Ground Penetrating Radar Imaging of a Circular Patterned Ground near King Sejong Station, Antarctica

The permafrost on the Qinghai-Tibet Plateau (QTP) is critically sensitive to temperature changes. The balance of heat transfer between the land and the atmosphere in permafrost regions were disturbed by the construction of man-made infrastructures, such as the Qinghai-Tibet Highway (QTH), the towers of power lines and telecommunications. Obviously, the characteristics of permafrost have been altered near the QTH. Reversely, thawing and degradation of the permafrost have a serious impact to the stability of QTH. Ground-penetrating radar (GPR) surveys can detect the subsurface structure of permafrost layer near the QTH that differentiate the situations in summer and winter and enable us to analyze the feature of permafrost table and active layer thickness (ALT) in different seasons. Consequently, it can provide the characterization of the relationship between the permafrost thawing and stability of QTH. Numerous studies have used the GPR to detect the permafrost and collected GPR data in summer in previous studies. However, due to the high loss of GPR signal in summer time caused by the blocking nature of the melted active layer limited the detection of formation features in greater depth. In this paper, we collected GPR data near the QTH in Beiluhe region in both summer and winter seasons and used the finite-difference reverse time migration (RTM) algorithm to process the GPR data. From the results of RTM profiles, we find that: 1) the RTM profiles in winter can provide high resolution interpretation image and clearly register the active layer/permafrost boundary and lithological interfaces within the active layer; 2) the top boundary of the permafrost and ALT have significant change near the QTH, which may be caused by the degradation of the surface vegetation and higher temperature on sides of QTH. With the accumulation of more GPR surveys, we can potentially analyze more details and wider coverage for the characteristics of permafrost top boundary and ALT in different seasons and provide more objective input to reduce the adverse impact from engineering constructions.

To provide a safe transportation system in an extremely cold region, evaluation needs to be conducted of the thickness and the volumetric water content of the active layer, as they significantly affect frost heave. The objective of this study was to evaluate the dielectric constant ( κ ) of the active layer using ground-penetrating radar (GPR) and a dynamic cone penetrometer (DCP); this evaluation was then used to estimate the thickness and the volumetric water content of the active layer. A field located in midwest Alaska was selected as the study site. A GPR survey and two DCP tests were conducted on the surface of the ground, and the ground temperature was measured. From the GPR survey, travel times of the electromagnetic wave in the active layer were obtained. In addition, the thickness of the active layer was determined by using the dynamic cone penetration index (DCPI) and ground temperature. By using the travel time and travel distance of the electromagnetic wave in the active layer, dielectric constants were calculated as 26.3 and 26.4 for two DCP points. From the mean dielectric constant, the volumetric water content was estimated to be 40%~43%, and the thickness of the active layer was evaluated along the GPR survey line. The spatial-scaled GPR image showed that the thickness of the active layer varied from 520 mm to 700 mm due to the presence of a puddle, which accelerated the heat exchange. The results show that evaluation of the dielectric constant using the GPR survey and the DCP test can be effectively used to estimate the thickness and the volumetric water content of the active layer.

Combined ERT and GPR methods for investigating two-stepped lateritic weathering systems

Twelve kilometers of ground penetrating radar (GPR) data have been collected over the Brookswood aquifer in southwestern British Columbia. The data have been analyzed to assess how GPR can be used to characterize the distribution and connectivity of hydraulic units. We have used GPR to locate the aquifer/aquitard boundary at several locations in the study area. The electrical contrast between these two materials makes the aquifer/aquitard boundary an excellent target for GPR surveys. GPR was also used to reconstruct the paleo-environment of one area of the Brookswood aquifer. This was accomplished by using a modification of the concept of architectural element analysis. Radar elements were identified in the survey and were assigned sedimentary parameters using data from trenching and drilling in the area. These elements were used to develop an interpretation of the paleo-environment that provides information about the spatial distribution of hydraulic units. INTRODUCTION Hydrogeologists require quantitative data to produce a realistic model of the spatial variabilities in hydraulic properties of an aquifer. Such data can be difficult and expensive to obtain. A possible solution is to develop geophysical techniques as a means of aquifer characterization. Ground penetrating radar (GPR), a shallow geophysical technique, is well suited for this purpose as it can be used to image to a depth of up to 30m in sand and gravel environments. However, the image produced by a GPR survey does not supply hydrogeologic parameters directly. The focus of this paper is to investigate how GPR can be used for aquifer characterization. At an aquifer scale of lo’s to 100’s of meters, the most fundamental aspect of aquifer characterization is the determination of the aquifer’s hydraulic connectivity through mapping of aquifer/aquitard interfaces. GPR can be used for this purpose due to the large contrast in electrical conductivity between the sand and gravel material of an aquifer, and the clay rich material of an aquitard. The electrical conductivity of a material affects the penetration depth of radar waves, such that radar waves penetrate well through resistive material, but poorly through conductive material. Aquifers, composed of sands and gravels, are resistive, while aquitards, composed of clay rich materials, are electrically conductive. Therefore a radar survey will show good penetration in aquifer materials and very poor penetration in aquitards. By exploiting this difference in radar response, the aquifer boundaries can be mapped. At a smaller scale of centimeters to meters, the determination of the internal structure of an aquifer is also important for aquifer characterization. For example, anisotropy within the aquifer can cause significant differences in hydraulic properties and so must be identified where present. In addition, identification of sedimentary features aids in the determination of the paleo-environment that can provide important insight into the probable arcal extent and orientation of geological units. GPR can be used to image these features because of changes in their electrical properties. GPR and Sedimentology GPR has received considerable attention as a means of imaging sedimentary stratigraphy (Jo1 and Smith, 1992; Smith and Jol, 1992; Pratt and Miall, 1993; Greenhouse et al, 1987; Rea et al, 1991; Huggenberger et al, 1994). The key question that needs addressing is exactly which sedimentary aspects of the subsurface are imaged with GPR. A GPR survey, conducted by transmitting radar waves into the subsurface and recording the reflected energy, will image changes in the subsurface dielectric constant and conductivity. If these electrical properties correspond to changes in sedimentary parameters, then a GPR survey can be said to image sedimentary features. The dielectric constant and conductivity of earth materials are dependent upon composition and geometry of the solid and liquid components. Sedimentological classification is based upon five fundamental properties from which all others can be derived: grain composition, size, shapes, orientation and packing (Blatt et al, 1980). These five properties clearly are related to the composition and geometry of the solid component of a system. It is therefore reasonable to assume that a change in sedimentological properties at some boundary will cause a change in electrical properties. If the resulting change in electrical properties is large enough, then the sedimentary boundary will be imaged in a radar survey. The complicating issue is the liquid, usually water, component which does not play a role in sedimentary

Characterization of the porosity distribution in the upper part of the karst Biscayne aquifer using common offset ground penetrating radar, Everglades National Park, Florida

Using hydrogeophysical methods to assess the feasibility of lake bank filtration

The estimation of propagation velocity is important for the correct processing and interpretation of ground penetrating radar (GPR) reflection data. Most, if not all, GPR surveys, are very limited in spatial extent and the common perception is that within the survey range, radar propagation velocity in the shallow subsurface has very slow or no lateral variation. Therefore, a single (1-D) velocity function is considered adequate to describe the subsurface. In this study it is shown that, in fact, lateral variation in radar velocity can be quite significant. An effective means of determining velocity is based on normal moveout velocity analysis of common midpoint multi-offset data. Applying this technique at many locations along a GPR survey provides a more accurate description of the actual 2-D velocity distribution. When the multi-offset acquisition geometry necessary for normal moveout velocity analysis is applied continuously in the GPR survey, an improved radar reflection image is attained by stacking traces at common midpoints. The 2-D normal moveout velocity description is used to make necessary adjustments to the data before the stack. The velocity analysis and common midpoint stack techniques are applied to an example of GPR data acquired using the multi-offset geometry at every survey station. The results show that reflection signal-to-noise and effective depth of penetration of stacked multi-offset data are improved, as compared to standard single-offset GPR data. It is also shown that, the stacked multi-offset data is itself improved as the number of velocity analysis locations is increased, up to some practical limit.

هر روش ژئوفیزیکی مزایا و معایب ویژه خود را دارد. تلفیق نتایج حاصل از برداشت به روش‌های مختلف ژئوفیزیکی سبب پوشش نقطه ضعف هر روش به وسیله روش‌های دیگر می‌شود. به همین دلیل بررسی‌های مختلف اکتشافی، مهندسی، زیست محیطی و غیره با استفاده از چندین روش مختلف ژئوفیزیکی، معمولا نتایج معتبرتری را در اختیار قرار می‌دهند. در این پژوهش نیز سعی شده است تا با تلفیق نتایج برداشت به روش‌های توموگرافی مقاومت ویژه الکتریکی (ERT)و رادار نفوذی به زمین (GPR) به بررسی نقاط قوت و ضعف هر یک از این دو روش‌ پرداخته و در پایان، در نتیجه تلفیق نتایج، تفسیر دقیق‌تر و با اطمینان بالاتری ارائه شود. روش ERT یکی از روش‌های برداشت بهینه از زیرمجموعه‌های روش مقاومت ویژه است که در مناطق با زمین‌شناسی پیچیده نتایج قابل اتکایی را در اختیار قرار می‌دهد. روش GPR نیز از روش‌های غیر مخرب ژئوفیزیکی با قدرت تفکیک بالا است که در آن با ارسال امواج الکترومغناطیس بسامد بالا به زمین و ثبت امواج بازتابی از فصل مشترک لایه‌های زیر سطحی، به بررسی‌ زیر سطح زمین در ژرفای کم پرداخته می‌شود. در این پژوهش، قنات به عنوان هدفی مناسب برای شناسایی با این دو روش انتخاب و سپس، برداشت‌های ERT و GPR بر روی منطقه دربرگیرنده هدف مزبور انجام شد. نتایج حاصل از پردازش، مدل‌سازی و تفسیر داده‌های برداشت شده نشان داد که از نقطه نظر مقایسه دو روش یادشده، روش GPR قدرت تفکیک بالاتری دارد ولی روش ERT دارای ژرفای نفوذ بیشتری است. این دو روش در نشان دادن پدیده‌هایی مانند وجود حفرات، تغییرات در ابعاد ذرات و نیز نفوذ رطوبت توافق و همخوانی خوبی دارند. همچنین با تلفیق نتایج حاصل از این دو روش با یکدیگر مشخص شد که دقت و اطمینان تفسیر به طور قابل ملاحظه‌ای افزایش ‌می‌یابد.

Identification of liquefaction and deformation features using ground penetrating radar in the New Madrid seismic zone, USA

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.

Abstract. We present the geophysical data set acquired in summer 2022 close to Ny-Ålesund (western Svalbard, Brøggerhalvøya Peninsula, Norway) as part of the project ICEtoFLUX. The aim of the investigation is to characterize the role of groundwater flow through the active layer as well as through and/or below the permafrost. The data set is composed of electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveys, which are well-known geophysical techniques for the characterization of glacial and hydrological processes and features. Overall, 18 ERT profiles and 10 GPR lines were acquired, for a total surveyed length of 9.3 km. The data have been organized in a consistent repository that includes both raw and processed (filtered) data. Some representative examples of 2D models of the subsurface are provided, that is, 2D sections of electrical resistivity (from ERT) and 2D radargrams (from GPR). The resistivity models revealed deep resistive structures, probably related to the heterogeneous permafrost, which are often interrupted by electrically conductive regions that may relate to aquifers and/or faults. The interpretation of these data can support the identification of the active layer, the occurrence of spatial variation in soil conditions at depth, and the presence of groundwater flow through the permafrost. To a large extent, the data set can provide new insight into the hydrological dynamics and polar and climate change studies of the Ny-Ålesund area. The data set is of major relevance because there are few geophysical data published about the Ny-Ålesund area. Moreover, these geophysical data can foster multidisciplinary scientific collaborations in the fields of hydrology, glaciology, climate, geology, and geomorphology, etc. The geophysical data are provided in a free repository and can be accessed at https://doi.org/10.5281/zenodo.10260056 (Pace et al., 2023).

In this study, we analyzed the effects of snow cover changes caused by snow fences (SFs) installed in 2017 in the Alaskan tundra to examine ground subsidence. Digital surface model data obtained through LiDAR-based remote sensing in 2019 and 2022, combined with a field survey in 2021, revealed approximately 0.2 m of ground subsidence around the SF. To investigate the relationship between SF-induced snow cover changes and ground subsidence, geophysical methods, electrical resistivity tomography (ERT) and ground-penetrating radar (GPR), were applied in 2023 to analyze subsurface characteristics. The increased snow cover due to the SF-enhanced insulation, delaying the penetration of winter cold into the subsurface. This delay caused subsurface temperatures to decrease more slowly, melting the upper permafrost and increasing the thickness of the active layer. ERT and GPR surveys well delineated the boundary between the active layer and permafrost, confirming that the increased snow cover thickened the active layer. This thickening led to the melting of pore ice, causing water runoff and ground compaction, which resulted in subsidence. The runoff also formed channels flowing eastward over the SF. This study highlights how changes in snow cover can influence active layer properties, leading to localized environmental changes and ground subsidence.

The US Department of Energy (DOE) is responsible for the cleanup of inactive DOE sites and for bringing DOE sites and facilities into compliance with federal, state, and local laws and regulations. The DOE's Office of Environmental Management (EM) needs advanced technologies that can make environmental restoration and waste management operations more efficient and less costly. These techniques are required to better characterize the physical, hydrogeological, and chemical properties of the subsurface while minimizing and optimizing the use of boreholes and monitoring wells. Today the cone penetrometer technique (CPT) is demonstrating the value of a minimally invasive deployment system for site characterization. Applied Research Associates, Inc. is developing two new sensor packages for site characterization and monitoring. The two new methods are: (1) Electrical Resistivity Tomography (ERT); and (2) Ground Penetrating Radar (GPR) Tomography. These sensor systems are now integrated with the CPT. The results of this program now make it possible to install ERT and GPR units by CPT methods and thereby reduce installation costs and total costs for ERT and GPR surveys. These two techniques can complement each other in regions of low resistivity where ERT is more effective and regions of high resistivity where GPR is more effective. The results show that CPT-installed GeoWells can be used for both ERT and GPR borehole tomographic subsurface imaging. These two imaging techniques can be used for environmental site characterization and monitoring have numerous and diverse applications within site cleanup and waste management operations.

We present a procedure to estimate the characteristics of small shallow landslides based on the application of ground penetrating radar (GPR) and 2D electrical resistivity tomography (ERT). Existing procedures based on either conventional or non-invasive geophysical methods, observe almost exclusively large and deep landslides. Verification has been done on a small shallow landslide in the village of Vinca, near Belgrade, Serbia. The proposed procedure is realized in two simultaneous steps. First, from high resolution raw data obtained by GPR survey, soil horizons inside and near landslide body are estimated up to 4 m deep. The rupture surface is defined and its depth is estimated at 1.7 m. Second, ERT technology confirmed and integrated the results obtained by GPR survey. Main advantages of proposed procedure are efficiency and applicability for small shallow landslides whose number and impact on environment is dominant.

In archaeo‐geophysical investigations, the accuracy and resolution of the generated geophysical models are crucial parameters for excavation decision. Therefore, the combined use of different geophysical data sets is necessary to improve the interpretability of archaeological ruins, particularly in case of low physical contrast objects. The present study's objective is to validate the outputs of integrated ground penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys in Tanis, which is considered one of the most important archaeological sites in the Nile Delta, Egypt. The GPR survey was carried out along an area of 24 × 31.5 m with profile interval of 0.5 m in two orthogonal directions using 100, 200 and 600 MHz shielded antenna. Moreover, nine ERT profiles were performed along the same GPR lines for comparison and integration using Wenner‐beta (WB) and dipole–dipole (DD) arrays with 1 m electrode spacing and 3 m profile spacing. In addition, the ERT measurements were executed by implementing two tie lines of the same length, electrode spacing and electrode arrays to reduce the effect of banding or directional bias. The processed 2D GPR and ERT profiles have illustrated series of mud‐brick walls within the top 2 m in silt–clay background which is underlined by the turtle‐back of Sand Island. In such conditions, the mud‐brick walls in conductive soils with complex spatial distributions have produced tricky and difficult anomalies to be interpreted using only 2D data sets. To overcome this challenging case, the GPR orthogonal profiles were collated in 3D domain, while the ERT profiles were gathered and inverted using 3D robust inversion algorithm and validated with an identified mud‐brick wall. Therefore, the created 3D visualizations demonstrated the efficiency of the joint use of the ERT and GPR surveys as an enhanced mapping tool for buried archaeological ruins and can be used at similar archaeological sites all over the world.