scholarly journals Coherent wavefield subtraction for diffraction separation

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. V157-V168 ◽  
Author(s):  
Benjamin Schwarz
Keyword(s):  
Ground Penetrating Radar ◽  
Input Data ◽  
Field Data ◽  
Separation Step ◽  
Subsequent Separation ◽  
Successful Separation ◽  
Major Direction ◽  
Ground Penetrating ◽  
2D And 3D

Diffractions encode subwavelength information and superior illumination but are weak in amplitude and strongly interfere with the more dominant reflected wavefield. Accordingly, the successful separation of diffractions in geophysical applications still forms a major direction of research. Confronting this challenge, an automatable and versatile framework for the separation of interfering wavefields through a sequence of coherent data summation and subtraction is proposed. In contrast to other studies using coherence measurements, the method specifically targets reflected contributions, which are normally favored in automated summation schemes, and it adaptively subtracts the resulting reflection stack from the input data. Complementing this natural selectivity of stacking, a variety of wavefront filters is presented, which can be derived from the local maximization of the semblance norm and additionally inform the subsequent separation step. Complex 2D and 3D synthetic pre- and poststack seismic examples together with a ground-penetrating radar field-data example suggest that the presented scheme can be applied to a variety of data configurations and bears the potential to uncover an extremely faint but surprisingly rich diffraction background that was previously not accessible for dedicated processing.

Exploring the Japan Cave in Taman Hutan Raya Djuanda, Bandung Using GPR

2018 ◽  
Vol 23 (3) ◽  
pp. 377-381
Author(s):  
Widodo Widodo ◽  
Azizatun Azimmah ◽  
Djoko Santoso
Keyword(s):  
Dielectric Permittivity ◽  
Ground Penetrating Radar ◽  
Field Data ◽  
Geophysical Methods ◽  
Forward Modeling ◽  
Additional Line ◽  
Reflection Amplitude ◽  
Underground Cavities ◽  
Ground Penetrating ◽  
Synthetic Models

Investigating underground cavities is vital due to their potential for subsidence and total collapse. One of the proven geophysical methods for locating underground cavities at a shallow depth is ground penetrating radar (GPR). GPR uses contrasting dielectric permittivity, resistivity, and magnetic permeability to map the subsurface. The aim of this research is to prove that GPR can be applied to detect underground cavities in the Japan Cave of Taman Hutan Raya Djuanda, in Bandung, Indonesia. Forward modeling was performed first using three representative synthetic models before field data were acquired. The data acquisition was then conducted using a 100 MHz GPR shielded antenna with three lines of 80 m and one additional line 10 m long. The result showed a region of different reflection amplitude, which was proven to be the air-filled cavities.

Diffraction imaging of ground-penetrating radar data

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. H1-H12 ◽  
Author(s):  
Hemin Yuan ◽  
Mahboubeh Montazeri ◽  
Majken C. Looms ◽  
Lars Nielsen
Keyword(s):  
Ground Penetrating Radar ◽  
Field Data ◽  
Velocity Structure ◽  
Velocity Estimation ◽  
Small Scale ◽  
Imaging Method ◽  
Surface Reflection ◽  
Diffraction Imaging ◽  
Saturated Media ◽  
Ground Penetrating

Diffractions caused by, e.g., faults, fractures, and small-scale heterogeneity localized near the surface are often used in ground-penetrating radar (GPR) reflection studies to constrain the subsurface velocity distribution using simple hyperbola fitting. Interference with reflected energy makes the identification of diffractions difficult. We have tailored and applied a diffraction imaging method to improve imaging for surface reflection GPR data. Based on a plane-wave destruction algorithm, the method can separate reflections from diffractions. Thereby, a better identification of diffractions facilitates an improved determination of GPR wave velocities and an optimized migration result. We determined the potential of this approach using synthetic and field data, and, for the field study, we also compare the estimated velocity structure with crosshole GPR results. For the field data example, we find that the velocity structure estimated using the diffraction-based process correlates well with results from crosshole GPR velocity estimation. Such improved velocity estimation may have important implications for using surface reflection GPR to map, e.g., porosity for fully saturated media or soil moisture changes in partially saturated media because these physical properties depend on the dielectric permittivity and thereby also the GPR wave velocity.

scholarly journals Stochastic Collocation Applications in Computational Electromagnetics

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Dragan Poljak ◽  
Silvestar Šesnić ◽  
Mario Cvetković ◽  
Anna Šušnjara ◽  
Hrvoje Dodig ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Stochastic Models ◽  
Human Exposure ◽  
Input Data ◽  
Review Paper ◽  
Computational Electromagnetics ◽  
Stochastic Collocation ◽  
Data Set ◽  
Mean And Variance ◽  
Ground Penetrating

The paper reviews the application of deterministic-stochastic models in some areas of computational electromagnetics. Namely, in certain problems there is an uncertainty in the input data set as some properties of a system are partly or entirely unknown. Thus, a simple stochastic collocation (SC) method is used to determine relevant statistics about given responses. The SC approach also provides the assessment of related confidence intervals in the set of calculated numerical results. The expansion of statistical output in terms of mean and variance over a polynomial basis, via SC method, is shown to be robust and efficient approach providing a satisfactory convergence rate. This review paper provides certain computational examples from the previous work by the authors illustrating successful application of SC technique in the areas of ground penetrating radar (GPR), human exposure to electromagnetic fields, and buried lines and grounding systems.

Crosshole reflection imaging with ground-penetrating radar data: Applications in near-surface sedimentary settings

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. H61-H69
Author(s):  
Niklas Allroggen ◽  
Stéphane Garambois ◽  
Guy Sénéchal ◽  
Dominique Rousset ◽  
Jens Tronicke
Keyword(s):  
Ground Penetrating Radar ◽  
Field Data ◽  
Electromagnetic Property ◽  
Velocity Model ◽  
Radar Data ◽  
Near Surface ◽  
Velocity Models ◽  
Reflection Image ◽  
Detailed Interpretation ◽  
Ground Penetrating

Crosshole ground-penetrating radar (GPR) is applied in areas that require a very detailed subsurface characterization. Analysis of such data typically relies on tomographic inversion approaches providing an image of subsurface parameters. We have developed an approach for processing the reflected energy in crosshole GPR data and applied it on GPR data acquired in different sedimentary settings. Our approach includes muting of the first arrivals, separating the up- and the downgoing wavefield components, and backpropagating the reflected energy by a generalized Kirchhoff migration scheme. We obtain a reflection image that contains information on the location of electromagnetic property contrasts, thus outlining subsurface architecture in the interborehole plane. In combination with velocity models derived from different tomographic approaches, these images allow for a more detailed interpretation of subsurface structures without the need to acquire additional field data. In particular, a combined interpretation of the reflection image and the tomographic velocity model improves the ability to locate layer boundaries and to distinguish different subsurface units. To support our interpretations of our field data examples, we compare our crosshole reflection results with independent information, including borehole logs and surface GPR data.

Non-Destructive Detection of Asphalt Concrete Stripping Damage using Ground Penetrating Radar

2021 ◽  
pp. 036119812110141
Author(s):  
Ye Ma ◽  
Mostafa A. Elseifi ◽  
Nirmal Dhakal ◽  
Mohammad Z. Bashar ◽  
Zhongjie Zhang
Keyword(s):  
Ground Penetrating Radar ◽  
Asphalt Concrete ◽  
Field Data ◽  
Visual Inspection ◽  
Asphalt Pavements ◽  
Reflected Waves ◽  
Ground Penetrating ◽  
The Relationship ◽  
Non Destructive ◽  
Difference Time

Ground penetrating radar (GPR) is a non-destructive evaluation technique, which has been applied to assess as-built pavement conditions and to evaluate damage and deterioration that develop over time. The objective of this study was to develop a methodology that uses GPR to detect moisture-related stripping damage in asphalt pavements. To achieve this objective, A Finite-Difference Time-Domain based simulation program was used to study the propagation of GPR signals in a stripped pavement. Field test data including GPR scans and visual inspection of cores of 202 pavement sections were used to study the relationship between GPR traces and asphalt concrete (AC) stripping damage. Based on this analysis, a novel GPR-based indicator, known as the accumulating in-layer peaks (AIP), was introduced to detect stripping damage in asphalt pavements. Field data and pavement cores were used to validate the proposed indicator and to evaluate its effectiveness in detecting the presence, extent, and severity of stripping in in-service pavement sections. Based on the results of the study, it was found that the presence of a void in the middle of the AC layer resulted in positive peaks in the reflected waves as indicated by the simulation of GPR signals. In addition, detected intermediate wave peaks between the surface and the interface between the AC and base layers on the GPR traces were associated with stripping damage in the AC layer. The AIP predicted accuracies for stripped and non-stripped sections were 80% and 96%, respectively, indicating its effectiveness in detecting stripping damage in flexible pavements.

scholarly journals GEOPHYSICAL METHODS FOR BR TAILINGS DAM RESEARCH AND MONITORING IN THE MINERAL COMPLEX OF TAPIRA - MINAS GERAIS, BRAZIL

2019 ◽  
Vol 37 (3) ◽  
pp. 275
Author(s):  
Demetrius Cunha Gonçalves da Rocha ◽  
Marco Antonio da Silva Braga ◽  
Camilla Tavares Rodrigues
Keyword(s):  
Electrical Resistivity ◽  
Water Table ◽  
Ground Penetrating Radar ◽  
Geophysical Methods ◽  
Minas Gerais ◽  
Minas Gerais State ◽  
Indirect Indicator ◽  
Mining Complex ◽  
Ground Penetrating ◽  
2D And 3D

ABSTRACT. The use of geophysical methods in the BR dam at Tapira mining complex in Minas Gerais state, Brazil, had as main objective to develop a research geophysical methodology complementary to the existing conventional monitoring system. Electrical resistivity and GPR (ground penetrating radar) methods were used. Ten geophysical sections were acquired parallel to the main axis of the BR dam. The water table level delineated by geophysics was later compared to five type-sections data, which comprised the readings of 9 water level indicators (INA’s). The electrical resistivity results delineated the level of the water table and showed the moisture areas in the BR dam. Low resistivity zones (LRZ) were correlated with regions saturated or with a high moisture content with resistivity responses below 250 ohm-m. The GPR responses, saturated zones presented strong attenuation in the reflectors, being this effect smaller with the decrease in the water content. In some sections it was possible to correlate, patterns of reflectors to different resistive zones. Geophysics results showed great efficiency in the BR dam investigation and monitoring, through the generation of continuous indirect indicator data. Which after processing resulted in a complete 2D and 3D view of the interior of the studied dam.Keywords: electrical resistivity, geotechnics, applied geophysics.RESUMO. A utilização de métodos geofísicos na barragem BR do complexo de mineração de Tapira no estado de Minas Gerais, Brasil, teve como principal objetivo desenvolver uma metodologia geofísica investigativa complementar ao monitoramento hoje existente. Foram utilizados os métodos geofísicos de eletrorresistividade e GPR (ground penetrating radar). Durante a aquisição de dados foram levantadas 10 linhas paralelas ao eixo principal do barramento. O nível freático delineado pela geofísica foi posteriormente comparado com o nível freático de 5 seções-tipo mapeado pelas leituras de 9 indicadores de nível d’água (INA’s). Os resultados da eletrorresistividade delinearam de forma precisa o nível freático, diferenciando áreas secas das úmidas ao longo do barramento. Zonas de baixa resistividade (ZBR), foram correlacionadas com regiões do maciço possivelmente saturadas ou com alto teor de umidade (< 250 ohm-m). Em resposta ao GPR, zonas saturadas apresentaram forte atenuação nos refletores, sendo esta atenuação menor com a diminuição no teor de água. Em algumas seções, foram correlacionados padrões dos refletores a diferentes zonas resistivas. A geofísica mostrou ter uma grande eficácia na investigação e monitoramento dessas estruturas, através da geração de indicadores indiretos contínuos, que após processamento resultaram em um imageamento completo em 2D e 3D do interior da barragem estudada.Palavras-chave: resistividade elétrica, geotecnia, geofísica aplicada.

scholarly journals Ground-Penetrating Radar Investigations along Hajipur Fault: Himalayan Frontal Thrust—Attempt to Identify Near Subsurface Displacement, NW Himalaya, India

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Javed N. Malik ◽  
Ashutosh Kumar ◽  
Sravanthi Satuluri ◽  
Bishuddhakshya Puhan ◽  
Asmita Mohanty
Keyword(s):  
Ground Penetrating Radar ◽  
Fault Plane ◽  
Thrust Fault ◽  
Nw Himalaya ◽  
Himalayan Frontal Thrust ◽  
Metal Pipe ◽  
Ground Penetrating ◽  
3D Profile ◽  
2D And 3D

The study area falls in the mesoseismal zone of 1905 Kangra earthquake (Mw 7.8). To identify appropriate trenching site for paleoseismic investigation and to understand the faulting geometry, ground-penetrating radar (GPR) survey was conducted across a Hajipur Fault (HF2) scarp, a branching out fault of Himalayan Frontal Thrust (HFT) in a foot hill zone of NW Himalaya. Several 2D and 3D profiles were collected using 200 MHz antenna with SIR 3000 unit. A 2D GPR profile collected across the HF2 scarp revealed prominent hyperbolas and discontinuous-warped reflections, suggesting a metal pipe and a zone of deformation along a low-angle thrust fault, respectively. The 3D profile revealed remarkable variation in dip of the fault plane and pattern of deformation along the strike of the fault.

Topographic migration of 2D and 3D ground‐penetrating radar data considering variable velocities

2014 ◽  
Vol 13 (3) ◽  
pp. 253-259 ◽  
Author(s):  
Niklas Allroggen ◽  
Jens Tronicke ◽  
Marcel Delock ◽  
Urs Böniger
Keyword(s):  
Ground Penetrating Radar ◽  
Radar Data ◽  
Ground Penetrating ◽  
2D And 3D
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