Radar Surveys Research Articles

Integration of in‐mine seismic and GPR surveys to gain advanced knowledge of Bushveld Complex orebodies

AbstractImproving the exploration of deep‐seated mineral deposits and assessing the stability of the mine pillars require that geophysical techniques are deployed in a fast and cost‐effective manner with minimal environmental impact. This research presents results from in‐mine reflection seismic experiments and a ground penetrating radar (GPR) survey conducted at the Maseve platinum mine, South Africa. The research aims to develop and implement methods to image platinum group metal (PGM) deposits and geological structures near mine tunnels and assess the stability of pillars. The seismic experiments were conducted using a sledgehammer source (10 lb), conventional cabled geophones (14 Hz), and a landstreamer with 4.5 Hz vertical component geophones. The GPR survey was conducted using a Noggin 500 GPR system with 500 MHz centre frequency. An image of the underlying orebody and geological structures down to 100 m from the mine tunnel floor (∼500 m below ground surface) was produced. We correlated the coherent reflections beneath the tunnel floor with a known Upper Group (UG2) PGM orebody. The final seismic section shows that the UG2 mineralisation is dissected by near‐vertical dykes, faults and fractures. These structures, faults in particular, are interpreted to have been active post‐mineralisation, implying that they may have contributed to the current complex geometry of the deposit. Four GPR profiles were collected around a stability pillar adjacent to the seismic lines. The radargram sections were processed to improve the signal‐to‐noise ratio (S/N). The results show different patterns of fracturing and stress‐induced structures. These fractures were shown to be sub‐vertical and, possibly, constitute complex micro‐structures within the pillar, which could compromise the pillar stability and integrity. The study demonstrates that in‐mine seismic and GPR surveys can be cost‐effective and valuable for mineral exploration.

Stagnant ice and age modelling in the Dome C region, Antarctica

Abstract. The European Beyond EPICA project aims to extract a continuous ice core of up to 1.5 Ma, with a maximum age density of 20 kyr m−1 at Little Dome C (LDC). We present a 1D numerical model which calculates the age of the ice around Dome C. The model inverts for basal conditions and accounts either for melting or for a layer of stagnant ice above the bedrock. It is constrained by internal reflecting horizons traced in radargrams and dated using the EPICA Dome C (EDC) ice core age profile. We used three different radar datasets ranging from a 10 000 km2 airborne survey down to 5 km long ground-based radar transects over LDC. We find that stagnant ice exists in many places, including above the LDC relief where the new Beyond EPICA drill site (BELDC) is located. The modelled thickness of this layer of stagnant ice roughly corresponds to the thickness of the basal unit observed in one of the radar surveys and in the autonomous phase-sensitive radio-echo sounder (ApRES) dataset. At BELDC, the modelled stagnant ice thickness is 198±44 m and the modelled oldest age of ice is 1.45±0.16 Ma at a depth of 2494±30 m. This is very similar to all sites situated on the LDC relief, including that of the Million Year Ice Core project being conducted by the Australian Antarctic Division. The model was also applied to radar data in the area 10–15 km north of EDC (North Patch), where we find either a thin layer of stagnant ice (generally <60 m) or a negligible melt rate (<0.1 mm yr−1). The modelled maximum age at North Patch is over 2 Ma in most places, with ice at 1.5 Ma having a resolution of 9–12 kyr m−1, making it an exciting prospect for a future Oldest Ice drill site.

The Aneto glacier's (Central Pyrenees) evolution from 1981 to 2022: ice loss observed from historic aerial image photogrammetry and remote sensing techniques

Abstract. The Aneto glacier, although it may be considered a very small glacier (<0.5 km2), is the largest glacier in the Pyrenees. Its surface and thickness loss have been continuous in recent decades, and there have been signs of accelerated melting in recent years. In this study, thickness and surface losses of the Aneto glacier from 1981 to 2022 are investigated using historical aerial imagery, airborne lidar point clouds and unoccupied aerial vehicle (UAV) imagery. A ground-penetrating radar (GPR) survey conducted in 2020, combined with data from photogrammetric analyses, allowed us to reconstruct the current ice thickness and also the existing ice distribution in 1981 and 2011. Over the last 41 years, the total glacierised area has decreased by 64.7 %, and the ice thickness has decreased, on average, by 30.5 m. The mean remaining ice thickness in autumn 2022 was 11.9 m, as against the mean thickness of 32.9, 19.2 and 15.0 m reconstructed for 1981 and 2011 and observed in 2020, respectively. The results demonstrate the critical situation of the glacier, with an imminent segmentation into two smaller ice bodies and no evidence of an accumulation zone. We also found that the occurrence of an extremely hot and dry year, as observed in the 2021–2022 season, leads to a drastic degradation of the glacier, posing a high risk to the persistence of the Aneto glacier, a situation that could extend to the rest of the Pyrenean glaciers in a relatively short time.

Ice-flow perturbation analysis: a method to estimate ice-sheet bed topography and conditions from surface datasets

Abstract One of the largest contributors to uncertainty in predictions of sea-level rise from ice-sheet models is a lack of knowledge about the bed topography beneath ice sheets. Bed topography maps are normally made by interpolating between linear radar surveys using methods that include kriging, mass conservation and flowline diffusion, all of which may miss influential mesoscale (2–30 km) bedforms. Previous works have explored an Ice-Flow Perturbation Analysis (IFPA) approach for estimating bed topography using the surface expression of these mesoscale bedforms. Using regions of Pine Island Glacier that have been intensively surveyed by ice-penetrating radar as test sites, and a refined IFPA methodology, we find that IFPA detects bedforms capable of influencing ice flow which are not represented in Bedmachine Antarctica and other interpolated bed products. We further explore the ability of IFPA to estimate relative bed slipperiness, finding higher slipperiness in the main trunk and tributaries. Alongside other methods which estimate ice thickness, bed topography maps from IFPA have the potential to constrain projections of future sea-level rise, especially where radar data are sparse.

Late Quaternary Deformation of the Ambon fault, Indonesia: Preliminary Results

The Ambon fault in the northern Banda Arc has capability of generating Mw 6.9 earthquake. The Ambon fault poses a significant seismic hazard to Ambon Island because the fault is located near populous areas, the Ambon City. Recent seismicity in Ambon Island and surrounding areas indicates that this region is actively deforming. Ambon Island has experienced many damaging earthquakes since the 17th century. However, the potential seismic hazard on this island remains enigmatic due to the lack of detailed geological information, such as fault traces, slip rate, and paleoseismic history. This study reports the preliminary results of tectonic geomorphic investigations and ground-penetrating radar (GPR) surveys on the Ambon fault. Tectonic geomorphic features, such as fault scarps, warped surfaces, and sag ponds indicate the late Quaternary activity of the Ambon fault. The Ambon fault predominantly shows a normal sense of motion with a dip of ~60-70°. The Ambon fault is related to the extensional tectonics in the Banda Sea.

The Role of Ground Penetrating Radar (GPR) Surveying for Indoor Building Information Modelling (BIM)

The Role of Ground Penetrating Radar (GPR) Surveying for Indoor Building Information Modelling (BIM)

GPR survey on underwater archaeological site: A case study at Jenipapo stilt village in the eastern Amazon region, Brazil

In this work we present and discuss the results of a pioneering Ground Penetrating Radar (GPR) survey performed at the underwater archaeological stilt village called Jenipapo in the eastern Amazon region. Jenipapo stilt village is located on the Turiaçu River, Maranhão State, Northeast of Brazil. The region is known as the Maranhense wetland where settlements were built by indigenous populations that inhabited this region during the pre-colonial period (∼AD 1 – 1100). These settlements were built on the margin of rivers and lakes, being supported by wooden pillars, corresponding to prehistoric stilt houses. The objectives of this research are to refine the wooden pillars location at the Turiaçu River bottom and guide the search for underwater archaeological artifacts. A total of twelve GPR profiles were acquired with 270 MHz antennas using a rubber boat. The GPR results indicated clear signal reflection from the river bottom and several diffraction hyperbolas suspended over the river bottom related to the top of the wooden pillars. To support the interpretation of the results, a GPR numerical modeling was performed to simulate the diffraction hyperbolas suspended in the water related to the wooden pillars. The synthetic result presented a good agreement with real data. Finally, the location of several diffraction hyperbolas can guide the divers to find and collect archaeological artifacts around the underwater wooden pillars that are the best evidence of the stilt houses of indigenous settlements found in the eastern Amazon region. Several archaeological artifacts were found during previous work, including ceramic materials. The results of this research show the capability of the GPR method to map an underwater wooden pillar and increase the probability of finding archaeological artifacts on the river bottom, which contributes to improve the knowledge of the Amazonian archaeology in Brazil.

Geophysical Prospecting of the Coptic Monastery of Apa Moses Using GPR and Magnetic Techniques: A Case Study, Abydos, Sohag, Egypt

As a result of new discoveries, there is a greater opportunity for development and investment in the Al-Arraba EL-Madfuna region of Abydos, Sohag Governorate, Egypt, which benefits tourism and increases the national economy. The Coptic monastery, which was originally established by Apa Moses, the patriarch of the Coptic Church during the ancient Roman Empire, has vanished inside the current market on this site, along with numerous tombs. As a result, the primary goal of this work is to prospect on this site for these potential archaeological features. Ground magnetic and ground-penetration radar (GPR) surveys were employed for discovering these archaeological issues. This work was done in coordination with the Supreme Council of Antiquities. Ground magnetic and GPR surveys were implemented using the G-857 proton-precession magnetometer and GSSI SIR 4000 with a 200 MHz antenna. The data were processed and interpreted using Geosoft Oasis Montaj and REFLEXW v.5.8 software packages. The magnetic data were filtered to separate the shallower anomalies representing the archaeological remains from those of the deeper ones. Butterworth high pass filter, first vertical derivatives, analytical signal, and tilt derivative were employed to carry out the processing stages. The results were analyzed qualitatively and quantitatively to describe these anomalies and determine their locations, geometrical shapes, and depths. The source parameter imaging technique and 3D Euler deconvolution were used to calculate the depths. The analysis of magnetic maps shows that the study site is characterized by a number of anomalies that occur and have geometric squares and rectangle shapes with depths ranging from 0.7 m to ≈4 m. Some of these anomalies are related to potential archaeological objects. GPR findings reveal considerably scattered hyperbolas along several profiles, which may indicate the presence of potential buried objects. The integration of magnetic and GPR results showed that there is some consistency in the identification of the locations of the likely buried archaeological objects and their depths (0.7 to 3 m) for the majority of the discovered targets. The findings of this study suggest excavating at this location and relocating the market in order to protect the buried antiquities from being lost to be safeguarded as a tourist destination target.

The evolution and preservation potential of englacial eskers: An example from Breiðamerkurjökull, SE Iceland

AbstractDirectly observing glacial drainage systems (englacial and subglacial) is challenging. The distribution, morphology and internal structure of eskers can provide valuable information about the glacial drainage system and meltwater processes. This work presents the annual evolution (meltout) and internal structure of an esker emerging from the Breiðamerkurjökull ice margin, southeast Iceland. Changes in esker morphology have been repeatedly mapped over a 1‐year period using high temporal and spatial resolution data acquired by an uncrewed aerial vehicle (UAV). The internal architecture of the esker was investigated using ground‐penetrating radar (GPR) surveys. These data are used to identify the dominant processes driving the formation of this englacial esker and to evaluate the preservation potential. The englacial esker was up to 2.6 m thick and ice‐cored. A large moulin upglacier of the esker, which evolved into an englacial conduit, supplied meltwater to the englacial channel. Upglacier dipping debris‐filled basal hydrofractures, formed by pressurised subglacial meltwater rising up the retrograde bed slope, likely supplied sediment to the englacial conduit. Over the 1‐year period of observation the crest morphology evolved from flat‐ to sharp‐crested and the esker footprint increased by a factor of 5.7 in response to post‐depositional processes. The findings presented here indicate that englacial eskers may have low preservation potential due to post‐depositional reworking such as slumping through ice‐core meltout and erosion by later meltwater flow. As englacial eskers may not be preserved in the landscape, they could represent important glacial drainage system components that are not currently captured in palaeo‐ice sheet reconstructions. This work highlights the value of creating a time series of high‐temporal resolution data to quantify morphological evolution and improve glacial process‐form models.

Late Tripolye Culture Settlement Spatial Pattering: Case study from the Gordineşti II-Stînca goală site, Northern Moldova

Abstract The Gordineşti II-Stînca goală is an archaeological site located in the northern part of the Moldavian Plateau in Edineț Region. Chronologically this settlement is linked to the later phase of the Tripolye Culture. Currently, in archaeological literature, the problems of human occupation, land management, and spatial arrangement of settlements in Moldova during the Eneolithic are highly understudied. In this paper, we present the results of recent archaeological works focusing on the spatial patterning of housing structures, Ground Penetrating Radar (GPR) survey, and desk-based Kernel Density Estimation (KDE) analysis, that has been undertaken to further the understanding of the spatial organisation of the Gordineşti II-Stînca goală settlement. The results indicate the high archaeological potential of this site, with the likely presence of multiple housing structures arranged in a planned and functional manner.

Brief communication: How deep is the snow on Mount Everest?

Abstract. Exploring the snow depth on Mount Everest, one of the most inaccessible places on our planet, has long been a topic of interest. Previously reported snow depths have been inconsistent and have large uncertainties. Here, we report the ground-penetrating radar survey of snow depth along the north slope of Mount Everest in May 2022. Our radar measurements display a gradual increasing transition of snow depth along the north slope, and the mean depth estimates at the summit are 9.5±1.2 m. This updated snow depth on Mount Everest is much deeper than previously reported values (0.9–3.5 m).

Investigating Wiradjuri marara (carved trees or dendroglyphs) and dhabuganha (burials) in the Central Tablelands, southeastern Australia

Marara (carved trees, dendroglyphs or tapholgyphs) are a distinct part of Wiradjuri Country in southeastern Australia. Each marara displays a unique muyalaang (tree carving) that a Wiradjuri person carved into the outer surface of a tree after removing bark. Marara mark the dhabuganha (burials) of Wiradjuri men of high standing, representing part of traditional cultural practices that extend into the deep past. Yet, the meaning of these sacred locations is not widely understood due to the lack of Wiradjuri teaching, knowledge and participation in previous studies. Here we present the first Wiradjuri-led archaeological study of marara, muyalaang and dhabuganha, completed in the Central Tablelands. We combine a review of previous studies with new information from interviews with Wiradjuri Elders and knowledge holders, Ground Penetrating Radar survey, and 3D modelling (photogrammetry) – guided by the Wiradjuri philosophy Yindyamarra (cultural respect). The results build new, culturally and scientifically informed understandings of practical and symbolic aspects of Wiradjuri culture, with marara and dhabuganha viewed not as individual objects or ‘sites’ but as connected parts of Wiradjuri Lore, beliefs, traditional cultural practices and Country. Consistent with Wiradjuri Elder requests, this paper is freely available and written in simple language for the Wiradjuri community and beyond.

Ice and Snow on Lake Stemmevatnet, Spitsbergen, in Winter 2019/20

Received January 19, 2023 ;revised March 22, 2023; accepted June 27, 2023The results of observations and modeling of the formation of the snow-ice cover of Lake Stemme (West Svalbard Island) in winter 2019/20 are presented. The main information was obtained by two radar (GPR) survey, performed on the floating ice of the Lake on March 12 and April 22 of 2020. Authors believe that probably these observations were the first ones on the Lake. The use of the radar made it possible to obtain data on the dynamics of the thickness of the layers of snow and ice cover, the so-called “snow ice” which is formed when the boundary between snow and ice was submerged under water. During the time between records, the thickness of the last “snow ice” increased two to three times, i.e., from units to the first tens of cm, and it spread to the entire deep-water part of the Lake area. In addition, analysis of high-precision positioning of the radar records revealed a significant deflection in the ice surface in the central part of the Lake under the influence of snow load and the decreasing level of the reservoir. The calculations of the thermodynamics of the floating ice cover have shown that its thickening occurs as a result of the processes of congelation and isostatic ice formation, replacing each other at its lower and upper boundaries, respectively. At the same time, the formation of “snow ice” violates the characteristic feature of decreasing of ice thickness with growth of the snow thickness, which significantly influences on the thermal and mass balance of the Lake snow-ice cover. Results of calculations of the ice cover deformation did show that it takes place not only due to the elastic, but also to the viscous properties of ice, and it is concentrated in a narrow coastal zone. The maximum radial stress is reached at a distance of several meters from the shore, where a circular crack parallel to the shoreline is formed. Such a crack is formed at all ice thicknesses at about the same distance from the shore.

Geomorphic mapping and analysis of neotectonic structures in the piedmont alluvial zone of Haryana state, NW-India: a remote-sensing and GPR based approach

The Himalayan Frontal Thrust (HFT) and the surrounding piedmont alluvial region represent a zone of active deformation in the Indo-Gangetic plains. We investigated the Piedmont zone between the Ghaggar and Yamuna River basins in Haryana, India, for geomorphic signatures of active tectonics using remotely sensed data and validated by Geophysical Ground Penetrating Radar (GPR) surveys. The possible locations and the types of active tectonic features such as sub-surface fault, ridges, lineaments and warps were identified based on the presence of geomorphic signatures such as drainage gradient anomalies, abrupt change in flow direction, river offset, compressed meanders, paleochannels and topographic breaks. We used various optical satellite imageries to detect and map the temporal changes in the flow pattern of rivers in the study area. GPR investigations were done at selected test sites to locate and verify the continuity of subsurface fault. The GPR profiles were taken in the North-South direction using the common midpoint technique with 40 and 100 MHz antennae. Low frequency bi-static GPR scanning confirmed a number of dipping reflectors due to fault planes and warp surfaces in the study area. It is concluded that the piedmont zone of Haryana is actively deforming and could become a future seismic hazard zone.

Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream

The dynamic mass loss of ice sheets constitutes one of the biggest uncertainties in projections of ice-sheet evolution. One central, understudied aspect of ice flow is how the bulk orientation of the crystal orientation fabric translates to the mechanical anisotropy of ice. Here we show the spatial distribution of the depth-averaged horizontal anisotropy and corresponding directional flow-enhancement factors covering a large area of the Northeast Greenland Ice Stream onset. Our results are based on airborne and ground-based radar surveys, ice-core observations, and numerical ice-flow modelling. They show a strong spatial variability of the horizontal anisotropy and a rapid crystal reorganisation on the order of hundreds of years coinciding with the ice-stream geometry. Compared to isotropic ice, parts of the ice stream are found to be more than one order of magnitude harder for along-flow extension/compression while the shear margins are potentially softened by a factor of two for horizontal-shear deformation.

Spatial characterization of near-surface structure and meltwater runoff conditions across the Devon Ice Cap from dual-frequency radar reflectivity

Abstract. Melting and refreezing processes in the firn of the Devon Ice Cap control meltwater infiltration and runoff across the ice cap, but their full spatial extent and effect on near-surface structure is difficult to measure with surface-based traverses or existing satellite remote sensing. Here, we derive the coherent component of the near-surface return from airborne ice-penetrating radar surveys over the Devon Ice Cap, Canadian Arctic, to characterize firn containing centimeter- to meter-thick ice layers (i.e., ice slabs) formed from refrozen meltwater in firn. We assess the use of dual-frequency airborne ice-penetrating radar to characterize the spatial and vertical near-surface structure of the Devon Ice Cap by leveraging differences in range resolution of the radar systems. Comparison with reflectivities using a thin layer reflectivity model, informed by surface-based radar and firn core measurements, indicates that the coherent component is sensitive to the near-surface firn structure composed of quasi-specular ice and firn layers, limited by the bandwidth-constrained radar range resolution. Our results suggest that average ice slab thickness throughout the Devon Ice Cap percolation zone ranges from 4.2 to 5.6 m. This implies conditions that can enable lateral meltwater runoff and potentially contribute to the total surface runoff routed through supraglacial rivers down glacier. Together with the incoherent component of the surface return previously studied, our dual-frequency approach provides an alternative method for characterizing bulk firn properties, particularly where high-resolution radar data are not available.

Эволюция межпланетных миссий радиолокационных исследований планет Солнечной системы с учетом развития бортовых радиолокационных средств космических аппаратов

The paper gives a detailed retrospective review of radio studies of the Solar system planets. The history of missions and the evolution of the spacecraft designed for radar research are considered. It presents analysis of the options in constructing the existing spacecraft radar facilities for interplanetary research. On the basis of this analysis, the appearance of a new generation of radar equipment for interplanetary research missions is proposed. Principles of construction and technical solutions for creation of the onboard radar equipment for the promising research spacecraft were determined. Promising missions of the Venus radar survey were analyzed, and approaches to construction of the spacecraft radar equipment based on the advanced technical solutions were proposed.

РАДИЭКОЛОГИЧЕСКИЙ МОНИТОРИНГ И ГЕОИНФОРМАЦИОННОЕ МОДЕЛИРОВАНИЕ РАСПРЕДЕЛЕНИЯ 137CS НА ЛАНДШАФТНОМ УРОВНЕ В БРЯНСКОЙ ОБЛАСТИ

The results of the landscape-radioecological monitoring and geoinformation modeling of the distribution of 137Cs in the Predpolesie landscapes (Vyshkov and Dubrovka sites), as well as in the Opolies (wide woodless plains) landscapes (Brakhlov and Kostitsa sites) in the Bryansk oblast are presented. The data on the radiation survey of arable lands in the Bryansk oblast carried out in 2017 at four test sites with different densities of 137Cs contamination are given. Based on the monitoring results, a data bank of the vertical distribution of 137Cs in the agrocenoses soils has been formed. The structure of the large-scale radioecological geoinformation system (RadGIS) comprises a digital terrain model based on the radar survey of the Earth topography from the SRTM shuttle. The second information layer contains the results of the aerial gamma (AG) survey performed in 1993 with a resolution of 100 m. A comparative analysis of the 2017 ground testing data with the results of the 1993 AG survey has allowed for assessment of the 137Cs radioactive contamination field transformation in various landscapes at four test sites. To assess the intensity of 137Cs lateral migration at the test sites, geoinformation modeling has been performed with the detection of surface flow streamlines.

Evaluating subsurface flow connectivity in a pine-covered hillslope with stemflow infiltration and ground-penetrating radar surveys

The hydrological response of sloping catchments is strongly conditioned by the connectivity of subsurface preferential flows. The objective of this paper is to investigate the role played by stemflow infiltration in subsurface water flow dynamics, focusing on a forested hillslope located in an Aleppo pine Mediterranean forest (Pinus halepensis, Mill.) located at Sierra Calderona, Valencia province, Spain. We combined stemflow artificial experiments with the ground-penetrating radar (GPR) as a non-invasive technique to investigate stemflow-induced preferential flow paths activated by different trees and the related hydrological connectivity at the hillslope scale. Our observations allowed us to identify different dynamics associated with the initiation of stemflow and then lateral preferential flow, including the activation of connected preferential flow paths that received stemflow water from different trees. These observations provided empirical evidence of the role of stemflow in the formation of lateral preferential flow networks. Our measurements also provided estimations for flow velocities, which provided new insight on the magnitude of stem-induced lateral preferential flow paths. The applied protocol offers a simple, repeatable and non-invasive way to conceptualize hillslope responses to rainstorms.

Reconstructing terrestrial ice sheet retreat dynamics from hummocky topography using multiscale evidence: An example from central Ireland

The research reported here combines high-resolution digital elevation models (DEMs) derived from airborne LiDAR with ground-penetrating radar (GPR) surveys and macro- and micro-scale sedimentological analyses to study the geomorphology and internal structure and composition of ridges and mounds within an area of hummocky topography in the Brosna basin, central Ireland. Our evidence indicates that much of the hummocky topography consists of fragmented mega-scale glacial lineations (MSGLs) indicating a phase of accelerated ice flow, overlain by groups of small ridges composed of subglacially derived till and sediment gravity flow deposits. Subtle differences in ridge morphology indicate they may be multi-genetic and formed both ice-marginally as moraines and subglacially as small ribbed moraine. We interpret MSGL-ridge associations as a subglacial bedform continuum reflecting the evolution from a deforming bed to brittle deformation, due to changing thermal and hydrological conditions at the ice-bed interface during ice sheet retreat. Adjacent glaciofluvial landforms indicate initial en- and supra-glacial meltwater drainage, possibly directly related to changing basal thermal/hydrological characteristics and subglacial ridge formation. Subsequently a subglacial conduit system evolved, and later retreat involved formation of ice-marginal ridges. The partially preserved landsystem reflects formation at a polythermal to active temperate ice marginal zone, rather than the stagnating temperate margin previously assumed for this area. Our work demonstrates the usefulness of hummocky topography in identifying changes in ice sheet bed thermal/hydrological characteristics during deglaciation and the importance of combining multiple evidence strands in reconstructing the processes involved in glacial landform construction.