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25th European Meeting of Environmental and Engineering Geophysics
- Conference date: September 8-12, 2019
- Location: The Hague, Netherlands
- Published: 08 September 2019
101 - 141 of 141 results
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Reducing Seismic Multiples in Very Shallow Water Archaeological Prospection
Authors M. Schwardt, D. Wilken and W. RabbelSummaryThe geophysical investigation of ancient harbour sites often includes the shallow water area close to the shore. In this environment, hydroacoustic methods are the methods of choice as they provide high resolution in the decimetre range with corresponding penetration depths of several meters. However, in shallow water areas multiple reflections are known to interfere with primary signals reflected by structures of interest. To overcome the problem of water layer multiples, we implemented and tested two model-driven approaches to remove water bottom multiple reflections, which are based on the forward modelling of seismic wave field including multiples. In the first approach, water column multiples are simply modeled and subtracted from the field data, the second approach takes advantage of reverse time migration and a deconvolution imaging condition. The methods are applied to synthetic and real multi-offset data in very shallow water. Both tested methods are able to reduce the signal amplitude of the water bottom multiple by up to ~85 %, if the reflection coefficient at the seafloor is determined with errors of less than 20 %.
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An Algorithm for 3D Modelling of Direct Current Resistivity and Full-Response Time-Domain Induced Polarization Data
Authors L.M. Madsen, G. Fiandaca and E. AukenSummaryWe present a flexible algorithm for modelling of 3D direct current (DC) resistivity and time-domain induced polarization (IP) data. A structured model mesh allows easy implantation of constrains, whereas the finite-element forward algorithm is based on unstructured tetrahedral meshes and therefore handles both topography, arbitrary shaped boundaries and local refinement. This, together with modelling of the secondary potential field for singularity removal around the sources, ensures high accuracy. Electrodes may be placed on the boundaries or arbitrarily in the subsurface thus allowing both surface and cross-borehole applications. The forward response is computed in frequency-domain and then transformed to time-domain using the Hankel Transform, taking into account the current waveform and system filters for a quantitative IP modelling of either full-decay IP responses or integral chargeability allowing the IP phenomenon to be parameterised using any IP parameterization. An accuracy test of the forward response shows the advantages of the singularity removal (computing primary and secondary potential fields separately) as it decreases the relative deviation to the analytic solution significantly compared to computing the total field.
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Metallogenic Mechanism of the North Qinhang Belt, South China, from Gravity and Magnetic Inversions
Authors Y. Liu, Q. Lu, C. Farquharson and J. YanSummaryQin—Hang metallogenic belt are famous tectonic units and important rich mineral resources in south China. Due to few geophysical data, there was previously lack of comprehensive geophysical research in this area. In this paper, based on priori geological information and exploration data, regional structures are divided and volcanic rocks are delineated, even the deep dynamic process and mineralization mechanism have been speculated from gravity and magnetic data inversion. The boundary between Cathaysia plate and the Yangtze plate, and five geological blocks, even major fractures can be identified, which is the main channel of magma upwelling. Some deep and large faults control magmatic activity, and those secondary faults control regional mineralization. Negative gravity anomaly can be used as a basis for searching magmatic rocks. Here abundant basic - ultrabasic magma in 220~250 Ma period, is the result of lithosphere stretching, thinning and mantle upwelling. It is a vital metallogenic mechanism in the belt that ancient subduction zone after modification or superimposed mineralization in yanshan epoch. Further, the “proterozoic + Mesozoic” bimodal age phenomenon of porphyry and its associated ore deposits in this region can be confirmed.
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Geophysical Investigation for Delineating Structures Favorable to Uranium Mineralization in Al-Amerat, Sultanate of Oman
Authors S. Narasimman, E. A, P. Bernhard and T. Al-HosniSummaryThe Amdeh Formation near Al-Amirat area south west of Muscat, Sultanate of Oman is characterized by well-bedded quartzite exhibiting tabular cross-beds and contorted bedding structures were geophysically investigated initially with a gamma ray spectrometry technique. The spectroscopic results of acquired gamma ray has indicated moderately high concentration of radioactive minerals showing ~100 ppm of uranium and ~1000 ppm of thorium in the placer deposit. In order to identify the extension and structural parameters of the Formation, the area was further investigated with very low frequency electromagnetic (VLF-EM) and magnetic surveys along five profiles of approximately 200 m long 20 m apart (10 m measurement intervals). In-phase and quadrature components of the VLF-EM signal were recorded at two different transmitter frequencies (15.1 and 16.4 kHz) as well as total magnetic field. Spatial location by amplitude of analytical signal and the depth to targets by Euler deconvolution and spectral analysis in the case of total magnetic field and the Fraser and K-H filtering as well as EMD based Hilbert transform analysis in the case of VLF-EM signals have revealed the possible uranium bearing structures as deep as 5-20 m. The salient features of results are highlighted and discussed in this presentation.
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Surface-Wave Tomography at Mining Sites - A Case Study from Central Sweden
Authors M. Papadopoulou, F. Da Col, L.V. Socco, S. Hu, E. Bäckström, M. Schön, P. Marsden and A. MalehmirSummaryIn mineral exploration, a detailed description of the near-surface is important when seismic reflection is applied, because the heterogeneity of the shallow layers can influence the imaging of deeper targets. The use of surface waves can provide valuable information about the shallow subsurface but multichannel methods might be limited by the existence of lateral variations in the subsurface. On the contrary, surface-wave tomography has the potential to locate more accurately subsurface heterogeneities and lateral variations without lacking penetration depth. We apply surface-wave tomography on the mining site of Blötberget (Ludvika Mines, Sweden). A checkerboard test provides information about the resolution and is used for the parameterization of the initial model for the tomographic inversion. The results provide a detailed description of the shallow subsurface, showing the potential of using surface-wave tomography in seismic exploration, also for challenging data from mining sites.
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AEMIP Inversion for Gold Exploration Using Maximum Phase Angle Parameterization - Case in Quadrilâtero Ferrífero Area, Brazil
Authors M.A. Couto Jr., G. Fiandaca, P.K. Maurya, E. Auken, A.V. Christiansen and J.L. PorsaniSummaryThis paper presents the results of the Airborne Electromagnetic Induced Polarization (AEMIP) 1D Laterally Constrained Inversion (LCI) using the Maximum Phase Angle (MPA) re-parameterization of the Cole-Cole model for an AeroTEMHD survey in Quadrilâtero Ferrifero area, MG, Brazil. The MPA LCI's were conducted using a robust inversion scheme and its results were compared with the usual Resisitivity-Only (RO) LCI's for gold mineralization zone in Lamego Mine structure. The MPA results seems to present a better recovery of the resistivity model in comparison with the RO usual approach, better agreement with the borehole lithological data and good correlation with previous conductive sheet modeling. An important chargeable body was identified in the MPA model, suggesting the definition of the carbonaceous units in Lamego Mine, an important chemical trap and structural control for gold mineralization in this area.
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CSAMT Soundings in the Band 16 - 50 000 Hz for the Study of Salt Deposit
Authors A. Simakov, A. Shlykov, A. Konkov and V. IgnatevSummaryThe CSAMT case study has been implemented at the potassium deposit in Perm region (Russia) in 2018. The main aim of the survey was to study the geological structure up to 300 m using CSAMT technique. Using of five main frequencies of the controlled source and their odd harmonics in the band 16- 45 000 Hz allowed obtaining of good quality data. New ARMT-5 system was successfully applied during this survey. Geoelectric sections obtained after the 1D inversion show good correlation with borehole data. High resistive salt layer covered with layer of rocks saturated by mineralized water was mapped at the entire survey area at depths 100 - 170 m from the surface.
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Current Status and Prospect of Agricultural Geophysics in S. Korea
More LessSummaryThe first agricultural geophysics in S. Korea was vertical electrical sounding (VES) for the purpose of groundwater survey in the 1970s. After the application of VES, various geophysical approaches to solve environmental problems in rural area have been mainly applied. Moreover, according to the diversity of agricultural activities since the 1990s, various geophysical methods such as electrical resistivity (ER), electromagnetic induction (EMI), and self-potential (SP) method were extensively applied to several agricultural fields including soil characteristics with saline concentration in vast reclaimed area, costal aquifer under seawater intrusion environment, reservoir dike with leakage problem, groundwater aquifer affecting by leachate from livestock mortality burial or waste burial site, and so on. Among them, three representative geophysical techniques that have been utilized in various agricultural fields are introduced and it is essential to apply core technologies in the development of leading technologies to prepare for future agricultural environment changes. Moreover, these geophysical technologies can be applied to the fundamental technology for the precision agriculture field in the future based on the past achievements.
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Mapping of Deltaic Aquifers with the Combined Application of DC and TEM Soundings
Authors J.D. Alexopoulos, S. Dilalos, G.S. Mitsika and S.E. PoulosSummaryThe current study aims to clarify the hydrogeological regime of the deltaic valley of Pinios river (Thessaly, Greece). Its purpose is to map the existing aquifers below the deltaic plain, but also to assess the quality of their water (detect possible seawater intrusion), through the combined application of VES and TEM soundings. The results of the geophysical data processing revealed that the shallow (phreatic) aquifer is not detected throughout the entire deltaic plain, but only in the central and northern parts of the region, with thickness of 5–10 meters. Additionally, a deeper aquifer has been detected, with a maximum thickness equal to 100 meters. The interpretation of the geophysical soundings indicated that great part of the deeper aquifer has been affected by a saline intrusion that has also been noticed by hydrochemical data. Based on the fact that Pinios deltaic plain is a highly productive agricultural area, the irrigation system has to be reevaluated in order to constrain the extension of the seawater intrusion.
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3D Geophysical Investigation from the Methods of Eletroresistivity, Self-Potential and Seismic Refraction in an Earth Dam
Authors L. Guireli Netto, O.C.B Gandolfo, W. Malagutti Filho, C.A Moreira, J.C. Dourado and P.L. CamareroSummaryThe use of non-destructive methods for investigations of the physical stability conditions of dams has become increasingly important, mainly comparing geophysical and geotechnical methods of subsurface research. This association allows understanding and evaluating processes that compromise the physical stability of the dam, such as possible internal erosion (piping), for example.
The recent disruption of mining tailings dams in Brazil generated an alert. The geophysical methods proved to be a research tool that can be worked in association with the classical geotechnical methods of dam instrumentation, assisting mainly in the maintenance, inspection and safety control of the structure, because of this the project becomes so important.
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Landfill Characterization with a Multi-Method Geophysical Approach - A Case Study from Emersons Green, UK
SummaryFor a large number of landfills, basic knowledge about extent, waste composition or environmental impact is incomplete. Therefore, effective tools are required for landfill characterization to be able to identify landfills with high priority for remediation or high potential for landfill mining. In contrast to conventional ground-truth methods, geophysical methods are relatively inexpensive and since they are minimally invasive, they entail less risk for environmental contamination. With our case study on the landfill in Emersons Green UK, we tested the effectiveness of multiple geophysical methods for landfill characterization. Electromagnetics (EM) and Magnetics (Mag) were able to provide a rapid overview of the landfill structure, and detected areas with higher metal content. Induced Polarization (IP) was the most suitable method to delineate the extent of the waste layer whereas Electrical Resistivity Tomography (ERT) seemed more sensitive to changes in moisture content. This study has shown that a multi-method geophysical approach in combination with targeted sampling is essential to avoid misinterpretations. Furthermore, planning the profile location of the more time-consuming methods such as IP and ERT based on the results of the rapid mapping methods such as EM and Mag can improve the survey efficiency.
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Optimum Use of Near Surface Resistivity Methods (i.e. -ERT, TDEM, AMT) for Improving Hydrogeological Concepts
By M. GroenSummaryNear surface geophysical methods are developing fast in instrumentation as well as data interpretation software. It is not always easy to choose the best method and instrument for a certain hydrogeological problem in a certain area.
Building a conceptual model from existing information and translate this concept into the expected distribution of the geophysical parameter and test the concept with forward models before will help in choosing the best method, instrumentation and field approach. During a fieldwork, comparing results directly with the concept improves the measurement strategy, speed and final interpretations. After fieldwork additional forward modelling can help to translate the inversion results into a hydrogeological concept.
This presentation will focus on the geophysical parameter of resistivity because of its useful applications in hydrogeology and relative simple methodology ,recent developments in instrumentation and user friendly software.
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The Contribution of Urban Gravity Survey to the Subsurface Geological Structure of the Athens Basin (Greece)
Authors S. Dilalos, J.D. Alexopoulos and S. LoziosSummaryThe gravity method has been applied, with a total of 1.122 gravity measurements for the subsurface investigation of the geotectonic structure beneath the urban and sub-urban areas of Athens basin. The aim was to gather new information for the subsurface geological and tectonic structure of Athens basin and re-assess the seismic hazard risk of the area that may damage its infrastructures. The standard corrections have been applied (drift, tide, latitude, free-air, Bouguer, terrain ones) along with an additional Building Correction that has been calculated based on the urban characteristics. Afterwards, the isolation of the residual anomaly has been accomplished with the contribution of the Fourier filters and the analysis of the power energy spectrum. The processing results provided important data regarding the geological and tectonic structure beneath the Quaternary formations that cover the basin. We managed to verify already proposed concealed fault zones or even discover and propose new ones that may affect the city in the future by generating disastrous earthquakes. In the context of the interpretation, two geophysical-geological profiles have been constructed, along which the geotectonic regime of the subsurface is clarified.
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Estimation of Tectonic Fault Systems of Mongolian Territory Using Geomagnetic Anomaly Data (Winner Best Poster EAGE-GMS Meeting)
Authors D. Badarch and B. TsermaaSummaryThe magnetic anomaly dataset was used to delineate fault parameters and terrane boundaries of the Mongolian territory. The spectral method has been implemented to separate shallow-, intermediate- and deep-seated faults and corresponding figures have been depicted. Also, locations of some new hypothetic faults have been estimated from the geomagnetic dataset.
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Hamiltonian Monte Carlo Inversion of Rayleigh Wave Dispersion Curves - Preliminary Results on Synthetic Data
Authors M. Aleardi, A. Salusti and S. PieriniSummaryWe present a Hamiltonian Monte Carlo (HMC) algorithm to infer S-wave velocity and layer thicknesses from the inversion of Rayleigh wave dispersion curves. The aim of this work is three-fold: derive a reliable uncertainty appraisal, implement an inversion method with global converge capabilities and fast-convergence rates. Differently from classical MC methods, HMC is a sampling algorithm that constructs an artificial Hamiltonian system in which a model is treated as a high-dimensional particle moving along a trajectory in an extended space. Using derivatives of the forward operator, HMC is able to make long-distance moves from the current towards a new independent model, thereby promoting model independence, while maintaining high acceptance ratios. To draw essential conclusions about the suitability of the HMC approach to dispersion curve inversion, we focus on synthetic data inversions and we limit to consider the fundamental mode, which is analytically computed from schematic 1D reference models. The combination of HMC algorithm with standard statistical tools (e.g. chi-squared value) is used to infer to most appropriate model parameterization. Our preliminary tests show that the HMC algorithm is a very promising approach for dispersion curve inversion that guarantees reliable uncertainty appraisals and accurate model predictions with an affordable computational effort.
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Transdimensional MCMC Inversion of Rayleigh Wave Dispersion Curves - Preliminary Results on Synthetic Data
Authors M. Aleardi, S. Pierini, A. Salusti and A. MazzottiSummaryWe implement a transdimensional Bayesian algorithm to invert Rayleigh wave dispersion curves considering as unknowns the number of model parameters, that is the locations of the layer boundaries together with the shear wave velocity and the Vp/Vs ratio of each layer. A reversible jump Markov Chain Monte Carlo (MCMC) algorithm is used to sample the variable-dimension model space, while the adoption of a parallel tempering strategy and of a delayed rejection updating scheme improve the efficiency of the probabilistic sampling. This work has a mainly theoretical perspective and is aimed at drawing general conclusions about the suitability of our approach for dispersion curve inversion. For this reason, we focus on synthetic data inversions, and we limit to consider the fundamental mode, which is analytically computed from schematic 1D reference models. Our tests prove that the implemented inversion algorithm provides a parsimonious solution and successfully estimates model uncertainty and model dimensionality. In particular, as expected, the posterior uncertainties increase passing from Vs, to layer thicknesses and to Vp/Vs ratio, and changes according to the expected resolution on model parameters.
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Combined Approach to Simultanous Source Data Separation
Authors A. Tarasov, A. Shuvalov, A. Konkov, V. Ignatev, B. Kashtan and A. OshkinSummarySeparation of signals is the main task when working with several simultaneously operating sources. In this paper, we propose the use of median filtering and singular decomposition. Both methods are performed in hyperbolic windows. The proposed algorithm demonstrates high efficiency on synthetic data.
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Active and Passive Combination of MASW Method to Obtain the Soil Classification of Murcia Town
Authors M.C. García-Nieto, M.A. Martínez-Segura, M.D. Vásconez-Maza and M. NavarroSummaryThe metropolitan area of Murcia is located in an area of moderate seismic hazard in SE Spain. It is one of the areas with the highest seismicity in this country. The Multichannel Analysis of Surface Waves (MASW), a non-invasive seismic method, well-suited for urban exploration, has been used in this work to characterize the shallow sediments in this urban area. The seismic source was a sledge hammer. Through the combination of active and passive forms, results show a depth around 40 meters and subsurface materials were classified in terms of Eurocode-8 soil types to facilitate the implementation of these results in seismic hazard studies.
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Seismic Imaging of Shallow Groundwater Resources in Glacial Deposits, Sweden
Authors R. Sun, A. Kaslilar and C. JuhlinSummaryWe re-process high-resolution shallow seismic reflection data collected over glacial deposits in Heby, Southeastern Sweden, to accurately map the dipping bedrock topographies and enhance the quality of the seismic images of groundwater bearing structures. We apply Kirchhoff pre-stack depth migration (PSDM) on the pre-stack processed data and compare our results with post-stack time migrated (PSTM) depth converted results. The velocity models calculated from first arrivals of shot gathers are used as initial models for travel time tomography. The velocity model estimated from the first-arrival tomography is used as a starting point for the pre- and post-stack migration. We observe that PSDM improves the seismic image. Especially reflections from the water table and dipping structures became prominent and continuous, and the reflectors are located more accurately, when borehole information is considered. The seismic image shows a water table around 35m elevation. The uppermost, about 20m overburden represents clay and constitutes sub-horizontal reflectors. This layer is underlain by sand/gravel deposits overlying the undulated bedrock. Our work shows that PSDM can help to obtain reliable near-surface images, contributing to reliable and sustainable groundwater management.
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Geophysical Contribution to the Reconstruction of the Hydrological Model of “Barcellona-Milazzo Plain” Groundwater Body, Northen Sicily
Authors P. Capizzi, R. Martorana, R. Favara, L. Albano, A. Bonfardeci, M. Catania, N. Costa and A.L. GaglianoSummaryThe “Barcellona-Milazzo plain” groundwater body in the northen Sicily, was analysed in detail, through numerous geophysical measurements that were integrated with stratigraphic data in order to reconstruct the hydrological model.
The “Barcellona-Milazzo plain” (BMP) groundwater body has been identified within the coastal sector between the village of Oliveri, to the west, and Capo Rasocolmo, to the east. It also includes several rivers that rise further south in correspondence with the Peloritani ridge and flow into the wide Barcellona-Milazzo alluvial plain. On the basis of several geophysical and geological data analysis and interpretation have been used to reconstruct the composition and thickness of the marine and alluvial deposits to construct the conceptual model of groundwater circulation in the Barcellon-Milazzo plain.
For the reconstruction of the subsurface model of the water body, 466 vertical electric surveys and 72 refraction seismic sections acquired in the 70s and 80s (CASMEZ surveys reports) have been reprocessed and reinterpreted. These data have been integrated with 50 HVSR surveys and 85 geognostic boreholes.
These data have been integrated with 85 stratigraphic boreholes to obtain the floods in contact with the clayey substrate has been reconstructed, which delimits in depth the groundwater body to calculate the hydrological model.
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Induced Polarisation (IP) Laboratory Measurements on Escherichia Coli (E. Coli)-Sand Mixtures
More LessSummaryFor the characterization and monitoring of in-situ remediation of chlorinated hydrocarbon contamination, interdisciplinary approaches and geophysical methods are needed to secure water supply of sufficient quality and quantity. Geophysical methods, such as IP (induced polarisation) could be used to investigate bioremediation processes. However, to interpret geophysical field IP data, lab investigations with different kinds of bacteria are necessary to assess the sensitivity of the methods for these specific applications. Therefore, a first experiment was conducted with E. coli bacteria in sterilised Ottawa sand environment. These bacteria-sand-mixtures were harvested at different days and measured with e.g., SIP (spectral IP) under laboratory conditions. A slight increase in phase and a decrease in resistivity were observed after several days of bacterial growth with sand, with a later decrease in phase appearing to coincide with die-off of the bacteria. Scanning electron microscope (SEM) images showed bacteria attached to the sand grains which could modify the grain surface (e.g. increasing the grain surface area and/or form a biofilm) and thus impact IP measurements. In future, the number of bacteria present in the sand will be determined using quantitative polymerase chain reaction (qPCR) to detect bacterial DNA (deoxyribonucleic acid).
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Electrical Resistivity Surveys to Delineate Hydrocarbon-Contaminated Zones in Military Units in Sourth Korea
More LessSummaryOil spills have occurred from storage facilities of military units in South Korea, which have been in use for more than 30 years. Among several units, the target unit of this study is in a small city that locates at about 100 km northeast of Seoul, South Korea. Only limited number of soil samplings have been made, and analyzed to locate highly contaminated zones within the area, which are mostly contaminated by light non-aqueous phase liquids (LNAPLs). Based the location of highly contaminated zones, electrical resistivity surveys along three survey lines are designed to further delineate the contaminated zones. Electrical-resistivity cross sections along each survey line are recovered through 2D inversion and compared with soil logging data. Each cross section showed high eelctrical resistivity values for the LNAPL contaminated region to confirm that the results of electrical surveys were in good agreement with those from the analysis on soil logging data. For more precise interpretation of electircal resistivity survey data, we further make inversion with considering the soil logging data including other available information on the area.
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Possibility of Using VIS-NIR Spectroscopic Methods to Determine the Sulfur Content in Brown Coal
Authors A. Wojciechowicz, L. Buczkowski, S. Bednarczyk, J. Kowalewski and M. ZiçbaSummaryThe aim of the research was to check the possibility of using VIS-NIR spectroscopic methods to determine the sulfur content in lignite. Spectroscopic studies were carried out on 10 lignite samples, taken directly from the deposit and 4 sulfur samples. Reflectance was measured by a wavelength from 400nm to 1000nm (VIS and VIS-NIR). The final spectrum was the arithmetic mean of reflectance registered during measurements, which was based on 441330 scans. Based on the results of laboratory tests, 6 samples were selected for further analysis, which were divided into two classes: with the lowest sulfur content (from 0.16% - 0.18%) and the highest sulfur content (from 1.0% to 2.3% ). The correlation coefficient of reflectance values of carbon samples (of the relevant classes) with reflectance of sulfur samples was calculated which allowed to evaluate correlation of the relationship between selected variables. For samples with sulfur content from 0.16% to 0.18%, correlation coefficient fluctuates from 0.26 to 0.37, while for samples with sulfur content from 1% to 2.3% ranges from 0.68 to 0, 74.
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TOPSOIL Project - Geophysical Input for Groundwater Models - Examples from Northern Germany
Authors H. Wiederhold, M.A. Rahman, Q. Zhao, R. Dlugosch, M. Grinat, E. Gonzalez, N. Deus, W. Scheer, R. Kirsch and B. SiemonSummaryExpected results of climate change in the North Sea region are rising groundwater table and sea level rise, both affecting the dynamics of the groundwater systems. In the EU INTERREG North Sea Programme project TOPSOIL consequences of climate change on groundwater and soil are investigated in 16 areas around the North Sea. In two German areas on both sides of the river Elbe groundwater flooding and saltwater intrusions are in the focus of interest. To quantify the enhanced demand for drainage and changes in groundwater salinity, groundwater flow models based on geological models are established. The contribution of geophysical measurements to the geological models is shown.
Area GE-1 in Schleswig-Holstein consists of flat marshland with marine sediments covering the aquifer. Resistivity methods give thickness of the covering layer and the aquifer, borehole NMR gives a first assessment of the hydraulic properties of both layers. Area GE-2 in Niedersachsen consists of moraine areas and marshland. Resistivity formation factor was determined from borehole results, formation factor combined with resistivity logs and HEM data gives the electrical resistivity of the groundwater, which was converted to chloride content. Interpolation of these values gives a map of groundwater salinization in different depths.
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Waterborne Electrical Resistivity and Land-Based GPR Surveys for Characterization of Potential River Erosion in Larvik, Norway
Authors S. Bazin, A. Lysdahl, H. Anschütz, V. Jørdre Øybekk, R. Frauenfelder, S. Glimsdal and U. EidsvigSummaryAn increased risk of erosion of riverbanks and coastal zones are among the expected effects of the present climate change. Erosion can be caused by several natural processes including more intense precipitation. Investigations of the subsurface structures of deltas, riverbanks and coastal areas can give better knowledge of the subsequent erosion risk. Our aim is to estimate the amount of erodible material per unit distance along a channel before an event or the eroded material per unit distance after an event. We present a case-study using near-surface geophysical investigations to image the sedimentary structures in a river mouth near Larvik, Southern Norway. Waterborne electrical resistivity tomography (ERT) measurements were conducted in brackish water above the delta and GPR profiles were collected on the river banks. This case-study shows that imaging the stratigraphy at a land/river boundary can be challenging. The waterborne ERT survey provided limited results for the purpose of the project which was to estimate the amount of erodible material. Due to the limited maximum penetration depth, the bedrock was not imaged in the whole area of interest. On the contrary, the fast-deployed GPR survey provided useful information on the geometry of the different layers.
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A Multidisciplinary Approach for Water Management in Saline Deposits
Authors A. Sendros, M. Himi, L. Rivero, R. Lovera, A. Urruela, R. Garcia and A. CasasSummaryThe production of potash as a key fertilizer generates gangues rich in sodium salts that are usually stored as large surface stockpiles. Stockpiles contain more than 90% of salts, which can be a future economic resource (saline deposits).
ICL Iberia manages salt deposits in NE of the Iberian Peninsula which requires an adequate research program for avoiding environmental impacts on water bodies. The objectives are minimize the entrance of fresh water into the system, the properly management of saline waters and preserve the future use of salty materials. For that reasons, ICL Iberia is developing a management plan that includes the use of the best available techniques for both preventive and corrective measures.
For the evaluation and design of the preventive and corrective measures, a detailed geological and hydrogeological characterization of the subsoil has been carried out using direct and indirect techniques.
The direct techniques, such as borehole sampling and execution of well pumping and recovery tests, are essential for performing an accurate characterization. However, the use of indirect techniques, such as ERT has shown its utility to provide very valuable information in a non-destructive manner, minimizing drilling works and the risk of putting in contact different water bodies.
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Predicting the Fate of Chlorinated Aliphatics by Hydrogeological Modelling and DCIP Data - Färgaren Case Study
Authors M. Lumetzberger, H. Rosqvist, C. Sparrenbom, T. Dahlin and S. JohanssonSummaryWe present a local flow model approach for the transport and the decay of a roughly 50 year old perchloroethylene contamination at a former dry cleaning facility at Kv. Färgaren in Kristianstad that sits above the largest aquifer in Sweden.
The study demonstrates an efficient workflow integrating ERT for conceptualising and calibrating a three dimensional transient, multi aquifer groundwater transport problem with a sequential first-order decay contamination where only limited sample data is available for calibration - i.e. non-ideal, real world conditions. The 3D hydraulic model geometry is based on information from ERT data. It was possible to map resistivity signatures correlated with boreholes to geological features with a high degree of accuracy. On the Färgaren site itself, a 3D IP inversion model displayed some IP effects that correlated with historical perchloroethylene source terms.
The simulations provide new information regarding the vulnerability of a critical groundwater resource, filling in knowledge gaps left by traditional sampling methods. It is concluded that there is potential for long term contamination of the regional sandstone aquifer, and that the plume front may already have reached its upper layers.
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Numerical Modelling of Self-Potential Signals Associated with Pumping Test of Heterogeneous Aquifer
Authors A. Mikhailenko, P. Konosavsky and K. TitovSummaryIn this paper, using three-dimensional numerical modelling, we study Self-Potential (SP) signals associated with pumping test of highly heterogeneous aquifer. We based the modelling on the use of (1) MODFLOW hydrogeological modelling system to obtain the hydraulic head distribution, (2) a special code to calculate the electrical sources produced by groundwater flow, and (3) again MODFLOW at steady-state conditions to calculate the electrical potential distribution. We considered models containing a composite aquifer subdivided into high and low hydraulic conductivity parts, and an aquifer crossed by a zone with high and low hydraulic conductivity values. The modelling revealed two main features of SP. When the pumping well is located at the lower hydraulic conductivity part of the aquifer the SP signals closely correlate with the drawdown. Otherwise, the correlation between SP and drawdowns is poor; however, the boundaries between high and low hydraulic conductivity areas are marked by separate SP anomalies.
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Investigating the Contrast of Wooden Objects from GPR/ERT in Water
Authors A. Fediuk, D. Wilken, T. Wunderlich and W. RabbelSummaryMotivated by archaeological prospection with marine GPR in a pond that was part of the early medieval Charlemagne's Summit canal, we investigated which material contrasts can be expected and thus which signals can arise from remains of submerged or wooden constructions in the water column. In a three-month laboratory experiment we determined the physical parameters electric resistivity and dielectric permittivity of oak and spruce wood with increasing water moisture content. The laboratory measurements show resistivity values > 1000 Ωm for dry wood and > 400 Ωm for water moisture contents of 80 %. The relative dielectric permittivity values increased from 2 to 5 in the same range. Both parameters show anisotropy effects in and across fibre direction. The laboratory experiments suggest GPR material contrasts of 20%, which is in good accordance to the signals observed during the field measurements. They also reveal resistivity contrasts of 250 % whereas comparable seismic studies in literature show relative contrasts of 30-50 %.
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Complex Geophysical Research of Near Surface Sustainability of Mining Waste-Storages in Central Ukraine
Authors O. Tiapkin, O. Kendzera, P. Pihulevskyi and M. DovbnichSummaryModern mining processes in Ukraine are accompanied by environmentally hazardous geomechanical events, including activization of exogenous geological processes and local increased induced seismicity. Using the example of Kryvyi Rih iron ore basin (Kryvbas) the interrelation between increase in technogenic overload and modern geodynamic activization is shown. Complex macro-seismic with micro-seismic research in deep mines solves the problem of determining of basic parameters of induced seismicity and activization of dangerous exogenous geological processes of not-seismic old-industrial Kryvbas. These data are necessary to prevent accidents at mining hydraulic facilities (and first of all - tailing ponds) and successfully design their increase. On an example of detailed geophysical research near the storage pond of highly mineralized mine waters in Svistunovo gorge (Southern Kryvbas) is shown that emergency sites of hydraulic objects can be not only dams, but also the bottom. Here intensive tectonic fragmentation of rocks (on joint interpretation of gravimetric, magnetic and electrometric observations) is the reason for increasing filtration parameters and deterioration of physical and mechanical properties of rocks and, as a result, dangerous intensification of exogenous geological processes, an emergency emptying of the pond and contamination of underground water.
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Characterization of a Mine Waste Rock Pile with the DC Resistivity and Induced Polarization (DC-IP) Method
Authors C. Power and P. TsourlosSummaryMine waste rock piles (WRPs) can contain sulphidic minerals, whose exposure to oxygen and water can produce acid mine drainage (AMD). Since AMD generation and release is dependent on the volume and composition of waste rock, effective characterization of WRPs is desired for successful long-term AMD management. In this work, DC resistivity and induced polarization (DC-IP) were combined to characterize an AMD-generating WRP in Nova Scotia, Canada. 2D DC-IP imaging was first performed with 6 long survey lines to capture the full WRP landform. DC results indicated a highly heterogeneous and moderately conductive waste rock underlain by a resistive bedrock, while IP results identified several highly-chargeable regions within the waste, with normalized chargeability delineating regions specific to waste mineralogy only. 3D DC-IP imaging, with 17 parallel lines, was then performed on the pile plateau to focus on the composition of the waste rock. 3D DC-IP distributions identified coincident and continuous zones of low resistivity (<30 ohm-m) and high normalized chargeability (>0.4 mS/m), which were inferred as generated AMD (leachate) and stored AMD (sulphides), respectively. Hydrogeological, geological and geochemical information was used to validate the geoelectrical interpretations.
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Imaging of a Waste Deposit Site Near Cologne City, Germany Using Magnetic and ERT Methods
Authors I. Ibraheem, B. Tezkan and R. BergersSummaryIn recent years, geophysical methods have been broadly used in investigating the environmental problems. One of the most important and serious environmental problem is the buried waste site deposits. In many cases, these kinds of waste sites constitute a main source for groundwater contamination. In the present study, a combination of magnetic and ERT methods was employed to determine the geometry of a landfill near Cologne city, Germany and detect the potential contaminated zones. The results of this research suggested that the waste site has an average length of 190 m and a width varies between 72 and 95 m. The depth of the dumpsite increases towards the center where it has a depth range of 6 to 14 m. Moreover, contamination plumes were detected using ERT survey. Furthermore, several ferromagnetic bodies were observed within and outside the dumpsite referring to possible bombs as remnants of the World War II.
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Geophysical Survey of the Grand Place in Brussels - An Example of Prospection in an Urban Context
Authors A. Tabbagh, M. Dabas, F. Blary, G. Catanzariti, P. Charruadas, S. Flageul, B. Van Nieuwenhoeve and P. SosnowskaSummaryIn urban contexts geophysical prospection faces specific difficulties resulting from the limited size of the available areas, the presence of numerous sources of both geophysical and electromagnetic noises, the soil surface material and eventually crowd. At the Grand Place in Brussels GPR and electrostatic (capacitively coupled resistivity) surveys were associated. The low resistivity of the clayed substratum limits GPR to very shallow depths, which is compensated by the use of three different offsets for the electrostatic arrays corresponding to 1, 1.5 and 2 m depth of investigation. The underneath features anterior to the end of the XVII century can thus be evidenced.
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Seismic Interferometry for Surface-Wave Attenuation - A Case Study from the Ludvika Mines of Sweden
Authors F. Balestrini, D. Draganov, A. Malehmir, P. Marsden and R. GhoseSummaryIn exploration seismology, surface waves generated by active sources usually mask events of interest like reflections and diffractions. This is exacerbated in high-noise, near-mine environments where the targets have often low-impedance contrasts. We present a purely data-driven approach for surface-waves attenuation in active-source reflection seismic data acquired at the Ludvika mining area of central Sweden in 2016. We apply seismic interferometry to the data in order to retrieve dominant surface waves between receivers. We then subtract them from the original data in an adaptive way for their attenuation. Our results show that the surface waves are well suppressed and the target mineralization signature is boosted allowing new features to be revealed. After a simple pre-stack processing, we obtain cleaner seismic sections with more continuous reflections.
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Ensuring the Sustainable Functioning of the Geotechnical System of Mineral Deposits in Difficult Engineering and Geological Conditions
Authors I. Abaturova, I. Savintsev, L. Storozhenko and O. BorisikhinaSummaryThe formation of the geotechnical system of mineral deposits is due to the complexity of the geological structure of the object, as well as the form of development, speed of penetration and mounting features. An important condition for assessing the stability of workings is knowledge of the structure, condition and properties of the rock mass. The article outlines the methods and techniques for studying the geological conditions of deposits, provides methodological techniques, the combination of which will allow to assess the stability of the geotechnical system.
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Solving of Hydrogeological Problems in Permafrost Zone Conditions of the Polar Part of Western Siberia by the TEM Method
More LessSummaryThe possibilities and limitations of the induction sounding (TEM method) in the permafrost zone for solving hydrogeological problems are described. On the one hand the fresh water promising layer must have increased electrical resistivity (sand layer in the clay section). On the other hand, it should be a talik zone and should have a lower electrical resistivity in comparison with the surrounding frozen rocks. In the context of such ambiguity, it is important to use additional independent information to take informed decisions in the data interpretation. Such information capabilities are provided by fast-decaying induced polarization associated only with the frozen state of rocks. A number of examples show the effectiveness of the TEM method taking into account fast-decaying induced polarization for complex geocryological conditions of the polar part of Western Siberia.
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Methodical Features of Studying the Geological Structure of the Coastal Part of the Sea of Okhotsk Based on the Integration of Continuous Aquatic Electrical Sounding and Seismoacoustics Data
Authors D. Lalomov, V. Glazunov, A. Tatarskiy, S. Burlutsky and N. EfimovaSummaryThe work is devoted to the methodological features of conducting studies of the geological structure of the coastal water area by the method of continuous aquatic sensing using seismoacoustic data under conditions of high salinity of sea water and a significant amount of tidal fluctuations of the water level. The studies were carried out in the Sea of Okhotsk in order to obtain engineering and geological information for designing a channel to the seaport. 2D data inversion, carried out with regard to seismoacoustic studies of the water area, made it possible to increase the reliability of constructing geoelectric sections and maps.
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Engineering Magnetic Survey for the Study of Underground Infrastructure of Urbanized Areas
Authors P. Novikova and A. DolgalSummaryThe application of the engineering magnetic survey for the underground technical objects detection is considered. The advantages of the presented method over the GPR and route finder technologies are discussed. Practical examples of the use of engineering magnetic surveys to public sewer localization and search for visually undetected abandoned wells under conditions of industrial noise are given.
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GPR Active Layer Monitoring at CALM Sites (European North) in 2015–2018
Authors M. Sadurtdinov, M. Sudakova, A. Tsarev, A.Skvortsov Skvortsov and G. MalkovaSummaryThe results of the application of ground penetrating radar (GPR) in a complex of geocryological studies at CALM (Circumpolar Active Layer Monitoring) sites in 2015–2018 are shown. Sites located in the North of the Nenets District in the delta of the Pechora River. Geological cross-sections consist of twaw and frozen sands which are a favorable media for the GPR signal. At both CALM sites, a correlation is observed between annual temperatures and the thawing depth and the moisture content in the Kashin site. At the Kumzha site in 2015, 2017 and 2018 thin lenses of frozen rocks in the active layer were observed and there weren’t any in 2016.
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Distinction of SP Anomalies Between Filtration and Diffusion-Adsorption Origin
By V. ShevninSummarySelf potential (SP) anomalies of diffusion-adsorption (DA) origin frequently considered as filtration (F) anomalies that is the case of false discovery. On the earth surface DA anomalies are widespread while filtration anomalies are more rear. To distinguish these anomalies we can consider correlation of SP potential and apparent resistivity values along the same profile. In case of DA anomalies there is linear correlation between SP potential and logarithm of apparent resistivity.
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The Latest Trends in Near-Surface Marine Seismic Survey at Arctic Shelf
Authors M. Tokarev, E. Biriukov, V. Ivanova, A. Pirogova and Y. TerekhinaSummaryIn present time, due to the active development of the Arctic shelf safety of offshore construction and exploitation is one of primary issues in oil and gas industry
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