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Near Surface Geoscience 2016 - 22nd European Meeting of Environmental and Engineering Geophysics
- Conference date: September 4-8, 2016
- Location: Barcelona, Spain
- Published: 04 September 2016
1 - 50 of 189 results
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Hydrogeophysical Survey of Groundwater Flow Pathways in an Alpine Headwater Basin
Authors C.W. Christensen, M. Hayashi and L.R. BentleyAlpine regions of the Canadian Rocky Mountains are important sources of freshwater for the semiarid Canadian Prairies. Yet, only recently have studies demonstrated that groundwater plays an important role in storage and subsequent release of snowmelt and rain. With limited case studies available in this region, a general understanding of groundwater flow processes in the alpine zone remains elusive.
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Groundwater Discharge along the Southern California Coast - Geophysical Images of Three States of Salt Water Intrusion
By J. JansenThe interface between fresh groundwater and saline water in coastal areas is frequently complex. The natural discharge of groundwater to the near shore zone is controlled by multiple factors including the permeability of the aquifer system, faults, confining units, and the hydraulic gradient in the aquifer. The natural balance is often disturbed by heavy pumping that can cause significant intrusion of salt water into the on-shore portion of the aquifer. The shape of the salt water wedge is affected by the pattern of pumping, the properties of the aquifer, and hydraulic boundaries like faults and confining units.
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Inversion of Frequency Domain Loop-loop Electromagnetic Data in 3D at Arbitrary Induction Numbers
Authors L. Cox, M. Endo and M. ZhdanovNear surface geophysics often uses man-portable electromagnetic instruments which can relatively quickly and inexpensively probe the earth for the 3D conductivity distribution.
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Evaluating Seasonal Variation of Groundwater Flow through an Alpine Meadow Using Passive Electrical Potential Measurements
Authors E.B. Voytek and K. SinghaAccurate quantification of groundwater flow patterns, both in magnitude and direction, is a necessary component of evaluating any hydrologic system.
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High-resolution Reflection Imaging for the Planning of a Double Train-track Tunnel in the City of Varberg, Sweden
Authors M. Dehghannejad, A. Malehmir, E. Lundberg, H. Möller and M. SvenssonA newly developed broadband MEMs-based seismic landstreamer system was employed for the planning of a double train-track tunnel in the city of Varberg, southwest Sweden. In addition to the refraction analysis and velocity tomographic modeling, reflection processing of the data was considered given the good quality of the data and realization of reflections in some raw shot gathers. Bedrock is strongly reflective in most cases and only at occasions when reaches near the surface it disappears in the reflection section. Bedrock undulation is clearly noticeable in most reflection sections and at one occasion it appears to be strongly diffractive. The diffraction signature is now known to be associated with a buried water tank used in fire emergency situations. Reflection seismic data greatly complements tomographic models and may support a deep bedrock at where the tunnel is planned to be excavated in the downtown Varberg.
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P- and S-wave Seismic Imaging of Overdeepened Alpine Valleys
Authors H. Buness, T. Burschil and G. GabrielOverdeepened valleys and basin can be found in glaciated regions worldwide. Due to their geological, ecological, and societal relevance they constitute a relevant geoscientific target. In preparation for an ICDP project (Drilling Overdeepened Alpine Valleys, DOVE), we carried out several reflection seismic surveys using high-resolution P-wave, horizontally pola¬ri¬zed SH-wave, and multi-component (SV- and SH-wave sources, 3-component re¬ceiver) techniques at a test site in the Tannwald basin north of Lake Constance. The first results of the P- and SH-wave reflection profiles are presented here. The seismic sections image well the internal valley structure of the Tannwald Basin; different facies are also distinguishable in the glacial sediments. The combined inter¬pretation of P-wave and SH-wave reflection seismics reveal more details than just one technique on its own by providing complementary information. P-wave seismics show a more coherent image with a higher penetration depth, while SH-wave seismics partly resolve more details due to their higher resolution. The combination promises to be an enhanced tool to investigate sedimentary successions in advance of scientific drilling.
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Surface-consistent Residual Statics Estimation with Genetic Algorithms - An Application to a Near-surface Seismic Survey
Authors M. Aleardi, E. Stucchi, A. Sajeva and B. GaluzziIn this work we apply a Genetic Algorithm (GA) approach to the residual statics computation problem. This type of geophysical optimization problem is characterised by many local minima produced by the so-called cycle-skipping phenomenon. The application of a global optimization method is particularly suitable in this context as it is able to jump out from local minima where gradient-based methods can easily be entrapped. We use an analytical objective function to test the capability of GA in finding the global minimum in case of highly non-linear multi-minima objective function. Because the residual statics optimization problem involves many unknown model parameters, in this analytical test we are particularly interested in analysing the rate of convergence (that is the number of evaluated models required to reach the global minimum) as the dimension of the model space increases. We then show the use of this methodology on a field seismic reflection data set acquired for near surface investigations. The application of the residual statics derived by the GA method produces final CMP gathers with flatter reflectors and a final stack section in which the continuity of the observed events increases.
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Rayleigh Waves Modelling Complexities in the Perspective of Full Waveform Inversion of Surface Waves - Synthetic Examples
Authors Z. Xing and A. MazzottiFull waveform inversion (FWI) has recently been considered for extracting detailed near surface information through the surface waves inversion. But the need of long computing time and the risk to get trapped into local minima make FWI cumbersome. Both these shortcomings are strongly dependent on forward modeling. In fact, forward modeling must yield very accurate seismograms and be computationally feasible. In this study we use an elastic finite difference modeling and discuss means to address, at least partially, these two conflicting requirements. In particular, we illustrate the possibility of attenuating the computing time problem by implementing the convolutional perfectly matched layers (CPML), and by performing the 3D to 2D correction on the observed data, thus allowing for using simple 2D forward modeling. It turns out that CPML has the ability to accelerate the computations compared with the standard tapering method, while maintaining the same efficiency in attenuating the unwanted artifacts from the model boundaries, and that 3D to 2D correction gives satisfactory results. Both of them result very useful in the perspective of surface waves FWI applications, also in view of the fact that other features, such as irregular topography, which cannot be neglected, require additional computing efforts.
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Towards 3D Inversions with Full System Modelling
Authors K.R. Andersen, E Auken and A.V. ChristiansenWe describe the setup for inversion of ground based TEM data using a 3D forward code and a full description of the measurement system. The response is calculated using a finite volume method where we solve for the electric field on the edges of a staggered grid and time step solutions using backward Euler steps. We convolve the calculated fields with the system response to compare with the measured data. In this way we include all system related effects in the calculation and this is important for the very early time signal. We describe how this is done for both forward and derivative calculations. For the forward calculation and the inversion we use an iterative solver. We show that the forward code is in good agreement with the analytic response from a half space.
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Determining the Depth of Gravity and SP Sources
Authors G.R.J. Cooper and R.C. WhiteheadCooper and Whitehead (2016) introduced a new method for determining the depth of magnetic sources that did not require a priori specification of the source type. This abstract shows that the method also works for various gravity and self-potential sources. References Cooper, G.R.J., and Whitehead, R.C., 2016. Determining the Distance to Magnetic Sources. Geophysics 81(2), p.J39-J48.
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Combined Land and River High-resolution Reflection Seismic Imaging of an Area Prone to Quick-clay Landslides in Sweden
Authors S. Salas-Romero, A. Malehmir and I. SnowballQuick-clay landslides are common in northern countries and the delineation of these materials is important when planning urban areas. High-resolution reflection seismic data were acquired on land along four profiles in an area prone to quick-clay landslides in southwest Sweden in 2013. These data complement previous investigations that show the influence of the underlying coarse-grained layers in the formation and thickness of the quick clays. The intercalation of the different glacial and postglacial sediments, and the structural information of the subsurface provide clues to the possible causes of a landslide. Apart from the land data, river seismic data, using one and six channels, were obtained. All the seismic sections show a clear undulating bedrock reflection, and signs of bedrock faults at shallower depth that maybe important in the generation of quick clays and landslides. The coarse-grained layer reflection is delineated on the land data, and several filled channels can be distinguished along the river. The presence of the coarse-grained layer indicates the possible large extension of the quick clays in the study area, which needs to be confirmed using geotechnical investigations.
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Detection and Analysis of Electromagnetic Radiation Emission from Macroscopic Fracturing of Cement-bound-granular Matter
Authors P.I.B. Ceralde and J.T. MaquilingCountries most prone to earthquake damage have been in search of a possible earthquake precursor. This thesis aims to detect and measure the magnetic field component of the Electromagnetic Radiation (EMR) emitted by quasi-brittle materials that undergo macroscopic fracturing. Cement-Bound Granular Material (CBGM) beam composites were prepared by mixing cement, sand and gravel. Fine sawdust was added to form another aggregate component of the CBGM variant. Impact loading was repeatedly performed on the beams to induce fracture until failure. Six Vernier software magnetic field sensors, with sensitivity range of ±6.4x10-3 T and 0.0002 mT precision, were strategically positioned around the beams to detect the magnetic field (MF) component of the EMR emission. Initial calibration was done to minimize noise in the laboratory. The time of impact was determined in the form of collision noise using a sound level meter at fast time setting. CBGM beams consisting of cement, sand and gravel produced magnetic field emissions measuring from 0.58-1.07 μT while the CBGM beams with dispersed fine sawdust emitted 0.55-1.28 μT. Increasing the input energy from the mass of weight drop by 150% resulted to a 10% increase on the mean value measurements of magnetic field emission magnitude.
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The Holocene Tordera Delta System - On/Offshore Sedimentary Sequences and Evolution
More LessThe Tordera River delta system is located on the NE coast of the Iberian Peninsula. It is a coarse-sand delta originated from the erosion of the granitoids in the Catalan Litoral mountain range system. The Tordera delta has originated in a Mediterranean fluvial regime and with the influence of coastal drift currents from the SW. The sediments carried by the Tordera, together with the contributions from local streams has originated the different sand bodies present in the Blanes inner shelf. From new marine seismic data we have described the internal structure of these sand bodies as well as defined three seismic sequences which are Ph, Sd2 and Sd3. At the same time, the seismic profiles have provided additional support to the correlation of these sequences with the sedimentary deltaic sequences, as well as detail to the evolution of these sand bodies during the last sea level rise. The samples obtained though vibrocores and dredges have allowed the sedimentary characterisation of the sand bodies and their correlation to the deltaic sequences (absolute and relative aging) as well as the absence of sedimentary drift transport from the NE.
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On the Characterization of a Geophysical Diagnostics Resolution Index within the Seismic Damage Scenario Construction
Authors A. Teramo, D. De Domenico, D. Termini, M. Romeo, C. Teramo, N. Morey and C. SaccàA methodological approach for selecting areas to be subjected to geophysical diagnostic is proposed to determine the damage susceptibility of territory elements within the construction of a seismic damage scenario for the city of Messina. The morphology of the urban context have made difficult the programming and execution of those geophysical surveys more consistent with the objective to be achieved. On the basis of different indicator typologies, an empirical relationship has been established to identify the territory elements of a higher significance where to focus a greater diagnostic commitment for the acquisition of specific data to be used for seismic vulnerability assessments at a large scale. To this end it was defined a diagnostic resolution index, related to the specific characteristics of the territorial system, stands out as a significant interest element in the study and evaluation of the regional multi-hazard conditions (shallow water-table, presence of debris of buildings referable to the past earthquakes, high level of heterogeneity of the lithotypes, the widespread presence of surface faults, ...) The analysis of preliminary results have made possible the assessment of the reliability of the proposed procedure in order to properly planning a diagnostic campaign related to the safety reducers of the area in study.
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TDR Measurements of Magnetic Characteristics of Materials
By R. PersicoIn this contribution, the possibility of measuring possible magnetic properties of materials by means of a TDR probe is studied. A transmission line model is adopted and data in time and frequency domain are exploited together. Simulation results are shown, at the moment based on a bifilar line model.
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Time Domain IP Profile by Multi-current Transmission Technique - Water Tank Experiment and SP Noise Effect Estimation
Authors Y. Yamashita and F. LebertWe conducted time domain chargeability measurement by multi-current transmission technique using a water tank and mineral ore which has certain IP effect in the purpose of verifying the method to calculate chargeability from the data acquired by multi-current transmission measurement using Code Division Multiple Access (CDMA) technique . We also evaluate the effect to chargeability calculation of SP noise thorough numerical experiment. We confirmed that time domain chargeability measurement is available through the experiment using water tank and mineral ore. We also evaluated the effect of SP noise to time-domain chargeability measurement by numerical experiment. The precise current control and appropriate SP management are important for reliable chargeability measurement with multi-current transmission measurement.
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Enhanced Characterisation of Radiologically Contaminated Sediments at Sellafield by MSCL Core Logging and X-ray Imaging
Authors O. Kuras, J. Shreeve, N. Smith, J. Graham and N. AthertonVisual observations and electrical geophysics alone showed limited ability to characterise a complex Quaternary sequence of glacial sediments at the Sellafield site with sufficient spatial detail, and conventional high-resolution logging was impracticable. By applying non-destructive high resolution MSCL and X-ray core logging we have parametrically characterised and imaged the stratigraphy in detail for the first time. This approach has allowed us to identify geological units with increased confidence, and link these units to a depositional process. The results open up the opportunity to link geological observations at Sellafield with regional type localities and the regional stratigraphy. The approach holds promise for applications where conventional high-resolution borehole logging is not possible, or not able to fully characterise the geology.
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2D Modeling of Controlled Source Radiomagnetotelluric Data Observed on Buried Faults Close to St. Petersburg/Russia
Authors B. Tezkan, I. Muttaqien and A. SaraevControlled source radiomagnetotellurics (CSRMT) is a new and innovative method of near surface geophysics. We applied this method for the detection of a buried fault beneath a test area close to St. Petersburg. During this survey, a rectangular current was injected into the ground using an electrical horizontal dipole with a length of 700 m and O.5, 11.5, 30 and 105 kHz – as well as their subharmonics - were used as main frequencies. The time series of two horizontal field components and three magnetic field components were observed at 97 stations with a station interval of 20 m in the near, the transition, and the far field zone of the electrical dipole. Transfer functions were derived in the frequency interval of 1 kHz to 1000 kHz from the observed electric and magnetic time series using the newly developed processing software. They showed a smooth dependence of frequency indicating the reliability of the observed CSRMT data. The CSRMT data were interpreted in the far field zone by using a 2D inversion algorithm and in the near zone by using 2D forward calculations. The derived 2D conductivity models showed clearly the location of buried faults as large resistivity contrasts.
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On One of Precise Solutions to Integrate Hydrocarbon Mobilization Rhythms, Dense Reservoir Development Stages and Sand Recovery Geological Evolution
Authors V.I. Popkov, A.M. Shterenberg, V.V. Gusev and Е.V. MitinaIt is quite possible to achieve the growth in efficiency of geo-exploration works through the increase in drilling operations and this is the strategy of permanent technology. The improved technology strategy supposes the growth of rate of success in each well and constant amount of drilling operations. The costs for technology improvement are significantly lower than exponentially increasing costs for well pad drilling. The authors present the systematic evolution/topological theory of global solution for Cis-Ural region hydrocarbon mobilization as subduction and generalized saturation of the middle chain of the Urals, deformation of tunneling, plastic decompaction of fracture porous geo-media. Migration deformation provides great effect upon the structure of fractured permeability in aqueous matrix, energy with sand recovery, ecology and economics. The paper presents analytical solution of Darcy-Fick’s energy law for secondary deformation moments, plastic saturation of miming concentrations and formation of oil and ore material fields. The authors substatiate the systematic methodology in search, exploration and development of decompacted reservoirs with classtic and unconventional traps. They also present lithological/facies rhythms of migration glimmering foamy structure, geological risks in drilling. The authors note unconformity of initial lithological stratification cycles and rhythms of secondary processes in neo-hydrodynamics and evolutionary sand production.
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Remediation Investigation of a Failing Retaining Wall Structure
Authors A.J. Verweerd, S. Williams and P. ArnoldThis presentation is a case study combining geophysical & geotechnical investigation as well as structural deformation monitoring of a failing drystone retaining wall structure in the United Kingdom. Data collected and interpreted during this project was used to design a remediation solution, stabilizing the structure while retaining the wall's original appearance. The approach chosen in this study includes seismics, ERT and GPR studies combined with a targeted intrusive campaign to limit further destabilization of the structure. The geophysical surveys were executed close to the retaining wall, on the highroad above the wall as well as on the wall face itself. Both data sets were combined into a geotechnical interpretation which formed the basis of the remediation solution. In addition to the geophysical and geotechnical investigation a remote structural monitoring system was deployed to monitor the behaviour of the structure, ensuring the safety of the general public and infrastructure.
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Seismic Investigation for the Characterization of a Gravity Concrete Dam
Authors P. Capizzi, R. Martorana, C. Pirrera and A. D'AlessandroMonitoring of large-scale infrastructures plays an important role for public safety and prevention. The control of the safety assessment of a dam is largely dependent on knowledge of the mechanical parameters of the actual construction, as well as its geological substratum. The application of geophysical methods can considerably contribute to the examination indicating the less consolidated material and the degradation of mechanical parameters. A seismic tomographic approach has been used in a typical gravity concrete dam without reinforcement to detect mechanical properties of the body of the dam and its geological setting. Three seismic travel time tomographies in the dam body as well as S-wave velocity values obtained by a down hole testify that the dam is composed of high quality concrete. Small variations on the P-wave velocities seem to be the effect of moisture and infiltration. In addition seismic surveys in the surrounding grounds of the dam confirmed the expected properties of the foundation terrain.
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Identification of Landslides Processes on the Slope Areas near Gas Pipeline Bovanenkovo-Ukhta Permafrost by GPR
By V. NoskevichIdentification of landslides processes on the slope areas near gas pipeline Bovanenkovo-Ukhta permafrost by the method of georadiolocation (GPR). SUMMARY The article presents the results of profiling radar scanning along the gas pipeline in sloping areas in the permafrost zone. The technique of GPR survey at two sites and describes setting choices of GPR emitting and receiving antennas, as well as methods of data processing. Criteria for the selection in the GPR cross-sections shifting blocks weakly bound soils, and set the curve slip line of these blocks, which is a boundary between the melt and frozen grounds.
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Tunnel Assessment with Borehole Radar
Authors V. Perez Gracia, O. Caselles, J. Clapes and J.A. CanasThe collapse of a tunnel and the damage in a second tunnel during the construction works, forced to the assessment of the ground in the front tunnel of the second structure, in order to avoid additional problems. The first evaluation was carried out with a borehole radar, because the structure was in a populated zone of a dense city. The uncertainty associated to the near surface studies is, in this case, greater because the unshielded antennas produce a rotational ambiguity. The imprecision in the location of the targets was reduced using seven non-parallel boreholes. The results shows the anomalies that could be associated to faults and also an irregular area of the B-scans that could be related to heterogeneous materials and the existence of a large number of voids.
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Using the Resistivity Method for Leakage Detection at Sant Llorenç de Montgai Embankment (Lleida, NE Spain)
More LessThe infiltration through the core of foundation of embankment dams is a main concern for maintenance and safety. The mechanism of infiltration induces internal erosion which can be progressive and can disturb the stability and the durability of the structures. Internal erosion occurs when water flows through a cavity, crack, and/or other continuous void within the embankment. Geophysical survey at Sant Llorenç de Montgai embankment has evinced the effectiveness of the ERT technique in assessing the state of the dam embankment. In particular, the method has revealed areas with high electrical resistivity values related with mortar injection. In the other side, we have registered areas with very low electrical resistivity values correlated with areas with possible abnormal seepage.
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Study of Integrated Geophysical and Geological Research Methods on Mapping Weakness Structures in Bedrock at Urban Areas
Authors T.K.T. Huotari-Halkosaari, M.H. Wennerstöm and I.A.S. SuppalaThis abstract present one example site from a short project where the idea was to develop integrated geophysical and geological research methods for the urban studies for detecting fracturing and mapping weakness structures in the bedrock. The sample case is located in the route of planned west metro line in the City of Espoo. The area is called Hannusjärvi. The geophysical methods included old airborne interpretations as well as different ground geophysical test measurements together with geological interpretations from existing data and interpretations. Bedrock drilling data for this project was distributed by the West Metro Project. The old interpretations of weakness zones were produced in two earlier projects using aerogeophysical data and topographic models combined with structural geological analysis. The use of different ground geophysical methods was considered according to methodological and geological features. Magnetic, gravimetric, ground penetrating radar, electrical resistivity tomography and electromagnetic methods were utilized in test with new geological mapping. The combined geological and geophysical interpretation gave promising results and new information about the possible fractures and weakness zones in the vicinity of the new metro line. The ongoing excavation of the metro tunnel gives data to verify the geophysical and structural geological interpretations made in this project.
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Investigation with Seismic Methods of the Sedimentary Cover of an Astrobleme at Outskirts of Sao Paulo City, Brazil
Authors R.L. Prado, I. Ullah and I.C.E. FenollThe paper shows the results obtained from seismic reflection and HVRS/MASW (horizontal and vertical ratio spectrum and multichannel analysis of surface waves) data acquired in a circular structure whose formation is attributed to a meteorite impact. The structure, known as Colonia crater, is partially located in urban area at São Paulo outskirts. The aspects presented here are related to data processing and interpretation.
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Landfill Geophysical Imaging - Babica Landfill Case Study
Authors R. Putiška, D. Kušnirák, I. Dostál, V. Vybíral, R. Pašteka and J. PapčoOne of major environmental challenges in Slovakia is to deal with numerous contaminated sites polluted by improper waste management in the past. We present a case study from Babica landfill located in western part of Slovakia near the village Bošany. The landfill was established in 1970, in a very inappropriate environment of abandoned meander. Waste composition of the Babica landfill is mainly formed by waste from the leather and footwear production. Broad spectrum of geophysical methods were applied on several profiles in order to describe the spatial limitation of landfill materials and to monitor the spread of contamination from the landfill in the surrounding environment. Combination of several geoelectrical methods (EMI, ERT, VES and SP) allows us to define the resistivity model of the area, where the contaminated area was clearly outlined by low resistivity values. Moreover VES measurements were sorted in four elementary classes defined by the shape of the VES curve, which allows us to create schematic model of the area. Self-Potential method proved the active connection of the abandoned meander with the river. Additionally, soil vapour method survey revealed three outbreaks of methane gas generation that are connected to the area near the old meander.
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Comparison of Fracture Models for Seismic Wave Propagation in a Medium with Multiple Parallel Fractures
Authors E. Parastatidis, M.W. Hildyard, G.W. Stuart and D.A. AngusRock fractures create a secondary porosity giving new fluid paths due to the increased permeability. Seismic waveforms can provide useful information on the fracture network of a rock as a result of wave interaction with the fractures. This study is targeted at improving the understanding of wave propagation modelling in fractured media. For this purpose we use numerical modelling to model wave propagation through multiple parallel fractures based on an experiment with ‘simulated’ fractures in a steel block from (Pyrak-Nolte et al. 1990). Three models (Transversely Isotropic, Heterogeneous Transversely Isotropic and explicit fracture representation), each one using a different solution to the wave propagation in fractured medium, are developed in order to compare the similarities and differences. We use a P- and S-wave source which we have inverted from the experiment to study propagation in two different orientations perpendicular and parallel, to the fractures.
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Geoelectrical Monitoring at the Reclaimed Landfill of Derveni, Thessaloniki (Greece)
Authors F. Kapeti, G.N. Vargemezis, P. Tsourlos, N. Kazakis, A. Tatsi and A. VoumvourakiInfiltration of rainwater is of major importance for old waste disposal sites where production of leakage is taking place even after reclamation. In this work we present an ERT monitoring case study in a reclaimed Derveni Landfill. Previous studies in the area showed that important amount of water flows within the waste volume or by lateral groundwater flow or by direct infiltration of rainwater. Maag permeability measurements showed differential behavior of the top soil. Thus, geophysical monitoring of resistivity changes during injection of known conductivity water in high resolution 2D and 3D tomographies has been applied in two selected sites according permeability distribution map. 4D inversion of 2D and 3D data sets showed the flow paths of the injected salty water within the top soil up to the depth of almost one meter. At the same time increase of the resistivity has been observed deeper than one meter that cannot be easily explained. A possible explanation, except the case of disturbed current flow which could lead to artefacts, could be the biogas flow that is interrupted by the water cap of the injection. Both explanation are to be examined as a next step to the integration of the geoelectrical monitoring.
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Comparison between the Measurement of SP and Resistivity Method to Detect Wastewater in the North and South Bantar Geban
Authors B. Prasetyo and M.T. AlfiansyahThe problem of waste day by day more noticeably for many people. Garbage heap from households in DKI Jakarta is the cause pollution and health problems, so the rest of the household garbage heap is collected and transported to Final Disposal (TPA) Bantar Gebang, Bekasi which far from residential areas in order to keep the environment clean. Now, in fact the problem is not only on the surface like the smell of garbage wafted until the hundreds of meters, but also below the surface. Many residents are complained that several wells have bad odor, and allegedly a result of polluted by leachate water. The garbage are mounting (open dumping) without a thick layer of skin geotextile and channel leachate container, so that oozes down the surface. Based on the study, leachate water conductivity higher than groundwater which means the resistivity value was low. Utilization of SP and resistivity method is used to review and determine the distribution of the leachate below the ground surface which already oozes to the well of residential areas. Keywords: resistivity, conductivity, SP, leachate water, waste
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Microtremor for Evaluating the Effect of Shallow Sediments on Earthquake Ground Motion at Quseir City, Red Sea, Egypt
More LessRecording microtremor data is increasingly used in determining the site effect on earthquake ground motion especially in regions of moderate to low earthquake activity. In this study we used microtremor data to evaluate the effect of shallow sedimentary layers on earthquake ground motion in Quseir city which is located in the Red Sea coast, Egypt. The increasing in urbanization and land use planning, and the constructions of tourist resorts in Quseir city are the motivation of this work. The microtremor data was recorded by single seismic stations and by array of seismic stations at number of sites at Quseir city. The single stations microtremor data was analyzed based on the horizontal-to-vertical (H/V) spectral ratio technique in order to get the fundamental site frequency (f0) and its associated amplitude of ground motion (A0). The raw data of array was analyzed by using the SPatial AutoCorrelation (SPAC) technique to infer the shear-wave velocity structure beneath Quseir city. The results demonstrate that the value of f0 is ranging between 0.56Hz and 2.5Hz. The retrieved shear-wave velocity profile is characterized by significant interfaces at depths 20m, 50m, and 80m corresponding to velocities 170, 240, and 365 m/s respectively. The resulted f0 values were used in the calculation of bedrock depth at the measured sites. The parameters obtained in this study show a good agreement with the geological setting of Quseir city.
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History of Geophysical Work for Potash Salt Investigation in the Catalonian Potash Basin - ICL Iberia Súria & Sallent
Seismic surveys have been used for potash prospection in the Catalonian Potash Basin since the early 1970’s. More recently, 3D high-resolution seismic surveys have proved to be a powerful tool for potash mine evaluation and planning when professionally designed by geophysicists in collaboration with mining companies. Interpretation by mining geologists for mining engineers is key to achieving an improved geological understanding of the mine. In this case study in-depth seismic interpretation made it possible to obtain a structural geology model as well as produce isobath and isopach maps. The resources were evaluated after a drilling campaign and a calculation of on-site resources was made using geostatistical methods in compliance with International Standard Codes for Reporting of Exploration Results, Mineral Resources and Ore Reserves (JORC Code).
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Near Field Modeling of the Explosion Waveforms and the Key Contributing Factors
Authors M. Saeidnezhad, A. Sadidkhouy and S. KeshavarzipourtaftiFor modeling the blast wave, first its Green function must be solved. Therefore, we use the Green function solution of explosive source by Herman (1979). Study area, was located around the gas pipes in high-speed rail project Qom – Isfahan, with the longitude of the 50.5 to 51 degrees north and the latitude of the 33.5 to 34.5 degrees east. In this study, was used the number of four-digit seismograph machine type CMG-6TD. Sort seismograph machines around the blast site in such a way that the three-component seismic energy radiation patterns of blast were recorded in the vertical, radial and transverse. A condition that has a component (the radial component) was placed in the site of the explosion; also the distance between two consecutive samples was determined at a digitize of 10 milliseconds.
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Case Study of Seismic Surveying and Data Processing for Small-scale Carbon Capture and Storage in the Pohang Basin
More LessCarbon capture and storage (CCS) can be manipulated in subsurface sediment, which is a porous and permeable interval, after geological characterisation. We conducted multichannel seismic surveying to image the subsurface for geological interpretation of the Pohang Basin, Korea. The length of the streamer could not stretch to a far offset, due to the limited area of Pohang Harbour. The 24-channel streamer allowed six folds, which provided a low signal-to-noise ratio for conventional seismic data. Investigation of the seismic processing enhanced the quality of the stack section, which showed a reflector at the 800-ms TWT time domain. Geological interpretation using the seismic investigation mapped the thickness of the sedimentary unit for feasible CO2 injection.
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Mapping the Thickness of Gyttja by Using the Pull-down Effect on Shallow Reflection Seismic Data
Authors E. Nørmark, H. Sabra, H. Lykke-Andersen, K.J. Andresen and O.R. ClausenA reflection seismic survey has been carried out in Vejle fjord in Denmark in order to map the thickness of organic rich gyttja sediments. The reflection seismic data was severely contaminated by multiples and suffered from high absorption in the near surface sediments. Consequently, a direct and reliable interpretation of gyttja in the entire survey area could not be accomplished. Alternatively, the interpretation has been based on the pull-down effect on reflections which in the present case is the only way to achieve a coherent estimate on sediment thicknesses. Borehole information has been used to estimate the velocity in the gyttja layer.
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Combination of Active and Passive Seismic Methods for Subsoil Characterization of Seismic Stations
Authors A. Macau, B. Benjumea, S. Figueras, R. Puig, A. Gabàs, F. Bellmunt and A. RocaWithin the framework of Alertes-RIM (Regional and on-site earthquake early warning system for the Ibero-Maghrebian region) project twenty five seismic stations located in this region have been characterized. The aim of this work is the application of a methodology based on combination of active and passive seismic techniques in order to study potential soil effects at these stations. During the first step of this study, seismic noise recordings are extracted from seismic stations in order to apply the H/V spectral ratio technique and classify sites as rock or soft soil. Once identified seismic stations installed on soft soil the second stage is done. This phase consists on carrying out the fieldwork in the location of seismic stations. Surface wave analysis (MASW) and linear seismic noise array analysis are performed to get the shear-wave velocity model of soil column. Seismic refraction tomography (SRT) provides a 2D P-wave velocity model to identify bedrock geometry and soil parameters. The H/V spectral ratio is used in different places along the seismic profiles in order to obtain soil fundamental frequencies and compare these values with the fundamental frequency obtained from seismic stations recordings. The proposed methodology ensures a good characterization of seismic station subsoil.
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Shallow Seismic Reflection Survey by Using Accelerated Weight Drop as Seismic Source
Authors A. Alfian, M.R. Sule and A. PriyonoOnshore reflection seismic surveying for shallow objectives is a challenging task in Indonesia. The use of AWD (accelerated weight drop) as seismic source for an eco-friendly onshore shallow seismic survey is tested. The experiment was conducted around Jepon-1 well in Central Java, Indonesia which is a candidate for CO2-injection. This experiment is as initial investigation before baseline seismic survey is carried out around mid-2016. The CO2-injection itself will be started end-2017. This site was chosen as the first carbon capture and storage (CCS) pilot project in Southeast Asian region. The purpose of this survey is only to study the effectiveness of the AWD source for shallow seismic survey. Moreover, this survey is intended only to test the performance of AWD (ESS-200) seismic source and determine the optimum survey parameters for subsequent seismic baseline survey for monitoring CO2 injection in wells Jepon-1 and its vicinity. We found that the deepest reflections that could be imaged is only 650 m below the surface. To complete the data acquisition of 500m, it took only two operation days with a total cost of about USD 2,000. Thus, the use of AWD needs much less investment than similar surveys that use dynamite or mini-vibroseis as source.
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New Airborne Methods and Procedures for the Exploration of Mineral Resources - An Overview of BGR Activities
Authors U. Meyer, B. Siemon, M. Becken, R. Stolz, U. Noell, M. Frei, P. Buchholz, A. Steuer, S. Costabel, T. Martin, M. Ibs-von Seht and C. NittingerOne of the major tasks of the Federal Institute for Geosciences and Natural Resources (BGR – Bundesanstalt für Geowissenschaften und Rohstoffe) is to contribute to a sustainable future supply for Germany with minerals for industrial use. Part of the BGR’s strategy is to develop innovative ways of mineral exploration. The presented study focusses on airborne technologies, being applied and developed in ongoing projects. The methods used can be classified in established methods and newly evolving systems. The repertoire of established methods includes airborne electromagnetics, magnetics, radiometry and hyperspectral imaging. Systems based on latest technologies are full tensor magnetic gradient (FTMG) systems and audio-frequency magnetics (AFMAG) systems. Since a single airborne system usually cannot reveal the whole complexity of mineral bearing structures, new combinations of survey systems are being tested and new techniques are under development. The projects used to demonstrate and develop new systems, combinations and designs are E3 (Ore exploration in the Ore Mountains of Saxony, Germany), HYPGEO (New procedures for exploration of mineral raw materials using hyperspectral and geophysical sensing systems) and DESMEX (Deep Electromagnetic Sounding for Mineral Exploration). HYPGEO is being introduced as a new conceptual project combining different sensing systems and resources of BGR and partners.
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Test Airborne EM Surveys at a Black-shale Type Uranium Deposit in Korea
Authors M.J. Yi, J.H. Kim, N.H. Sung, M.H. Han, K. Motschka, R. Supper, A. Ahl and A. Johmorilogy in Korean geologic environment, test airborne geophysical surveys were conducted over a known uranium deposit using two AEM systems; GSA’s frequency domain loop-loop EM system and time domain EM system with grounded electrical source (GREATEM system). The main geologic feature of the test site is the phyllite formation with uranium mineralization in a graphitic zone and AEM surveys by two systems successfully delineated the graphitic conductors in this site. Considering the field condition with tough topographic variation, GREATEM system seems to have better performance in terms of data acquisition and depth of investigation, while GSA’ system provides better resolution for shallow subsurface structures, which is due to underlying EM principles used in the two systems. By this comparative study, we could convince that AEM technology is a very effective tool to the exploration of mineralized zone in Korean geologic environment.
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Archaeological and Resources Assessment of Sand and Gravel Deposits Using 3D ERT and Automated Interface Detection
Authors S.S. Uhlemann, J.E. Chambers, P.B. Wilkinson, M. Kirkham and M. BeamishRiver terrace deposits form one of the major sources for Palaeolithic artefacts and are of economic importance for the groundwater and aggregates industry. Their depositional history and thus structure can be highly complex. We present automated interface detection techniques applied to 3D geoelectrical data in order to guide archaeological prospecting and mining activities. Three different interface detection techniques were applied, which were based on resistivity iso-surfaces defined from clustering techniques and comparison to intrusive investigation, and on the steepest gradient in resistivity depth sections. Their results were compared to intrusive investigations. All three methods successfully imaged an incised channel underlying 3 – 8 m of sand and gravel deposits. The results showed good agreement with bedrock depths obtained from boreholes. The extracted bedrock topography was used to define archaeological trenching locations, within which Palaeolithic artefacts were recovered. The remaining sand and gravel resource of this extraction phase was estimated to be more than 1 350 000 m3.
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Mapping Alteration Zones over Botija Deposit, Using Reinterpretation of TDEM Data Flown for Geotechnical Purposes
Authors A. Viezzoli, V. Kaminski, A. Menghini and M. HopeCurrent study describes a case of reinterpretation of legacy TDEM geotechnical data for mining purposes. This reinterpretation allowed to extract new valuable information about alteration in Botija Cu porphyry deposit (Panama) and shine light on such phenomena as airborne IP effect and Cole-Cole modelling of airborne TDEM data.
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Application of Joint Inversion of Seismic and Gravity Data for Geological Characterization of Near Surface Zone
Authors A. Cygal, J. Pilch, M. Stefaniuk and T. MackowskiA comprehensive research on developing P-wave near-surface velocity models conducted during classic seismic data processing enabled not only a calculations of reliable values of static corrections, but also obtaining a detailed geological characterization of the shallow deposits and structures. Such a solution was possible to obtain by application of joint inversion of seismic refraction and gravity data and aimed to deal with complex geological and hydrogeological conditions of the Polish Lowlands. The presence of large thickness of glacial and post-glacial deposits typical for this region became an essential challenge for the presented experimental seismic study. This Quaternary formation comprises problematic for seismic acquisition unconsolidated material: gravel, sand and clay, which are additionally characterized by remarkable lateral and vertical lithological heterogeneity. In order to improve the quality of near-surface interpretation, it was inevitable to support the traditional interpretation methods, mainly seismic refraction tomography, with incorporation of the other, independent geophysical data. High-quality seismic data together with gravity anomaly gave an opportunity for the wider application of the joint inversion method to near-surface imaging for groundwater aquifers and mineral deposits prospection.
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Localization of Underwater Objects Using DC Resistivity Method with Two Detection Line
More LessSeveral methods were introduced as a technique to detect underwater objects such as submarines. Acoustic methods were generally exploited for underwater objects detection. However, they are prone to be disturbed by acoustically noisy marine conditions. To solve this problem, a new method adopting the geophysical DC resistivity method is introduced. Detection feasibility of underwater objects using this method was verified through numerical modeling and physical scale modeling. When we use a detection line, a peak point of responses indicates an object position along a detection line, however, the position along the perpendicular direction is not verified. However, fast localization of the target object is required since the final goal is real-time tracking of underwater object. In this study, a localization method for moving underwater objects is introduced using two detection lines and localization algorithm is developed with response library. A feasibility of detection and localization using the algorithm is confirmed through the experiments using physical scale modeling data.
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pyDFERM - Towards a Versatile and Efficient Environment for ERT Monitoring Data Management and Processing
Authors O. Kaufmann and A. WatletWe developed a Data Format for Electrical Resistivity Monitoring alongside a Python package (pyDFERM) as a novel approach for managing long-term ERT monitoring experiments. Large datasets produced in such experiments are indeed quickly difficult to handle with conventional data storing techniques. In parallel, long-term experiments are subject to changes in experimental conditions that are not always easy to report. Our approach covers 4 aspects that aim at improving the management and processing of ERT monitoring measurements. These can be listed as (1) checking and logging data acquisition job status, (2) structuring, documenting and storing incoming data, (3) efficiently retrieving and processing subsets of stored data, (4) structuring, documenting and storing processed results. Current developments show the added value of the project for subsurface imaging and data management in long-term ERT monitoring.
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Optimizing Geoelectrical Arrays for Special Geoelectrical Monitoring Instruments
Authors P. Tsourlos, B. Jochum, R. Supper, D. Ottowitz and J.H. KimIn this work we adopted an array optimization scheme for a special geoelectrical monitoring instrument for which no standard geoelectrical arrays exists. Optimized measurements are selected on the basis of their Jacobian matrix values. Application is demonstrated though model and real examples from a landslide site in Austria. Synthetic and real tests demonstrated that though measurement optimization it is possible to reduce the number of collected data without reducing the overall geoelectrical imaging quality. This is a very important for reducing both the power consumption as well the time-lapse data processing time.
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Modelling of Seismic Amplitude Anomalies Observed During Sub-surface Gas Injection Monitoring
Authors H. Perroud, P. Pezard, J. Lofi, N. Denchik and H. AbdoulghafourSeismic amplitude anomalies have been observed at the Maguelone site in the course of sub-surface gas injection experiments. To allow the interpretation of the seismic monitoring in terms of physical parameter changes, various modelling attempts were conducted that all share the elastic wave theory principles. We show in this presentation that we cannot reproduce the experimental results with this theory, thus some form of anelastic energy dissipation would be required.
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Time-lapse Electrical Resistivity Monitoring of Subsurface CO2 Storage at the Maguelone Experimental Site (France)
Authors N. Denchik, P. Pezard, H. Perroud, J. Lofi, H. Abdoulghafour, D. Neyens and G. HenryCO2 geological storage remains a recent research field and many questions are still open, particularly for saline formations, which are expected to provide over time a larger storage capacity than depleted hydrocarbon reservoirs. The Maguelone shallow experimental site for shallow CO2 injection (Mediterranean coastline, Gulf of Lions, France) has been developed to study in an integrated manner surface and in-situ (downhole) monitoring methods. The presence of two small reservoirs with impermeable boundaries (R1: 13-16 m and R2: 8-9 m) provides an opportunity to study a saline formation for gas geological storage both in the field and in a laboratory context. During the shallow injection experiment (~48 m3 of CO2 was injected over ~2 hours on December 4, 2014), traces of the CO2 plume were detected by time-lapse downhole and surface electrical resistivity monitoring techniques, although some of the injected CO2 appeared to leak along the new injection hole, which should be corrected in the future with additional cementing around the new holes.
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Monitoring Transport of Contaminants During Snowmelt Infiltration with Invasive and Non-invasive Techniques
Authors E. Bloem, H.K. French and A. BinleyThe impact of agriculture, industry, airport activities on soil and water quality is strongly influenced by soil heterogeneity. At Oslo airport large amounts of de-icing chemicals are used for removal of snow and ice. The objective is to quantify how the different processes occurring during snowmelt infiltration of meltwater contaminated with de-icing chemicals affects the geophysical signals. The study describes two field experiments were tensiometers, suction cups, and multi- compartment sampler (MCS) techniques have been combined with non-invasive time-lapse electrical resistivity measurements (ERT). The MCS combines variable-suction with multi-compartment aspects to measure spatial and temporal distribution of water flow and solute transport. The tracer experiments were performed at the research station at Oslo airport. The low resistivity values at the top of the ERT profiles on day 6 and 12 are explained by rapid increase of water saturation (Day 6), derived from tensiometer data, and infiltration of tracer (Day 12), derived from suction cup data. The low resistivity is also explained with MCS by saturation conditions at day 3 and increased electrical conductivity at day 12. By combining ERT, tensiometers, water sampling via suction cups or MCS, we can observe the contributions from water content and solute concentration to ERT.
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Seasonal Monitoring of Soil Water Content and Infiltration Using Soil Temperature Measurements
Authors A. Tabbagh, R. Guérin, B. Cheviron, H. Henine and M. BechkitWe use high precision Pt 100 sensors and apply numerical models of convective and conductive heat transfer to temperature experimental data recorded versus depth and time along a vertical soil profile. After having determined the thermal diffusivity and the convective flux rate it is possible to calculate the water content and the Darcy’s velocity using empirical soil properties models. The results obtained at Boissy-le Châtel site between April 16, 2009 and March 8 2010 are presented here. The ten day period results are reliable in accordance with local rain and potential evapotranspiration data.
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The Use of Surface Geophysics to Determine the Aquifer Characteristics in the Folldal Mining Site, Norway
Authors S. Puig, C. Duque, T. Pabst and P. AagaardOver two centuries of mining activity in Folldal area (Norway), now an industrial cultural heritage site, led to large amounts of uncovered waste materials. The exposure and subsequent oxidation of these materials produces acid mine drainage, which is discharging into the River Folla. Integration of surface geophysical and hydrogeological field methods was necessary to further obtain hydrogeochemical numerical models to assess the fate of the acidic groundwater, its contribution to the river and predict the effect of remediation. Seismic refraction and electrical resistivity tomography (ERT) were essential tools to characterize the aquifer geometry, locate the water table and obtain an overview of the topsoil sedimentological changes without altering the historical site. From the integration of the methods, the aquifer was characterized as a one single sedimentary layer aquifer of 30-40 m depth and areas with different hydraulic conductivity were defined, which permitted to obtain accurate groundwater flow.
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