information ◽  
Ground Penetrating

Snow stratigraphy and liquid water content are key contributing factors to avalanche formation. Upward-looking ground-penetrating radar (upGPR) systems allow nondestructive monitoring of the snowpack, but deriving density and liquid water content profiles is not yet possible based on the direct analysis of the reflection response. We have investigated the feasibility of deducing these quantities using full-waveform inversion (FWI) techniques applied to upGPR data. For that purpose, we have developed a frequency-domain FWI algorithm in which we additionally took advantage of time-domain features such as the arrival times of reflected waves. Our results indicated that FWI applied to upGPR data is generally feasible. More specifically, we could show that in the case of a dry snowpack, it is possible to derive snow densities and layer thicknesses if sufficient a priori information is available. In case of a wet snowpack, in which it also needs to be inverted for the liquid water content, the algorithm might fail, even if sufficient a priori information is available, particularly in the presence of realistic noise. Finally, we have investigated the capability of FWI to resolve thin layers that play a key role in snow stability evaluation. Our simulations indicate that layers with thicknesses well below the GPR wavelengths can be identified, but in the presence of significant liquid water, the thin-layer properties may be prone to inaccuracies. These results are encouraging and motivate applications to field data, but significant issues remain to be resolved, such as the determination of the generally unknown upGPR source function and identifying the optimal number of layers in the inversion models. Furthermore, a relatively high level of prior knowledge is required to let the algorithm converge. However, we feel these are not insurmountable and the new technology has significant potential to improve field data analysis.

scholarly journals Microwave Tomographic approach for masonry investigation: some real results

2010 ◽  
Vol 24 ◽  
pp. 83-88 ◽  
Author(s):  
M. Bavusi ◽  
R. Di Napoli ◽  
F. Soldovieri
Keyword(s):  
Data Processing ◽  
A Priori ◽  
Microwave Tomography ◽  
Raw Data ◽  
Fracture Geometry ◽  
Host Medium ◽  
Historical Heritage ◽  
Priori Information ◽  
Definition Of ◽  
Ground Penetrating

Abstract. Ground Penetrating Radar (GPR) is an electromagnetic technique very appreciated by the community of the archaeologist and cultural heritage end-users community thanks to its appealing features in terms of non invasivity and rapidity of measurement and diagnostics. However, GPR data requires a high operator expertise in the data processing and interpretation. In the archaeological investigation, this drawback can be mitigated by the availability of a priori information about the archaeological scenario. On the other hand, in the case of the historical heritage, when the knowledge of constructive modalities and material of the structure may be completely missed, it is necessary to undertake other strategies of processing and interpretation. One of these can be provided by the use of novel inversion algorithms such as the Microwave Tomography (MT) which allows to reduce the subjectivity and the time consuming during the data processing. In this paper the MT was applied on raw data collected at two historical buildings of Chania (Crete, Greece). The first edifice is the Venizelo's House affected by visible fractures in its walls made up of cemented irregular stones. The second one is the headquarters of Prefecture of Chania showing some fractures along the floors. For these raw data, microwave tomography provided well detailed images which allowed to infer the fracture geometry and their extension in the host medium. This suggests microwave tomography can be a reliable complete processing tool requiring only the definition of the background scenario in terms of the dielectric permittivity and the conductivity of the host medium.

scholarly journals A joint thermal and electromagnetic diagnostics approach for the inspection of thick walls

2017 ◽  
Vol 6 (1) ◽  
pp. 81-92 ◽  
Author(s):  
Nicolas Le Touz ◽  
Jean Dumoulin ◽  
Gianluca Gennarelli ◽  
Francesco Soldovieri
Keyword(s):  
Temperature Field ◽  
Ground Penetrating Radar ◽  
Preliminary Analysis ◽  
A Priori ◽  
Reconstruction Method ◽  
A Priori Information ◽  
Priori Information ◽  
Ground Penetrating ◽  
Surface Temperature Field ◽  
Evolution With Time

Abstract. In this study, we present an inversion approach to detect and localize inclusions in thick walls under natural solicitations. The approach is based on a preliminary analysis of surface temperature field evolution with time (for instance acquired by infrared thermography); subsequently, this analysis is improved by taking advantage of a priori information provided by ground-penetrating radar reconstruction of the structure under investigation. In this way, it is possible to improve the accuracy of the images achievable with the stand-alone thermal reconstruction method in the case of quasi-periodic natural excitation.

Enhancing the Resolving Ability of ERT for Imaging Saltwater Intrusion through Improvements in Inversion Methods: A Laboratory and Numerical Study

Geophysics ◽  
2021 ◽  
pp. 1-65
Author(s):  
Meredith Goebel ◽  
Rosemary Knight ◽  
Seogi Kang
Keyword(s):  
Saltwater Intrusion ◽  
Reference Model ◽  
Numerical Study ◽  
A Priori ◽  
Geophysical Methods ◽  
Resistivity Tomography ◽  
Porosity And Permeability ◽  
Priori Information ◽  
High Level

Mapping and monitoring of saltwater intrusion are critical to the sustainable management of groundwater in coastal aquifers around the world. Increasingly, geophysical methods, such as electrical resistivity tomography (ERT), have been used to address these needs. We identified methods for the inversion of ERT data that would most accurately map the location and geometry of an intrusion wedge. This was accomplished using both laboratory and synthetic experiments, with the classic representation of an intrusion wedge perpendicular to the coast. The laboratory experiments allowed us to collect ERT data on a saltwater intrusion wedge in an environment where we had supporting data that provided (1) the distribution of salinity within the tank with which to verify our inversion results, (2) the resistivity, porosity and permeability of the porous medium, and (3) the transform between resistivity and salinity. The synthetic experiments allowed to explore issues of specific interest related to the presence of lithologic heterogeneity at a field site: the role of lithologic heterogeneity in introducing complexity both the resistivity-salinity relationship and the geometry of the saltwater intrusion wedge. We found that using a reference model with a good approximation of the wedge to inform the inversion greatly improved the ability of the resulting resistivity profile to map the wedge. Where there was no, or limited lithologic heterogeneity, a parametric approach, which constrained the range of possible solutions by solving for a sharp interface between the saltwater and freshwater regions, was very effective at capturing the wedge location and geometry. Where there was lithologic heterogeneity, a hybrid between the parametric and informed inversion approaches was most effective, resolving the wedge with a high level of accuracy with little a priori information.

Innovative Approach to Information Search by Example of a Patent Analysis of an Important Substitution Plan

2020 ◽  
pp. 143-157
Author(s):  
Maria A. Milkova
Keyword(s):  
Information Search ◽  
Topic Modeling ◽  
Cognitive Biases ◽  
A Priori ◽  
Import Substitution ◽  
Innovative Approach ◽  
Iterative Search ◽  
Comprehensive Picture ◽  
Priori Information ◽  
Selection Of

Nowadays the process of information accumulation is so rapid that the concept of the usual iterative search requires revision. Being in the world of oversaturated information in order to comprehensively cover and analyze the problem under study, it is necessary to make high demands on the search methods. An innovative approach to search should flexibly take into account the large amount of already accumulated knowledge and a priori requirements for results. The results, in turn, should immediately provide a roadmap of the direction being studied with the possibility of as much detail as possible. The approach to search based on topic modeling, the so-called topic search, allows you to take into account all these requirements and thereby streamline the nature of working with information, increase the efficiency of knowledge production, avoid cognitive biases in the perception of information, which is important both on micro and macro level. In order to demonstrate an example of applying topic search, the article considers the task of analyzing an import substitution program based on patent data. The program includes plans for 22 industries and contains more than 1,500 products and technologies for the proposed import substitution. The use of patent search based on topic modeling allows to search immediately by the blocks of a priori information – terms of industrial plans for import substitution and at the output get a selection of relevant documents for each of the industries. This approach allows not only to provide a comprehensive picture of the effectiveness of the program as a whole, but also to visually obtain more detailed information about which groups of products and technologies have been patented.

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