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NSG2021 27th European Meeting of Environmental and Engineering Geophysics
- Conference date: August 29, 2021 - September 2, 2021
- Location: Hybrid
- Published: 29 August 2021
121 - 134 of 134 results
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Ground-penetrating radar evidence of faulting in unconsolidated coarse sediments
Authors S.S. Bricheva, E.V. Deev, I.O. Dubrovin, M.M. Doroshenkov, A.L. Entin and A.V. PaninSummaryThis study presents the new data from the faults within Upper Pleistocene-Holocene deposits, presented by pebbles, cobbles, and boulders with a coarse-medium sandy matrix. Such sediments produce complex and diffuse wave patterns on GPR data, and it is challenging to recognise the faulting among them. Thus, we solved the direct problem of detecting fault zone features by GPR using numerical modelling. Comparing numerical simulation results with field data (GPR profiles and trench wall sketches), we proposed a summary of signs of the fault zone on GPR profiles.
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Application of a stochastic algorithm for 3D inversion of EM sounding data
Authors D. Bogdanovich, K. Antashchuk, I. Pesterev, D. Shimianskii, A. Bashkeev and A. PolitcinaSummaryStochastic algorithms belong to methods of global search which are able to find global minimum of discrepancy function in the presence of multiple local minima. Modified cultural algorithm is implemented for 3D inversion of EM sounding data. The algorithm is tested on data of electromagnetic investigations of detecting the gold mineralization zones. The algorithm uses information about the number of candidates for the role of a parent, the number of parents and the probability of mutation as a belief space together with information about global minimum area. Starting from a homogeneous half-space and using no priori information, results obtained by modified cultural algorithm are in good agreement with the data of the 2D inversion.
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Location accuracy of seabed nodes during 3D seismic survey for seep studying at Laptev sea.
By D. IlinskiySummaryRecent years marine surveys have provided a large and important data for mapping gaseous emissions from the seabed (the so-called seeps) of the North Seas of Russia. A number of researchers associate these phenomena with the release of methane from buried layers of permafrost on the shelf of the Arctic seas, which can potentially change the ratio of greenhouse gases in the Arctic and affect global climate change. The several important questions on the structure, composition and nature of these phenomena still remain unresolved. One of the ways to solve the questions posed is to perform detailed 3D seismic survey of high accuracy. During the 73th scientific voyage of R/V “Akademik Mstislav Keldysh” (AMK), 3-D reconnaissance seismic survey with seabed nodes was carried out. To study the internal structure of the sedimentary cover around the mega seep, we use a 3D reflection seismic method with seabed seismic nodes. The observation template consists of 16 4-component seismic seabed nodes with 300 meters spacing in both directions. Despite the absence of differential corrections for GPS/GLONASS, the obtained positioning accuracy of nodes on the sea bottom is sufficient for carrying out 3-D seismic survey.
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Induced Polarization of ion-conducting porous media: A review of mathematical models. Pt.1.Phenomenology and Electrical Double Layer
Authors K. Titov, B. Mehalli, G. Gurin and A. TarasovSummaryIn this paper, we review mathematical models of the Induced Polarization (IP) of ion-conducting porous media. In the first part we consider the IP phenomenological description based on the classical Debye and Pelton models, and we review the Electrical Double Layer (EDL) theory. We concluded that IP can be represented by an equivalent circuit, which consists of a parallel connection of (i) a resistance and (ii) a serial connection of another resistance and a non-ideal capacitor. We stress that IP can be considered as a “twice coupled” phenomenon in sense of the non-equilibrium thermodynamics, because the initial electric field produces the chemical force, which produces, in turn, a secondary electric field. We also note that the phenomenological models predict a parallel connection of conductive and polarizable elements within the studied porous media. Finally we note that an existence of EDL coating the solid phase is a necessary ingredient for appearance of the Induced Polarization.
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Induced Polarization of ion-conducting porous media: A review of mathematical models. Pt.2. Granular and capillary models
Authors K. Titov, B. Mehalli, G. Gurin and A. TarasovSummaryBased on the review of the phenomenological models of the Induced Polarization (IP), and the Electrical Double Layer theory, which is done in Part I, in Part 2, we review the capillary and granular models of porous media. These mechanistic models are derived for (i) an individual dielectric particle and (ii) a sequence of pores with different radii. For the polarizing spherical particle, following an approach of A. Revil, we show an easy way to upscale the particle response to the scale of the representative elementary volume. However, we stress that even the IP capillary model is “younger” than the IP granular model, the capillary model is less elaborated, and has not been properly upscaled. We believe this review will be useful for further development of specific IP theories for specific classes of soils, sediments, and rocks.
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Universal aero-ground overhauser magnetometer-gradiometer. POS-2Aero vertical gradiometer testing with DJI-600Pro drone
Authors E. Narkhov, V. Sapunov, A. Denisov, A. Sergeev, A. Fedorov, A. Shirokov, V. Ushakov, I. Kozlova and L. MuravyovSummaryThe modernization of a commercial magnetometer produced by the Ural Federal University for use in aeromagnetic exploration is presented. New special Overhauser sensors with a weight of up to 400 grams (diameter 50, length 105 millimeters) with a new working substance, providing Heisenberg hyperpolarization in quantum spin exchange, were used. The tests were carried out on the basis of the DJI 600 Pro industrial copter at a weakly magnetic test site. An object in the form of a 2-ton car was used. Sensitivity up to 0.03 nT/meter with magnetic card accuracy up to 1 nT (0.05 nT/meter) at copter speeds of 5–10 meters/sec with suppression of the gyroscopic effect of the proton sensor was demonstrated.
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Lightweight TEM and VLF systems for low-altitude UAV-based geophysical
Authors A. Parshin, Y. Davidenko, S. Yakovlev, V. Vinokurov and A. BashkeevSummaryTo create a complete set of UAV-based aerogeophysical methods, two lightweight UAV-electromagnetic systems were developed. The first one (VLF-type) is designed to first-stage geophysical mapping over large areas; it can be performed simultaneously with magnetic and gamma surveys on one UAV. In this case, the receiver with mutually orthogonal ferrite antennas provides measurement of the vertical and horizontal components of the electromagnetic field in the audio frequency range (10 – 48 kHz), at the far field region of the electromagnetic field of navigation radio stations. The second variant is the UAV-TEM, where the time-domain transmitter located on the ground and connected to a galvanically grounded line several kilometers long, and the receiver with coil is towed by the multirotor UAV. From one line placement, it is possible to perform surveys in areas up to several square kilometers. This variant is optimal for detailed electromagnetic soundings in local sites identified at the previous stage of geophysical mapping, it provides the possibility of data inversion to a depth more than 300 meters. Together with UAV-magnetic prospecting and gamma-spectrometry, the created systems provides a solution to a wide range of geological tasks in any complexity of landscape conditions.
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Re-appraising legacy seismic data using modern processing algorithms: case studies from South African Goldfields.
Authors M. Sihoyiya, M. Manzi, M. Westgate, I. James, R. Durrheim and P. StaleySummaryThe reflection seismic method is proving and will continue to prove its significance in mineral exploration and mine development. The study from the Witwatersrand Basin demonstrates the insight given by 2D legacy seismic data in imaging the thin, layered gold deposits. A case study from the Witwatersrand goldfields in South Africa is presented, demonstrating the significance of re-appraising 2D legacy seismic data. The 18 km long seismic line located near Burnstone mine in the South rand goldfields, collected in 1993 is being reprocessed and modelled to calculate the synthetic seismic response of the gold-bearing horizons.
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Reprocessing of legacy seismic data for gold exploration: case study from Witwatersrand goldfields, South Africa
Authors N. Mutshafa, M. Manzi, M. Westgate, I. James, R. Durrheim and P. StaleySummaryLegacy data are defined as previously acquired data that are no longer in use. Their restoration requires substantial time and money, without the promise of yielding rewarding results. These legacy data sets are often accompanied by poorly preserved documentation, outdated coordinates, and are stored on old tech (e.g., tapes or printed versions/hard copies) that make the data hard to use. The new information acquired from the legacy data may profit future mine planning operations by finding new ore deposits, giving a superior estimation of the resources and information that will assist with sitting and sinking future shafts. In this study we present results from the reprocessed legacy seismic data from Witwatersrand goldfields (South Africa). The purpose of the study is to improve the imaging of the gold orebody known as the Ventersdorp Contact Reef (VCR), which is mined at the Kloof Gold Mine. The VCR occurs at an interface between the Ventersdorp Supergroup and Central Rand Group with contrasting densities and seismic velocities, which makes it a good target for the seismic methods.
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UAVs and ground-based geophysical surveys and 3D inversion when studying archeological objects in Baykal Region
Authors C. Tepeшкин, S. Davydenko, Y. Davydenko, A. Davydenko, A. Parshin and S. SnopkovSummaryAncient iron-making complexes are in many places on the western coast of the central part of Lake Baikal. The objects are located in the folded frame of the Siberian platform, represented by deeply metamorphosed rocks of the Olkhon crystalline complex. The possibilities of terrestrial and UAV magnetic surveys and electrical resistivity tomography (ERT) are considered to optimize searches and study archaeological sites with minimizing excavating by applying. They use 3D inversions of geophysical surveys’ data to localize and estimate parameters of physical-geological models of archeological and geological near-surface objects. Comparing the modeling results on a well-known archaeological site has given a chance to estimate the effectiveness of the methods used. Inversion of magnetic fields using vector scanning and elastic net regression allows receiving a geometrical image, spatial distribution of susceptibility, and remanent of furnaces by terrestrial and UAV magnetic surveys data and distinguish object artificial and geological origins.
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Applying Multivariate Statistical Analysis to Marine Electromagnetic Sounding Data
Authors Y. Davydenko, S. Iakovlev, A. Bashkeev, E. Krainova, A. Davydenko and M. PersovaSummaryIn 2012-2015, on the Norwegian shelf, a marine electromagnetic sounding surveys were carried out using the differential-normalized electro prospecting method (DNME) with length of several thousand kilometers. The effectiveness of the method is confirmed in reference fields such as Troll. More than 20 wells were drilled, a significant part of forecasts was confirmed. However, new deposits were later discovered at the survey sites, which anomalies had not previously distinguished according to the inversion data. The fact of lack of anomalous effects made us look at the results of the shooting of those years in a new way.
For one of the survey lines crossing the reference field, the following results are presented: a multivariate statistical analysis applied to the reprocessed data; one-dimensional inversion of transients simultaneously with the apparent resistivity curve with a more detailed step; inversion within the 2.5D model.
The research carried out shows that at the first stage, it is advisable to highlight the area of most significant interest based on the result of multivariate statistical analysis. The results of the multivariate statistical analysis do not contradict the results of 2D modeling.
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Mineral Prospectivity Mapping for Forecasting Gold Deposits in the Central Kolyma Region (North-East Russia)
Authors I. Goryachev and A. ParshinSummaryThe emergence of a junior geological business in Russia requires support for decision-making on the choice of sites for geoprospecting on the basis of the application principle. The territory of Russia is very large, but it is completely covered by geological surveys at a scale of 1: 200,000, as well as fragmentarily by various types of geochemical and geophysical surveys on a scale of 1:50,000 - 1: 500,000. These data, together with modern remote sensing data, allow the use of MPM methods to assess the resource potential of various regions. This paper discusses the options for such a forecast, implemented on the basis of open GIS technologies, for the territory of the North-East of Russia, promising for gold and a number of other minerals.
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Examples of Seismic Shallow Subsurface Characterisation and Deep Electromagnetic Monitoring
Authors E. Slob, D. Draganov, M. Eltayieb, G. Drijkoningen, D. Werthmüller and R. GhoseSummaryDifficulties in detecting and characterising shallow objects close the surface with seismic shear waves are often problematic because of dominant surface waves. By sequencing a specific combination of two data driven processing steps followed by diffraction tomography can overcome these problems. Small scattering objects become visible in the final image that can have importance of the understanding of subsurface locations, such as areas of archaeological interest. On the other hand, deep changes in the electric resistivity on land are often problematic to detect and especially to monitor time-lapse change over long periods of time. The usual electrodes slowly erode and vanish. Geothermal heat production environments often lead to changes in the resistivity between in-situ water-filled formations and cooler injected water-filled formations of less than one order of magnitude. A dedicated set of capacitively coupled electrode could overcome to erosion problem. When placed in a well with composite casing, these could be used in measurements of much enhanced detectability. In that case it is necessary to have electrodes in a zone from below to above the target layer. By changing the source offset at the surface, optimal measurements can be done to detect the small and deep changes in resistivity.
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Nature-Based Solution - Deep Rooting, Potential Assets for Plant Resilience to Climate
By J. MaeghtSummaryToday, more than ever, there is a need for numerous and reliable data on the parameters of shallow and deep rooting systems in order to propose possible evolution scenarios for plant nature solution for plant resilience to climate change. It is still extremely difficult to study root systems and especially to understand how they evolve in time and space with respect to the constraints that plants may have to face. In many cases it is the technological challenges that pose the greatest difficulty in understanding growth capacity, lifespan, carbon conservation and how they involve in depth. These are major issues for resources and the future of ecosystems. In the text we will mention the challenges of deep rooting research, interest for plant development and the possible advantage that deep rooting can bring in the face of climate change.
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