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24th European Meeting of Environmental and Engineering Geophysics
- Conference date: September 9-12, 2018
- Location: Porto, Portugal
- Published: 09 September 2018
1 - 20 of 203 results
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Modern Electro-prospecting Technologies for Searching and Exploration of Ore Deposits
By S. ZaytsevSummaryThe emergence and widespread introduction of computer technologies and satellite navigation systems into various industries has led to the emergence of a new class of compact high-precision geophysical equipment. There has been a qualitative improvement of existing technologies and the emergence of completely new geophysical techniques. New directions in ground-based electrical prospecting are associated with the development of audio-magnetotelluric sounding (AMT), magnetovariance techniques (MVS, HMT), electrical resistivity tomography (ERT), spectral induced polarization (SIP), etc.
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Influence of the Ground Surface Relief on the Results of Electrical Tomography
More LessSummaryThe Soviet geophysics S.G. Komarov and L.P. Gorbenko first noticed to the problem of the influence of ground surface relief on the distribution of electric field. The main features of the electric field anomalies, which arise on the relief were clear already then. It was found that anomalies of apparent resistivity of the minimum type arise over a positive relief forms due to a decrease of the current density, and anomalies of the maximum type arise over negative forms of relief due to an increase in the current density ( Chanturishvili, 1983 ). At the moment, the electrical tomography has a complicated situation during observations in conditions of complex Earth’s surface relief. There are several commercial inversion programs ( Loke, 1997–2000 ; Günther at al., 2017 ; Kaminsky, 2016 ; ERTLab Solver, 2017; Zonge, 1997 ) and a small number of academic programs ( De-Bao Lu at al., 2015 ; Jian-ke Qiang at al., 2013; Erdogan at al., 2008; Pidlisecky at al., 2007 , Marchenko, 1999) available to a wide range of geophysicists. However, none of these programs is open, although these programs are often successfully used in practice. Therefore, there always arises the question of the degree of reliability of those calculations that we obtain using one or another inversion code. So, it should always be remembered that the construction of the result geoelectric section is usually obtained through solving a direct problem.
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Sunnyside Deposit: A Calibration Site for Airborne EM Systems
Authors A. Viezzoli, A. Menghini, G. Selfe and V. KaminskySummaryThe Sunnyside deposit is a part of the Selebi-Phikwe nickel mine (Botswana), which has a resource of 68 Mt at 0.8% Ni and 0.88% Cu ( Figure 1 ). It is small, but has some high grade intersections of up to 2.3% Ni and 1.12% Cu over 1 m. The nickel belt has been flown by several airborne EM systems including GeoTEM, Spectrem, VTEM, SkyTEM and XCite. Albidon (Pty) Ltd started the airborne surveys in 2008 by flying VTEM system. African Nickel Limited followed, having flown a Spectrem survey in late 2012, which was succeded by a SkyTEM survey in early 2013. At the same time, moving loop ground EM survey was carried out, and then in early 2014 two AMT surveys were performed. The sulphide body was drilled extensively to a depth of 200 m, but little deep drilling has taken place. In May 2016 NRG offered to fly Sunnyside with their new Xcite heli-EM system, as a test survey. The possibility to compare a generous selection of AEM systems, makes the Sunnyside deposit a defacto test site for airborne EM in southern Africa.
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Possibility of Distributed Acoustic Sensing (DAS) for Geophysical Problems Solution
By A. ShuvalovSummaryIn systems based on fiber-optic sensors, an optical fiber can serve as both a medium for transmitting information and a sensitive element. The DAS (Distributed Acoustic Sensing) technology deploys optical fiber as a sensor for measuring acoustic effects with high spatial resolution over entire length of receiving system. The range of application of this technology is very wide and includes the protection of perimeters of long objects, monitoring of roads and railways, monitoring of the pipelines condition, dams and other complex and highly sensitive engineering structures, microseismic monitoring, hydraulic fracturing monitoring, permanent monitoring of deposits, etc. The technology of distributed acoustic sounding for vertical seismic profiling (VSP) was applied relatively recently ( Mestayer et al., 2011 ; Mateeva et al., 2014 ).
Compared to classic borehole tools based on geophones, the fiber optic distributed measuring system is much lower in price, provides real time seismic data acquisition over the entire length of the well and limits operational risks, as it requires a one-time setup for all subsequent observations ( Barfoot, 2013 ).
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Different Scale Complex Airborne Geophysical Survey In the Central African Ridge Area
By E. MoilanenSummaryAirborne geophysical survey was started by 12th of October 2016 in Rwanda. EQUATOR ( fig. 1 ) technology ( Felix et al., 2014 , Karshakov et al., 2017 ) was used. A survey was fully completed by 12th of April 2017. A survey at a scale 1:50 000 and infill works was completed on a square of 26 000 km2. Total survey volume is 57 718 line km. About half of the survey time was in the rain season. And half of the survey area are situated in the rough terrain conditions. Average productivity of airborne geophysical survey is 9620 line km per month. Detailed characteristics of EQUATOR system are described by Karshakov et al. (2017) .
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Complex of Geophysical Methods During the Survey of the Underwater Diapir Volcano of the Taman Peninsula
Authors A.V. Kozlova, D.A. Korshunov and T.S. KlapyshevaSummaryMud volcanoes could be found almost everywhere on the areas with sediments thickness about the first kilometres. Their forms are conical structures with a truncated vertex. The vertex has crater, outer slopes could be strongly indented by radially diverging ravines. Cone’s form changes depending on the consistence of the erupting mud: if it is liquefied the cone is low with smooth slops, if consistence is viscous it leads to high cone formation with steep slopes. The mud volcanoes eruptions are accompanied by fire arising from spontaneous combustion of gases exhaled from the vents.
The main factors causing the possibility of occurring of mud volcanism: existence of tectonically dislocated intensely fractured clay rocks which are able to deliqate, confined groundwater and underground gas accumulation. The main principle of mud volcanism lies in the exhalation of combustible gases coming to the surface along weakened zones, blending gas flow with clayey breccia, which is liquefied by confined groundwater and mud mixture effusion to the surface ( Rakhmanov, 1987 ; Kholodov, 2012 , Mironuk, 2014 ).
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Assessment of the State of Stability of a Road Tunnel on the Basis of Data from a Multilevel Seismic Survey
Authors V. Pisetsky, A. Zudilin and S. ChevdarSummaryThe presented report discusses the results of a survey of the technical condition of the unfinished construction of a road tunnel on the object: Bashkortostan - a new exit from the city of Ufa to the federal highway M-5 “Ural” (Eastern exit).
The purpose of the work was to study the engineering geological and hydrogeological conditions within the zone of interaction of the enclosing mountain massif and all previously executed parts and tunnel elements to obtain the initial data necessary to verify the compliance of the design documentation and to assess the possibility of their further use during the continuation of construction and future accident-free operation or the need for their replacement, restoration, repair and reinforcement. Note that to date, along the route of the future tunnel from the beginning of construction (2001), three parallel galleries from the western portal have been traversed for a distance of about 900 m. Up to the design position of the eastern portal, about 200 m have been drilled. The side of the tunnel is partly finished by finishing, the rest - temporary.
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Engineering-Geological Conditions for Construction of Highways in the Cryolithozone
Authors I. Abaturova, I. Koroleva, I. Savintsev, L. Storozhenko and I. KovyazinSummaryAt the present time the expanses of Yakutia are becoming more and more active. This is due to the exploration and exploitation of deposits located in hard-to-reach places. Intensification of the development of natural resources has necessitated the construction of highways, paved in the most complex engineering and geological conditions. Underreporting, which will entail incorrect choice of design solutions, million construction costs and as a result the inability to operate is often the only transport route.
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Multiple, Concurrent GPR Data Acquisition - The WARR Machine
Authors Nectaria Diamanti and A. Peter AnnanSummaryGPR WARR (wide angle reflection and refraction) and the closely related CMP (common-mid-point) soundings have been a standard survey method since GPR first existed. Earliest efforts demonstrated the variation in ice sheet velocity versus depth. While a valuable survey method, the technique has seen little adoption.
Unlike seismic, commercial GPR systems with multiple concurrent data acquisition receivers have not existed. Multiple offset GPR data had to be acquired using a single transmitting and receiving antenna pair moved to the desired offset sequentially. With the recent advances in GPR timing and control technology, modern instrumentation with multiple concurrent sampling receivers enables continuous, rapid acquisition of WARR data. Two dimensional reflection surveys (i.e., simple, common offset profiles in the past) can now rapidly yield a multi-offset sounding at each recording station, providing WARR profiling at the same speed as a standard, single fold GPR sounding.
We have recently developed the first embodiment of a GPR WARR system called the WARR machine. We have dealt with design and implementation challenges as well as the concomitant issues of dealing with large volumes of WARR data. The key conclusions derived from the initial in-field deployments are that the approach is now viable, timing stability in distributed units is sufficiently reliable for multi-channel data to be merged, and that standardized work flow coupled to data processing is essential for the method to see broad adoption.
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Application of the Small-Loop TDEM Method to the Quantification of Both Electrical and Magnetic Parameters of the Subsurface (Numerical Approach)
Authors Cécile Finco, Cyril Schamper and Fayçal RejibaSummaryThe inductive electromagnetic geophysical method in the temporal domain (TDEM) allows, in certain conditions, the measurement of a signal integrating information from several physical independent parameters (electrical resistivity, magnetic viscosity, polarization). Being able to separate and quantify those physical and independent contributions is a real issue. It is particularly important when one of those contributions overwhelms the others which can happen depending on the geological context and the specific setup used.
The non-conventional use of this method with small transmission and reception loops (a few meters wide at most for the transmitter loop) increases the sensitivity to the magnetic viscosity in addition to the usual electrical resistivity. Through numerical modeling and field tests, we are designing a setup geometry that would allow us to discriminate between the influences of these parameters on the signal. The most promising option would be to make a measurement in the central configuration, which is very sensitive to the magnetic viscosity, and another one with an offset between the two loops as the sensitivity to the magnetic properties decreases with the distance separating the transmission and reception loops.
This use of small loops also increases the sensitivity to the noise from the system itself. The interactions between the reception and transmission loops and the measurement device create a distortion on the measured signal. This distortion depends on the setup geometry and on the electrical characteristics of the ground. Current work concerns the study of equivalent electrical circuits to model the mutual characteristic and complex impedance between both the transmitter and receiver coils of the TDEM setup. The accurate evaluation of the mutual impedance over a wide band of frequency is necessary to deconvoluate the instrumental response (including all electronic and coils parts) from the part of the measured transient signal coming from the subsurface.
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Sediment Volume Search Sonar
Authors Tom E. Blanford, Daniel C. Brown, Shawn F. Johnson and Cale F. BrownsteadSummaryThe Sediment Volume Search Sonar is a sensor whose goal is to improve buried unexploded ordinance (UXO) detection and classification performance through the design, build and demonstration of a sonar system that is deployed from a shallow-draft surface vessel. This sonar system produces a novel form of three-dimensional synthetic aperture sonar (SAS) imagery of surficial and buried UXO across a range of environments. The sensor is particularly suited for use in water depths less than 3 meters, and it provides sufficient detection and classification performance against objects of interest in water less than 5 meters depth.
The sensor’s hardware design was based in part upon data created in a modeling and simulation collaboration with the Applied Physics Laboratory at the University of Washington. This collaboration produced synthetic sensor data where the sensor/environment/target space could be modified to explore the expected operating conditions. The simulated data were also used to adapt a set of existing signal processing algorithms for formation of three-dimensional acoustic imagery.
Recently, the sediment volume search sonar has been integrated to a shallow-water surface craft, and experiments have been conducted at a trial site in the Foster Joseph Sayers Reservoir near Howard, PA. This test site has been prepared with several buried man-made objects. Results will be presented showing the use of the sensor for detecting and localizing these objects.
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Integrating Multiple Geophysical Methods to Understand Groundwater Storage and Discharge in Tropical Proglacial Catchments
Authors Robin Glas, Laura Lautz, Jeff McKenzie, Rob Moucha and Bryan MarkSummaryThe Cordillera Blanca in Northwestern Peru is home to a quarter of the world’s tropical glaciers, where hydrologic regimes are rapidly changing due to warming- induced glacier recession. Proglacial alpine meadows are storing a significant portion of annual basin discharge, and buffer dry season low flows as glaciers continue to lose their influence on the regional hydrologic cycle. We used integrated seismic (refraction, H/V passive seismic) and electrical (2D ERT and 1D soundings) in conjunction with borehole data to characterize the nature of proglacial talus aquifers in alpine meadows at elevations above 3500 masl. The meadow subsurface exhibits a transition from relatively slow (400–800 m/s) to fast (∼2500 m/s) seismic p-wave velocity at depths of 4 to 8m, coinciding with the top of a composite layer of buried talus boulders, according to borehole data. Artesian pressure head in piezometers screened at the boulders indicate the presence of an aquifer confined by clay sediments. Resistivity profiles suggest that the upper most portions of the buried talus deposit are infilled with saturated clay, which dissipates with depth where sediments become more electrically resistive. Passive seismic and 1D electrical soundings suggest that total sediment thickness extends deeper than 20 m, allowing for first estimates of talus aquifer storage volumes and groundwater residence times. Based on the results from this study, we present a refined conceptual model of talus aquifers, from their formation to hydrologic function. Throughout the Cordillera Blanca, buried talus aquifers have the potential to store between 7 and 20% of annual basin discharge, which will allow for future predictions of dry season base flow for the region’s principal river.
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Variability of Electrical Conductivity and Water Content in a Soil under Irrigation in the Pampean Region, Argentina
Authors C.M. Sainato, M.S. Iseas and J.J. Márquez MolinaSummaryThe complementary irrigation in the Pampean Region of Argentina may result in a deterioration of soil properties, such as sodification and salinization. It is important then to evaluate soil water content to decide the sheet of water to be applied. The aim was to study the distribution of electrical conductivity (EC) and water content, using electromagnetic soundings to evaluate the effect of irrigation on the soil. Two areas of a lot with corn were studied: one which had been irrigated since 2011 (1) and another one without irrigation (2). Volumetric water content (VWC) was measured with TDR (Time domain reflectometry) in transects along the areas. The geostatistical variograms were estimated for ECa and VWC. The range of correlation of ECa for Area 1 is approximately 8–9 m, while for Area 2 is almost 12 m. The TDR variograms showed pure nugget effect except for two transects with a range of 5 m and 7 m. The periodicity in the series of moving average of ECa and VWC is very similar at the first part of the transects. The TDR measurements of volumetric water content followed the trend of conductivity being the variability greater in the area without irrigation.
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Electrical Resistivity Survey to Locate Buried Colonial Structures in the Santo Domingo’s Historic Complex, Panama
Authors M. Lezcano, A. Mojica, G. Arosemena, F. Durán, C. Ho, M. Llubes, L. Pastor, C. Camerlynck and F. RéjibaSummaryElectrical resistivity tomography is a powerful tool for investigating hispanic structures in the tropic. This technique of geophysical prospecting was developed in one of the most important ruins that are part of the archaeological site of Panama Viejo: Santo Domingo’s complex. The prospection was carried out in three zones with the aim to detect buried archaeological structures linked to church and the convent. In all zones, we detected a set of strong electrical anomalies at shallow depths associated with debris from walls and fallen roofs, and deeper we detected high electrical anomalies linked to walls, pebble floors, stone pillars and footing.
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A Multidisciplinary Study of Soils from the Sha’ar Ha-Golan (Israel) as a Method for Determining Ancient Human Activity
Authors S. Itkis and L. BityukovaSummaryThe multidisciplinary study of soils is an important tool in the investigation of archaeological sites. In order to investigate the relationships between magnetic susceptibility (κ) and geochemical characteristics of soil a detailed study of two areas in the Sha’ar Ha-Golan Prehistoric site was performed. Magnetic and self-potential surveys were carried out prior to soil sampling. Soil samples were collected along a 2 ×2 m grid within revealed geophysical anomalies. The content of ten oxides (SiO2, Al2O3, TiO2, Fe2O3, CaO, MgO, MnO, K2O, Na2O and P2O5) was determined by bulk silicate analysis by X-ray fluorescence method. The concentrations of 12 trace elements were measured by optical emission spectrography. For the study of the relationships between main chemical components and geophysical data we constructed maps and profiles geophysical and geochemical data distribution and applied correlation analysis. Comparison of κ and geochemical elements distributions along with correlation matrix analysis enabled us to reveal different correlation models in areas of ancient human activities in different archaeological periods. The complex study of magnetic properties and the specific chemical characteristics of the topsoil is an additional tool in the investigation of archaeological sites.
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Can magnetometry detect sediment-filled caves? The case study of the Sierra de Atapuerca Sites (Burgos, Spain)
Authors L. Bermejo, A.I. Ortega, J. Thiesson, J.M. Parés, R. Guérin, I. Campaña, J.M. Bermúdez de Castro and E. CarbonellSummaryThis work evaluates the potential of magnetometry to detect the inaccessible sediment-filled caves of the Sierra de Atapuerca karstic system. This karst consists of numerous caves filled with sediments that bear outstanding archaeo-paleontological remains from the Early and Middle Pleistocene. In order to find the continuity of the caves, the Sierra de Atapuerca sites have already been the target of ERT and GPR surveys, which have revealed their suitability for detecting different karstic features. Although our expectations were to find positive anomalies when crossing these filled conduits, the results showed a negative anomaly of the magnetic field where these sediments were expected. So far, the only explanation for this phenomenon is that these sediments were deposited in a reversed magnetic polarity period. This theory is supported by the fact that the Matuyama-Brunhes boundary is present in many of the studied caves.
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Digital Museum from Integrated 3D Aerial Photogrammetry, Laser Scanner and Geophysics Data
Authors G. Ranieri, A. Trogu, F. Loddo, L. Piroddi and M. CogoniSummaryThe hypogeum of San Salvatore di Sinis (Sardinia, Italy) is one of the oldest signs of the presence of the first Christians in Sardinia (IV century a.C.). Its walls are finely decorated with drawings from different periods, today strongly degraded. The present knowledge of the monument and of the site is not complete therefore, to check the presence of buried remains that could be related to the hypogeum, an extensive geophysical survey using ground penetrating radar (GPR), 3D ERT, seismic survey was carried out in the area around the church and inside it. The walls and floor of the hypogeum were also investigated. The results of the survey shown numerous buried structures in the surround of the hypogeum, furthermore some other voids are probably present near the hypogeum.
The data collected were used to implement a tool that can be utilized both to explore the subsoil and to see the lost drawings on walls as a virtual archaeology. The system also allows the musealization and the use by disabled people.
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Automatic ERT Monitoring System Installation at Crater Lake, Deception Island, Antarctica
Authors M. Farzamian, G. Vieira, F. Monteiro santos, B. Yaghoobi Tabar, C. Hauck, M. Catarina Paz, I. Bernando, M. Ramos and M.A. PabloSummaryAn automated-electrical resistivity tomography (A-ERT) with repeated measurements at 4-hour intervals was installed in the vicinity of air and ground temperature boreholes in the Crater Lake site at Deception Island in 2010 in order to study the dynamics of the active layer. All apparent resistivity raw data, collected during one year, were analyzed regarding daily and monthly resistivity changes and then compared to the spatiotemporal temperature variability. Preliminary investigation of apparent resistivity data reveals that the thawing and freezing sequences of the active layer can be well identified using the installed A-ERT monitoring system.
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Electrical Resistivity Tomography of Celtic Burial Mounds in Nonnweiler (Germany)
Authors O.S. Al-Saadi, V. Schmidt and P. LendleSummary2D and 3D electrical resistivity tomography (ERT) measurements have been applied for the investigation of Celtic burial mounds. The results show the general structure of the mounds and also indications of previous excavations. The archaeological interpretation of the result is complicated by the complex geological structure of the subsurface and the effect of trees, which also prohibit a regular electrode layout for 3D measurements. A reference measurement on undisturbed ground helps to assess the anomalies in the resistivity tomogram.
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Geophysics Applied in Precision Agriculture – Experimental Resistivity Studies for Plant Root Detection and Analysis
Authors A.G. Gerea and A.E. MihaiSummaryThe aim of this study is to conduct new experiments with higher precision and building new complementary equipment in which we can detect the plant roots extent with more accuracy, their behaviour in natural environments by carrying tests in both laboratory and agricultural fields. We’ve been able to create ERT (electrical resistivity tomography) with electrode arrays both classical and new experimental types, using flexible equipment created in the laboratory and Matlab programming. We’ve developed new test settings for the experiments in order to minimize the human errors and come up with high quality data and a more precise interpretation compared to previous studies on plant root detection using resistivity measurements.
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