scholarly journals Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion

2019 ◽  
Author(s):  
Siobhan F. Killingbeck ◽  
Adam D. Booth ◽  
Philip W. Livermore ◽  
Charles R. Bates ◽  
Landis J. West
Keyword(s):  
Electrical Resistivity ◽  
Time Domain ◽  
Saline Water ◽  
Radar Data ◽  
High Resistivity ◽  
Fractured Bedrock ◽  
Geological Interpretation ◽  
Seismic Shear ◽  
Time Domain Electromagnetics ◽  
Ground Penetrating

Abstract. Subglacial water influences the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude, hence liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of time domain electromagnetics (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (MuLTI) to the inversion of TEM data constrained by independent depth constraints, to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier Midtdalsbreen, with depth constraints provided by co-located ground penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 102 Ωm ± 100 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (100 Ωm ± 15 %). High resistivity material, 5 × 104 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydro-geological interpretation of the subsurface, we propose a new 3D interpretation of the Midtdalsbreen subglacial material partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water.

scholarly journals Characterisation of subglacial water using a constrained transdimensional Bayesian transient electromagnetic inversion

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 75-94 ◽  
Author(s):  
Siobhan F. Killingbeck ◽  
Adam D. Booth ◽  
Philip W. Livermore ◽  
C. Richard Bates ◽  
Landis J. West
Keyword(s):  
Electrical Resistivity ◽  
Saline Water ◽  
Radar Data ◽  
High Resistivity ◽  
Transient Time ◽  
Fractured Bedrock ◽  
Transient Electromagnetic ◽  
Seismic Shear ◽  
Time Domain Electromagnetic ◽  
Ground Penetrating

Abstract. Subglacial water modulates glacier-bed friction and therefore is of fundamental importance when characterising the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude; hence, liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of transient (time-domain) electromagnetic (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (Multimodal Layered Transdimensional Inversion – MuLTI) to the inversion of TEM data using independent depth constraints to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier, Midtdalsbreen, with depth constraints provided by co-located ground-penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 102 Ωm ± 1000 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (100 Ωm ± 15 %). High-resistivity material, 5×104 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with those from co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydrogeological interpretation of the subsurface, we propose a new 3-D interpretation in which the Midtdalsbreen subglacial material is partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water.

scholarly journals Application of Laplace Domain Waveform Inversion to Cross-Hole Radar Data

2019 ◽  
Vol 11 (16) ◽  
pp. 1839
Author(s):  
Xu Meng ◽  
Sixin Liu ◽  
Yi Xu ◽  
Lei Fu
Keyword(s):  
Time Domain ◽  
Waveform Inversion ◽  
Radar Data ◽  
Dominant Frequency ◽  
Data Set ◽  
Laplace Domain ◽  
Full Waveform ◽  
Highly Nonlinear ◽  
The Time Domain ◽  
Ground Penetrating

Full waveform inversion (FWI) can yield high resolution images and has been applied in Ground Penetrating Radar (GPR) for around 20 years. However, appropriate selection of the initial models is important in FWI because such an inversion is highly nonlinear. The conventional way to obtain the initial models for GPR FWI is ray-based tomogram inversion which suffers from several inherent shortcomings. In this paper, we develop a Laplace domain waveform inversion to obtain initial models for the time domain FWI. The gradient expression of the Laplace domain waveform inversion is deduced via the derivation of a logarithmic object function. Permittivity and conductivity are updated by using the conjugate gradient method. Using synthetic examples, we found that the value of the damping constant in the inversion cannot be too large or too small compared to the dominant frequency of the radar data. The synthetic examples demonstrate that the Laplace domain waveform inversion provide slightly better initial models for the time domain FWI than the ray-based inversion. Finally, we successfully applied the algorithm to one field data set, and the inverted results of the Laplace-based FWI show more details than that of the ray-based FWI.

scholarly journals Seepage investigations of heterogeneous soils beneath some buildings using geophysical approaches: example from southwestern Nigeria

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Adebayo Olayinka Salako ◽  
Abayomi Gaius Osotuyi ◽  
Adekunle Abraham Adepelumi
Keyword(s):  
Electrical Resistivity ◽  
Ground Penetrating Radar ◽  
Flood Plain ◽  
High Resistivity ◽  
Safe Haven ◽  
Southwestern Nigeria ◽  
Heterogeneous Soils ◽  
Ground Conditions ◽  
Southwest Nigeria ◽  
Ground Penetrating

AbstractBuildings along the flood plain of River Osun, southwest Nigeria, are usually thought of as been a safe haven for residence over the years. But in recent times with vast (increasing) population and growing urbanization, some of the buildings currently experience structural damages not related to constructional designs but rather ground conditions around building foundations. The ground conditions (seepages in this case) and how it influences properties of soils (water moisture, permeability etc.) to support the foundation of buildings. This paper attempts to map out seepages in heterogeneous soils around buildings in Erinle, southwest Nigeria where building cracks probably as a result of water seepages from subsurface through fissures and fractures where noticed. These cracks are a probable manifestation of a weakened foundation that could overtime result to a collapse, hence the need to investigate seepage prone zones. To achieve this, electrical resistivity (ER) and Electromagnetic Ground Penetrating Radar (EM-GPR) surveys were made along affected buildings to map out possible causes of deterioration. Geo-sections (analyzed ER data) shows high resistivity layer (topsoil) underlain by low resistivity layer (weathered basement) confirmed by planer reflections (topsoil) and fairly smooth to smooth reflections (weathered basement) in Radargrams (analyzed GPR data). An integration of the geo-section and radargram produced from ER and GPR data shows that buildings along traverses 1, 2, 3 and 5 is most prone to seepages especially as it exhibits very low anomalously resistivity values (< 25 Ωm) but this is not the case for buildings along traverses 4, 6, 7 and 8.

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 Pore resistivity variation by Resistivity imaging technique in sedimentary part of main Gadilam river basin, Cuddalore District, Tamil Nadu, India

2021 ◽  
Vol 13 (1) ◽  
pp. 268-277
Author(s):  
R. Ravi ◽  
S. Aravindan ◽  
C. Ramachandran ◽  
Sanjay Kumar Balabantaray ◽  
B. Selvaraj ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
River Basin ◽  
Tamil Nadu ◽  
Saline Water ◽  
Groundwater Potential ◽  
High Resistivity ◽  
Clay Layer ◽  
Clayey Sand ◽  
Low Resistivity ◽  
Matching Techniques

Electrical resistivity is the only property of physics which give information of subsurface moisture content in the formation, Hence geophysical electrical resistivity survey was carried out to investigate the nature of shallow subsurface formations and geological contact in the main Gadilam river basin of Cuddalore District in Tamil Nadu. Twenty-seven vertical electrical soundings (VES) were conducted by Schlumberger configuration in the basin. Data is interpreted by curve matching techniques using IPI2 WIN software, layer parameters like apparent resistivity (?a) and thickness (h) interpretation were exported to Geographic Information System (GIS). Interpretation distinguishes three major geoelectric layers like topsoil, sandy clay layer, clayey sand layer along the contact zone in the basin. Interpreted VES sounding curves are mostly four-layer cases of QH, H, HA and KH type. Investigation demarcates lithology of subsurface and hydrogeological set up by employing maximum possible electrode sounding to infer saline water and freshwater occurrence based on resistivity signals. Zone of groundwater potential map was prepared with the combination of resistivity (?= ?1+ ?2+ ?3+ ?4) and corresponding thickness (T= T1+T2+T3+T4). High resistivity value of >200 ? m and low resistivity value of <10 ? m show the occurrence of alkaline and saline water within the formation aquifers as a result of possible rock water interaction and saline water dissolution. Four-layer resistivity cases from the matched curve (namely KH, AH, QA, and KA type) show the resistivity distribution/variation. It separates the freshwater depth wish from 1 to 140 ? m in fluvial sediments. Flood basin, sandstone and clay layer with low resistivity value of 3.16 - 7.5 ? m indicates contact with saline and freshwater aquifer. The Iso – resistivity map delineates saline water and freshwater zones with in the fourth layer cases in the same locations to indicate the irrational way of abstracting groundwater, resulting in saltwater ingress.

scholarly journals Applying Electrical Resistivity Tomography in Ornamental Stone Mining: Challenges and Solutions

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 491 ◽  
Author(s):  
Sebastian Uhlemann ◽  
Jonathan Chambers ◽  
W. Falck ◽  
Avelino Tirado Alonso ◽  
José Fernández González ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Radar Data ◽  
Resistivity Tomography ◽  
Non Invasive ◽  
Ornamental Stone ◽  
Resistivity Model ◽  
Independent Observations ◽  
Ground Penetrating ◽  
Resistivity Meter

In this study, the use of electrical resistivity tomography (ERT) as a tool to guide ornamental stone extraction is investigated. ERT is not conventionally used in highly resistive environments, such as on rock faces, due to the high contact resistances that can impede current injection. Here, the challenges of conducting ERT in such environments are discussed and possible solutions suggested. For this, an example of the application of ERT in a deep and narrow marble quarry is used. The marble deposit is affected by fracturing and karstification. Due to the nature of these features, they present a significant resistivity contrast to the background resistivity of the marble and thus excellent targets to test the application of ERT. Their location was mapped using field observations and complementary ground penetrating radar data. By using an appropriate sensor deployment, a suitable resistivity meter, and advanced data processing routines, the derived 3D resistivity model is in good agreement with the independent observations. This shows that despite the challenges, ERT can be used as a non-invasive tool to obtain information on the stone properties prior to extraction. This will help in guiding quarry operations and will allow for a targeted, safe and efficient extraction of high quality stone, thereby increasing sustainability and economical competitiveness.

Recognizing surface scattering in ground‐penetrating radar data

Geophysics ◽  
1995 ◽  
Vol 60 (5) ◽  
pp. 1378-1385 ◽  
Author(s):  
Jingsheng Sun ◽  
Roger A. Young
Keyword(s):  
Wave Velocity ◽  
Ground Penetrating Radar ◽  
Radar Data ◽  
Relative Strength ◽  
Surface Scattering ◽  
Geological Interpretation ◽  
Vertical Scale ◽  
Survey Line ◽  
Ground Penetrating ◽  
Ground Wave

Ground‐penetrating radar (GPR) data may show strong noise events as a result of scattering by surface objects on the ground or above the survey line. The relative strength of these events can be large in comparison to reflections from geologic features, because radar signals in the ground attenuate exponentially whereas signals that travel in the air attenuate geometrically. Migration of GPR field data from clastic and carbonate sequences in central Oklahoma distinguishes between scattered events and geologic events because the former are focused at the air‐wave velocity, while the latter are focused at the ground‐wave velocity. Forward modeling using locations of scatterers derived from migration confirms the presence of scattered events, and common midpoint (CMP) gathers are helpful in identifying surface scattering. Scattered events displayed at a horizontal/vertical scale of 1:1 are easily mistaken for subhorizontal, geologic reflections. Methods of recognizing scattered events and removing them, if possible, are therefore crucial to correct geological interpretation of GPR data.

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.

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