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1

Shipp, Richard Michael. "Two-dimensional full wavefield inversion of wide-aperture marine seismic streamer data." Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/251747.

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2

Johansson, Linnéa. "Modelling and interpretation of VTEM data from Soppero, Sweden." Thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64879.

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The geological and geophysical knowledge about the northernmost part of Sweden has recently increased due to the Barents project, which includes acquisition of modern geophysical and geological information on behalf of the Swedish Geological Survey (SGU). During August 2013, a helicopter-borne versatile time domain electromagnetic (VTEM) survey was performed by Geotech Ltd, in the Soppero area northeast of Kiruna. From the VTEM measurements, a number of TEM anomalous zones have been identified and two of them are located south and southeast of the Lannavaara village. The main conductive features in the Lannavaara area can be explained by the presence of graphitic schist, which is spatially associated with a number of sulphide and iron oxide mineralisation occurrences. In this project, Maxwell thin sheet modelling and EM Flow conductivity-depth-imaging (CDI) software have been applied to selected anomalies in the Lannavaara area, for the purpose of extracting geometrical parameters of conductive features. This information has been used in order to confirm the structural framework of the area and evaluate the utility of VTEM measurements in this geological environment. In general, Maxwell thin sheet models of anomalies with small amplitudes show a better correlation with existing drill holes than models of anomalies with large amplitudes. The use of small amplitudes managed to confirm the structural model in the central part of the investigated area, which is an anticline. However, the use of different models and their distribution across the area is limited. Compared with Maxwell, CDIs from EM Flow provided a better way of confirming the general structural model in the area, although they include artefacts due to strong lateral gradients in conductivity. The Lannavaara area has also been investigated by VLF, Slingram and magnetic measurements and based on these data, multivariate analysis in SiroSOM reveals a strong correlation between VTEM and Slingram data, while VLF data appears to have much less or more complicated correlation with the other data sets. In summary, the results from the various software raise a question about the geological complexity in parts of the Lannavaara area, which may include multiple layers of graphitic schist, possibly expressed as smooth transitions in conductivity when represented by data from electromagnetic methods.
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3

Pairmain, D. "Image processing in geophysics." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375293.

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4

Cheung, See Nga Cecilia. "Experimental deformation in sandstone, carbonates and quartz aggregate." Thesis, State University of New York at Stony Brook, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3717020.

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The first part of my thesis is mainly focused on the effect of grain size distribution on compaction localization in porous sandstone. To identify the microstructural parameters that influence compaction band formation, I conducted a systematic study of mechanical deformation, failure mode and microstructural evolution in Bleurswiller and Boise sandstones, of similar porosity (∼25%) and mineralogy but different sorting. Discrete compaction bands were observed to develop over a wide range of pressure in the Bleurswiller sandstone that has a relatively uniform grain size distribution. In contrast, compaction localization was not observed in the poorly sorted Boise sandstone. My results demonstrate that grain size distribution exerts important influence on compaction band development, in agreement with recently published data from Valley of Fire and Buckskin Gulch, as well as numerical studies.

The second part aimed to improve current knowledge on inelastic behavior, failure mode and brittle-ductile transition in another sedimentary rock, porous carbonates. A micritic Tavel (porosity of ∼13%) and an allochemical Indiana (∼18%) limestones were deformed under compaction in wet and dry conditions. At lower confining pressures, shear localization occurred in brittle faulting regime. Through transitional regime, the deformation switched to cataclastic flow regime at higher confining pressure. Specifically in the cataclastic regime, the (dry and wet) Tavel and dry Indiana failed by distributed cataclastic flow, while in contrast, wet Indiana failed as compaction localization. My results demonstrate that different failure modes and mechanical behaviors under different deformation regimes and water saturation are fundamental prior to any geophysical application in porous carbonates.

The third part aimed to focus on investigating compaction on quartz aggregate starting at low (MPa) using X-ray diffraction. We report the diffraction peak evolution of quartz with increasing pressures. Through evaluating the unit cell lattice parameters and the volume of the quartz sample, macroscopic stress and strain were resolved. Moreover, we observed quartz peak broadened asymmetrically at low pressure, such extent is more prominent in axial than in radial direction. Our evaluation on peak [101] (highest intensity among peaks) demonstrated that full width at half maximum can be a good proxy for microscopic stress distribution. We observed deviations in the pressure-volume curves at P = ∼0.4 GPa and speculated that it was the point of which onset of grain crushing and pore collapse occur in quartz. This is on the same order of which onset of grain crushing (commonly known as P*) is observed in sandstones in the rock mechanics literature. This demonstrated that there is potential in estimating grain crushing and pore collapse pressure with our technique.

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5

Perez, Altimar Roderick. "Brittleness estimation from seismic measurements in unconventional reservoirs| Application to the Barnett shale." Thesis, The University of Oklahoma, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3617030.

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Brittleness is a key characteristic for effective reservoir stimulation and is mainly controlled by mineralogy in unconventional reservoirs. Unfortunately, there is no universally accepted means of predicting brittleness from measures made in wells or from surface seismic data. Brittleness indices (BI) are based on mineralogy, while brittleness average estimations are based on Young's modulus and Poisson's ratio. I evaluate two of the more popular brittleness estimation techniques and apply them to a Barnett Shale seismic survey in order to estimate its geomechanical properties. Using specialized logging tools such as elemental capture tool, density, and P- and S wave sonic logs calibrated to previous core descriptions and laboratory measurements, I create a survey-specific BI template in Young's modulus versus Poisson's ratio or alternatively λρ versus μρ space. I use this template to predict BI from elastic parameters computed from surface seismic data, providing a continuous estimate of BI estimate in the Barnett Shale survey. Extracting λρ-μρ values from microseismic event locations, I compute brittleness index from the template and find that most microsemic events occur in the more brittle part of the reservoir. My template is validated through a suite of microseismic experiments that shows most events occurring in brittle zones, fewer events in the ductile shale, and fewer events still in the limestone fracture barriers.

Estimated ultimate recovery (EUR) is an estimate of the expected total production of oil and/or gas for the economic life of a well and is widely used in the evaluation of resource play reserves. In the literature it is possible to find several approaches for forecasting purposes and economic analyses. However, the extension to newer infill wells is somewhat challenging because production forecasts in unconventional reservoirs are a function of both completion effectiveness and reservoir quality. For shale gas reservoirs, completion effectiveness is a function not only of the length of the horizontal wells, but also of the number and size of the hydraulic fracture treatments in a multistage completion. These considerations also include the volume of proppant placed, proppant concentration, total perforation length, and number of clusters, while reservoir quality is dependent on properties such as the spatial variations in permeability, porosity, stress, and mechanical properties. I evaluate parametric methods such as multi-linear regression, and compare it to a non-parameteric ACE to better correlate production to engineering attributes for two datasets in the Haynesville Shale play and the Barnett Shale. I find that the parametric methods are useful for an exploratory analysis of the relationship among several variables and are useful to guide the selection of a more sophisticated parametric functional form, when the underlying functional relationship is unknown. Non-parametric regression, on the other hand, is entirely data-driven and does not rely on a pre-specified functional forms. The transformations generated by the ACE algorithm facilitate the identification of appropriate, and possibly meaningful, functional forms.

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6

TROTTER, BENNETT. "Pore Pressure Prediction in the Point Pleasant Formation in the Appalachian Basin, in parts of Ohio, Pennsylvania, and West Virginia, United States of America." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524213528591632.

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7

Bey, Scott Michael. "Reservoir Characterization and Seismic Expression of the Clinton Interval over Dominion's Gabor Gas Storage Field in North-East Ohio." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1347391687.

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8

Persson, Kjell. "Integrated geophysical-geochemical methods for archaeological prospecting." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279.

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9

Chapel, Brian Ernie. "Digital disk recorder for geophysics." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24592.

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This thesis describes the design and testing of a floppy disk drive based digital recorder. The device was originally built for a geomagnetic research project, but is also suitable for other phenomena with time scales from fractions of a second to approximately one day. The system is designed specifically to improve the reliability for long-term observing programs and to enhance the efficency of the subsequent data analysis procedures. Using an STD-Z80 BUS microcomputer, under the control of a Forth language program, the recorder stores digital data on removable 8-inch floppy disks. This thesis explicitly addresses the issue of cost and provides the necessary detail for reproduction of the device. A procedure is described for preparing the acquired data for analysis using computing facilities equiped with an appropriate disk reader. Also presented is a quantitative and qualitative evaluation of the recorder's performance when applied to both synthetic and natural signals. The latter include geomagnetically induced currents in power transmission lines.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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10

Garrick-Bethell, Ian 1980. "Early lunar geology and geophysics." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/47845.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2009.
Includes bibliographical references.
Despite a number of human and robotic missions to the Moon, there are still important unanswered questions about its early evolution, and how it came to be the object we observe today. Here we use observational, experimental, and theoretical techniques to examine three important events that took place early in lunar history and have left a lasting signature. The first event is the formation of the largest basin on the Moon, the South Pole-Aitken Basin. We develop a systematic method to define the previously unknown boundaries of this degraded structure and quantify its gross shape. We also combine a number of remote sensing data sets to constrain the origin of heat producing elements in its interior. The second event we examine is the evolution of the lunar orbit, and the coupling between the Moon's early geophysical properties and the growth of orbital eccentricity. We use analytical models for tidal deformations and orbit evolution to show that the shape of the Moon suggests its early orbit was highly eccentric. However, we are also able to explain the presently high eccentricity entirely by traditional, secular tidal growth while the early Moon was hot. The third event we examine is the magnetization of lunar samples. We perform extensive paleomagnetic measurements of an ancient, deep-seated lunar sample, and determine that a long-lived magnetic field like that of a core dynamo is the most plausible explanation for its magnetic remanence. In sum, the earliest portion of lunar history has been largely obscured by later geologic events, but a great deal can still be learned from this formative epoch.
by Ian Garrick-Bethell.
Ph.D.
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11

Spurr, Charles. "Seismic Analyses of the Crust and Moho beneath the Foreland Fold and Thrust Belt of the Southern Urals, Russia." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1441883731.

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12

Shank, Jared Wyatt. "A geophysical investigation to locate missing graves utilizing ground penetrating radar, electromagnetic, and magnetic methods." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1389704983.

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13

Torikka, Niklas. "3D Modelling of TEM Data : from Rajapalot Gold-Cobalt prospect, northern Finland." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75756.

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The Rajapalot gold-cobalt project in northern Finland is an exciting, relatively new discovery, still being explored with hopes to start mining in the future. The area was found by a IP/Resistivity survey in 2013. Extensive geophysical follow-up surveys have delineated several electromagnetic targets, one of which, named Raja, is the target anomaly this master thesis is built upon. A TEM survey was carried out during late August to early September 2018. The data collected was analyzed, processed and later modelled in Maxwell using Leroi, a CSIRO module. Three separate models are produced with one, two, and three plates respectively. The result is compared to existing VTEM and resistivity models.
Rajapalot guld-kobolt-projektet i norra Finland är en spännande, relativt ny upptäckt som fortfarande undersöks med hopp om att starta gruvbrytning i framtiden. Området upptäcktes via en IP/Resistivitets-undersökning under 2013. Omfattande geofysiska undersökningar har avgränsat flera elektromagnetiska anomalier, varav en, döpt Raja, är den anomali som den här masteruppsatsen är uppbyggd kring. En TEM-undersökning utfördes under slutet av augusti, början av september 2018. Insamlade data analyserades, bearbetades och modellerades senare i Maxwell med hjälp av Leroi, en insticksmodul från CSIRO. Tre separata modeller togs fram med respektive, en, två, och tre plattor. Resultatet jämfördes mot befintliga VTEM-, och resistivitetsmodeller.
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14

Schmidt, Armin R. "Visualisation of multi-source archaeological geophysics data." Rome: Fondazione Ing. Carlo M. Lerici, 2002. http://hdl.handle.net/10454/3281.

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15

Flocco, Daniela. "The geophysics of Antarctic coastal polynyas." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613014.

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16

Morse, David L. "Glacier geophysics at Taylor Dome, Antarctica /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/6801.

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17

Linde, Niklas. "Characterization of Hydrogeological Media Using Electromagnetic Geophysics." Doctoral thesis, Uppsala universitet, Geofysik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5912.

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Radio magnetotellurics (RMT), crosshole ground penetrating radar (GPR), and crosshole electrical resistance tomography (ERT) were applied in a range of hydrogeological applications where geophysical data could improve hydrogeological characterization. A profile of RMT data collected over highly resistive granite was used to map subhorizontal fracture zones below 300m depth, as well as a steeply dipping fracture zone, which was also observed on a coinciding seismic reflection profile. One-dimensional inverse modelling and 3D forward modelling with displacement currents included were necessary to test the reliability of features found in the 2D models, where the forward models did not include displacement currents and only lower frequencies were considered. An inversion code for RMT data was developed and applied to RMT data with azimuthal electrical anisotropy signature collected over a limestone formation. The results indicated that RMT is a faster and more reliable technique for studying electrical anisotropy than are azimuthal resistivity surveys. A new sequential inversion method to estimate hydraulic conductivity fields using crosshole GPR and tracer test data was applied to 2D synthetic examples. Given careful surveying, the results indicated that regularization of hydrogeological inverse problems using geophysical tomograms might improve models of hydraulic conductivity. A method to regularize geophysical inverse problems using geostatistical models was developed and applied to crosshole ERT and GPR data collected in unsaturated sandstone. The resulting models were geologically more reasonable than models where the regularization was based on traditional smoothness constraints. Electromagnetic geophysical techniques provide an inexpensive data source in estimating qualitative hydrogeological models, but hydrogeological data must be incorporated to make quantitative estimation of hydrogeological systems feasible.
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18

Cox, James. "Baker Wood creosoting site investigation using geophysics /." Connect to resource, 1999. http://hdl.handle.net/1811/28563.

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19

Saunders, Jonathan Howard. "Electrical inversion and characterisation methods in geophysics." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413721.

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20

Rio, Joao Filipe Meneses Espinheira. "Advances in laboratory geophysics using bender elements." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1348997/.

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Bender element transducers are used to determine the small-strain shear stiffness,Go, of soil, by determining the velocity of propagation of mechanical waves through tested samples. They are normally used in the laboratory, on their own or incorporated in geotechnical equipment such as triaxial cells or oedometers. Different excitation signals and interpretation methods are presently applied, each producing different results. The initial assumptions of unbounded wave propagation, generally used in bender element testing and inherited from seismic cross-hole testing, are quite crude and do not account for specific boundary conditions, which might explain the lack of reliability of the results. The main objective of this study is to establish the influence of the sample and transducer geometry in the behaviour of a typical bender element test system. Laboratory and numerical tests, supported by a theoretical analytical study, are conducted and the results presented in order to achieve this goal. An independent monitoring of the dynamic behaviour of the bender elements and samples is also carried out. Using a laser velocimeter, capable of recording the motion of the subjects without interference,their dynamic responses can be obtained and their mechanical properties verified. A parametric study dealing with sample geometry is presented, where 24 samples with different geometries are tested. Synthetic rubber is used as a substitute for soft clay, due to the great number of samples involved and the necessity of guarantee the constancy of their properties. The numerical analysis makes use of three-dimensional finite difference models with different geometries.A regressive analysis is possible since the elastic properties of the system are pre-determined and used to evaluate the results. A numerical analysis also has the benefit of providing the response not only at a single receiving point but at any node in the model.
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Al-Gezeri, Salem Mohammed. "Modelling of multivariate data in archaeological geophysics." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427765.

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22

Vichabian, Yervant. "An environment application of self-potential geophysics." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46086.

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23

Pierce, Christian William. "Three-dimensional geophysics and visualisation in archaeology." Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/272182.

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24

Costall, Alexander Ross. "Hydro-geophysics in High-Quality Coastal Aquifers." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/82107.

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Electrical resistivity imaging (ERI) and groundwater solute transport modelling are developed for recovery of the hydrogeological architecture of coastal margins. ERI acquisition and processing parameters, along with the influence of hydraulic anisotropy and heterogeneity in karstic aquifers, are explored with examples selected along more than 100 km of coastline proximal to Perth Western Australia. The methods will contribute to accurate predictive groundwater modelling and sustainable management of high-quality coastal aquifers worldwide.
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25

Warino, Charles T. "Resistivity and Radar Images of Collapse Features Attributed to a Previously Undocumented Shallow Coal Mine in Summit County, Ohio." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1225717244.

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26

Unterborn, Cayman Thomas. "Before Biology: Geologic Habitability and Setting the Chemical and Physical Foundations for Life." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461193916.

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27

Veire, Helene Hafslund. "Combined Inversion of PP and PS Seismic Data for Static and Dynamic Reservoir Characterization." Doctoral thesis, Norwegian University of Science and Technology, Norwegian University of Science and Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-564.

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Reservoir properties are mainly determined based on well log information. However, wells in most reservoirs are sparse and widely spread compared to the size of the reservoir. Seismic data is thus one of the most important complementary sources of information used to build 3D models of hydrocarbon reservoirs. The need for a high quality reservoir description starts as soon as a discovery is made. In the appraisal phase, hydrocarbons in place and the amount of recoverable reserves are estimated based on the reservoir model. Improved structural models are also needed in optimal well placement during the production and development phase of a reservoir. Knowledge about saturation and pressure distributions in a reservoir are valuable both in the exploration and development phase of a reservoir. This knowledge is used to evaluate the size of a field, determine an optimal drainage pattern, and decide on optimal well design to reduce risks for blow-outs and damage on production equipment. Reducing uncertainty in reservoir property estimates from seismic data have large economic impact on the development of a hydrocarbon reservoir.

Quantitative reservoir property information can be obtained either through direct estimates of reservoir properties from seismic data or through estimates of elastic properties (velocities and densities) that are related to reservoir properties. The relationship between physical properties of rocks and fluids and P-wave seismic data are often empirical and non-unique. This leads to large uncertainties in reservoir models derived from pressure wave seismic data alone. Since shear waves do not propagate through fluids, combined use of pressure wave seismic data and shear wave seismic data might increase our ability to derive fluid and lithology properties from seismic data. One way to obtain information about shear wave velocities over a large area is to acquire multicomponent seismic data (for instance x, y, and z component geophone data). Parts of this thesis focus on methods to combine the information from multicomponent seismic data with pressure wave (hydrophone) seismic data. In this way we improve the accuracy in the estimates of pressure wave velocity, shear wave velocity and density in the subsurface.

To obtain information about changes in reservoir parameters like fluid saturation and pore pressure during production, comparisons between different vintages of seismic data acquired over the field can be performed. Differences in the seismic signal from the same area over a time period (time-lapse seismic data) can be interpreted as changes in reservoir properties. Benefits of improved reservoir characterization include ability to locate bypassed oil and mapping of fluid fronts. This leads to saved costs due to reduced number of misplaced wells, and increased production because of optimized well placement. In the early days of seismic reservoir monitoring, the analyses were qualitative, e.g. to identify undrained areas, analyzing the sealing capacity of faults, and detect drainage patterns. Today, time-lapse seismic analysis is still mainly qualitative. To be able to obtain more quantitative estimates of changes in reservoir properties from the time-lapse seismic data, we need to establish links between the rock parameters and the seismic data. I have used both time-lapse surface seismic data and time-lapse multicomponent seismic data to estimate production related changes in fluid saturation and pressure.

Finally, to be able to utilize rock physical information obtained from seismic reservoir characterization in reservoir modelling, information about uncertainties in the estimates are essential. One way to do this is to use deterministic models (rock physics models) that relates reservoir properties to seismic data, and assume that the model parameters are independent. However, the variables in these estimations are inherently dependent and should be treated as such. By formulating the problem in a Bayesian framework, dependencies between the different variables and spatial dependencies can easily be included. I have used both deterministic uncertainty analysis and Bayesian estimation methods to quantify uncertainties in the estimates.

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Yan, Fangzhou. "Application of Time-Frequency Analysis to Characterize Gas Shadows from the Clinton interval in Ohio Seismic Reflection Data." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1484039877315876.

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29

Fourie, Christoffel Johannes Stephanus. "In-situ subsurface density estimations using a seismic technique." Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01162009-110629/.

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Ortega, Gelabert Olga. "Advanced numerical techniques for inverse problems in geophysics." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670631.

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This thesis presents an efficient methodology to couple Model Order Reduction techniques within the framework of geophysical probabilistic inversion problems. Accurate models of the interaction between Earth inner processes and surface features are essential to make reliable predictions of the observables which are a fundamental part of Bayesian inference. Markov Chain Monte Carlo (MCMC) methods have become standard in dealing with probabilistic inversions and they rely on sampling strategies that require solving forward problems many times. Computationally expensive large-scale forward problems are the principal bottleneck that can limit the capabilities and potential of multi-observable geophysical probabilistic inversions. In particular, dynamical effects arising from the sub-lithospheric mantle flow are not usually taken into account in the estimation of surface elevation due to the high computational cost of the associated 3D Stokes flow problem. The main idea of this thesis is to use the Reduced Basis (RB) method as a surrogate of the true forward problem (3D Stokes flow) to provide fast and accurate approximations. The surrogate is then used to generate samples of the posterior distribution at a much lower computational cost. RB strategies are based on expressing the solution of a problem in a low dimensional space, i.e. a reduced basis. Taking advantage of the convergence nature of the MCMC, we propose a greedy strategy that builds the reduced basis on the fly and as required by the inverse problem. In doing so, the basis is specifically tailored to the posterior features of the problem. In addition, to guarantee an accurate surrogate we define a goal-oriented error estimator which focuses on a particular Quantity of Interest of the problem and, therefore, it guides the basis to achieve the required accuracy in such particular features. All this translates into a problem-shaped basis that is more compact and smaller than if it had to be accurate everywhere in the domain. Moreover, to deal with the costly assembly of matrices, we use the specific parametrization of the problem and sampling strategy to define an assembly procedure that efficiently updates the matrices only with the contribution of the elements that changed between successive inversion steps. The benefits and limitations of the method are illustrated through several numerical examples. Finally, to demonstrate the applicability of the method two more realistic inverse problems are presented. The first one uses dynamic topography to infer the Lithosphere-Asthenosphere Boundary depth of a spherical domain representing a portion of Earth and the second one is applied to a larger problem in which the African lithospheric structure is discretized in 1225 inversion parameters.
Aquesta tesi introdueix una metodologia eficient per acoblar tècniques de Reducció d’Ordre del Model dins el marc de problemes d’inversió probabilística en geofísica. Disposar de models precisos sobre la interacció entre els processos interns de la Terra i les característiques superficials és essencial per tal de fer prediccions fiables dels observables, ja que aquests són una part fonamental de la inferència Bayesiana. Els mètodes de Markov Chain Monte Carlo (MCMC) s’han convertit en un estàndard per tractar amb inversions probabilístiques i es basen en estratègies de mostreig que requereixen solucionar molts problemes directes moltes vegades. L’elevat cost computacional dels problemes directes a gran escala és el principal coll d’ampolla que pot limitar les capacitats i potencial de les inversions probabilístiques multi-observables en geofísica. En concret, els efectes dinàmics provinents del flux del mantell sub-litosfèric no es solen tenir en compte per a l’estimació de l’elevació de la superfície degut a l’elevat cost computacional derivat de resoldre el problema associat de flux de Stokes en 3D. La idea principal d’aquesta tesi es fer servir el mètode de la Base Reduida (RB) com a substitut del problema directe real (flux 3D Stokes) per tal d’obtenir aproximacions ràpides i precises. El substitut es fa servir per generar mostres de la distribució posterior amb un cost computacional molt inferior. Les estratègies RB es basen en expressar la solució d’un problema en un espai de baixa dimensió, i.e. una base reduïda. Aprofitant la naturalesa convergent del MCMC, proposem una estratègia “greedy” que construeix la base sobre la marxa i segons ho requereixi el problema invers. D’aquesta forma, la base està feta a mida per adaptar-se a les característiques posteriors del problema. A més, per tal de garantir la precisió del substitut, definim un estimador d’error “goal-oriented” que es centra en una Quantitat d’Interès específica del problema i, per tant, guia a la base per tal d’aconseguir la precisió necessària en aquelles característiques en particular. Tot això es tradueix en una base adaptada al problema que es més compacta i petita que si hagués de ser precisa en tot el domini. A més, per tal d’afrontar el car assemblatge de les matrius, utilitzem la parametrització del problema i l’estratègia de mostreig per definir una estratègia d’assemblatge que actualitza eficientment les matrius només amb la contribució d’aquells elements que han canviat entre passos successius de la inversió. Els beneficis i limitacions del mètode s’il·lustren a traves de varis exemples numèrics. Finalment, per demostrar l’aplicabilitat del mètode, es presenten dues inversions de problemes més realistes. El primer fa servir la topografia dinàmica per a obtenir la profunditat del límit Litosfera-Astenosfera en un domini esfèric que representa una part de la Terra i el segon s’aplica a un problema més gran en que l’estructura litosfèrica d’Àfrica està discretitzada en 1225 paràmetres.
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31

Shaw, Harold, and Francis A. Lawrence. "AIR FORCE GEOPHYSICS LABORATORY PORTABLE PCM GROUND STATION." International Foundation for Telemetering, 1985. http://hdl.handle.net/10150/615726.

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International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, Nevada
In early 1981, the Physical Science Laboratory (PSL) was tasked by the Air Force Geophysics Laboratory (AFGL) to develop a portable Pulse-Code Modulation (PCM) telemetry station that would acquire and support the higher PCM data rates from Ariestype rocket payloads. The station would have to provide real-time and near real-time calibration, prelaunch and launch test support to AFGL researchers involved in space vehicle probe analysis. The station would also have to utilize a flexible software system, transportable hardware, and be easily expanded to meet the continually growing and varied needs of the researchers.
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32

Abaunza, Víctor Eduardo Martínez. "Performance optimization of geophysics stencils on HPC architectures." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/183165.

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A simulação de propagação de onda é uma ferramenta crucial na pesquisa de geofísica (para análise eficiente dos terremotos, mitigação de riscos e a exploração de petróleo e gáz). Devido à sua simplicidade e sua eficiência numérica, o método de diferenças finitas é uma das técnicas implementadas para resolver as equações da propagação das ondas. Estas aplicações são conhecidas como estênceis porque consistem num padrão que replica a mesma computação num domínio multidimensional de dados. A Computação de Alto Desempenho é requerida para solucionar este tipo de problemas, como consequência do grande número de pontos envolvidos nas simulações tridimensionais do subsolo. A optimização do desempenho dos estênceis é um desafio e depende do arquitetura usada. Neste contexto, focamos nosso trabalho em duas partes. Primeiro, desenvolvemos nossa pesquisa nas arquiteturas multicore; analisamos a implementação padrão em OpenMP dos modelos numéricos da transferência de calor (um estêncil Jacobi de 7 pontos), e o aplicativo Ondes3D (um simulador sísmico desenvolvido pela Bureau de Recherches Géologiques et Minières); usamos dois algoritmos conhecidos (nativo, e bloqueio espacial) para encontrar correlações entre os parâmetros da configuração de entrada, na execução, e o desempenho computacional; depois, propusemos um modelo baseado no Aprendizado de Máquina para avaliar, predizer e melhorar o desempenho dos modelos estênceis na arquitetura usada; também usamos um modelo de propagação da onda acústica fornecido pela empresa Petrobras; e predizemos o desempenho com uma alta precisão (até 99%) nas arquiteturas multicore. Segundo, orientamos nossa pesquisa nas arquiteturas heterogêneas, analisamos uma implementação padrão do modelo de propagação de ondas em CUDA, para encontrar os fatores que afetam o desempenho quando o número de aceleradores é aumentado; então, propusemos uma implementação baseada em tarefas para amelhorar o desempenho, de acordo com um conjunto de configuração no tempo de execução (algoritmo de escalonamento, tamanho e número de tarefas), e comparamos o desempenho obtido com as versões de só CPU ou só GPU e o impacto no desempenho das arquiteturas heterogêneas; nossos resultados demostram um speedup significativo (até 25) em comparação com a melhor implementação disponível para arquiteturas multicore.
Wave modeling is a crucial tool in geophysics, for efficient strong motion analysis, risk mitigation and oil & gas exploration. Due to its simplicity and numerical efficiency, the finite-difference method is one of the standard techniques implemented to solve the wave propagation equations. This kind of applications is known as stencils because they consist in a pattern that replicates the same computation on a multi-dimensional domain. High Performance Computing is required to solve this class of problems, as a consequence of a large number of grid points involved in three-dimensional simulations of the underground. The performance optimization of stencil computations is a challenge and strongly depends on the underlying architecture. In this context, this work was directed toward a twofold aim. Firstly, we have led our research on multicore architectures and we have analyzed the standard OpenMP implementation of numerical kernels from the 3D heat transfer model (a 7-point Jacobi stencil) and the Ondes3D code (a full-fledged application developed by the French Geological Survey). We have considered two well-known implementations (naïve, and space blocking) to find correlations between parameters from the input configuration at runtime and the computing performance; thus, we have proposed a Machine Learning-based approach to evaluate, to predict, and to improve the performance of these stencil models on the underlying architecture. We have also used an acoustic wave propagation model provided by the Petrobras company and we have predicted the performance with high accuracy on multicore architectures. Secondly, we have oriented our research on heterogeneous architectures, we have analyzed the standard implementation for seismic wave propagation model in CUDA, to find which factors affect the performance; then, we have proposed a task-based implementation to improve the performance, according to the runtime configuration set (scheduling algorithm, size, and number of tasks), and we have compared the performance obtained with the classical CPU or GPU only versions with the results obtained on heterogeneous architectures.
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33

DIAZ, DE ALBA PATRICIA. "Numerical treatment for inverse problems in applied Geophysics." Doctoral thesis, Università degli Studi di Cagliari, 2017. http://hdl.handle.net/11584/249578.

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This thesis is concerned with numerical methods for inverse problems in applied Geophysics. Its main purpose is to reconstruct the electrical conductivity and the magnetic permeability of the soil by Electromagnetic induction (EMI). By taking measurements at several heights by a Ground Conductivity Meter (GCM), we can gain information about the depth profile of electrical conductivity. Nevertheless, the noninvasive determination of it, using only above-ground electromagnetic induction measurements, remains difficult since it involves inverse problems which typically lead to mathematical models that are not well–posed. This means especially that their solution is unstable under data perturbations. Numerical methods that can cope with this problem are the so–called regularization methods. This thesis reports distinct algorithms and techniques to overpass these difficulties since mathematical problems having these undesirable properties pose severe numerical adversities. Along the thesis we deal with linear and nonlinear models, that involve the solution of ill–conditioned problems for reconstructing the electrical conductivity and the magnetic permeability of the soil, and we propose for each of these problems an inversion procedure to get a good approximation of the solution.
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34

Gigandet, Katherine M. "Processing and Interpretation of Illinois Basin Seismic Reflection Data." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1401309913.

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35

Levik, Odd Ivar. "Thermophysical and compositional properties of natural gas hydrate." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-510.

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Thermophysical properties (dissociation enthalpy, heat capacity, metastability) and compositional properties (hydrate number, free water and fractionation) of natural gas hydrate were studied experimentally on samples that contained large amounts of ice. Methods for continuous hydrate production and sampling, and for quantification of the properties were developed. Hydrate was produced from a natural gas of ethane (5 %mol) and propane (3 %mol) in methane.

A low temperature scanning calorimetry method was developed to measure dissociation enthalpy, heat capacity, hydrate number and free water (ice). During the analysis, the hydrate samples were pressurized to 1.7 MPa with methane and the system operated between the hydrate equilibrium curves of methane and the hydrate forming natural gas. A sample conditioning procedure eliminated thermal effects of desorption as the ice melted. Desorption occurred since the samples were produced and refrigerated to 255 K under a natural gas pressure of 6-10 MPa, but were analyzed and melted under a methane pressure of 1.7 MPa.

A low temperature isothermal calorimetry method was developed to quantify the metastability properties. Metastability was confirmed for temperatures up to 268 K and quantified in terms of the low dissociation rate.

Fractionation data were obtained in the range 3.0 to 7.5 MPa and for subcoolings between 2 and 16 K. High pressure and large subcooling is desirable to suppress fractionation. A fractionation model was proposed. The model coincides with the van der Waals-Platteeuw model for zero subcooling. No fractionation is assumed for hypothetical hydrate formation at infinite driving force (subcooling). Between these two extremes an exponential term was used to describe the fractionation. The model predicted fractionation with an accuracy of about 1%abs corresponding to 1-10%rel.

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36

Gonsiewski, James P. "Bedrock Mapping Using Shear Wave Velocity Characterization and H/V Analysis." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1453247272.

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37

Peterman, David Joseph. "Seismic Reflection Profiling near Middletown, Ohio and Interpretation of Precambrian Deformational Settings." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1463936515.

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38

Lewis, Gregory. "The scale invariant generator technique and scaling anisotropy in geophysics /." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68198.

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Recently, there has been a dramatic increase in the use of scale invariance in the study of geophysical fields. However, very little attention has been paid to the anisotropy that is invariably present in these fields, in the form of stratification, differential rotation, texture and morphology. In order to account for scaling anisotropy, the formalism of Generalized Scale Invariance (GSI) was developed. Until now, only a single analysis technique has been developed which incorporates this formalism and which can be used to study the differential rotation of fields.
Using a two-dimensional representation of the linear approximation to GSI, a new, greatly improved, technique for quantifying anisotropic scale invariance in geophysical fields is developed: the Scale Invariant Generator technique (SIG).
The ability of the technique to yield valid estimates is tested by performing the analysis on multifractal (scale invariant) simulations. It was found that SIG yields reasonable estimates for fields with a diversity of anisotropic and statistical characteristics. The analysis is also performed on three satellite cloud radiances and three sea ice SAR reflectivities to test the applicability of the technique. SIG also produced reasonable estimates in these cases.
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39

Seiler, Christina. "Structural and thermal evolution of the Gulf Extensional Province in Baja California, Mexico : implications for Neogene rifting and opening of the Gulf of California /." Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/4212.

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40

Wedmark, Mats. "A small scale, high resolution magnetic survey at the archaeological site of Birka, Sweden." Thesis, Uppsala universitet, Geofysik, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303228.

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A high resolution magnetic survey was carried out at the archaeological site of Birka, situated approximately 20 km west of Stockholm. A new-generation optically pumped cesium magnetometer, G-858 from Geometrics, with a maximum sensitivity of 0.01 nT was used in the survey. An area of totally 504 m2 was covered in three windy days in September 1997 with the cesium magnetometer working in vertical-gradient mode. Remnants of the old houses, some of the oldest ditches and an earlier excavation could be seen in the gradient data after processing. Also a total-field measurement was carried out to search for the oldest defence wall at Birka. The bad positioning that followed with the continuous-scan mode made the data very difficult to process efficiently. Some processing was done in Matlab to eliminate effects that might be caused by the geology, but no substantial archaeological results emerged.This work shows that high resolution magnetic surveys can be efficient in detecting archaeological remains even in a very heterogeneous soil, provided very sensitive equipment and correct choice of method. It also emphasized the importance of good positioning in a survey.
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41

Anderson, Michael D. "Analysis of Upper Mantle Reflections Beneath the Trans-Uralian and East-Uralian Zones of the Ural Mountains, Russia." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1418482740.

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42

Fan, Chengliang. "Extracting P-primary transmission and reflection impulse responses from teleseismic data." [Bloomington, Ind.] : Indiana University, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3199414.

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Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2005.
Source: Dissertation Abstracts International, Volume: 66-11, Section: B, page: 5867. Adviser: Gary L. Pavlis. Title from dissertation home page (viewed Oct. 11, 2006).
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43

Katsev, Sergei. "Pattern formation in geochemical systems." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6237.

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Compositional patterns are extremely common in natural minerals. While, in many cases, variations in the solid mineral composition reflect the external changes in the environment at the time of the mineral formation, the role of self-organization is increasingly acknowledged. For example, in reaction-transport systems, the patterns may form spontaneously from an unpatterned state at the time of crystal growth and then become preserved by being "frozen" in the solid mineral. In this work, the pattern formation by self-organization is investigated by means of model construction and computer simulations in several minerals from different geologic environments. The impact of environmental noise is investigated on a model of oscillatory zoning in plagioclase feldspar. It is shown that environmental noise can lead to pattern formation such as oscillatory zoning, even when no deterministic periodic solutions exist. Coherence resonance close to the Hopf bifurcation is observed. Oscillatory zoning in barite-celestite system is simulated to quantitatively describe the results of the previously reported nucleation and growth experiments. The zoning is thought to be formed by autocatalytic growth from an aqueous solution. In addition to the description of the reaction-diffusion system in terns of partial and ordinary differential equations, a cellular automata model is proposed for the first time for this oscillatory crystallization type of problems. A quantitative model of banding in Mississippi Valley-type sphalerite is presented. Banded ring-like patterns are shown to arise due to a self-propagating sequence of growth and dissolution (coarsening wave). A two-dimensional model is presented for the first time and the conditions for the pattern generation and preservation are discussed. A number of time series analysis techniques are applied to characterize the compositional patterns observed in natural minerals as well as in the colored rythmites found in the marine clay sediments of the Ottawa Valley. Several caveats in interpreting the results of such analyses are outlined.
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44

Ber, Tomasz Jan. "The geochemistry of shocked and country rocks from the Lake Wanapitei impact structure, Ontario." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7830.

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Lake Wanapitei is located in central Ontario, 40 km northeast of Sudbury. The geophysical and morphological evidence suggest that the crater originally measured 8500 m in diameter. The original ground surface has been lowered by some 300 m; material scoured from the crater floor has been deposited as glacial float on and south of the southern shoreline. The shock metamorphosed rock fragments in these deposits consist of glassy melt rocks and suevitic breccias with lithic clasts of mainly quartzite, arkose, wacke, siltstone, and diabase. This work concentrates on establishing a compositional relationship between the Wanapitei crater lithologies and the unshocked country rocks at the area. Due to the relatively young age of the structure, the impact melt glasses are well preserved, with a low content of quench plagioclase and other alterations resulting from devitrification. Presented here are the results of bulk rock XRF and microprobe analyses of the Wanapitei crater rocks together with analyses of country rocks, that may have been exposed to the impact at the time of event. The suspected target rocks are represented by Proterozoic quartzitic sediments of Mississagi, Bruce, and Gowganda Formations, and diabase dikes of Nipissing Intrusions. A least-squares mixing model has been applied to determine which of the country rocks, were mixed to produce the observed impact glass lithologies. The results indicate 56% of Mississagi and 44% of Gowganda Formations; however, secondary evidence suggests a limited contribution of the Nipissing rocks. Based on these results, the meteoritic content of the impact melts has been established, and by comparison of siderophile geochemical data with the Wanapitei samples, a chondrite has been confirmed as the most probable projectile. The grade of shock metamorphism recorded in the Wanapitei shocked rocks suggests at least 65-70 GPa for maximum pressures and up to 2500$\sp\circ$C for maximum temperatures.
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45

Scott, Ronald Glenn. "The origins of magnetic anomaly lows associated with three impact structures." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9822.

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Drill cores from three Canadian impact structures were analysed for rock magnetic properties and mineralogy, in order to explain the reduced magnetizations associated with these structures. Samples from the drill cores were cut and measured for AMS and NRM parameters. Drill cores from the twin impact craters of the Clearwater structure exhibited different natural remanent magnetization (NRM) characteristics and samples from their respective drill cores were subject to demagnetization by alternating field and thermal techniques. The difference noted in their NRM characteristics was attributed to the acquisition of a viscous remanent magnetization (VRM) at depth in Clearwater East. Both magnetic susceptibilities and remanent magnetizations are well below regional values in impact generated breccias, melt rocks, shocked crystalline rocks, and in post-impact sedimentary infill. The processes of brecciation, alteration, shock, and infill by non-magnetic sediments contribute to the development of the magnetic lows. However, a significant component of the magnetic anomalies was found by forward modeling to derive from the unshocked basement rocks beneath the impact structures. This zone of reduced magnetization may be caused by the partial demagnetization of magnetite by the impact-induced transient stress wave travelling away from the point of impact, and the possible acquisition of a lower intensity shock remanent magnetization in the target rocks at depth. (Abstract shortened by UMI.)
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46

Pacheco, Anna. "Contribution of hyperspectral remote sensing to the estimation of leaf area index in the context of precision agriculture." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26734.

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The estimation of Leaf Area Index (LAI) is a key parameter controlling biophysical processes of the vegetation canopy, and ultimately yield. Defined as one half the total green leaf area per unit ground surface area, LAI is an essential component of precision crop management. Direct field techniques are tedious, time-consuming and labour-intensive. Indirect techniques, such as determining gap fraction with optical instruments have proven to be a good alternative, but their use is limited to rigid field sampling techniques. Vegetation indices have been useful to estimate LAI but are limited mostly due to its background reflectance noise. LAI can be estimated using different types of data, but only hyperspectral remote sensing has the potential to distinguish effectively the crop from other field components using spectral mixture analysis. Once the crop fraction has been derived, LAI is estimated using a crop fraction inversion technique. The application of this technique under agricultural field conditions has been very limited and not rigorously validated. The main objective of this study is to validate the crop fraction inversion technique for LAI estimation, and to examine the potential for LAI estimation using hyperspectral remote sensing data in the context of precision agriculture. This research will provide a unique scientific contribution to the field of hyperspectral remote sensing and greatly contribute to the advancement of remote sensing agriculture applications in Canada. (Abstract shortened by UMI.)
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47

Par, Andrew R. "DC Resistivity Inversion for Structural Information." Thesis, Colorado School of Mines, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10744014.

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The DC resistivity method has been an important tool for mineral exploration for the direct detection of conductive bodies with economic value. It has also been used for the structural mapping of lithology and alteration where boundaries are zones of economic interest and the detection of edges is the primary goal of surveying. Edge preserving inversion has been explored extensively within the context of potential field methods but has seen relatively little attention for the DC resistivity method. The focus of this thesis is to develop and implement methods which employ specific advantages of the DC method to aid the recovery of edges in the earth’s resistivity distribution.

I begin by utilizing sparse a priori geologic knowledge to create a geologic concept of pervasive blocky resistivity. l1 and l0 approximating measures of model values and model gradients are used as a vehicle to inject the a priori knowledge into a regularized inversion. An iterative method is used to solve for the model that minimizes a total objective function using these general measures.

A series of synthetic modelling and inversion scenarios demonstrate the effectiveness of l1 and minimum gradient support regularization to recover boundaries when compared to traditional sum-of-squares regularization. These blocky inversion schemes also exhibit an improved recovery of the resistivity value of distinct bodies. Additionally, I recognize that the various regularization types have different strengths and weaknesses. I exploit this property to create a new composite regularization that combines smooth model and blocky model regularization. This composite regularization exhibits the strengths of both regularization styles and less of the weaknesses.

A case study on field data from the Sabajo gold deposit was performed utilizing this methodology. Sharp lithologic contacts from drillholes informed the creation of a sharp resistivity concept. A blocky inversion was performed to recover a blocky model that was consistent with this concept and compared to the results of a smooth model inversion. Important differences were noted with their economic implications. I observed that the blocky regularized inversion may have recovered better estimates of the conductivity of features and this can greatly aid prioritization of targets for drilling. Finally, the differences between the inversions utilizing diverse regularization styles provided a proxy for model uncertainty.

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48

Miles, Warner Frederick. "An interpretation of high resolution aeromagnetic data over the Manitouwadge greenstone belt, Ontario, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ36726.pdf.

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49

Shepley, Karen Anne Bernice. "Regional geophysical modelling and paleo-reconstruction in and around the southern Slave Structural Province." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0020/MQ57172.pdf.

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50

Nagarajan, Badrinath. "A numerical study of the 15 December 1992 TOGA COARE mesoscale convective system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/NQ64626.pdf.

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