Joint inversion of full-waveform ground-penetrating radar and electrical resistivity data: Part 1

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. H97-H113 ◽  
Author(s):  
Diego Domenzain ◽  
John Bradford ◽  
Jodi Mead
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Ground Penetrating Radar ◽  
Joint Inversion ◽  
Geophysical Methods ◽  
Data Types ◽  
Full Waveform ◽  
Electrical Permittivity ◽  
Ground Penetrating ◽  
Subsurface Geometry

We have developed an algorithm for joint inversion of full-waveform ground-penetrating radar (GPR) and electrical resistivity (ER) data. The GPR data are sensitive to electrical permittivity through reflectivity and velocity, and electrical conductivity through reflectivity and attenuation. The ER data are directly sensitive to the electrical conductivity. The two types of data are inherently linked through Maxwell’s equations, and we jointly invert them. Our results show that the two types of data work cooperatively to effectively regularize each other while honoring the physics of the geophysical methods. We first compute sensitivity updates separately for the GPR and ER data using the adjoint method, and then we sum these updates to account for both types of sensitivities. The sensitivities are added with the paradigm of letting both data types always contribute to our inversion in proportion to how well their respective objective functions are being resolved in each iteration. Our algorithm makes no assumptions of the subsurface geometry nor the structural similarities between the parameters with the caveat of needing a good initial model. We find that our joint inversion outperforms the GPR and ER separate inversions, and we determine that GPR effectively supports ER in regions of low conductivity, whereas ER supports GPR in regions with strong attenuation.

Joint inversion of full-waveform ground-penetrating radar and electrical resistivity data — Part 2: Enhancing low frequencies with the envelope transform and cross gradients

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. H115-H132 ◽  
Author(s):  
Diego Domenzain ◽  
John Bradford ◽  
Jodi Mead
Keyword(s):  
Electrical Resistivity ◽  
Ground Penetrating Radar ◽  
Material Properties ◽  
Joint Inversion ◽  
Low Frequency ◽  
Model Parameters ◽  
Frequency Content ◽  
Low Frequencies ◽  
Full Waveform ◽  
Ground Penetrating

Recovering material properties of the subsurface using ground-penetrating radar (GPR) data of finite bandwidth with missing low frequencies and in the presence of strong attenuation is a challenging problem. We have adopted three nonlinear inverse methods for recovering electrical conductivity and permittivity of the subsurface by joining GPR multioffset and electrical resistivity (ER) data acquired at the surface. All of the methods use ER data to constrain the low spatial frequency of the conductivity solution. The first method uses the envelope of the GPR data to exploit low-frequency content in full-waveform inversion and does not assume structural similarities of the material properties. The second method uses cross gradients to manage weak amplitudes in the GPR data by assuming structural similarities between permittivity and conductivity. The third method uses the envelope of the GPR data and the cross gradient of the model parameters. By joining ER and GPR data, exploiting low-frequency content in the GPR data, and assuming structural similarities between the electrical permittivity and conductivity, we are able to recover subsurface parameters in regions where the GPR data have a signal-to-noise ratio close to one.

Joint full-waveform GPR and ER inversion applied to field data acquired on the surface

Geophysics ◽  
2021 ◽  
pp. 1-77
Author(s):  
diego domenzain ◽  
John Bradford ◽  
Jodi Mead
Keyword(s):  
Ground Penetrating Radar ◽  
Joint Inversion ◽  
Waveform Inversion ◽  
Shallow Groundwater ◽  
Computational Domain ◽  
Alluvial Deposits ◽  
Subsurface Structures ◽  
Full Waveform ◽  
Stable Source ◽  
Ground Penetrating

We exploit the different but complementary data sensitivities of ground penetrating radar (GPR) and electrical resistivity (ER) by applying a multi-physics, multi-parameter, simultaneous 2.5D joint inversion without invoking petrophysical relationships. Our method joins full-waveform inversion (FWI) GPR with adjoint derived ER sensitivities on the same computational domain. We incorporate a stable source estimation routine into the FWI-GPR.We apply our method in a controlled alluvial aquifer using only surface acquired data. The site exhibits a shallow groundwater boundary and unconsolidated heterogeneous alluvial deposits. We compare our recovered parameters to individual FWI-GPR and ER results, and to log measurements of capacitive conductivity and neutron-derived porosity. Our joint inversion provides a more representative depiction of subsurface structures because it incorporates multiple intrinsic parameters, and it is therefore superior to an interpretation based on log data, FWI-GPR, or ER alone.

scholarly journals Magnetic resonance tomography constrained by ground-penetrating radar for improved hydrogeophysical characterization

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. JM13-JM26
Author(s):  
Chuandong Jiang ◽  
Jan Igel ◽  
Raphael Dlugosch ◽  
Mike Müller-Petke ◽  
Thomas Günther ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Resonance ◽  
Ground Penetrating Radar ◽  
Geophysical Methods ◽  
Magnetic Resonance Tomography ◽  
Aeolian Deposits ◽  
Aquifer Systems ◽  
Resolution Limits ◽  
Depositional Architecture ◽  
Ground Penetrating

Geophysical methods can characterize aquifer systems noninvasively and are particularly helpful to image the complex depositional architecture of the subsurface. Among these, ground-penetrating radar (GPR) is an effective tool for detailed investigations of shallow subsurface geometry, but it provides only limited information on hydraulic properties. Magnetic resonance tomography (MRT) provides parameters such as water content (porosity) and relaxation time/hydraulic conductivity, but it suffers from resolution limits. Furthermore, it requires knowledge of subsurface electrical resistivity, which can be obtained by electrical resistivity tomography (ERT) also suffering from resolution limits. To overcome the limitations in resolution, we have incorporated GPR reflectors as structural information into the ERT and MRT data inversion. We test the methodology on a synthetic example and find improved imaging properties compared to standard inversion, particularly at greater depths, where the resolution is limited. We apply the methodology to a test site that is characterized by a complex depositional architecture. The Quaternary deposits consist of interbedded meltwater deposits (aquifers) and till (aquitards), overlain by aeolian deposits. To image the subsurface depositional architecture in three dimensions, a [Formula: see text] area was surveyed by GPR. The use of GPR constraints clearly improves the resolution and zonation of the subsurface image, which is validated by drill-core analyses. We develop a workflow to combine GPR, MRT, and ERT, leading the way to high-resolution hydrogeologic models that can be used for groundwater studies.

scholarly journals Ground penetrating radar and electrical resistivity tomography for locating buried building foundations: A case study in the city centre of Thessaloniki, Greece

2016 ◽  
Vol 47 (3) ◽  
pp. 1355
Author(s):  
G. Vargemezis ◽  
N. Diamanti ◽  
I. Fikos ◽  
A. Stampolidis ◽  
Th. Makedon ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Ground Penetrating Radar ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Geological Structure ◽  
City Centre ◽  
High Resistivity ◽  
Resistivity Tomography ◽  
Ground Penetrating ◽  
The City

Ground penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys have been carried out in the city centre of Thessaloniki (N. Greece), for investigating possible locations of buried building foundations. Geophysical survey has been chosen as a non-destructive investigation method since the area is currently used as a car parking and it is covered by asphalt. The geoelectrical sections derived from ERT data in combination with the GPR profiles provided a broad view of the  subsurface.  Regarding  ERT,  high  resistivity  values  can  be  related  to  buried building remains, while lower resistivity values are more related to the surrounding geological materials. GPR surveying can also indicate man-made structures buried in the ground. Even though the two geophysical methods are affected in different ways by the subsurface conditions, the processed underground images from both techniques revealed great similarity. High resistivity anomalies and distinct GPR signals were observed in certain locations of the area under investigation, which are attributed to buried building foundations as well as the geological structure of the area.

Joint acoustic full-waveform inversion of crosshole seismic and ground-penetrating radar data in the frequency domain

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. H41-H56 ◽  
Author(s):  
Xuan Feng ◽  
Qianci Ren ◽  
Cai Liu ◽  
Xuebing Zhang
Keyword(s):  
Frequency Domain ◽  
Ground Penetrating Radar ◽  
Joint Inversion ◽  
Waveform Inversion ◽  
Structural Similarity ◽  
P Wave ◽  
Full Waveform Inversion ◽  
Full Waveform ◽  
Frequency Domain Methods ◽  
Ground Penetrating

Integrating crosshole ground-penetrating radar (GPR) with seismic methods is an efficient way to reduce the uncertainty and ambiguity of data interpretation in shallow geophysical investigations. We have developed a new approach for joint full-waveform inversion (FWI) of crosshole seismic and GPR data in the frequency domain to improve the inversion results of both FWI methods. In a joint objective function, three geophysical parameters (P-wave velocity, permittivity, and conductivity) are effectively connected by three weighted cross-gradient terms that enforce the structural similarity between parameter models. Simulation of acoustic seismic and scalar electromagnetic problems is implemented using 2D finite-difference frequency-domain methods, and the inverse problems of seismic FWI and GPR FWI are solved using a matrix-free truncated Newton algorithm. The joint inversion procedure is performed in several hierarchical frequencies, and the three parameter models are sequentially inverted at each frequency. The joint FWI approach is illustrated using three numerical examples. The results indicate that the joint FWI approach can effectively enhance the structural similarity among the models, modify the structure of each model, and improve the accuracy of inversion results compared with those of individual FWI approaches. Moreover, joint inversion can reduce the trade-off between permittivity and conductivity in GPR FWI, leading to an improved conductivity model in which artifacts are significantly decreased.

scholarly journals Ground penetrating radar and electrical resistivity tomography for locating buried building foundations: A case study in the city centre of Thessaloniki, Greece

2016 ◽  
Vol 47 (3) ◽  
pp. 1355
Author(s):  
G. Vargemezis ◽  
N. Diamanti ◽  
I. Fikos ◽  
A. Stampolidis ◽  
Th. Makedon ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Ground Penetrating Radar ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Geological Structure ◽  
City Centre ◽  
High Resistivity ◽  
Resistivity Tomography ◽  
Ground Penetrating ◽  
The City

Ground penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys have been carried out in the city centre of Thessaloniki (N. Greece), for investigating possible locations of buried building foundations. Geophysical survey has been chosen as a non-destructive investigation method since the area is currently used as a car parking and it is covered by asphalt. The geoelectrical sections derived from ERT data in combination with the GPR profiles provided a broad view of the  subsurface.  Regarding  ERT,  high  resistivity  values  can  be  related  to  buried building remains, while lower resistivity values are more related to the surrounding geological materials. GPR surveying can also indicate man-made structures buried in the ground. Even though the two geophysical methods are affected in different ways by the subsurface conditions, the processed underground images from both techniques revealed great similarity. High resistivity anomalies and distinct GPR signals were observed in certain locations of the area under investigation, which are attributed to buried building foundations as well as the geological structure of the area.

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.

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