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Добірка наукової літератури з теми "Electromagnetic induction geophysic"

Автор: Grafiati

Опубліковано: 11 березня 2023

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Статті в журналах з теми "Electromagnetic induction geophysic"

Ahmad Alhassan, Auwal Aliyu, Abubakar Magaji, M.Nuruddeen Abdulkareem, and Mohammed Abdullahi. "An Insight Into The Importance Of Application Of Geophysical Methods In Agriculture For National Economic Development." Global Sustainability Research 1, no. 1 (August 12, 2022): 1–4. http://dx.doi.org/10.56556/gssr.v1i1.301.

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One of the keys to national development in developing countries like Nigeria is the diversification of economy. Nigeria’s economy depends majorly on crude oil. The oil sector continue to face challenges like price drop in international market, corruption, reduced quantity of production as forecasted (although new oils are been drilled). These among others makes it necessary for the country to diversify its economy. Agriculture is one of the areas Nigeria have started investing into. New methods are necessary for fast improvement in the sector among which is geophysics. The need for Agricultural Geophysics to be considered for national economic development is discussed. Geophysics as a branch of science that deal with physical processes and phenomena occurring in the earth and its vicinity is applicable to many fields that contribute to the development of the economy of any nation. Such fields include oil, Agriculture, natural resources among others. Geophysical methods applicable in Agriculture like resistivity, electromagnetic induction, and Ground penetrating radar are discussed with their applications in agriculture. The various geophysical methods that are useful in agriculture are reviewed and necessity of their application is also emphasized.

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Chave, Alan D., and John R. Booker. "Electromagnetic induction studies." Reviews of Geophysics 25, no. 5 (1987): 989. http://dx.doi.org/10.1029/rg025i005p00989.

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WANNAMAKER, PHILIP E., and GERALD W. HOHMANN. "Electromagnetic Induction Studies." Reviews of Geophysics 29, S1 (January 1991): 405–15. http://dx.doi.org/10.1002/rog.1991.29.s1.405.

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Alte-da-Veiga, Nuno M. S., Luis Fernando Sánchez-Sastre, Jesús Martín-Gil, Salvador Hernández-Navarro, and Pablo Martín-Ramos. "Using EM Induction and ERI Geophysical Methods in Undergraduate Teaching: A Case-Centered, Discussion-Based Approach." Geosciences 12, no. 12 (December 2, 2022): 444. http://dx.doi.org/10.3390/geosciences12120444.

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In the last decades, the application fields of exploration geophysics have considerably broadened, reinforcing the relevance of exploration geophysics courses both within geosciences and non-geosciences degrees. Among these courses, those with a hands-on, place-based pedagogical approach and aligned with problem-based and case-based learning methodologies have proven to be particularly successful in regard to addressing the recognized difficulty that students experience in transferring their classroom knowledge to the field environment. In this article, we report a theoretical–practical module for the teaching of exploration geophysics methods to undergraduate non-geoscience major students, and in particular, to forestry engineering students. The in-field activity, based on a combination of Electrical Resistivity Imaging (ERI) and electromagnetic induction (EM) methods, was complemented with in-class sessions covering the fundamentals of these methods and Archie’s equation, software usage, data analysis and interpretation, and critical in-group discussions. This situated, context-rich teaching and learning example may be reproduced in other teaching institutions to provide technology-driven educational experiences in their curricula, helping students recognize the relevance of the abovementioned geophysical methods to address research questions beyond geology.

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Reynolds, J. M. "The role of surface geophysics in the assessment of regional groundwater potential in Northern Nigeria." Geological Society, London, Engineering Geology Special Publications 4, no. 1 (1987): 185–90. http://dx.doi.org/10.1144/gsl.eng.1987.004.01.22.

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AbstractAn analysis has been made of the usefulness of surface geophysical site investigations as part of a rural water supply programme carried out in southern Kano State, northern Nigeria. Field work was undertaken under the auspices of the Kano State Agricultural Rural Development Project in conjunction with Groundwater Development Consultants (International) Ltd, Cambridge. The database for this study consists of the results of surface geophysical site investigations at over 200 rural villages and comprised electrical resistivity and/or electromagnetic ground conductivity methods together with hydrogeological data from boreholes drilled as tubewells. The groundwater potential of southern Kano State was determined as a result of field studies of hand-dug wells, water table levels, geological and geomorphological mapping, the use of aerial photographs and, in particular, surface geophysics. Areas with poor groundwater potential were successfully highlighted. A drilling programme was planned on the basis of these field studies which allowed the drilling rigs to be used to maximum effectiveness providing successful tubewells whilst the more problematical sites were investigated further. Wildcat wells sited without the aid of geophysics and drilled in the Basement Complex of the Younger Granite terrain in Kano State resulted in unacceptably high failure rates (c. 70%). Once geophysical methods were introduced, the failure rate fell to less than 32% and, following further development of geophysical field and interpretation techniques, the final failure rate was around 17%. For a project whose target was 1000 successful tubewells, each costing of the order of £15,000, the saving to the client as a result of reduced number of failures was of the order of £5 million. The use of resistivity surveys, especially in conjunction with electromagnetic induction methods, has proved invaluable in the evaluation of groundwater potential and the planning of extensive drilling programme in southern Kano State.

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Everett, Mark E., and Alan D. Chave. "On the physical principles underlying electromagnetic induction." GEOPHYSICS 84, no. 5 (September 1, 2019): W21—W32. http://dx.doi.org/10.1190/geo2018-0232.1.

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This paper provides a theoretical overview of some of the fundamental concepts underlying electromagnetic (EM) induction exploration methods using marine controlled-source EMs as an exemplar. In particular, it will be shown, from different vantage points, that EM induction operates in the magnetoquasistatic regime in which inductive effects dominate, capacitive effects are ignored, and the displacement current is negligible; hence, charge polarization and dielectric phenomena play no role. We determine some of the major physical consequences of this approximation, and we make a distinction between wave physics and diffusive behavior, which is of particular interest in the special case of time-periodic excitation. We distinguish the fundamentally different roles of mobile charge carriers and bound charges in EM induction. It is emphasized that EM induction cannot be fully understood by comparing and contrasting Maxwell’s equations with governing equations from other disciplines that possess a similar mathematical structure. It is suggested that visualizations of energy flow using the Poynting vector and the Joule heating parameters provide a powerful tool to understand how the geologic medium shapes EM induction responses.

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Roberts, R. G. "Global electromagnetic induction." Surveys in Geophysics 8, no. 3 (September 1986): 339–74. http://dx.doi.org/10.1007/bf01904064.

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Adams, Ryan F., Benjamin V. Miller, Wade H. Kress, Scott J. Ikard, Jason D. Payne, and Walter H. Killion. "Evaluation of Electrical and Electromagnetic Geophysical Techniques to Inspect Earthen Dam and Levee Structures in Arkansas." Journal of Environmental and Engineering Geophysics 26, no. 4 (December 2021): 287–303. http://dx.doi.org/10.32389/jeeg20-063.

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Within the State of Arkansas, there is an increasing number of aging dams and levees that have little to no documentation concerning their construction or composition. Surface geophysical surveys offer a non-intrusive method for investigating these structures to describe their lithologic makeup, evaluate the materials constructed upon, and identify potential flow paths through them. Techniques such as electrical resistivity tomography, seismic refraction, and electromagnetic induction have been used to image dams and levees. They require additional information from geologic outcrops, geotechnical borings, or drill cores to make informed geologic interpretations of the geophysical models. These geologic models then allow the owners of these structures to make more informed decisions about their operation and maintenance. Between 2011 and 2018, the U.S. Geological Survey conducted geophysical and geotechnical investigations of three earthen structures in Arkansas. Electrical and electromagnetic geophysical data were used to develop lithologic models of these structures and characterize the underlying geology. Self-potential surveys were utilized to detect the movement of water through these structures and identify any possible seepage pathways. Geotechnical methods such as electric and hydraulic direct-push well logs and cores acted as a control on the geophysical interpretations and a confirmation of anomalies. This integrated approach detected the lack of an impermeable core within a levee, imaged a change in lithology of the bedrock forming the seal beneath a gravity dam, and identified a potential seepage feature within the core of an earthen dam. These results further support that this method of extending known lithologic features via surface and borehole geophysics is a useful approach for characterizing earthen water-control structures.

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Wilson, Gavin, Jacob Conrad, John Anderson, Andrei Swidinsky, and Jeffrey Shragge. "Developing a low-cost frequency-domain electromagnetic induction instrument." Geoscientific Instrumentation, Methods and Data Systems 11, no. 2 (August 5, 2022): 279–91. http://dx.doi.org/10.5194/gi-11-279-2022.

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Abstract. Recent advancements and the widespread availability of low-cost microcontrollers and electronic components have created new opportunities for developing and using low-cost, open-source instrumentation for near-surface geophysical investigations. Geophysical methods that do not require ground contact, such as frequency-domain electromagnetics, allow one or two users to quickly acquire significant amounts of ground resistivity data in a cost-effective manner. The Colorado School of Mines electromagnetic system (CSM-EM) is a proof-of-concept instrument capable of sensing conductive objects in near-surface environments, and is similar in concept to commercial-grade equipment while costing under USD 400 to build. We tested the functionality of the CSM-EM system in a controlled laboratory setting during the design phase and validated it over a conductive target in an outdoor environment. The transmitter antenna can generate a current of over 2.5 A, and emit signals that are detectable by a receiver antenna at offsets of up to 25 m. The system requires minor refitting to change the functioning frequency, and has been operationally validated at 0.4 and 1.6 kHz. The receiver signal can be measured by off-the-shelf digital multimeters. Future directions will focus on improving the electronic and mechanical stability of the CSM-EM with the goal of using acquired data to make quantitative measurements of subsurface resistivity.

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Parshin, Alexander, Ayur Bashkeev, Yuriy Davidenko, Marina Persova, Sergey Iakovlev, Sergey Bukhalov, Nikolay Grebenkin, and Marina Tokareva. "Lightweight Unmanned Aerial System for Time-Domain Electromagnetic Prospecting—The Next Stage in Applied UAV-Geophysics." Applied Sciences 11, no. 5 (February 26, 2021): 2060. http://dx.doi.org/10.3390/app11052060.

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Nowadays in solving geological problems, the technologies of UAV-geophysics, primarily magnetic and gamma surveys, are being increasingly used. However, for the formation of the classical triad of airborne geophysics methods in the UAV version, there was not enough technology for UAV-electromagnetic sounding, which would allow studying the geological environment at depths of tens and hundreds of meters with high detail. This article describes apparently the first technology of UAV-electromagnetic sounding in the time domain (TDEM, TEM), implemented as an unmanned system based on a light multi-rotor UAV. A measuring system with an inductive sensor—an analogue of a 20 × 20 or 50 × 50 m receiving loop is towed by a UAV, and a galvanically grounded power transmitter is on the ground and connected to a pulse generator. The survey is carried out along a network of parallel lines at low altitude with a terrain draping at a speed of 7–8 m/s, the maximum distance of the UAV’s departure from the transmitter line can reach several kilometers, thus the created technology is optimal for performing detailed areal electromagnetic soundings in areas of several square kilometers. The results of the use of the unmanned system (UAS) in real conditions of the mountainous regions of Eastern Siberia are presented. Based on the obtained data, the sensitivity of the system was simulated and it was shown that the developed technology allows one to collect informative data and create geophysical sections and maps of electrical resistivity in various geological situations. According to the authors, the emergence of UAV-TEM systems in the near future will significantly affect the practice of geophysical work, as it was earlier with UAV-magnetic prospecting and gamma-ray survey.

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Дисертації з теми "Electromagnetic induction geophysic"

Callegary, James Briggs. "Spatial sensitivity of low-induction-number frequency-domain electromagnetic-induction instruments." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/282901.

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Numerical simulations were used to study spatial averaging in low-induction-number frequency-domain electromagnetic induction (LIN FEM) instruments. Local ( LS) and cumulative (CS) sensitivity were used to analyze three different aspects of LIN FEM spatial sensitivity. LS is the variation in a measured property given a small change at a given location of the property of interest. CS contours are derived from LS and reveal the shape and the fraction of total instrument sensitivity enclosed within the contours. The first study re-evaluated the asymptotic approach to LIN FEM spatial sensitivity. Using this approach, LIN FEM measurements have often been assumed to represent electrical conductivity (sigma) at discreet depths that do not vary with the sigma of the ground. This assumption was tested using simulations of electromagnetic fields in environments with homogeneous and layered sigma distributions. When the induction number was greater than 0.01, the 1-D vertical CS distribution and the depth of investigation varied up to 20% over the range of sigma simulated. As sigma increased, CS contours and depth of investigation decreased in depth. In the second study a small perturbation approach was used to calculate CS distributions so that each distribution is unique to a given LS distribution. CS was summed from regions of high to low LS, and retained information on the magnitude and location of LS. As sigma increased, CS became focused around the highest LS values. The maximum reduction in depth of investigation was about 40% at the highest sigma investigated. In the final study, a series of small, electrically conductive perturbations was simulated in a three-dimensional, homogeneous environment. Three-dimensional LS varied markedly with a large difference between horizontal (HMD) and vertical (VMD) orientations of the transmitter and receiver dipoles. In some regions, the calculated magnetic field intensity with the perturbation was less than that calculated for the host without the perturbation. This occurred for both VMD and HMD orientations of the transmitter. CS contours were highly complex. One dimensional, vertical LS curves extracted from the three-dimensional data were very different from curves from infinite layer simulations.

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Stalnaker, Jack Lee. "A finite element approach to the 3D CSEM modeling problem and applications to the study of the effect of target interaction andtopography." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2770.

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The solution of the secondary coupled-vector potential formulation of Maxwell??s equations governing the controlled-source electromagnetic (CSEM) response of an arbitrary, threedimensionalconductivitymodelmust be calculatednumerically.The ﬁnite elementmethod is attractive, because it allows the model to be discretized into an unstructured mesh, permitting the speciﬁcation of realistic irregular conductor geometries, and permitting the mesh to be reﬁned locally, where ﬁner resolution is needed. The calculated results for a series ofsimple test problems, ranging from one-dimensionalscalar diﬀerentialequations to three-dimensional coupled vector equations match the known analytic solutions well, with error values several orders of magnitude smaller than the calculated values. The electromagnetic ﬁelds of a fully three-dimensional CSEM model, recovered from the potentials using the moving least squares interpolation numerical diﬀerentiation algorithm, compares well with published numerical modeling results, particularly when local reﬁnement is applied. Multiple buried conductors in a conductive host interact via mutual induction and current ﬂow through the host due to the dissipation of charge accumulated on the conductor boundary. The eﬀect of this interaction varies with host conductivity, transmitter frequency, and conductor geometry, orientation, and conductivity. For three test models containingtwo highly conductive plate-like targets, oriented in various geometries (parallel, perpendicular, and horizontal), mutual coupling ranges as high as twenty times the total magnetic ﬁeld. The eﬀect of varying host conductivity is signiﬁcant, especially at high frequencies. Numerical modeling also shows that the vorticity of the currents density induced in a vertically oriented plate-like conductor rotates from vertical at high frequencies, to horizontal at low frequencies, a phenomenon conﬁrmed by comparison with time domain ﬁeld data collected in Brazos County, Texas. Furthermore, the eﬀect of the presence of a simple horst on the CSEM response of a homogeneous conductive earth is signiﬁcant, even when the height of the horst is only a fraction of the skin depth of the model. When the transmitter is placedon topofthe horst, the currents inducedtherein account for nearly all of the total magnetic ﬁeld of the model, indicating that topography, like mutual coupling must be accounted for when interpreting CSEM data.

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Harris, Jane C. "Pieces of a Puzzle: Fitting Electromagnetic Induction into Geophysical Strategies to Produce Enhanced Archaeological Characterisation." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/15743.

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Electromagnetic induction (EM) methods have been utilised in a recent surge of archaeological applications across continental Europe, Ireland and Scandinavia. Development of multi-exploration depth instruments and improvements to instrument stability have improved its reputation as an effective method for mapping archaeological remains. Despite these advances, EM methods are comparatively lacking in rigour when for British sites. Through a structured scheme of experimental analysis and fieldwork, this thesis develops an understanding of the responses of EM instruments over a range of British archaeology, including earthworks, field systems, burials, modern remains, and a Cistercian abbey; the results of which demonstrate its effective over a diversity of environments. The impact of instrument-based issues on the collected measurements was quantified through a scheme of experiments targeting instrument drift, calibration and elevation. Dedicated instrument operation and processing workflows were developed based on the collective field and experimental results, which recommend best practice guidelines for improving the quality and accuracy of collected data. The link between instrument measurements and buried archaeology was further developed through a structured analysis of the EM datasets with complementary earth resistance and magnetic results. The integration of the EM, earth resistance and magnetic datasets was utilised to develop an enhanced archaeological characterisation of subsurface features. While the earth resistance and magnetic methods generally responded to different aspects of the buried archaeology, the EM surveys were able to detect a range of responses evident in the results of the former methods. Therefore, the role of EM methods within this characterisation are shown to “bridge the gap” between the earth resistance and magnetic methods, while providing a comprehensive characterisation of the remains in their own right.

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Parks, Eric M. "Analysis of Electromagnetic and Seismic Geophysical Methods for Investigating Shallow Sub-surface Hydrogeology." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2007.

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An integrated electromagnetic (EM) and seismic geophysical study was performed to evaluate non-invasive approaches to estimate depth to shallow groundwater in arid environments with elevated soil salinity where the installation of piezometers would be impractical or prohibited. Both methods were tested in two study areas (semi-arid and arid respectively), one in Palmyra, Utah, USA near the shore of Utah Lake where groundwater is shallow and unconfined in relatively homogeneous lacustrine sediments. The other area is Carson Slough, Nevada, USA near Ash Meadows National Wildlife Refuge in Amargosa Valley. The area is underlain by valley fill, with generally variable shallow depths to water in an ephemeral braided stream environment. The methods used include frequency domain electromagnetic induction allowing for multiple antenna-receiver spacings. High resolution compressional P-wave seismic profiles using a short (0.305 m) geophone spacing for common depth-point reflection stacking and first arrival modeling were also acquired. Both methods were deployed over several profiles where shallow piezometer control was present. The semi-arid Palmyra site with its simpler geohydrology serves as an independent calibration to be compared to the Carson Slough Site. EM results at both sites show that water surfaces correspond with a drop in conductivity. This is due to elevated concentrations of evaporative salts in the vadose zone immediately above the water table. EM and seismic profiles at the Palmyra site were readily correlated to depth to groundwater in monitoring wells demonstrating that the method is ideal under laterally homogeneous conditions. Interpreting the EM and seismic profiles at Carson Slough was challenging due to the laterally and vertically variable soil types, segmented perched water surfaces, and strong salinity variations. The high-resolution images and models provided by the seismic profiles confirm the simple soil and hydrological structure at the Palmyra site as well as the laterally complex structure at Carson Slough. The EM and seismic results indicate that an integrated geophysical approach is necessary for an area like Carson Slough, where continued leaching of salts combined with braided stream deposition has created a geophysically complex soil and groundwater system.

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McGarr, Jeffery T. "Geophysical Imaging of Hyporheic Mixing Dynamics Within Compound Bar Deposits." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1617109253147661.

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Carsillo, Vincent John. "MONITORING STORMWATER INFILTRATION IN A VACANT LOT COMPARING TIME-LAPSE ELECTROMAGNETIC INDUCTION AND ELECTRICAL RESISTIVITY TOMOGRAPHY." Master's thesis, Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/518905.

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Geology
M.S.
Vacant lots in cities and surrounding urban areas can potentially be used for stormwater management because they are pervious. However, the extent to which vacant lots provide pervious cover to increase infiltration and reduce stormflow is poorly understood. The goal of this study was to develop faster methods for monitoring stormwater infiltration to improve characterization of heterogeneous urban systems. Geophysical techniques are capable of mapping and characterizing subsurface materials, but are often limited by time and sensitivity constraints. In this study, the infiltration characteristics of a vacant lot created by the demolition of a house was characterized using a series of modeling, field and lab experiments. Site characterization under background conditions with an EM Profiler was used to map zones of different fill materials. Three zones were identified in the study site: grass area, driveway area, and a former house area. Transient soil moisture conditions were monitored during irrigation tests using two geophysical methods (electrical resistivity tomography [ERT] and electromagnetic induction [EM]) to evaluate method sensitivity and differences between the three zones. ERT proved more sensitive than EM profiling at detecting changes in the three zones. Soil moisture changes in the driveway area were particularly difficult to detect using EM. The EM Profiler showed a reduction rather than increase in conductivity at the start of irrigation and storms, which was attributed to flushing of high conductivity pore fluids by dilute irrigation or rain water. This explanation was supported using Archie’s Law to model the response of apparent conductivity under highly conductive pore fluid conditions. The EM Profiler was also used under natural precipitation conditions to quickly monitor areas too large for the ERT to reasonably survey. The results suggested that EM instrument drift needs to be corrected to make the method more sensitive. It was difficult to detect differences in hydrologic characterization between areas of the vacant lot using traditional soil point measurements because of the inherent spatial variability. The most useful point measurement was soil moisture loggers. Data from soil moisture loggers was used to parameterize the model; in addition, the soil moisture loggers showed a slow drying period. By combining the EM Profiler method with soil moisture data and applying corrections for drift, some improvement in sensitivity might be achieved. Quantitative characterization of fill material was shown by ERT, which detected more heterogeneous infiltration in the area of the former house than in the grass area.
Temple University--Theses

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Kruske, Montana L., and Dr Eileen G. Ernenwein. "Paleochannel or Palisade? Preliminary Geophysical Investigations of a Linear Feature at the Runion Archaeological Site, Washington County, Tennessee." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/74.

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Runion is a protohistoric Native American village located on the floodplain of the Nolichucky River in western Washington County. Previous archaeological excavations and radiocarbon dates suggest that the village was occupied during the mid-16th to mid-17th century. The Nolichucky River, in contrast, has been flowing through the area for millennia. Geophysical surveys are used to image the subsurface non-invasively, without disturbing protected land and/or organisms. Preliminary geophysical data collected at Runion include ground penetrating radar (GPR), electromagnetic induction (EMI), and magnetometry. These data show a linear feature surrounding the protohistoric village. Given its placement around the margins of the village, the feature could be interpreted as a fortification ditch, which is often paired with a palisade wall to defend a village from attack. The feature is also consistent with typical meandering floodplain stratigraphy, where sections of channel are often abandoned to form oxbow lakes. Over time these abandoned channels fill in and are called paleochannels. Each geophysical method measures the properties and characteristics of the linear feature, a presumed paleochannel. GPR sends electromagnetic radar waves into the ground, which reflect off different subsurface layers and are recorded as radargrams. Magnetometry measures subtle changes in earth magnetism, including the magnetization of rocks, soils, and/or ferrous objects. EMI systems transmit low frequency electromagnetic waves to measure both electrical conductivity (EC) and magnetic susceptibility (MS). Each of these instruments are used to collect data in transects and then processed to produce profiles, maps and, in the case of GPR, three-dimensional datasets of the subsurface. It is anticipated that GPR will reveal details about the stratigraphy of the linear feature. Magnetic, EC, and MS measurements will further help to interpret the GPR data by distinguishing between different types of sediments. These data may show if the feature is a paleochannel or a ditch excavated into older stratigraphic layers by village inhabitants for fortification. Ultimately, the feature will be tested with soil cores to study the sediments directly. At this preliminary stage the feature is interpreted to be a paleochannel. The stratigraphic layers revealed by GPR show a broad depression with stratigraphic layers characteristic of a paleochannel. In addition, magnetic readings are anomalously low on the eastern margin (closer to the modern river channel) and high on the western margin. This could indicate paired point bar sands and paleochannel fill, respectively. This interpretation is still tentative, however, because we have not yet integrated the EMI data, extracted soil cores, or dated the feature. Radiocarbon dates might help determine the relative age of the feature if organic carbon is present. In conclusion, preliminary data currently suggests that the structure is geological rather than archaeological. In the coming months we will collect more GPR data with different frequency GPR antennas, integrate the EMI data, and test the findings by extracting soil cores and reconstructing the stratigraphy.

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Beskardes, Gungor Didem. "Geophysical Imaging of Earth Processes: Electromagnetic Induction in Rough Geologic Media, and Back-Projection Imaging of Earthquake Aftershocks." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77891.

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This dissertation focuses on two different types of responses of Earth; that is, seismic and electromagnetic, and aims to better understand Earth processes at a wider range of scales than those conventional approaches offer. Electromagnetic responses resulting from the subsurface diffusion of applied electromagnetic fields through heterogeneous geoelectrical structures are utilized to characterize the underlying geology. Geology exhibits multiscale hierarchical structure which brought about by almost all geological processes operating across multiple length scales and the relationship between multiscale electrical properties of underlying geology and the observed electromagnetic response has not yet been fully understood. To quantify this relationship, the electromagnetic responses of textured and spatially correlated, stochastic geologic media are herein presented. The modelling results demonstrate that the resulting electromagnetic responses present a power law distribution, rather than a smooth response polluted with random, incoherent noise as commonly assumed; moreover, they are examples of fractional Brownian motion. Furthermore, the results indicate that the fractal behavior of electromagnetic responses is correlated with the degree of the spatial correlation, the contrasts in ground electrical conductivity, and the preferred orientation of small-scale heterogeneity. In addition, these inferences are also supported by the observed electromagnetic responses from a fault zone comprising different lithological units and varying wavelengths of geologic heterogeneity. Seismic signals generated by aftershocks are generally recorded by local aftershock networks consisted of insufficient number of stations which result in strongly spatially-aliased aftershock data. This limits aftershock detections and locations at smaller magnitudes. Following the 23 August 2011 Mineral, Virginia earthquake, to drastically reduce spatial aliasing, a temporary dense array (AIDA) consisting of ~200 stations at 200-400 m spacing was deployed near the epicenter to record the 12 days of the aftershocks. The backprojection imaging method is applied to the entire AIDA dataset to detect and locate aftershocks. The method takes advantage of staking of many seismograms and improves the signal-to-noise ratio for detection. The catalog obtained from the co-deployed, unusually large temporal traditional network of 36 stations enabled a quantitative comparison. The aftershock catalog derived from the dense AIDA array and the backprojection indicates event detection an order of magnitude smaller including events as small as M–1.8. The catalog is complete to magnitude –1.0 while the traditional network catalog was complete to M–0.27 for the same time period. The AIDA backprojection catalog indicate the same major patterns of seismicity in the epicentral region, but additional details are revealed indicating a more complex fault zone and a new shallow cluster. The b-value or the temporal decay constant were not changed by inclusion of the small events; however, they are different for two completeness periods and are different at shallow depth than greater depth.
Ph. D.

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Gaona, Garcia Jaime. "Groundwater-stream water interactions: point and distributed measurements and innovative upscaling technologies." Doctoral thesis, Università degli studi di Trento, 2019. http://hdl.handle.net/11572/242544.

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The need to consider groundwater and surface water as a single resource has fostered the interest of the scientific community on the interactions between surface water and groundwater. The region below and alongside rivers where surface hydrology and subsurface hydrology concur is the hyporheic zone. This is the region where water exchange determines many biogeochemical and ecological processes of great impact on the functioning of rivers. However, the complex processes taking place in the hyporheic zone require a multidisciplinary approach. The combination of innovative point and distributed techniques originally developed in separated disciplines is of great advantage for the indirect identification of water exchange in the hyporheic zone. Distributed techniques using temperature as a tracer such as fiber-optic distributed temperature sensing can identify the different components of groundwater-surface water interactions based on their spatial and temporal thermal patterns at the sediment-water interface. In particular, groundwater, interflow discharge and local hyporheic exchange flows can be differentiated based on the distinct size, duration and sign of the temperature anomalies. The scale range and resolution of fiber-optic distributed temperature sensing are well complemented by geophysics providing subsurface structures with a similar resolution and scale. Thus, the use of fiber-optic distributed temperature sensing to trace flux patterns supported by the exploration of subsurface structures with geophysics enables spatial and temporal investigation of groundwater-surface water interactions with an unprecedented level of accuracy and resolution. In contrast to the aforementioned methods that can be used for pattern identification at the interface, other methods such as point techniques are required to quantify hyporheic exchange fluxes. In the present PhD thesis, point methods based on hydraulic gradients and thermal profiles are used to quantify hyporheic exchange flows. However, both methods are one-dimensional methods and assume that only vertical flow occurs while the reality is much more complex. The study evaluates the accuracy of the available methods and the factors that impact their reliability. The applied methods allow not only to quantify hyporheic exchange flows but they are also the basis for an interpretation of the sediment layering in the hyporheic zone. For upscaling of the previous results three-dimensional modelling of flow and heat transport in the hyporheic zone combines pattern identification and quantification of fluxes into a single framework. Modelling can evaluate the influence of factors governing groundwater-surface water interactions as well as assess the impact of multiple aspects of model design and calibration of high impact on the reliability of the simulations. But more importantly, this modelling approach enables accurate estimation of water exchange at any location of the domain with unparalleled resolution. Despite the challenges in 3D modelling of the hyporheic zone and in the integration of point and distributed data in models, the benefits should encourage the hyporheic community to adopt an integrative approach comprising from the measurement to the upscaling of hyporheic processes.

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Downs, Christine Marie. "Imaging Wetland Hydrogeophysics: Applications of Critical Zone Hydrogeophysics to Better Understand Hydrogeologic Conditions in Coastal and Inland Wetlands and Waters." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7397.

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This dissertation consists of three projects utilizing electric and electromagnetic (EM) methods to better understand critical-zone hydrogeologic conditions in select Florida wetlands and waters. First, a time-lapse electrical resistivity (ER) survey was conducted in section of mangrove forest on a barrier island in southeast Florida to image changes in pore-water salinity in the root zone. ER data show the most variability in the root zone over a 24-hour period, and, generally, the ground is more resistive during the day than overnight. Second, a suite of three-dimensional forward models, based on varying lateral boundaries and conductivities typical of a coastal wetland, were run to simulate the EM response of a commerical electromagnetic induction instrument crossing over said boundaries. Normalized profiles show the transition is sharper in a hypersaline regime than one where freshwater and clay are present. Furthermore, enough variability exists in hypersaline regimes to justify collecting profile measurements in multiple coil configurations to constrain the nature of a lateral boundary. Also, under certain circumstances, there are kinks in the EMI response even across abrupt boundaries due to concentrated current density at a layer's edge. Lastly, geophysical surveys were conducted at six wetlands in west-central Florida to characterize potential hydrostratigraphic units and compare/contrast them to the current conceptual model for cypress dome wetlands. ER was used to image the geometry of the top of limestone; ground penetrating radar (GPR) was used to image stratigraphy beneath and surrounding wetlands. These wetlands can be grouped into two models. Topographic highs surrounding wetlands are controlled by the undulating top of limestone at sites where the region is characterized by limestone ridges. In contrast, topographic highs are controlled by thick sand packages at sites regionally characterized by sand dunes over scoured limestone.

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Книги з теми "Electromagnetic induction geophysic"

Handbook of geophysics and archaeology. London, U.K: Equinox Pub., 2004.

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Kaufman, Alex A., and Gregory Itskovich. Basic Principles of Induction Logging: Electromagnetic Methods in Borehole Geophysics. Elsevier, 2017.

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Kaufman, Alex A., and Gregory Itskovich. Basic Principles of Induction Logging: Electromagnetic Methods in Borehole Geophysics. Elsevier Science & Technology Books, 2017.

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(Editor), A. A. Kaufman, and Yu A. Dashevsky (Editor), eds. Principles of Induction Logging (Methods in Geochemistry and Geophysics). Elsevier Science, 2003.

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Частини книг з теми "Electromagnetic induction geophysic"

Jardel, Karine, Paul Chesnais, and John Nicholls. "Archaeological field evaluations in Vieux-Aregenua: the benefits of combining geophysical surveys and trial trenches." In Advances in On- and Offshore Archaeological Prospection, 251–60. Kiel: Universitätsverlag Kiel | Kiel University Publishing, 2023. http://dx.doi.org/10.38072/978-3-928794-83-1/p26.

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The Roman city Vieux-Aregenua was already the subject of a pilot test. Magnetometer and electromagnetic induction (EMI) surveys were carried out. The trial trenches of the archaeological field evaluation were strategically placed as to take into account the results of the survey. The surveys allowed definition of the general layout, to characterise the areas and surfaces, and the identification of the buildings. The combined analysis of geophysics and trial trenches permitted the re-examination of the interpretation of geophysical anomalies.

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Wilken, Dennis, Fritz Jürgens, Dirk Bienen-Scholt, Bente Sven Majchczack, and Ruth Blankenfeldt. "Barge or tjalk? A wreck investigation in the tidal flats of North Frisia." In Advances in On- and Offshore Archaeological Prospection, 121–30. Kiel: Universitätsverlag Kiel | Kiel University Publishing, 2023. http://dx.doi.org/10.38072/978-3-928794-83-1/p13.

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"Electromagnetic Induction Methods." In Handbook of Agricultural Geophysics, 131–50. CRC Press, 2008. http://dx.doi.org/10.1201/9781420019353-13.

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"Electromagnetic Induction: A New Frontier." In Handbook of Geophysics and Archaeology, 147–98. Routledge, 2017. http://dx.doi.org/10.4324/9781315093260-7.

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"Case Studies in Electromagnetic Induction." In Handbook of Geophysics and Archaeology, 199–213. Routledge, 2017. http://dx.doi.org/10.4324/9781315093260-8.

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Florsch, Nicolas, Frédéric Muhlach, and Michel Kammenthaler. "The Electromagnetic Induction or “Slingram” Method." In Everyday Applied Geophysics 2, 93–128. Elsevier, 2018. http://dx.doi.org/10.1016/b978-1-78548-280-9.50002-4.

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Fitterman, David V., and Victor F. Labson. "10. Electromagnetic Induction Methods for Environmental Problems." In Near-Surface Geophysics, 301–56. Society of Exploration Geophysicists, 2005. http://dx.doi.org/10.1190/1.9781560801719.ch10.

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Shin, Ho-Chul, Guillaume Blanchy, Ian Shield, Peter Fruen, Timothy Barraclough, Christopher W. Watts, Andrew Binley, and William R. Whalley. "Geophysical methods to assess soil characteristics." In Advances in measuring soil health, 139–74. Burleigh Dodds Science Publishing, 2021. http://dx.doi.org/10.19103/as.2020.0079.12.

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This chapter explores the use of geophysical methods to assess soil physical characteristics. The chapter begins by reviewing the geophysical properties of soil, such as clay content and organic matter content. It then moves on to discuss the electromagnetic induction method and its application, then examines electrical resistivity and its application. Acoustic-to-seismic coupling is also reviewed in terms of creating a model and its application. The chapter concludes by providing an overview of the several geophysical methods that can be used to measure various characteristics of agricultural soils.

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"Mapping Pesticide Partition Coefcients By Electromagnetic Induction." In Handbook of Agricultural Geophysics, 255–62. CRC Press, 2008. http://dx.doi.org/10.1201/9781420019353-23.

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West, G. F., and J. C. Macnae. "1. Physics of the Electromagnetic Induction Exploration Method." In Electromagnetic Methods in Applied Geophysics, 5–46. Society of Exploration Geophysicists, 1991. http://dx.doi.org/10.1190/1.9781560802686.ch1.

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Тези доповідей конференцій з теми "Electromagnetic induction geophysic"

Won, I. J., Dean Keiswetter, and Elena Novikova. "Electromagnetic Induction Spectroscopy." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 1998. Environment and Engineering Geophysical Society, 1998. http://dx.doi.org/10.4133/1.2922497.

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Won, I. J., Dean Keiswetter, and Elena Novikova. "Electromagnetic Induction Spectroscopy." In 11th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems. European Association of Geoscientists & Engineers, 1998. http://dx.doi.org/10.3997/2214-4609-pdb.203.1998_016.

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Huang, Haoping, and I. J. Won. "Real Time Electromagnetic Induction Soundings." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 2002. Environment and Engineering Geophysical Society, 2002. http://dx.doi.org/10.4133/1.2927078.

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Huang, Haoping, and I. J. Won. "Real Time Electromagnetic Induction Soundings." In 15th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems. European Association of Geoscientists & Engineers, 2002. http://dx.doi.org/10.3997/2214-4609-pdb.191.13eem8.

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Norton, Stephen J., William A. San Filipo, and I. J. Won. "Reciprocity Formulas for Electromagnetic Induction Systems." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 1999. Environment and Engineering Geophysical Society, 1999. http://dx.doi.org/10.4133/1.2922699.

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Won, I. J., Dean Keiswetter, Thomas H. Bell, Jonathan Miller, and Bruce Barrow. "Electromagnetic Induction Spectroscopy for Landmine Identification." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 2000. Environment and Engineering Geophysical Society, 2000. http://dx.doi.org/10.4133/1.2922817.

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Won, I. J., Dean Keiswetter, Thomas H. Bell, Jonathan Miller, and Bruce Barrow. "Electromagnetic Induction Spectroscopy For Landmine Identification." In 13th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems. European Association of Geoscientists & Engineers, 2000. http://dx.doi.org/10.3997/2214-4609-pdb.200.2000_091.

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J. Norton, Stephen, William A. San Filipo, and I. J. Won. "Reciprocity Formulas For Electromagnetic Induction Systems." In 12th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems. European Association of Geoscientists & Engineers, 1999. http://dx.doi.org/10.3997/2214-4609-pdb.202.1999_105.

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Becker, A. "Resistivity Mapping with Airborne Electromagnetic Induction Apparatus." In Symposium on the Application of Geophysics to Engineering and Environmental Problems. Environment and Engineering Geophysical Society, 1990. http://dx.doi.org/10.4133/1.2921876.

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Becker, A. "Resistivity Mapping With Airborne Electromagnetic Induction Apparatus." In 3rd EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems. European Association of Geoscientists & Engineers, 1990. http://dx.doi.org/10.3997/2214-4609-pdb.212.1990_001.

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