This thesis deals with both mathematical and analogue models for studying electromagnetic variations at the earth's surface. The field components are studied for frequencies in the range 10ˉ⁴ to 10³ cycles/sec and for earth conductivities in the range 10ˉ¹⁶ to 10ˉ¹º emu. Expressions are developed for the electric and magnetic field components at the surface and within the upper layer of a horizontally stratified flat conducting earth in the field of incident plane waves. Extensive results of amplitudes and phase angles are obtained for various frequencies, angles of incidence, layer thicknesses, depths, and conductivities. As an extension of this problem, expressions for a multilayer earth (n layers) are developed and evaluated. Each of several thick layers is divided into a sufficient number of sublayers, with changing conductivity, to represent to a good approximation a continuous change in conductivity. The conductivity distributions used are of interest in geophysics. The results for the plane wave model indicate that the amplitudes and phase angles are strongly affected by the conductivity structure. The electric and magnetic fields at the surface of a flat homogeneous conducting earth in the near field of an oscillating line current are studied. The equations for the amplitudes and phase angles developed by Law and Fannin (1961) are used for the calculations. Extensive results of amplitudes and phase angles are obtained for various frequencies, conductivities, source heights, and locations with respect to the overhead current. The results indicate that the vertical to horizontal magnetic field ratios are in the range of experimentally observed values. An analogue model suitable for studying the behavior of the natural geomagnetic and telluric field variations for various geological structures was constructed. The two types of field sources used were an oscillating sheet current and an oscillating line current. Extensive measurements of amplitudes and phase angles for the horizontal electric, the horizontal magnetic, and the vertical magnetic field components are obtained and discussed for various geological structures including a flat layered earth, cylindrical bodies embedded in the surface layer, vertical faults and dykes, sea mounts and conducting domes, coastline structures (sea-land interface and an upwelling in a high-conductivity zone within the mantle), and islands in an ocean channel. The results obtained for the coastline structures and islands in an ocean channel tend to support the proposed structures suggested by various workers (Schmucker 1964, Lambert and Caner 1965, Lokken and Maclure 1966) in describing the experimentally observed coastal magnetic field anomalies. The analogue model constructed and used for this work readily lends itself to studying a wide range of geological structures for a variety of source fields in addition to the ones used here. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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Seismic explosion data obtained by the Dominion Observatory in the Vancouver Island region from 1953 to 1963 have been restudied by both the travel-time and the time-term methods. From the first method, a new four layer model crust was constructed: In addition to the sedimentary, a granitic, and basaltic layers, suggested by White (1962), an ultrabasic layer of more than 22 km in thickness and Vp = 7.1 km/sec was recognized. From the time-term method, this layer structure was supported and the possibility of a major structural feature running across the island is suggested by the faults on each side and the gravity anomaly extending between them. The Mohorovicic discontinuity was not observed. A possibility interpretation of the abnormal character is given, and the complementary gravity and geomagnetic depth sounding evidence presented. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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<p>Rivers are constantly undergoing change due to erosion and sedimentation along their banks. Although these processes generally occur gradually, flood events can significantly accelerate river migration, creating a risk for human life and infrastructure. As a result, it is important to identify river reaches that are prone to channel migration and determine the extent of migration. However, detailed information about river migration across entire river networks is not readily available. This study seeks to develop a Python-based tool that can generate river migration rasters across large watersheds using Landsat imagery. The methodology involves extracting the centerlines of river features in Landsat imagery using the Modified Normalized Difference Water Index (MNDWI) and the Skeletonize function available in the scikit-image library, followed by the application of the Particle Image Velocimetry (PIV) algorithm to compute the river channel migration. The PIV algorithm generates a set of migration rasters that are analyzed to extract the long-term migration of each of the reaches. The tool also creates intermediate outputs, such as the MNDWI raster, binary land-water raster, and skeletonized river centerlines, which can be further analyzed to gain insights into the river's behavior. The methodology is implemented in the Wabash and Lower Mississippi River Basins, and the tool's effectiveness is validated against manual measurements of the river migration available for the Wabash Basin. In addition, this study analyzes the correlation between long-term migration and various factors, such as reach sinuosity, drainage area, geology, and streamflow. The results of the analysis show that drainage area is highly correlated with river migration. The correlation results are compared with the prior literature, thereby serving to validate the developed framework. This framework has the potential to aid decision-makers and policymakers in identifying the long-term patterns of river channel migration, facilitating their efforts to plan for infrastructure resilience. By utilizing this methodology, river managers and other stakeholders can gain insights into river migration across large watersheds and identify areas that require further monitoring and management.</p>

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<div><div><div><p>The radionuclide 10Be is produced in the atmosphere and is delivered to Earth’s surface in meteoric rain and aerosols. The stable nuclide 9Be is present in trace concentrations within rocks in Earth’s crust and is released via chemical weathering. Together, these two isotopes have been employed to study a wide range of Earth processes. Here I explore new terrestrial archives of Be isotopes: cave speleothems and terrestrial Mn-oxides. Until this point, these archives have barely been studied. Only one published dataset of Be isotopes in cave speleothems exists (Lundblad, 2006), and to my knowledge, terrestrial manganese oxides are yet to be explored. However, since speleothems and Mn-oxides precipitate from groundwater, they have the potential to encode temporal variations in the 10Be/9Be ratio of water and colloids in the vadose zone.</p><p>I develop a framework for using the 10Be/9Be ratio in the dissolved phase and/or secondary weathering products as a metric of chemical weathering rate. I am motivated by several over-arching questions:</p><ol><li><p>1) Which factor, or factors, is/are dominant in controlling Be isotopes in speleothems and terrestrial Mn-oxides?</p></li><li><p>2) Can Be isotopes in speleothems be used as a metric of weathering rate over time, particularly across glacial/interglacial cycles?</p></li><li><p>3) Can Be isotopes be used to date the formation of terrestrial Mn-oxides?</p></li></ol><p>I measure Be-isotope concentrations in speleothems from Soreq Cave, Israel. By applying an equation that I derive in this thesis, I use the temporal variation in the speleothem10Be/9Be ratio to calculate chemical weathering rates over the last 168 ka. Chemical weathering varies with independent proxies for temperature. The weathering-temperature relationship can be fit to an Arrhenius relationship, and the calculated activation energy (Ea) matches other field-based estimates for feldspar, an abundant mineral in the soil above the cave. In the Appendices I present additional results of Be-isotope measurements in a flowstone from Buffalo Cave in South Africa, as well as Mn-oxides from the Appalachians.</p></div></div></div>

A commonly used tool in data analysis is to compute a sample mean. Assuming a uni-modal distribution, its mean provides valuable information about which value is typically found in an observation. Also, it is one of the simplest and therefore very robust statistics to compute and suffers much less from sampling effects of tails of the distribution than estimates of higher moments. In the context of a time series, the sample mean is a time average. Due to correla- tions among successive data points, the information stored in a time series might be much less than the information stored in a sample of independently drawn data points of equal size, since correlation always implies redundancy. Hence, the issue of how close the sample estimate of a time average is to the true mean value of the process depends on correlations in data. In this thesis, we will study the proba- bility that a single time average deviates by more than some threshold value from the true process mean. This will be called the Large Deviation Probability (LDP), and it will be a function of the time interval over which the average is taken: The longer the time interval, the smaller will this probability be. However, it is the precise functional form of this decay which will be in the focus of this thesis. The LDP is proven to decay exponentially for identically independently distributed data. On the other hand we will see in this thesis that this result does not apply to long-range correlated data. The LDP is found to decay slower than exponential for such data. It will be shown that for intermittent series this exponential decay breaks down severely and the LDP is a power law. These findings are outlined in the methodological explanations in chapter 3, after an overview of the theoretical background in chapter 2. In chapter 4, the theoretical and numerical results for the studied models in chapter 3 are compared to two types of empirical data sets which are both known to be long- range correlated in the literature. The earth surface temperature of two stations of two climatic zones are modelled and the error bars for the finite time averages are estimated. Knowing that the data is long-range correlated by estimating the scaling exponent of the so called fluctuation function, the LDP estimation leads to noticeably enlarged error bars of time averages, based on the results in chapter 3. The same analysis is applied on heart inter-beat data in chapter 5. The contra- diction to the classical large deviation principle is even more severe in this case, induced by the long-range correlations and additional inherent non-stationarity. It will be shown that the inter-beat intervals can be well modeled by bounded fractional Brownian motion. The theoretical and numerical LDP, both for the model and the data, surprisingly indicates no clear decay of LDP for the time scales under study.

The theme of this thesis are surfaces made of unburned earth and used in architecture. The thesis focuses mainly on detailed mapping and analysis of the present state. However, it does not omit the historical roots of earthen surfaces in the area of today`s Czech Republic. In these roots it looks for connections with contemporary practice. The thesis deduces conclusions from thorough evaluation of the present situation – it shows perspectives and possible drift of the future development of earthen surfaces. Both in the field of architecture and in areas broadening this field.