Seismic inversion using a global optimization algorithm is a non-linear, model-driven process. It yields an optimal solution of the cost function – reflectivity/acoustic impedance, when prior information is sparse. The inversion result offers detailed interpretations of thin layers, internal stratigraphy, and lateral continuity and connectivity of sand bodies. This study compared two stable and robust global optimization techniques, Simulated Annealing (SA) and Basis Pursuit Inversion (BPI) as applied to post-stack seismic data from the Gulf of Mexico. Both methods use different routines and constraints to search for the minimum error energy function. Estimation of inversion parameters in SA is rigorous and more reliable because it depends on prior knowledge of subsurface geology. The BPI algorithm is a more robust deterministic process. It was developed as an alternative method to incorporating a priori information. Results for the Gulf of Mexico show that BPI gives a better stratigraphic and structural actualization due to its capacity to delineate layers thinner than the tuning thickness. The SA algorithm generates both absolute and relative impedances, which provide both qualitative and quantitative characterization of thin-bed reservoirs.

Seismic waves are used to study the Earth, exploit its hydrocarbon resources, and understand its hazards. Extracting information from seismic waves about the Earth’s subsurface, however, is becoming more challenging as our questions become more complex and our demands for higher resolution increase. This dissertation introduces two new methods that use scattered waves for improving the resolution of subsurface images: natural migration of passive seismic data and convergent full-waveform inversion. In the first part of this dissertation, I describe a method where the recorded seismic data are used to image subsurface heterogeneities like fault planes. This method, denoted as natural migration of backscattered surface waves, provides higher resolution images for near-surface faults that is complementary to surface-wave tomography images. Our proposed method differ from contemporary methods in that it does not (1) require a velocity model of the earth, (2) assumes weak scattering, or (3) have a high computational cost. This method is applied to ambient noise recorded by the US-Array to map regional faults across the American continent. Natural migration can be formulated as a least-squares inversion to furtherer enhance the resolution and the quality of the fault images. This inversion is applied to ambient noise recorded in Long Beach, California to reveal a matrix of shallow subsurface faults. The second part of this dissertation describes a convergent full waveform inversion method for controlled source data. A controlled source excites waves that scatter from subsurface reflectors. The scattered waves are recorded by a large array of geophones. These recorded waves can be inverted for a high-resolution image of the subsurface by FWI, which is typically convergent for transmitted arrivals but often does not converge for deep reflected events. I propose a preconditioning approach that extends the ability of FWI to image deep parts of the velocity model, which significantly improves the chances for finding hydrocarbon deposits.

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In the aftermath of the failed revolution of 1848, which had been sparked by demands for democracy and constitutional reform, Germany’s princes reluctantly introduced new freedoms regarding print and the right to assembly. However, reactionary forces in governments unwilling to cede power quickly repressed these freedoms, leading to tighter controls on public and private life. Consequently, dispirited citizens clutched at the old Biedermeier ways, withdrawing to an “ill-remembered social order of bygone days” (Shorter 169). It was against this backdrop that the illustrated works of Wilhelm Busch (1832–1908) appeared in the popular Bilderbogen (“picture broadsheets”) of the day, and later as stand-alone Bildergeschichten (“picture stories”), using satire and symbolic inversion to mock German society by skewering assorted political, social, and cultural sacred cows. The aim of my dissertation is as follows. I will start by examining Busch’s use of symbolic inversion as a way of implying a shift in power between figures of authority and the disgruntled “second-class” citizens of Biedermeier society: women and children. Next, I will examine how Busch’s animal characters, particularly apes with their close resemblance to mankind, mock human pretensions of biological superiority. Finally, I will show how objects meant to serve their human “masters” overpower them, even in their homes, suggesting that there was no refuge from the vagaries of a rapidly changing world. Key to my analysis will be an exploration of the mechanism of “inside out” and “upside down,” described by Mikhail Bakhtin with regards to the carnival scenes of Gargantua et Pantagruel, as a sanctioned and mocking way of questioning the power of the state and its institutions. Along the way, I will compare and contrast Busch’s picture stories with similar strips in the Fliegende Blätter, in order to prove how groundbreaking the author’s exposé of nineteenth-century German society truly was. As I explore the synergy between image and word, I will demonstrate how Busch’s use of symbolic inversion is slyly subversive, undermining established authority in the political, social, and cultural arenas, and providing a safety valve in the form of humour that transcends the boundaries of class, education, and gender. / Thesis (Ph.D, German) -- Queen's University, 2013-04-19 14:01:35.498

The need to monitor geophysical properties of first year ice (FYI) in the Arctic is increasing as this type of sea ice becomes more prevalent. One such method of monitoring the Arctic is the use of electromagnetic remote sensing techniques. These methods determine dielectric properties of the illuminated sea ice by interpreting how the electromagnetic waves interact within the medium. In the literature, there are empirical formulas relating these dielectric properties to the geophysical properties of the sea ice. The contributions of this research are the development and testing of a surface based active microwave remote sensor to monitor sea ice growth in the winter through the reconstruction of the time series complex permittivity profile of FYI. / October 2017

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Northern Sweden is one of the largest hosts for mineral resources in Europe and always has been an interesting area for researchers from various disciplines of Earth sciences. This dissertation is a comprehensive summary of three case study papers on airborne VLF, gravity gradient and magnetic data in the area. In the first paper, tensor VLF data is extracted from an old data set which contains only the total and the vertical magnetic components. The anomalous part of the horizontal magnetic field components is computed by a Hilbert transform of the vertical magnetic field. The normal part of the horizontal magnetic field component is computed as a function of total, vertical and anomalous part of horizontal magnetic fields. The electric field is also calculated for TE mode and impedance tensor and apparent resistivity are computed. In addition tippers are calculated for two transmitters and inverted by a 3D inversion algorithm. Comparison of the estimated model and geology map of bedrock shows that lower resistivity zones are correlated with mineralizations. The second paper deals with the internal consistency of airborne gravity gradient data. The six components of the data are estimated from a common potential function. It is shown that the data is adequately consistent but at shorter land clearances the difference between the estimated data and the original data is larger. The technique is also used for computing the Bouguer anomaly from terrain corrected FTG data. Finally the data is inverted in 3D, which shows that the estimated density model in shallow depth is dominated by short wave length features. Inversion of TMI data is the topic of the third paper where a new type of reference model for 3D inversion of magnetic data is proposed by vertically extending the estimated magnetization of a 2D terrain magnetization model. The final estimated 3D result is compared with the magnetization model where no reference model is used. The comparison shows that using the reference model helps the high magnetization zones in the estimated model at shallow depths to be better correlated with measured high remanent magnetization from rock samples. The high magnetization zones are also correlated with gabbros and volcanic metasediments.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.