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EAGE-GSM 2nd Asia Pacific Meeting on Near Surface Geoscience and Engineering
- Conference date: April 24-25, 2019
- Location: Kuala Lumpur, Malaysia
- Published: 24 April 2019
41 - 60 of 80 results
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Characterization of Dolostone and Limestone in Perlis by Using X-Ray Powder
Authors F.H.A. Fadzil, N.M. Mustaza and Y.J. TeohSummaryCarbonate rock are sedimentary rock that contained carbonate mineral such as calcite, dolomite and aragonite. Limestone (calcite) and dolostone (dolomite) are two main carbonate rocks. Perlis is made up of continuous succession of Paleozoic rock, which are Machinchang Formation, Kubang Pasu Formation, Setul Group, Chuping Formation and Quaternary alluvium (Jones, 1983). Carbonate rocks are found in Setul Group and Chuping Formation. In Perlis, new location of these carbonate rock formations was discovered (Lee, 2001; Harun and Jasin, 2000). In this study, geochemistry method (XRD) is used to characterize carbonate rock at the new site. The findings show that Setul Group’s carbonate rock consist of ankerite while Chuping Formation’s carbonate rock consist of calcite and dolomite with high quartz content. Presence of ankerite depicts the rock underwent a very high temperature during its lifespan.
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Magnetic source depth delineation of the Mulgathing Trough beneath cover in the Gawler Craton, South Australia
Authors C. Foss, T. Wilson, G. Gouthas, L. Katona and P. HeathSummaryA new regional aeromagnetic survey over the Gawler Craton of South Australia has provided new constraints on the extent, structure and depth of the Mulgathing Trough, a Permian age extensional basin developed over a strongly magnetised Proterozoic basement and completely concealed beneath younger cover. We present a study using sweet-spot depth analysis to map depth to basement beneath the trough.
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Aeromagnetic anomaly mapping of possible heavy mineral accumulations in the Coompana area of South Australia
More LessSummaryAn aeromagnetic survey over the Coompana area of South Australia has revealed magnetic anomalies distributed across the area due to near-surface magnetizations. Surface rocks are limestones and calcretes in an arid plain. A possible source of the anomalies is magnetite in heavy mineral concentrates introduced in a previous cover material that is now removed.
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A wavenumber-domain iterative approach for magnetic 3-D imaging with depth constraints
More LessSummary3-D imaging is a significant approach for qualitative and quantitative interpretation of magnetic data. In this paper, a wavenumber-domain iterative approach for 3-D imaging is proposed, which can improve the imaging efficiency and is suitable for rapid imaging of large-scale magnetic data. The wavenumber-domain forward and imaging equations of total magnetic anomaly, magnetic three components, magnetic gradients and magnetic full-tensor gradients are derived. Then, depth-scale factor and magnetic interface constraint algorithm are involved into the imaging processing, which dramatically improve the depth resolution. In order to reduce the deviation and improve the imaging accuracy, an iterative algorithm is utilized. The validity and feasibility of this approach can be verified by the synthetic data.
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State of the arts and new advanced ERT instrumentation and methods for Urban planning challenges
Authors C. Truffert, J. Gance and O. LeiteSummaryMany countries will face challenges in meeting the needs of their fast growing urban populations, including housing, water resource, transportation facilities, energy supply, and other essential infrastructures. Geotechnics has been on a dominant position in the tool box of urban planners. Nevertheless, challenges are getting more crucial since megacities grows so fast and human health being becomes more and more a non-negotiable objective. Underground comprehensive geological knowledge is then the key issue for a safe urban planning. Among the geophysical tools box, urban planner and decision makers have ERT state of the art and advanced development for accessing to a comprehensive underground geological knowledge.
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Developing Geological Model From Electrical Resistivity (ERT) Survey Data for Construction Purposes: Case Studies
Authors F. Dali, A.R. Jaapar, A.F. Abdul Rahim, M.F.S. Md Aripin and Z. MohamadSummaryElectrical resistivity survey is a geophysical method widely used in construction industries to investigate the subsurface geological profile anomalies of the section. Subsurface profile is depicted by pseudo section model that shows difference range of resistivity value. This indicates the different layer of soils, presence of groundwater, boulders or fractured bedrocks zones. The complexity of geomaterial subsurface cause the interpretation of geophysical data become tedious and sometimes inaccurate especially for tropical region like Malaysia as the physical and chemical weathering are very rapid. These weathering change the parent behaviour of bedrock and makes underground very complicated. Ten (10) resistivity set up established at two (2) different sites in Selangor/Kuala Lumpur. The problem encountered by geotechnical engineer during the early phase of the ground investigation was the existences of boulders/rocks fragments in the subsurface that give will affect the construction foundation (Site A); and potential geohazards along the slope section near to the residential areas (Site B). Apart from resistivity survey, boreholes information that was conducted by drilling contractor also optimized to interpret and develop the geological model for the study areas. A very good geological interpretation really appreciated by geotechnical engineers/decision makers to solve construction issues regarding the geological materials at site.
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Distinction of the Type of Mudstone at Bukt Chondong, Perlis Using 2-D Resistivity Method
Authors N. Mohd Muztaza, N. Ahmad Nawawi, M.T. Zakaria and T.O. AdeekoSummaryThe study explores the use of 2-D resistivity method to identify the type of mudstone from the outcrop of Bukit Chondong (BC), Perlis. The distinction of mudstone is based from the comparison of resistivity values of different mudstone, which are the red mudstone and the grey mudstone from outcrop of Guar Jentik (GJ) and Utan Aji (UA) in Perlis. All the survey outcrops was identified within the same classification of Kubang Pasu Formation. The resistivity survey was performed using SAS4000 Terrameter with Pole-dipole array configuration. The resistivity was implemented on a single 40 m survey line with minimum 1 m electrode spacing. The resistivity data was processed by utilizing RES2DINV and Surfer 10 software which the inversion results was displayed in a form of contouring values. The range of resistivity value for red mudstone is 10 to 150 Ωm and grey mudstone is 120 to 500 Ωm. The resistivity value for mudstone of BC is 20 to 130 Ωm, which fall in the range values of red mudstone. Thus, mudstone of BC has the possible to be classified as red mudstone.
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An Accuracy Test of “Schlumberger” Vertical Electrical Sounding Method in a Sandbox Modelling
Authors I. Arifianto, R.C. Wibowo and M.R.F. PrianaSummaryIn groundwater exploration, a geophysical method is needed to provide information and an overview of the subsurface conditions of the study area, and the most common practice for giving subsurface information is a geoelectric method or resistivity method. During the acquisition of groundwater exploration, Schlumberger Vertical Electrical Sounding (VES) is the most preferred due to convenience and effectiveness. Schlumberger configuration will produce a subsurface profile vertically at an observation point and is the initial step to estimate the presence of aquifers in the groundwater exploration area. However, this method has several geological considerations leading to the inaccurate subsurface interpretation that the presence of dipping layers and subsurface structures such as fault are the main factors. Thus, the presence of that features can affect the modeling of resistivity values and subsurface thickness during interpretation process of the resistivity method. This then becomes the basis of the authors conducting a study that aims to determine the accuracy of the layer thickness produced by the VES resistivity method. However, the existence of subsurface structures is also difficult to predict if there are no supporting by surface data, hence the study modeling of subsurface conditions using a sandbox model will be carried out.
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Installation and validation of a customized resistivity system for permanent monitoring of a river embankment
Authors A. Hojat, D. Arosio, L. Longoni, M. Papini, G. Tresoldi and L. ZanziSummaryDevelopment of early warning alarm systems for hydrogeological risk assessment is seriously under research in different European countries. In this paper, we discuss the installation and validation of a prototype electrical resistivity tomography (ERT) system for permanent monitoring of river levees. ERT measurements were performed on various candidate sections of river embankments in Lombardy and Emilia-Romagna regions in Italy for preliminary evaluation of critical sites to be monitored. Based on careful analysis of all datasets, a critical part along an earthen embankment of the Parma river in Colorno was selected to be permanently monitored. A customized ERT monitoring system using the Wenner array with 48 stainless steel plate electrodes was installed in November 2018. The system is making two measurements every day, sending the datasets to a Cloud platform through the mobile-phone network. Time-lapse analysis of datasets measured by the prototype and control measurements with commercial equipment show that the installed system is operating well. The research is in progress to define the thresholds of instability based on water saturation maps calculated from resistivity sections.
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Geophysical Investigation of Seawater Intrusion at a Coastal Site in Phuket, Thailand
Authors T. Nontapot, P.H. Giao and A. PuttiwongrakSummaryIn this study, the resistivity and induced polarization (IP) surveys were conducted to investigate the extension of seawater intrusion at a coastal site in Phuket island Thailand, whose results in combination with geotechnical data indicated that seawater intrusion at the study site occurs at 5 to 26 m deep and has reached about 175 m far from the shoreline. The seawater-intruded aquifer resistivity varies from 9 to 22 Ωm, while that of freshwater zone is from 50 to 119 Ωm. Additionally, chargeability of sand aquifer was found less than 20 mV/V, whereas that of clayey sand is more than 20 mV/V. It is expected that the methods presented in this study can be applied at more coastal sites in Phuket to help propose and design better measures for mitigation and control of seawater intrusion to protect the invaluable groundwater resources of this island.
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Groundwater identification using VES With Regressive-Regressive PSO Inversion in Pacitan Region, Indonesia
Authors B. Ramadhany, S. Sungkono and A. RahmawatiSummaryPacitan Region are located in Alluvium formation that has a good potential in groundwater but has a side effect of high liquefaction when shacked by an earthquake. The experiment’s purpose is to map the distribution of aquifer zone in the designated area and in shallow surface below 30 meter underground. One of geophysics method that can be used in this experiment is Vertical Electrical Sounding (VES) with Schlumberger configuration. This measurement has been done in several points in Pacitan region. Once the data has been gathered, an algorithm method called Regressive-Regressive Particle Swarm Optimization is used to obtain the apparent resistivity that can be used for interpretation purpose, according to the integration of inversion result and local geology, the area is dominated by the sand, gravel and the clay and the free aquifer zone is located in 1 through 4 meter deep and pressurized aquifer zone is located between 4 to 9 meter below the surface and the aquifer layer thickness is ranged between 2 to 25 meter.
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Integration of airborne (SkyTEM) and ground (Dias) large-volume electrical survey data for delineation of new deposits
Authors V. Kaminski, E. Taikulakov, E. Janseitov, A. Daraev, J. Rudd and C. ThibaudSummaryThe study is a result of integrated interpretation of SkyTEM data collected in 2017 and Dias ground data, collected in 2018 as a follow-up survey. The integrated interpretation is a result of collaboration between Aurora Minerals Group of Kazakhstan and Canadian-based Promiseland exploration, Ltd. Analysis and inversions of SkyTEM data resulted in successful discovery of a new gold-bearing deposit with Au contents up to 10 g/t as well as delineation of four new areas with potential for gold-bearing mineralization, which were further followed up by Dias ground 3D DC/IP surveys. The main challenges in the application of electrical methods were low contents of sulphides in mineralized zones, which result in weak EM anomalies, which however yield high apparent chargeability values (not detectable directly by airborne surveys). Another challenges were presence of highly conductive overburden, limiting penetration of airborne EM sygnal as well as extremely large ground data-sets due to 3D multi-electrode configurations. The challenges were met by using state of the art 3D inversions of ground DC/IP data run on a dedicated server, which resulted in 7 new drill-targets subject to upcoming 2019 drilling operations.
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Investigating parameters m, n, and a in the extended Archie’s Equation for clayey soils
By H. DuerrastSummaryThe resistivity of sandy soils and sediments can be explained by Archie’s Equation, whereas for clay bearing soil the extended version of the equation can be used. However, the parameters tortuosity factor (m), saturation exponent (n) and the constant (a) in this equation are not fully explored for clayey soil, although often used for calculation. In this study laboratory electrical resistivity measurements on soil samples from granitic and sandstone bedrock with increasing saturation were fitted with the extended Archie’s Equations, which was solved using physical properties measured in the laboratory. The tortuosity factor, m, shows a larger variation within the same soil type, but less difference to the other soil type. The saturation exponent, n, however, shows a larger variation between the soil types but less variation within.
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Assessment of 3D geometry effects on 2D ERT data of a permanent monitoring system along a river embankment
Authors A. Hojat, D. Arosio, M.H. Loke, L. Longoni, M. Papini, G. Tresoldi and L. ZanziSummaryTo permanently monitor a river embankment in Colorno, Italy, a customized electrical resistivity tomography (ERT) system was installed in November 2018. ERT data are measured twice a day to monitor the internal hydrogeological conditions of the embankment. In this paper, we present the initial assessment of site-specific 3D geometry effects on 2D ERT data measured with the monitoring system. Using average resistivity values of the levee material, 2D and 3D models of the embankment were reconstructed in RES2DMOD and RES3DMODx64. Apparent resistivity pseudosections were calculated for different profiles along the embankment and pseudosections of resistivity differences between 2D and 3D modellings were then calculated for all profiles. The results show that regardless of the lateral position, all measurements along the embankment are distorted by 3D effects, especially in deeper parts. For the smallest electrode spacings, the profile in the middle of the embankment measures data closer to real values. Our next research perspective is to use 3D field measurements and samples of the embankment to more precisely quantify the site-specific 3D effects. Considering that clay is one of the main materials used in constructing this embankment, we also plan to explore the 3D effects on 2D induced polarization (IP) measurements.
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High-Resolution Seismic Tomographic Imaging: A Case Study from Kuala Lumpur, Malaysia
Authors T. Fechner, J.K. von Ketelhodt, M.S.D. Manzi, R.J. Durrheim and A. DevendranSummaryAn integrated P- and S-wave cross-borehole tomographic survey was performed in the city center of Kuala Lumpur, Malaysia, with the aim of exploring a karstic limestone area near an area that previously encountered cavities. High quality sparker signals were generated to record P-waves. Additonally, horizontally polarized S-waves were generated with two opposing, perpendicular strike directions and recorded with a multi-level, three component receiver array. The P- and S-wave traveltimes were used to invert for two tomograms. The tomograms enabled the calculation of the elastic parameters, i.e., P- to S-wave velocity (Vp/Vs) ratio, Poisson’s ratio, bulk modulus, Young’s modulus and the shear modulus, on a 2D surface between the boreholes. The interpretation of the tomograms was constrained by two additional boreholes, which provided more confidence on the delineation and location of cavities at depths. The survey shows the benefit of co-locating P- and S-wave tomography surveys.
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Processing of crosshole seismic testing (CST) data via tomographic inversion on real object
Authors A. Konkov, A. Oshkin, V. Ignatev, A. Turchkov, A. Simakov, I. Polikarpov and N. RagozinSummaryThis study describes an experience in crosshole seismic testing (CST) data acquisition and processing. The corresponding survey was carried out in the system of boreholes, that included four lateral wells located around central well thus constituting a total of 8 observation planes. It was shown that contemporary equipment and software favor high-performance, dense and detailed shooting and reliable calculation of the CST data obtained. The data quality made it possible to determine the arrival times of elastic waves with high accuracy for surveys of such a type (up to 0.1 ms), which has a positive effect on the resolution power. None of the land geophysical methods that were previously implemented at the experimental site (nuclear power plant) demonstrated such an accuracy and detail.
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Prediction of Coal Top by Conductively-Guided Borehole Radar Waves: Results from Field Trials
Authors B. Zhou and M. van de WerkenSummaryBlasting damage to coal seam tops due to incorrect blast stand-off distances is a serious issue in Australian coal mining industry, resulting in coal losses of up to 10-15%. The problem stems from a lack of accurate coal-top location information to inform the driller when to stop drilling and to date, no effective and economically-sound techniques have been developed that map and characterize coal seam exact location and structures in the open cut environment. We propose to use a new forward-looking imaging technique based on the borehole radar (BHR) technology to predict the coal seam top in real-time, while drilling blast-holes, to reduce coal top damage and subsequent loss of product. This is achieved by electrically coupling the conventional BHR waves on to a conductive wire or steel drill-rod to induce a guided wave along the axial drill-rod. The drill-rod ahead of the BHR behaves as a forward-looking antenna for the guided waves. Field trials at Australian open-cut coal mines to test the feasibility of the proposed technique demonstrated that guided BHR waves could be observed and used for prediction of coal top ahead of drill bit during blast-hole drilling in resistive open cut environments.
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1-D inversion of surface-to-borehole TEM data based on grounded wire source
More LessSummaryThe surface-to-borehole TEM method has shown great potential in detecting deep minerals. This configuration mostly uses rectangular loops as its source. Considering the advantages of grounded wire sources in EM exploration, which had been successfully applied in ground and marine EM methods, we propose a new surface-to-borehole TEM system that utilizes a grounded wire source with relative short offsets. The ID inversion of surface and borehole data was realized according to an OCCAM’S inversion scheme. The inversion results of synthetic data indicates that only inversion of surface or borehole data will lead to resolution loss in deep or shallow earth. However, joint inversion of both surface and borehole data is an effective way to improve the results obtained from the inversions of individual data sets.
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Pavement diagnostics using flexural standing waves
Authors Y. Kolesnikov, K. Fedin and L. NgomayezweSummaryTo ensure road safety, periodic monitoring of road surfaces’ quality and conditions is necessary. Lately, near-surface geophysical methods have gained prominence in such studies. This article presents field experiments’ results that demonstrate the possibilities of cavities detection under a rigid pavement using flexural standing waves. Accumulation of numerous amplitude spectra of acoustic noise records was used to study standing waves arising in the interior of the pavement. It is shown, joint visualization of the averaged spectra obtained by profile observations over a cavity under pavement allows one to identify several flexural standing wave modes by alternation nodes and antinodes along profile. Amplitude distribution map of one of the flexural standing wave modes over a cavity (gully) under pavement was constructed. At a qualitative level, this distribution is consistent with computer simulation results using the finite element method. The fact that flexural standing waves are formed under acoustic noise influence in some part of pavement indicates absence of rigid contact at its lower boundary. Thus, horizontal cavity dimensions can be estimated from the area size on which flexural standing waves are formed.
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