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Dissertations / Theses on the topic 'Structural Geophysics Geophysics'

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Published: 4 June 2021
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1

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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2

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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3

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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4

Sutton, Daniel Scott. "Structural and geophysical interpretation of Roatan Island, Honduras, Western Caribbean." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10002482.

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Roatán Island is the largest of the Bay Islands of Honduras. These islands form an emergent crest off the Caribbean coast of Honduras called the Bonacca Ridge. The Bartlett Trough to the north and subsequent Bonacca Ridge were likely formed due to the transform fault system of the Motagua-Swan Islands Fault System. This fault system forms the tectonic plate boundary between the North American and Caribbean plates. Although the timing and kinematics are poorly constrained, the Bay Islands and the Bonacca Ridge were likely uplifted due to transpression along this left-lateral strike-slip system. With limited regional exposures along the adjacent tectonic boundary, this study aimed to present a structural interpretation for Roatán. This new interpretation is further explained through regional considerations for a suggested geologic history of the northwestern Caribbean.

In order to better constrain the kinematics of uplift and exhumation of Roatán Island, structural, gravity, and magnetic surveys were conducted. Principal attention was directed to the structural relationship between the geologic units and their relationship to one another through deformation. Resulting geologic cross-sections from this study present the metamorphic basement exposed throughout the island to be in a normal structural order consisting of biotite schist and gneiss, with overlying units of chlorite schist, carbonate, and conglomerate. These units have relatively concordant strike and dip measurements, consistent with resultant magnetic survey readings. Additionally, large and irregular bodies of amphibolite and serpentinite throughout the island are interpreted to have been emplaced as mafic and ultra-mafic intrusions in weakness zones along Early Paleogene transform system fault planes.

The interpretation and suggested geologic history from this study demonstrate the importance of transpressive tectonics both local to Roatán and regionally throughout geologic history. Consideration of this interpretation will help to further constrain regional studies over the northwestern Caribbean.

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5

Sussman, Aviva. "Thrust belt curvature: Structural and paleomagnetic analyses in the Catalunyan Pyrenees and Sevier orogen." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280086.

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The question of how curved geologic structures form, from arcuate faults to curvilinear orogenic belts, is one that transcends scale as well as rock properties. Many scale-independent lines of evidence suggest that material within fold-thrust belts is transported in three dimensions. Paleomagnetic analysis is the primary method for determining distribution and magnitude of vertical-axis rotations in arcuate regions. Thus paleomagnetic information is essential to deciphering the three-dimensional kinematic evolution of a curved orogen. In addition, most studies of foreland fold-and-thrust belts focus on geometries and timing relationships, but do not identify the deformations internal to the thrust-bounded rock packages. The Southern Pyrenean and Sevier orogenic systems both provide an outstanding opportunity to investigate thrust-belt curvature by integrating paleomagnetic and structural studies. This dissertation addresses the interplay between three-dimensional motions and the structures they cause. In the Pyrenees, the Oliana anticline is a foreland structure related to the South Central Salient, a major curve in the thrust belt. Paleomagnetic data from the Oliana anticline document counter clockwise rotations about a vertical axis. The average rotation is R ± Δ R = -19.6° ± 10.5°. Based on the stratigraphic horizons that record the rotation, as well as the structural evolution of the Oliana anticline, the age of rotation is ≥ 35 Ma. This rotation is attributed to continued motion along the Serres Marginals thrust, causing rotation along the blind thrusts that underlie the Oliana anticline. Mode I fracture data from this region highlights the progressive development of joints in growing structures. Measurements were taken from four regions around the anticline, and from four sequential synorogenic conglomerates. A consistent NW-SW orientation for the development of joints was determined by performing sequential restorations of the Oliana anticline and incrementally analyzing joint orientations. Reanalysis of previously published data from the Wyoming salient of the western United States demonstrates the relationship between irregular fault traces and the three-dimensional motions that caused them to form. Interaction between rotation, strain and net translation is a global phenomenon and suggests that geologic shortening estimates can be improved by incorporating the effects of tectonic rotations.
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6

Gillam, Daniel J. "Structural and geomechanical analysis of naturally fractured hydrocarbon provinces of the Bowen and Amadeus Basins: onshore Australia /." Title page, table of contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phg4758.pdf.

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7

Meirita, Maria Fransisca. "Structural and depositional evolution, KH field, West Natuna Basin, offshore Indonesia." Texas A&M University, 2003. http://hdl.handle.net/1969/411.

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8

Motta, João Gabriel [UNESP]. "Gravimetria no estudo da extremidade sudeste da faixa de dobramentos Brasília." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/133957.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
A extremidade sudeste da Faixa de Dobramentos Brasília tem sido alvo de extensa discussão em vista de sua geometria complexa e a diversidade de interpretações postuladas ao longo do avanço do conhecimento, sem integração ou abordagem por modelagem até então. A geofísica é baseada em uma abordagem indireta à geometria das massas rochosas, imageando propriedades físicas das mesmas, sendo assim, a gravimetria representa uma alternativa para a observação das massas de rocha presentes na região e sua geometria. Nesta temática o presente trabalho apresenta resultados de análise e modelagem de dados gravimétricos neste segmento da crosta, mais especificamente a região da Nappe de Socorro-Guaxupé e arredores, entre os orógenos Brasília e Ribeira com o Cráton do São Francisco e sua zona de interferência estrutural. A filtragem e modelagem gravimétrica indicam uma geometria de crosta duplicada, onde o Cráton do São Francisco se apresenta como anteparo na colisão do bloco Paraná-Paranapanema e Vitória, durante o ciclo Brasiliano, com a formação de extensos sistemas de empurrão subsequentemente deformados por tectônica lateral ao término do evento orogênico, com a instalação dos Cinturões de Cisalhamento Paraíba do Sul e Campo do Meio, com assinaturas geofísicas marcantes. Aspectos geofísicos e petrológicos indicam a similaridade da região com áreas de alto grau metamórfico, agora com uma visão integrada de seus níveis inferiores de arquitetura com a confirmação de modelos anteriores com evidências de superfície.
The southern edge of Brasília Fold Belt has an extensive research past dealing with its complex geometry with several interpretations on its evolution, poorly constrained by geophysical modeling. Geophysics is a non-direct approach to crust geometry by means of its physical properties presenting a prospective way to observe crust geometry. This works follows this scenario for gravity modelling in the southern tip of Brasilia Fold belt, especially in the Socorro- Guaxupé Nappe area along the syntax and interference zone to the Ribeira Belt (Mantiqueira Orogen) by São Francisco Craton margin. Filtering and modeling of gravity data into 2D sections shows crust duplication along the nappe system with São Francisco Craton acting as a rigid- to subducting block during Neoproterozoic tectonics. Extensive fold and shear belts (Campo do Meio e Paraíba do Sul) formed in the area during late Neoproterozoic as the final acts of deformation during collision of Paranapanema and Vitória cratons/blocks with São Francisco craton. Geophysical, structural and petrology constraints shows that the nappe system pertains a high metamorphic grade lower crust slice with strong near- vertical shear zone imprint. This work proposes a geology- constrained gravity model along the structural interference zone for the main tectonic elements with information by seismology and magnetic data.
CNPq: 830839/1999-2
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9

Shackleton, John Ryan. "Numerical Modeling of Fracturing in Non-Cylindrical Folds: Case Studies in Fracture Prediction Using Structural Restoration." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/open_access_dissertations/82/.

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10

Magyari-Köpe, Blanka. "Structural stability of solids from first principles theory." Doctoral thesis, KTH, Physics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3366.

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11

Balcerski, Jeffrey. "Modeling and Mapping of the Structural Deformation of Large Impact Craters on the Moon and Mercury." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1436539210.

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12

Silva, Francisco Heury Fernandes da. "Estudo geolÃgico-estrutural e sensoriamento remoto como contribuiÃÃo a hidrogeologia de terrenos cristalinos no distrito de JuÃ-CE." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2209.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
A pesquisa foi desenvolvida a sul do MunicÃpio de IrauÃuba, englobando o distrito de JuÃ, em uma Ãrea de 130kmÂ. A RegiÃo Nordeste do Brasil, especificamente no do Estado do CearÃ, à marcada, geralmente, pelo clima seco e distribuiÃÃo irregular da quadra chuvosa. A captaÃÃo de Ãgua subterrÃnea, muitas vezes, à a Ãnica alternativa para suprir a falta deste recurso quando a estiagem prolongada compromete o abastecimento. Tendo em vista minimizar os erros inerentes da locaÃÃo de um poÃo realizou-se a anÃlise em detalhe das estruturas rÃpteis que afetam os terrenos prÃcambrianos. Litologicamente à constituÃda por rochas Ãgneas e metamÃrficas pertencentes as unidades Pelito-CarbonÃtica e MigmatÃtica. As rochas destas unidades foram submetidas a retrabalhamentos durante o Evento Brasiliano, registrando estruturas dÃcteis e rÃpteis. Nestes terrenos configura-se o âdomÃnio hidrogeolÃgico do cristalinoâ, com a ocorrÃncia de Ãgua subterrÃnea condicionada por estruturas rÃpteis que podem estar interconectadas, e adquirir porosidade secundÃria capaz de facilitar a percolaÃÃo e o armazenamento de fluidos. A caracterizaÃÃo estrutural das feiÃÃes rÃpteis, em escala de detalhe, foi realizada por meio da tÃcnica do âmetro linearâ. O estudo de imagens de sensoriamento remoto consistiu na aplicaÃÃo de tÃcnicas de processamento digital. De forma complementar, utilizou-se a geofÃsica terrestre atravÃs do caminhamento eletromagnÃtico. As direÃÃes de alinhamentos estruturais obtidas pela interpretaÃÃo das imagens de satÃlite sÃo compatÃveis com os resultados da interpretaÃÃo dos dados de fraturas, estudadas nas rochas. As principais famÃlias de fraturas identificadas sÃo a N-S e E-W, secundariamente, NE-SW e NW-SE. O uso da geofÃsica terrestre revelou zonas condutivas relacionada à presenÃa de fraturas em subsuperfÃcie. Com a integraÃÃo dos dados gerados foram selecionadas duas Ãreas potencialmente importantes para exploraÃÃo hidrogeolÃgica, correspondentes as concentraÃÃes C-01, norte de Juà e C-04 nas imediaÃÃes de JuÃ.
This research was carried out in a 130 km2 area, in the Juà village, south of the IrauÃuba town. The Northeast of Brazil, specially the countryside, is marked by arid climate and irregular distribution of rain. The captation of groundwater is normally the only solution to provide water during dry weather. To minimize the natural errors that occur during the location of a well we made detailed analysis of the reptile structures that affect the Precambrian terrains. Lithologically it is constituted by igneous and metamorphic rocks belonging to the Migmatitic and Pelitic-Carbonatic Units. These rocks were reworked during the Brasilian Event, which registered both ductile and ruptile structures. In these terrains the âhydrological domain of the crystallineâ is represented, in which the groundwater is controlled by ruptile structures that may be interconnected to the point of acquiring enough secondary porosity to facilitate the percolation and the storing of fluids. The structural characterization of these ruptile features was made in a detailed scale by means of the âlinear-meterâ technique. The remote sensing images study consisted on the application of digital processing techniques, as well as terrestrial geophysics by means of electromagnetic profiles. The structural trends obtained by satellite images are compatible with the results taken from fracturing data. The main fracture sets are N-S and E-W and secondarily, NE-SW and NW-SE. Geophysical studies revealed conductive zones related to the presence of subsurface fractures. Data integration led to two potentially important areas for hydrogeological exploration, which correspond to the C-01 (north of JuÃ) and C-04 (JuÃ) concentrations.
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13

Koehl, Daniel Grant. "Investigating an Apparent Structural High in Seismic Data in North Terre Haute, Indiana, Through First-Arrival Traveltime Tomography and Gravity Analysis." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1559120344838085.

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14

Mahon, Luke Evan. "Morphostructural and paleo-seismic analysis of fault interactions in the Oxford–Cust–Ashley fault system, Canterbury." Thesis, University of Canterbury. Geological Sciences, 2015. http://hdl.handle.net/10092/11224.

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This study investigates evidence for linkages and fault interactions centred on the Cust Anticline in Northwest Canterbury between Starvation Hill to the southwest and the Ashley and Loburn faults to the northeast. An integrated programme of geologic, geomorphic, paleo-seismic and geophysical analyses was undertaken owing to a lack of surface exposures and difficulty in distinguishing active tectonic features from fluvial and/or aeolian features across the low-relief Canterbury Plains. LiDAR analysis identified surface expression of several previously unrecognised active fault traces across the low-relief aggradation surfaces of the Canterbury Plains. Their presence is consistent with predictions of a fault relay exploiting the structural mesh across the region. This is characterised by interactions of northeast-striking contractional faults and a series of re-activating inherited Late Cretaceous normal faults, the latter now functioning as E–W-striking dextral transpressive faults. LiDAR also allowed for detailed analysis of the surface expression of individual faults and folds across the Cust Anticline contractional restraining bend, which is evolving as a pop-up structure within the newly established dextral shear system that is exploiting the inherited, now re-activated, basement fault zone. Paleo-seismic trenches were located on the crest of the western arm of the Cust Anticline and across a previously unrecognised E–W-striking fault trace, immediately southwest of the steeply plunging Cust Anticline termination. These studies confirmed the location and structural style of north-northeast-striking faults and an E–W-striking fault associated with the development of this structural culmination. A review of available industry seismic reflection lines emphasised the presence of a series of common structural styles having the same underlying structural drivers but with varying degrees of development and expression, both in the seismic profiles and in surface elevations across the study area. Based on LiDAR surface mapping and preliminary re-analysis of industry seismic reflection data, four fault zones are identified across the restraining bend structural culminations, which together form the proposed Oxford–Cust–Ashley Fault System. The 2010–2012 Canterbury Earthquake Sequence showed many similarities to the structural pattern established across the Oxford–Cust–Ashley Fault System, emphasising the importance of identification and characterization of presently hidden fault sources, and the understanding of fault network linkages, in order to improve constraints on earthquake source potential. Improved understanding of potentially-interactive fault sources in Northwest Canterbury, with the potential for combined initial fault rupture and spatial and temporal rupture propagation across this fault system, can be used in probabilistic seismic hazard analysis for the region, which is essential for the suitability and sustainability of future social and economic development.
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15

Uchoa, Juliane Cristina Ferreira. "Analise espacial dos corpos plutonicos do cinturão mineiro atraves da integração de dados geologicos, aerogeofisicos e geoquimicos." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287404.

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Orientadores: Adalene Moreira Silva, Catarina Laboure Benfica Toledo
Acompanha um mapa em folha dobrada, em bolso
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias
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Resumo: A aquisição de dados aerogeofísicos sobre o Cinturão Mineiro, porção sul do Craton São Francisco, Minas Gerais, exibiu padrões diferentes daqueles mapeados em trabalhos de campo. Uma análise integrada de dados aerogamaespectrométricos, magnetométricos, gequímica e geológicos de campo resultaram num mapa destes padrões, destacando as relações entre as principais unidades geológicas, como suas estruturas internas e limites. O realce e análise dos dados aerogamespectrométricos a partir da classificação não supervionada apresentaram os principais litotipos, bem como suas variações internas, complementando os dados geológicos existentes. O produto principal é um mapa geológico na escala 1:100.000, onde as principais anomalias geofísicas foram checadas em campo, conferindo-se litologias, contatos geológicos e estruturas. A interpretação dos dados aerogeofísicos permitiu também a redefinição dos limites dos batólitos São Tiago e Ritápolis difícies de serem reconhecidos apenas em trabalhos de campo. A análise integrada da aerogamaespectrometria, magnetometria, geoquímica e dados de campo forneceu novas ferramentas para traçar a extensão areal destes corpos. Os padrões estruturais dentro dos batólitos trouxeram novas idéias dos mais prováveis processos de sua origem. Três corpos plutônicos foram estudados em detalhe: Ritápolis, Cassiterita e Manuel Inácio. A principal proposta foi a comparação das assinaturas geofísicas, geoquímicas e dados geológicos destes corpos. A assinatura do Ritápolis revelou uma similaridade com os outros granitóides, tais como, Itumirim e de Itutinga. Do mesmo modo, a assinatura do corpo Cassiterita é semelhante aos plútons Tabuões e Rezende Costa. O plúton Manuel Inácio pode ser mapeado nos dados geofísicos, semelhantemente aos outros corpos máficos conhecidos na região, mas devido suas baixas razões de radioelementos não foi possível correlacionar as variações de K, eTh e U com sua mineralogia. Fiinalmente, o contraste das propriedades físicas e características geoquímicas dos corpos plutônicos do Cinturão Mineiro puderam ser comparadas com dados isotópicos e geológicos adquiridos antes desta pesquisa. A integração dos dados ilustra a geração de corpos plutônicos relacionados espacial e temporalmente , contrastando diferentes fontes genéticas
Abstract: Airborne geophysical data acquired over the Mineiro Belt in the southern portion of the São Francisco Craton, Minas Gerais, Brazil display patterns not previously identified by geological field mapping. The lack of rock exposures and connections among rock formations at surface poses problems for regional geologic mapping and interpretation, which are difficult to be surpassed. An integrated analysis of gamma-ray spectrometric, magnetic, geochemical and field geological data was conducted to map and analyse these patterns, and highlight the relationships between the principal geological units, as well as their internal structures and boundaries. Enhancement and cluster analysis of the gamma-ray spectrometry data showed their usefulness in mapping subtle compositional variations in the area, which concur with and complement available geological data. The main product is a new geological map at 1:100.000 scale that was ground-checked in other to examine lithological, structural and stratigraphic relationships. The new geological map based on geophysical data enable better definition of geological units and contribute directly to more effective and efficient geological mapping. The gamma-ray spectrometry data also allowed the boundaries definition of São Tiago and Ritapolis batoliths that have not been all recognized in fied mapping and with geochemical data. The integrated analysis of gamma-ray spectrometric, magnetic, geochemical and field geological data provided a tool to map the extent of the composicional and structural patterns within the batholits and provides insigth into the most probable processes of origin. Because the subtle differences in mineralogy is associated the radioelement zoning in the plutonic bodies of Mineiro Belt may be difficult to detect in the field, enhacement and spectral analysis of gamma ray spectrometric data by unsupervised classification were applied to detected variations that are difficult to interpret from ternary images of the K, eTh and eU grids. The main results allowed the understanding of the geophysical properties and correlation with geochemical and isotopic data. Three plutonic bodies were studied in detail: Ritapólis, Cassiterita e Manuel Inácio. The main goal was define the geophysical and geochemical signatures of these bodies and extrapolate to another areas and provide new insigths to the origin of such plutons. The Ritapolis signature reveals a similarity with the Itumirim and Itutinga granitoids, while the Cassiterita signature is well mapped at the Tabões and Rezende Costa domains. The Manuel Inacio plutonic bodie can be mapped in the airborne geophysical data as well as similar bodies known at this region, but they are poor in radioelements what difficult the mapping of subtle differences in mineralogy. Finally, the physical property contrast and geochemical characteristics of the plutonic bodies of the Mineiro Belt can be well related with isotopic and geological data acquired before this research. The data integration illustrates the generation of plutonic bodies with close spatial/temporal relationships and contrasting source regions.
Mestrado
Metalogenese
Mestre em Geociências
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16

Brennan, Jeanne L. "Interpretation of Vibroseis reflections from within the Catoctin Formation of central Virginia." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/76030.

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Large amplitude seismic reflections from within the Catoctin Formation of central Virginia are interpreted to originate from acoustically thin beds of interlayered metabasalts and metasediments. Large acoustic impedance contrasts exist between epidotised layers ( epidosites and volcanic breccia) and non-epidotised layers (greenstones and phyllites) within the Catoctin Formation. Acoustic impedance contrasts also exist between greenstones (metabasalts) and phyllites (metasediments). Constructive interference of small amplitude reflections from thin beds result in large amplitude, reverberating reflections. Thin bed reflections that approximate the first derivative of the source wavelet constructively interfere to give even larger amplitude reflections than those originating by conventional tuning. Computer modeling based on two geologic sections of thin beds of epidosites interlayered with greenstones and of greenstones interlayered with phyllites and epidosites indicates that large amplitude reflections result from constructive interference of thin bed reflections.
Master of Science
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17

Kruse, Stefan. "Structural evolution of the northern Thor–Odin Culmination, Monashee Complex southern Canadian Cordillera." Thesis, University of New Brunswick, 2007. http://hdl.handle.net/1882/941.

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The Monashee Complex is a structural culmination which exposes rocks from the lowest stratigraphic levels of the Canadian Cordillera. The Monashee Complex is subdivided into two lesser structural culminations; the Frenchman Cap and Thor–Odin culminations. The lithostratigraphic succession of the Thor–Odin Culmination is completely transposed by penetrative isoclinal folds with amplitudes from microscopic (<1 mm) to regional (10’s km). Lower structural levels are occupied by Proterozoic gneisses and migmatites of the Monashee basement assemblage. These are infolded with overlying metasedimentary rocks of the Monashee cover assemblage, which are Proterozoic to possibly Paleozoic in age. The basement and cover assemblages were subsequently intruded by Eocene granitic pegmatite, aplite and lamprophyre dykes. Regional metamorphism of the basement and cover assemblages reached upper amphibolite to lower granulite facies. The northeastern portion of the Thor–Odin Culmination of the Monashee Complex contains a suite of structures and fabrics, which are classified into four sets, based on their interpreted kinematic significance. These are: 1) transposition related structures (DT); 2) open, upright folds (DO); 3) exhumation related structures (DE); and 4) brittle faults (DB). Each successive set of structures exerted a control on the geometry of the next set. The large-scale geometry of the culmination is an interference structure between DT folds, a DE arch and high-strain zones, and a DB brittle horst. Early, DT fold style varies from intrafolial isoclinal “mature” style folds to upright or inclined asymmetric “immature” folds. This continuum of fold styles, along with evidence of anticlockwise rotation (looking down a vertical axis toward the shear plane) of fold axes and lineations is interpreted as being a result of penetrative triclinic non-coaxial flow. DO upright, symmetrical folds overprint early structures and fabrics, but are only preserved at low structural levels in the culmination where the DE coaxial stretching overprint is weak. DE normal shear bands and boudins overprint all earlier structures. A complex high-strain zone, the Thor–Odin High-Strain Zone, outcrops at high structural levels and along the margins of the culmination. The Thor–Odin High- Strain Zone developed as a result of material moving away from the crest of the culmination, outwards toward the flanks. Eocene brittle faults (DB) and fractures within the Thor–Odin Culmination of the Monashee Complex are divisible into three distinct sets. Initial 340–010º trending strikeslip faults (Set 1) were locally overprinted and reactivated by normal faults with a 325– 020º trend (Set 2). A third set of 255–275º trending fractures (Set 3) are interpreted as conjugates to Set 1, reactivated as transfer faults to the Set 2 normal faults. Large regional faults weather recessively forming topographic lineaments that transect the Monashee Complex. The Victor Creek Fault defines one such lineament. Detailed mapping within the northern Thor–Odin Culmination, reveals piercement points (fold hinges) on the east side of the fault, which are not readily matched on the west side. The minimum displacement required on the Victor Creek Fault to down-drop the fold hinge below the level of exposure on the west side is 1370 m, assuming normal down-to-the west displacement. However, the geometry of the fault is consistent with a Set 1 dextral strike-slip fault. Matching the piercement points in the study area with possible equivalents to the north indicates 55–60 kms of dextral strike-slip displacement. The Monashee Reflection (MR) is a major crustal-scale, cross-cutting reflection appearing on two mutually perpendicular Lithoprobe seismic profiles in the southern Omineca Belt of the Canadian Cordillera. It has previously been interpreted as the downplunge extension of an arched regional ductile thrust fault, the Monashee Décollement, and is described as separating the Monashee Complex from the overlying Selkirk Allochthon. Recent mapping demonstrates that this boundary is not a discrete ductile thrust, but rather transposed and gradational. Overprinting the transition zone is a complex, outward-dipping, normal, structure; the Thor−Odin High-Strain Zone. Three alternative 3-D geometric models have been developed for the MR in order to project the reflection to the surface. The favoured model correlates the surface trace of the Thor−Odin High-Strain Zone with MR. Normal shear sense kinematics are interpreted for the MR based on: 1) the overall geometry and asymptotic relationship between the MR and reflections in the hanging wall and footwall; 2) offset of metamorphic and geochronological gradients, consistent with an extensional zone, rather than with thrust fault interpretation and 3) the cross-cutting nature of the MR is consistent with normal structures throughout the region.
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18

Brandeberry, Jessica L. "A Passive Seismic Investigation of the Crustal Structure under Ohio." Connect to full text in OhioLINK ETD Center, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1196909328.

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Thesis (M.S.)--University of Toledo, 2007.
Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science in Geology." "A thesis entitled"--at head of title. Accompanied by CD-ROM which contains the following files: 2000-2003 Teleseismic Reduced Traveltimes.xls; 2000-2003 Teleseismic Traveltimes.xls; 2004 Teleseismic Reduced Traveltimes.xls; 2004 Teleseismic Traveltimes.xls; 2005 Teleseismic reduced Traveltimes.xls; 2005 Teleseismic Traveltimes, xls; 2006 Teleseismic Reduced Traveltimes. xls; 2006 Teleseismic Traveltimes. xls; Complete Thesis.doc; Regional Earthquake Data.xls; Teleseismic Earthquake Data.xls. Bibliography: leaves 78-80.
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19

Rabin, Mickael. "Caractérisation de la déformation récente dans une chaine orogénique lente : l'arc du Jura. Approches combinées morphotectonique, géodésique et géophysique." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2008/document.

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L'objectif de cette thèse était de caractériser la déformation récente, tant dans son style que dans son partitionnement, d'un arc orogénique lent à travers une approche pluridisciplinaire à grande échelle.La déformation récente et actuelle de l'arc du Jura a été caractérisée par l'analyse des indices géomorphologiques le long des profils de rivières ainsi qu'à travers le traitement des données sismiques et géodésiques. Les essais de caractérisation et de datation des évènements tectoniques et sismiques à travers l'analyse des failles décrochantes tardives et des enregistrements spéléologiques n'ont pas permis d'apporter de nouvelles données sur la néotectonique du Jura. Cependant la combinaison des données et observations géomorphologiques, géophysiques et géodésiques confrontée aux données des précédentes études nous permets de proposer un modèle de répartition de la déformation dans le système orogénique Alpes occidentales-Jura. [...]
No abstract available
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20

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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21

Martínez, Granado Pablo. "Inversion Tectonics in the Alpine Foreland, Eastern Alps (Austria)." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/435684.

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In this thesis, the 3D structure and kinematics of the locally and mildly inverted Lower Austria Mesozoic Basin beneath the Alpine-Carpathian fold-and-thrust belt is described. This study has been carried out by the integrative interpretation of 2D and 3D seismic surveys, well and geophysical logs data and gravity maps. A basin-scale, 3D structural model has been carried out, focused on the sub-thrust and foreland zones. The Late Eocene to Early Miocene Alpine–Carpathian fold-and-thrust belt resulted from the subduction of the European plate beneath the Adriatic one, and the subsequent continental collision between both plates. The Alpine–Carpathian foredeep and fold-and-thrust belt recorded the long-lasting involvement of the European crystalline basement in several deformation events: from late Variscan transtension, to Jurassic rifting, and Cretaceous to Neogene shortening. In this thesis, two additional basement fault reactivation events have been defined in relation to the Alpine-Carpathian Cenozoic shortening: an extensional reactivation event related to the bending of the European plate coeval with Egerian to Karpatian (ca. 28–16 Ma) thin-skinned thrusting; followed by the selective positive inversion of the basement faults in the sub-thrust and in the foreland during Karpatian to Badenian times (ca. 16-12.5 Ma). The flexural bending of the European plate and the associated extensional fault reactivation were promoted by high lateral gradients of lithospheric strength in addition to the slab pull forces associated with subduction. Delamination of the European lithosphere during the final stages of collision around Karpatian times (ca. 16 Ma) promoted a large-wavelength uplift and an excessive topographic load. This topographic load was compensated by broadening the orogenic wedge through the compressional reactivation of the inherited fault array in the Euroepan plate beneath and ahead of the thin-skinned thrust system. Ultimately, collapse and deep burial of the Alpine-Carpathian tectonic wedge took place by the formation of the Pannonian basins system. To gain further insights in the deformational processes in sub-thrust and foreland settings, sandbox analogue models of brittle and brittle-viscous sand wedges have been carried out. The models aimed testing the influence of different topographic loads (i.e., thrust wedges) on the sub-thrust inversion of extensional basins, as well as the influence of the initial orientation of the extensional basins, and the presence or absence of weak detachment layers. Segmented half-graben basins -striking at 90º, 45º and 15º to the extension direction- were created first, and then shortened using different angles for the basal detachment and topographic slope. A shallow layer of viscous polymer over the half- graben basin was included in one of the models. The experiments were analysed using time-lapse photography, topography laser scans and image-based 3D voxels. The modelling results indicate a deformation sequence characterised by layer-parallel compaction, fault reactivation, thrust propagation and related folding. Fault reactivation and basin inversion were associated with layer-parallel compaction accomplished by slip along the basal detachment, prior to and in between pulses of thrusting. The results of the sandbox analogue models reveal a fundamental control imposed by the vertical load of the tectonic wedge and its integrated strength profile in the inversion of sub-thrust basins. Small vertical loads or strong gradients of vertical load have revealed as fundamental factors aiding in the inversion of buried, sub-thrust basins. The integrated strength profile resulted from the combination of inherited, strain-softened fault zones, as well as the presence or absence and distribution of weak, viscous horizons. The results of the sandbox models carried out indicate that the vertical load, its gradient over the sub-thrust basins and the inherited, strain-softened faults, are more important than the obliquity between the direction of shortening and the orientation of pre-existing fault systems. As indicated by the results of sandbox analogue models, the recurrent and long-lasting frictional reactivation of the Lower Austria basement fault array may have been favoured by fault-weakening mechanisms, as well as by steep gradients of vertical loads generated by thin-skinned out- of-sequence stacking of the Rhenodanubian Flysch located south of the inverted basement fault array.
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22

Wijns, Christopher P. "Exploring conceptual geodynamic models : numerical method and application to tectonics and fluid flow." University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0068.

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Geodynamic modelling, via computer simulations, offers an easily controllable method for investigating the behaviour of an Earth system and providing feedback to conceptual models of geological evolution. However, most available computer codes have been developed for engineering or hydrological applications, where strains are small and post-failure deformation is not studied. Such codes cannot simultaneously model large deformation and porous fluid flow. To remedy this situation in the face of tectonic modelling, a numerical approach was developed to incorporate porous fluid flow into an existing high-deformation code called Ellipsis. The resulting software, with these twin capabilities, simulates the evolution of highly deformed tectonic regimes where fluid flow is important, such as in mineral provinces. A realistic description of deformation depends on the accurate characterisation of material properties and the laws governing material behaviour. Aside from the development of appropriate physics, it can be a difficult task to find a set of model parameters, including material properties and initial geometries, that can reproduce some conceptual target. In this context, an interactive system for the rapid exploration of model parameter space, and for the evaluation of all model results, replaces the traditional but time-consuming approach of finding a result via trial and error. The visualisation of all solutions in such a search of parameter space, through simple graphical tools, adds a new degree of understanding to the effects of variations in the parameters, the importance of each parameter in controlling a solution, and the degree of coverage of the parameter space. Two final applications of the software code and interactive parameter search illustrate the power of numerical modelling within the feedback loop to field observations. In the first example, vertical rheological contrasts between the upper and lower crust, most easily related to thermal profiles and mineralogy, exert a greater control over the mode of crustal extension than any other parameters. A weak lower crust promotes large fault spacing with high displacements, often overriding initial close fault spacing, to lead eventually to metamorphic core complex formation. In the second case, specifically tied to the history of compressional orogenies in northern Nevada, exploration of model parameters shows that the natural reactivation of early normal faults in the Proterozoic basement, regardless of basement topography or rheological contrasts, would explain the subsequent elevation and gravitationally-induced thrusting of sedimentary layers over the Carlin gold trend, providing pathways and ponding sites for mineral-bearing fluids.
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23

Bolós, Granados Xavier de. "Geological and structural controls on La Garrotxa monogenetic Volcanic Field (NE Iberia) and structural controls on La Garrotxa monogenetic Volcanic Field (NE Iberia)." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/284848.

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Monogenetic volcanism represents the most common volcano type on Earth. The distribution of it depends in each case on their regional and local tectonic controls. The great variety of eruptive styles, edifice morphologies, and deposits shown by monogenetic volcanoes is the result of a complex combination of internal (magma composition, gas content, magma rheology, magma volume, etc.) and external (regional and local stress fields. stratigraphic and rheological contrasts of substrate rock, hydrogeology, etc.) parameters during magma transport from the source region to the surface. The present PhD Thesis focuses on the geological and structural controls of monogenetic volcanism. It pays particular attention to the uppermost part of the lithosphere and its role to determine the distribution of eruptive vents and eruptive styles. We have selected La Garrotxa Volcanic Field (GVFj as a case study. This Quaternary volcanic field is located in the Northeast of the Iberian Peninsula and includes more than SO well-preserved volcanoes. It covers an area of 600 km2, between the cities of Olot and Girona and belongs to the Catalan Volcanic Zone, one of the alkaline volcanic provinces of the European Rift System. The GVF is still poorly known and has become an ideal place for the application of the multidisciplinary studies, including geophysical methods, geological fieldwork and geomorphological and structural analyses, which constitute this PhD Thesis. The first work was carried out at the Northern sector of the GVF. This study was mainly based on the application of gravimetry and self-potential techniques, in order to identify the main tectonic structures of the volcanic area at depth. A second work was performed in order to obtain a much better detail of the shallower structures and to relate the subsurface geology to the feeding system of these monogenetic volcanoes. In this case, we applied the electrical resistivity tomography method, comparing the new data with the self-potential results. A third work was carried out at the Southern sector of the GVF, at La Crosa de Sant Dalmai volcano (10 km SW of Girona), one of the biggest maar-diatreme edifices of the Iberian Peninsula. Here, several geophysical techniques were applied, including gravimetry, magnetometry, self-potential and electrical resistivity tomography. A model of the uppermost part of the diatreme was obtained, determining the internal structure and its origin. The results obtained with the application of these geophysical methods in this volcanic field suggest that electrical resistivity tomography is a useful tool for the study the internal structures of different types of monogenetic landforms. In this way we present a short work that illustrates different examples of internal structures of monogenetic volcanic cones from GVF. Furthermore, combining the results from these geophysical studies with the geological informations obtained by fieldwork, we performed the first volcanic stratigraphy map of the GVF. Finally, we also led a detailed volcano-structural analysis of the whole volcanic field, including geostatistical distribution of faults, fissures and vents, morpho structural lineaments identified by remote sensing, a morphometrical analysis of the volcanic cones and craters, location of regional seismic events recorded in the area (since 1978), and mantle derived gases in springs and water wells, as a guide to identify active faults and open fractures and to define the structural controls of this volcanism. The results obtained from all these studies have permitted understanding how magma was transported into the lithosphere and erupted at the surface, and represent an essential tool for a correct volcanic hazard assessment of the GVF. Furthermore, the methodologies described in this PhD Thesis establish general guidelines to study active monogenetic volcanic fields and we hope that it will contribute to improve their understanding.
La present Tesi Doctoral es centra en els controls geològics i estructurals del vulcanisme monogenètic. S'ha posat especial atenció a la part més superficial de la litosfera i en el paper que juga aquesta zona en determinar la distribució de punts emissors i estils eruptius. S'ha seleccionat com a cas estudi el Camp Volcànic de la Garrotxa (GVF) (NE d'lberia). Aquest és encara poc conegut i ha esdevingut un lloc ideal per l'aplicació d'estudis multidlsciplinaris com els treballs que constitueixen aquesta Tesi Doctoral, integrant mètodes geofísics. treballs de camp, ¡ anàlisis geomorfològics i estructurals. Els primers dos treballs s'han portat a terme al sector Nord del GVF. Aquests estudis s'han basat en l'aplicació de diverses tècniques geofísiques, identificant així les estructures tectòniques principals I obtenint una informació detallada del basament. El tercer treball també s'ha realitzat a partir d'un estudi multigeofísic. En aquest cas al sector Sud del GVF, concretament al volcà de la Crosa de Sant Dalmai. Els resultats han permès la realització d'un model de la part superior de la diatrema, determinant la seva estructura interna i origen. Els resultats obtingut suggereixen que la tomografia elèctrica resulta una eina eficaç per l'estudi dels diferents tipus d'edificis monogenètics. D'aquesta manera es presenta un treball breu amb diferents exemples de l'estructura dels cons volcànics de la zona. Combinant aquests resultats amb informació geològica de camp, s'ha realitzat la primera cartografia vulcanoestratigràfica del GVF. Finalment, s'ha fet un anàlisi volcanoestructural de tot el camp volcànic, el qual Inclou la distribució geoestadística de falles, fissures i punts emissors, identificació morfo-estructural de lineacions, anàlisi morfomètric dels cons i cràters, localització de la sismicitat registrada de la zona i gasos derivats del mantell en surgències i pous, com a guia per identificar falles actives o fractures obertes, amb l'objectiu de definir els controls estructurals d'aquest vulcanisme. Tot els resultats obtinguts han permès entendre el transport del magma des de la litosfera fins la superfície, i representen un eina essencial per una correcta avaluació de la perillositat volcànica al GVF. Tanmateix, les metodologies descrites estableixen una pauta general per l'estudi dels camps monogenètics actius.
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24

Nwaodua, Emmanuel Chukwukamadu. "Subsurface Facies Analysis of the Rose Run Sandstone Formation in south eastern Ohio." Bowling Green State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1213202313.

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25

Okojie-Ayoro, Anita Onohuome. "An Approach to Mapping of Shallow Petroleum Reservoirs Using Integrated Conventional 3D and Shallow P- and SH-Wave Seismic Reflection Methods at Teapot Dome Field in Casper, Wyoming." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1219.

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Using the famous Teapot Dome oil field in Casper, Wyoming, USA as a test case, we demonstrate how high-resolution compressional (P) and horizontally polarized shear (SH) wave seismic reflection surveys can overcome the limitations of conventional 3D seismic data in resolving small-scale structures in the very shallow subsurface (< 100-200 m (~328-656 ft)). We accomplish this by using small CMP intervals (5 ft and 2.5 ft, respectively) and a higher frequency source. The integration of the two high-resolution seismic methods enhances the detection and mapping of fine-scale deformation and stratigraphic features at shallow depth that cannot be imaged by conventional seismic methods. Further, when these two high-resolution seismic methods are integrated with 3D data, correlated drill hole logs, and outcrop mapping and trenching, a clearer picture of both very shallow reservoirs and the relationship between deep and shallow faults can be observed. For example, we show that the Shannon reservoir, which is the shallowest petroleum reservoir at Teapot Dome (depth to the top of this interval ranging from 76-198 m (250-650 ft)) can only be imaged properly with high-resolution seismic methods. Further, northeast-striking faults are identified in shallow sections within Teapot Dome. The strike of these faults is approximately orthogonal to the hinge of Teapot Dome. These faults are interpreted as fold accommodation faults. Vertical displacements across these faults range from 10 to 40 m (~33 to 131 ft), which could potentially partition the Shannon reservoir. The integration of 3D and high-resolution P-wave seismic interpretation helped us determine that some of the northeast-striking faults relate to deeper faults. This indicates that some deeper faults that are orthogonal to the fold hinge cut through the shallow Shannon reservoir. Such an observation would be important for understanding the effect on fluid communication between the deep and shallow reservoirs via these faults. Furthermore, the high-resolution seismic data provide a means to better constrain the location of faults mapped from drill hole logs. Relocation of theses faults may require re-evaluation of well locations as some attic oil may have not been drained in some Shannon blocks by present well locations. Therefore our study demonstrates how conventional 3D seismic data require additional seismic acquisition at smaller scales in order to image deformation in shallow reservoirs. Such imaging becomes critical in cases of shallow reservoirs where it is important to define potential problems associated with compartmentalization of primary production, hazard mitigation, enhanced oil recovery, or carbon sequestration.
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26

Bauer, Mark. "The seismic structure of southeast Alaska." Thesis, Indiana University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3611120.

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The convergent motion of the Pacific and North American Plates in Alaska has produced geologic features associated with subduction zones and has transported displaced terranes along the Queen Charlotte-Fairweather fault system that forms the northeastern boundary of the Pacific Plate. These subduction features stop abruptly at the edge of the Yakutat Block displaced terrane, approximately 300 km from the Queen Charlotte-Fairweather fault. The purpose of this study was to determine the type and geometry of the boundary between the Yakutat Block and North American as well as the cause of the offset volcanic arc and missing Wadati-Benioff zone.

I calculated P and S-wave receiver functions for 57 broadband seismic stations located in southeast Alaska. S-wave data was migrated using a Common Conversion Point procedure. P-wave data was imaged via a three-dimensional, pre-stack migration using plane-wave decomposition weighted by an inverse generalized Radon transform to calculate the scattering potential for each event. I also calculated the temperatures at the top of the Yakutat slab and mantle wedge using three different analytical thermal models.

The 3-D images and animations I produced show that the Yakutat Block is being subducted, continuous with the Pacific slab, and extends to the Queen Charlotte-Fairweather strike-slip fault systems. The subducted slab extends north to the Wrangell Volcanic Field with a dip than increases gradually from 10° in the west to 15° in the east, stripping approximately 15 km of overlying sediments. The location of the Wrangell Volcanic Field and lack of Wadati-Benioff zone are consistent with the temperatures I calculated for the top of slab and mantle wedge after stripping 15 km of sediment.

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27

Myers, Stephen Christopher. "Lithospheric-scale structure across the Bolivian Andes." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/289045.

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I have developed a three-dimensional, lithospheric-scale model of the Bolivian Andes at ∼20°S. The model is based on tomographic images of velocity and attenuation for both P- and S-waves. Observations of travel-time and attenuation for this study are from regional, mantle earthquakes in the subducted Nazca plate recorded on a portable, broadband seismic array in Bolivia. The shallow mantle under the Altiplano from ∼18°S to ∼20°S is high velocity, but seismic Q is relatively low (Vp∼8.3, Vs∼4.9, Qp∼150, Qs∼100). These seismic properties suggest lithospheric mantle, approaching solidus conditions. High velocity material in the Altiplano extends to a depth of ∼150 km at 18.5°S, shallowing to ∼100 km at 20.5°S. Anomalously low velocity and Q anomalies are imaged in the mantle beneath the Eastern (fold and thrust) and Western (volcanic arc) Cordilleras of Bolivia. In the Western Cordillera, velocity and attenuation anomalies are locally strong (Vp∼7.8, Vs∼4.25, Qp∼80, Qs∼20), consistent with partial melt conditions. However, there is a segment of higher velocity and Q between 19°S and 20°S, that is correlated with reduced Quaternary arc volcanism. In the Eastern Cordillera, shallow mantle velocity and Q generally decrease from Altiplano values, but there is a localized low velocity and Q anomaly (Vp∼7.8, Vs∼4.1, Qp∼50, Qs∼10) underneath the Los Frailes volcanic center. The strong velocity and attenuation anomalies and the spatial correlation with the volcanic complex favor an interpretation of partial melt. From the subduction trench into parts of the Western Cordillera, processes associated with Nazca Plate subduction dominate shallow mantle structure. Structural constrains from the tomographic results and the geologic history of the Bolivian Andes favor a model of lithospheric shortening for the development of shallow-mantle structure in the Eastern Cordillera and Altiplano. A delamination/partial-continental-subduction process is favored for the production of both shallow mantle structure and volcanism in the Eastern Cordillera. This process may remove mafic components in thickened lower crust, refining the crust towards a more felsic composition.
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28

Munk, Jens. "An equivalent source inversion method for imaging complex structures /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488191667184336.

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29

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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Portal, Angélie. "Etude géophysique de la structure interne d'un dôme volcanique : le Puy de Dôme et son environnement (Chaîne des Puys, France)." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22647/document.

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Les dômes de lave sont associés à des éruptions volcaniques violentes et des indices d’explosivité élevés. L’observation et la surveillance de dômes actifs (e.g. St. Helens, Unzen, Montserrat) ont mis en évidence des modes de croissance caractérisés par des phases d’extrusion, d’explosion et des phénomènes d’effondrement, impliquant une structure interne souvent complexe de ces édifices volcaniques. L’étude du Puy de Dôme (Massif Central français), un dôme trachytique âgé de 11 000 ans, grâce à l’apport de l’imagerie géophysique et à la modélisation des données, ainsi qu’à une analyse morpho-structurale détaillée, a permis d’établir un modèle précis de la structure interne du dôme et a fourni de nouvelles contraintes concernant sa croissance et son évolution. L’analyse du Modèle Numérique de Terrain haute résolution (0,5 m) a permis d’identifier différentes unités sur le dôme, morphologiquement distinctes, et associées à des dynamismes éruptifs différents, ainsi que des structures volcano-tectoniques remarquables sur les édifices volcaniques voisins (Petit Puy de Dôme et Puy des Grosmanaux). Différentes méthodes géophysiques (tomographie des résistivités électriques – ERT -, gravimétrie et magnétisme) ont été mises en oeuvre afin d’étudier la structure interne du dôme, et de caractériser la nature des mécanismes à l’origine des zones de déformations identifiées dans l’environnement du Puy de Dôme. L’utilisation de plusieurs méthodes a permis d’étudier des paramètres physiques différents mais complémentaires, bien que l’interprétation globale des résultats géophysiques ait parfois été délicate dans le cas d’un édifice volcanique aussi complexe. Les modèles géophysiques 2D et 3D obtenus montrent que le Puy de Dôme repose sur des édifices volcaniques préexistants, un ensemble de volcans stromboliens dont la présence et/ou l’extension exacte étaient partiellement méconnues jusqu’alors. La structure interne de l’édifice, très hétérogène, est constituée d’une partie centrale très massive, entourée d’une ceinture de brèches d’effondrement, la zone sommitale du conduit étant affectée de nombreuses évidences d’une forte altération hydrothermale, caractéristique des dômes volcaniques. La partie supérieure du dôme est définie par une carapace de roches consolidées, de quelques dizaines de mètres d’épaisseur au maximum, alors que la base de l’édifice forme un talus constitué des dépôts d’effondrements gravitaires et d’écoulements pyroclastiques associés à la croissance du dôme. Enfin, les données gravimétriques et magnétiques ont permis la mise en évidence de la présence d’intrusions sous les édifices du Petit Puy de Dôme et du Puy des Grosmanaux. La géométrie de ces intrusions, déterminées grâce à différentes approches de modélisation, ainsi que la nature des roches qui les composent indiquent des processus de mise en place complexes
Volcanic domes are associated to violent volcanic eruptions and high explosivity indexes. Observation and monitoring of active domes (e.g. St. Helens, Unzen, Montserrat) underlined growth patterns characterized by extrusion phases, explosions and collapse events, involving the complex inner structure of these volcanic edifices. The study of the Puy de Dôme volcano (French Massif Central), a 11,000 years old trachytic lava dome, through geophysical imaging and data modelling, as well as a detailed morpho-structural analysis, allowed to build a precise model of the inner structure of the dome and provided new constraints about its growth and its evolution. The analysis of the high resolution Digital Terrain Model (0.5 m) allowed to identify distinct morphological units on the dome, as well as volcano-tectonic structures on the neighboring volcanic edifices (Petit Puy de Dôme and Puy des Grosmanaux). Different geophysical methods (Electrical Resistivity Tomography – ERT -, gravity and magnetism) have been implemented in order to study the inner structure of the dome and to characterize the initiating mechanisms of the deformations areas identified in the Puy de Dôme vicinity. The use of several methods allowed to study different, but complementary physical parameters, although the overall interpretation of the geophysical results is sometimes difficult in the case of a volcanic edifice so complex. The 2D and 3D geophysical models obtained indicate that the Puy de Dôme is based on preexisting volcanic edifices, a cluster of strombolian volcanoes whose the presence and/or the exact extension were partially unknown until now. The internal structure of the edifice, highly heterogeneous, is composed of a massive central part, encompassed of collapse breccia, and its summit part highlights evidences of a strong hydrothermal alteration, characteristic feature of volcanic domes. The upper part of the dome is defined by a carapace of consolidated rocks, a few meters thick, whereas the base of the edifice forms a talus composed of collapses and pyroclastic flows deposits associated to the dome growth. Finally, gravity and magnetic data pointed out the presence of intrusions beneath the Petit Puy de Dôme and the Puy des Grosmanaux edifices. The geometry of these intrusions, determined through different modelling approaches, and the nature of the rocks that composed them, indicate complex emplacement processes
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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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32

Uzun, Sibel. "Estimating Parameters of Subsurface Structures from Airborne Gravity Gradiometry Data Using a Monte-Carlo Optimization Method." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376943930.

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33

Boland, Andrew V. "A geophysical analysis of the Kapuskasing Structural Zone." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29012.

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A crustal scale seismic refraction experiment was conducted over the Kapuskasing Structural Zone, Northern Ontario, in 1984. The zone cuts obliquely across the east-west structural grain of the Superior Province in the Canadian shield and has been proposed as a cross-section of Archean crust exposed by thrust faulting along the Ivanhoe Lake Cataclastic Zone during early Proterozoic time. Five seismic refraction lines of 360-450 km in length were shot over the area to obtain a velocity structure for the uplift region. There were 18 profile shots and two fan shots with a recorder spacing of 2 to 5 km. Single trace processing has been developed for enhancement of secondary arrivals. Homomorphic filtering was used to obtain an estimate of the wavelet and then spectral division and cross-correlation with that wavelet were implemented to enhance the later arrivals on the trace. The improved secondary arrivals were used to locate lower crustal refracted phases and wide-angle reflections which were combined with the first arrivals to construct the velocity models. The wide-angle reflections were also correlated with events from coincident Vibroseis reflection data. The travel-times and amplitudes of the data from the profile lines have been modeled using asymptotic ray theory methods. We have imaged a low velocity zone, ranging from 4-5 km to 9-12 km depth, under the Abitibi greenstone belt; it is underlain by a highly reflective zone. There is a considerable deepening of the Moho from 40-43 km to 50-53 km under and to the west of the southern end of the Kapukasing Structural Zone. Analysis of wide-angle reflections on the fan shots has corroborated this thickening of the crust under the structure. A high velocity anomaly of 6.5-6.6 km/s has been imaged in the upper crust down to 20 km depth beneath the Kapuskasing structure with a suggested dip of 15° ± 2° to the west. High Poisson's ratio values (0.26), determined from shearwave arrivals, were imaged in the structure, suggesting a high mafic content for that material. Gravity profile modeling has been performed along the five seismic lines. The observed Bouguer anomaly variations have been matched using the structure as delineated by the seismic modeling and velocity-density values that fall within the scatter of the Nafe-Drake set of data points. 2d frequency domain filtering techniques have been applied to the regional gravity and magnetic data. Directional, bandpass, continuation and derivative filtering have been used to locate faults and terrane boundaries. The main thrust fault, the Ivanhoe Lake Cataclastic Zone (ILCZ), has been more clearly delineated by this filtering and agrees well with the surface geological mapping. An extension of the Lepage Fault has been outlined and indicates that this normal fault may have been important in the post-thrust stabilising period. Seismic estimates of the soling depth for the ILCZ were further constrained by considering the rheological properties of the constituent lithologies. From the results of previous heat flow and heat production work in this region and the structures inferred from the seismic interpretation, geotherms and strength curves were constructed for the present, a period after the stabilisation of the Superior craton, and the time of uplift. Present day heat flows were successfully matched using a mantle heat flow of 20 mW m⁻². The formation pressures and temperatures of the Kapuskasing granulites were achieved using only a 25 % increase in the mantle heat flow. From analysis of the strength curves for the time of uplift, estimates of the depth to the brittle-ductile transition for dry quartz ranged from 17 to 21 km. This depth is corroborated by the results of the seismic refraction and reflection analysis. The results of this thesis support the Percival and Card thrust model but with a soling depth of 17-21 km. This corresponds to a granulite zone thrust up from the mid to lower crust and is indicative of large scale horizontal tectonic processes in late Archean to early Proterozoic times.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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34

Turk, Sezer. "SEISMIC STRUCTURE AND TECTONICS OF THE ALASEHIR GRABEN,WESTERN TURKEY." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1399655393.

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35

Attias, Eric. "Geophysical analysis of marine gas hydrate structures." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/416892/.

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Gas hydrate deposits are known to store vast amounts of methane, and occur worldwide in marine and permafrost regions. Methane emissions driven by hydrate dissociation may contribute to submarine slope failures, geohazards to deep water infrastructures, and possibly climate change. Alternatively, hydrates are perceived as a viable energy resource. These environmental and economic implications mean that gas hydrate research is of both academic and industrial interest. To determine the environmental impact or economic potential of gas hydrate accumulations in any given geologic setting with a high level of confidence, it is mandatory to acquire lithological and geophysical information for a well-constrained joint interpretation. Robust delineation and quantification of gas hydrate structures is not a trivial task, due to inherent uncertainties from the absence of information regarding the physical properties of the reservoir of interest. In this thesis, I develop a rigorous joint interpretation scheme using marine controlled-source electromagnetic (CSEM), seismic and core data coupled by effective medium modelling, for the detection, delineation, and quantification of marine gas hydrate structures. The study area for this research is the CNE03 pockmark, situated on the Norwegian continental slope, Nyegga region, offshore Norway. The CNE03 pockmark is underlain by a pipe-like structure, where gas hydrate and free gas coexist. Marine CSEM data and sediment cores were acquired from the CNE03 pockmark, integrated and interpreted with collocated high-resolution two-dimensional seismic reflection and three-dimensional tomographic seismic data. The CNE03 pipe-like hydrate structure is detected and characterised using unconstrained and seismically constrained CSEM inversions of data obtained by ocean bottom electric field receivers (OBE). The unconstrained CSEM inversions detected the CNE03 pipe-like structure satisfactorily though with undefined and diffusive margins, which is mitigated by the seismically constrained inversions that improved the delineation of the CNE03 boundaries significantly. High-resolution resistivity imaging of the CNE03 pipe-like structure is achieved by a combined CSEM inversion of both the OBE and 3-axis towed electric field receiver (Vulcan) data. Robust quantification of hydrate content within the CNE03 structure is derived by comparison between CSEM and seismic datasets with joint elastic-electrical effective medium modelling scheme. The work I present in this thesis provides an integrated approach to elucidate both structural and fluid properties of sub-seafloor gas hydrate and free gas deposits. The joint interpretation framework applied here could also be utilised to map and monitor seafloor mineralisation, freshwater reservoirs, carbon capture and storage sites, and near-surface geothermal systems.
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36

Swenson, Jennifer Lyn. "Broadband regional waveform modeling to investigate crustal structure and tectonics of the central Andes." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/282873.

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We use broadband regional waveform modeling of earthquakes in the central Andes to determine seismic properties of the Altiplano crust. Properties of the shear-coupled P-wavetrain (SPL ) from intermediate-depth events provide particularly important information about the structure of the crust. We utilize broadband seismic data recorded at the BANJO and SEDA stations, and synthetic seismograms computed with a reflectivity technique to study the sensitivity of SPL to crustal and upper mantle parameters at regional distances. We find that the long-period SPL-wavetrain is most sensitive to crustal and mantle Poisson's ratios, average crustal velocity, and crustal thickness. A comprehensive grid search method developed to investigate these four parameters suggests that although trade-offs exist between model parameters, models of the Altiplano which provide the best fit between the data and synthetic seismograms are characterized by low Poisson's ratios, low average crustal velocity and thick crust. We apply our grid search technique and sensitivity analysis results to model the full waveforms from 6 intermediate-depth and 2 shallow-focus earthquakes recorded at regional distances by BANJO and SEDA stations. Results suggest that the Altiplano crust is much thicker (55-65 km) and slower (5.75-6.25 km/s) than global average values. Low crustal and mantle Poisson's ratios together with the lack of evidence for a high-velocity lower crust suggests a bulk felsic crustal composition, resulting in an overall weak crust. Our results favor a model of crustal thickening involving large-scale tectonic shortening of a predominantly felsic crust. To better understand the mechanics of earthquake rupture along the South American subduction zone, we have analyzed broadband teleseismic P-waves and utilize single- and multi-station inversion techniques to constrain source characteristics for the 12 November 1996 Peru subduction zone earthquake. Aftershock locations, intensity reports, directivity, and spatial locations of seismic moment pulses indicate that the 1996 Peru event ruptured primarily southeast. This earthquake re-ruptured a portion of the 1942 Peru event. We find no indication that the 1996 Peru earthquake ruptured to the northwest, suggesting a sizable gap along the Peru trench corresponding to the position of the northwest flank of the subducting Nazca Ridge.
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Ross, Christopher P. "AVO limitations near salt structures." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/31010.

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38

Qiu, Xuelin. "Lithospheric structure of southern Africa from seismic waveform modelling." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264286.

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39

Zhu, Lupei Helmberger Donald V. "Broadband waveform modeling and its application to the lithospheric structure of the Tibetan plateau." Diss., Pasadena, Calif. : California Institute of Technology, 1998. http://etd.caltech.edu/etd/available/etd-12072006-152420/.

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40

Grinc, Michal. "Lithospheric structure in Central Europe : integrated geophysical modelling." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00921044.

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The main aim of this thesis is to gain new knowledge about the lithospherical structure and tectonics of the Carpathian-Pannonian Basin region. We applied three different methods: 1Dautomatic modelling, 2D integrated geophysical modelling and 3D inversion to achieve this goal.These methods are similar concerning the used databases but differ by used processing andinterpretation. At first we apply 1D automatic modelling to get a very first overview of thestudied region. Secondly, we apply 2D integrated modelling of the lithosphere which combines the interpretation of surface heat flow, geoid, gravity, and topography data in the Carpathian-Pannonian Basin region and surrounding areas. This approach is able to constrain the complicated lithospheric structures of the studied region better than interpreting each data set onits own. We present four 2D integrated models of the lithosphere in the Carpathian-PannonianBasin region and surrounding areas. Finally, based on the 3D Inversion algorithm, we present the geophysical models of the lithosphere in the Carpathian-Pannonian region. The algorithm returns the density structure of the lithosphere from joint inversion of free air gravity, geoid andtopography data based on a Bayesian approach. The models are based on different input data sets and constrained by different a priori data. Based on our modelling we cannot confirm theextreme thinning (less than 70 km) of the Pannonian Basin lithosphere proposed by other authors.On the other hand, the results show the increasing trend of the lithospherical thickness of theCarpathian Arc from the Western Carpathians toward the Eastern Carpathians which confirms theprevious theories about the propagation of subduction process. We got some controversial resultsin the area of the Southern Carpathians. The results based on 3D inversion show extremely thinlithosphere in the area; on the other hand, the results based on 2D integrated modelling do notsupport such thinning. However both methods indicate that it is probable that the MoesianPlatform is bend and underthrusted underneath the Southern Carpathians. The south-eastern edge of the Pannonian Basin based on 3D inversion shows unexpected and surprisingly thinlithosphere. Since the area is quite large, we could exclude an effect of flexure, therefore this area might be potentially interesting for further investigation.
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Plotka, Hanna. "The structure, stability and interaction of geophysical vortices." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3729.

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This thesis examines the structure, stability and interaction of geophysical vortices. We do so by restricting our attention to relative vortex equilibria, or states which appear stationary in a co-rotating frame of reference. We approach the problem from three different perspectives, namely by first studying the single-vortex, quasi-geostrophic shallow-water problem, next by generalising it to an (asymmetric) two-vortex problem, and finally by re-visiting the single-vortex problem, making use of the more realistic, although more complicated, shallow-water model. We find that in all of the systems studied, small vortices (compared to the Rossby deformation length) are more likely to be unstable than large ones. For the single-vortex problem, this means that large vortices can sustain much greater deformations before destabilising than small vortices, and for the two-vortex problem this means that vortices are able to come closer together before destabilising. Additionally, we find that for large vortices, the degree of asymmetry of a vortex pair does not affect its stability, although it does affect the underlying steady state into which an unstable state transitions. Lastly, by carefully defining the "equivalence" between cyclones and anticyclones which appear in the shallow-water system, we find that cyclones are more stable than anticyclones. This is contrary to what is generally reported in the literature.
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42

Barkels, David, and Johan Åberg. "Mapping leachates and subsurface structures using different geophysical methods." Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171814.

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The enrichment of ore produces large amounts of sulfur and metal-rich residual waste called tailings, which need to be deposited and stored for a long time. When the tailing is oxidized, large amounts of protons and metals are dissolved and diffuse to the groundwater. This poses a major environmental threat to biological life forms in the downstream ecosystem (Karltorp, 2008). In this study, leachate plumes and geological structures surrounding the tailings impoundment at the Kringelgruvan mine in northern Sweden have been successfully mapped using geophysical methods. Three methods have been used in parallel, slingram, ground penetrating radar (GPR) and electrical resistivity measurements, known as continuous vertical electrical sounding (CVES). The resulting data from GPR and CVES have been co-analyzed using Matlab. Algorithms have been produced that plots underground structures from CVES and compares them with interpreted structures from GPR. Studies have shown that the GPR is more sensitive than CVES to local variations of substructures when used in shallow soil cover, while CVES gives considerably more information regarding localization of the leachates and other electrically conductive materials, such as ore. Slingram EM31 has been shown to be the most time-efficient method to localize groundwater flow.
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43

Heimgartner, Michelle N. "The geophysical structure of the Sierra Nevada crustal root." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442856.

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44

Avila, Victor Manuel. "Geophysical constraints on the Hueco and Mesilla Bolsons| Structure and geometry." Thesis, The University of Texas at El Paso, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10133864.

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The Hueco and Mesilla Bolsons are part of the intramountain basins of the Rio Grande Rift system. These bolsons are the primary source of groundwater for the El Paso-Ciudad Juarez metropolitan area and contain faults that show evidence of repeated earthquakes during the Quaternary. The region is also associated with has low-level (M<4) seismicity. The collection and analysis of precision gravity data, coupled with information from water wells, multichannel analysis of surface waves (MASW) studies and previously published seismic reflection lines, have been used to examine the structure and faulting within these bolson. This study reveals that the Hueco and Mesilla Bolsons are very different structurally. The southern Mesilla Bolson contains about 500 m of sediment. Faults are difficult to trace and have less than 50-100 m of displacement across them. The southernmost bolson contains numerous Tertiary intrusions and the thickness of Cretaceous bedrock appears to decrease from south to north, possibly delineating the edge of Laramide age deformation within the bolson. The northern Hueco Bolson contains 1800 to 2500 m of basin fill. Displacement along the East Franklin Mountains fault (EFMF), a fault with evidence for repeated earthquakes within the past 64,000 years, is about 1500 m, and displacement on intrabasin faults is 200-300 m. Several intrabasin faults appear to control the saline to freshwater contact within the bolson. The EFMF may extend over 30 km south of the end of its mapped trace at the end of the Franklin Mountains and a number of intrabasin faults also extend south into the urbanized regions of the study area. The EFMF and other basin structures appear to be offset or disrupted at the speculated edge of Laramide deformation that lies beneath the bolson. Horizontal Gradient Methods (HGM) were applied to the gravity data and were successful for tracing faults and older Laramide features within the Hueco Bolson beneath the urbanized regions of the cities. HGM were not as successful at tracing faults within the Mesilla Bolson, however they were helpful for tracing the subsurface extent of igneous intrusions including the Mt. Cristo Rey, River, Three Sisters, and the Westerner outcrops. Some of these features appear linked at depth by a series of dikes and faults. MASW data were used to determine the average shear wave velocity in the upper 30m (Vs 30) at ∼70 sites within the Hueco Bolson. These observations were combined with similar data collected previously in Juarez to produce regional velocity and site classification maps. The results show low velocities are found close to the river within fluvial deposits with higher velocities close to the Franklin Mountains where bedrock is close to the surface and higher velocities in upland regions of northeast El Paso were soils appear to be more highly cemented. These data will be used in conjunction with information on bolson geometries to model the expected effects of strong ground motion from earthquakes in the El Paso-Ciudad Juarez region.

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45

Chaudhury, Suman. "Marine geophysical studies of the southern margins of the Iberian Peninsula." Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:1ee8721f-9324-48bd-8d57-b645e02d75fd.

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A wide variety of tectonic settings are juxtaposed at the southern margins of the Iberian Peninsula. The regional geology comprises an Atlantic passive margin in western Iberia, the convergent eastern part of the Azores-Gibraltar plate boundary zone between Africa and Eurasia, and an orogenic arc (the Betic-Rif mountains) surrounding an extensional basin (the Alboran Sea). The complex tectonic history of the southern Iberian margins is recorded in its sediments and structure, and these were investigated in this study using multichannel seismic reflection techniques in conjunction with other marine geophysical data. Multichannel seismic reflection and well data from the Gulf of Cadiz have shown that the earliest sediments are Triassic evaporites, followed by Jurassic carbonates, which form rotated fault blocks in the Gulf of Cadiz. Backstripping and thermal modelling has indicated that a rifting event took place in the Late Jurassic, which stretched the crust by ~20-50%. Gravity modelling, and mapping of stretching factors, has suggested that two zones of thinning underlie the Gulf of Cadiz, which are related to the original rifting event. Backstripped subsidence curves indicate passive margin thermal subsidence until the Miocene, when westward-directed thrusting and loading from the Betic-Rif mountain belt is reflected in a typical foreland basin tectonic subsidence signature of accelerated subsidence with time. A giant, chaotic body of allochthonous sediment was emplaced into the central Gulf of Cadiz as westward migration of the Gibraltar Arc led to oversteepening of the margin west of the Gibraltar Straits, while the Alboran Sea was simultaneously undergoing active extension. These allochthonous deposits are composed mainly of Triassic evaporites and Palaeogene shales. In the Gulf of Cadiz and Seine Abyssal Plains this body has the appearance of an accretionary wedge, but a 300 km long northern lobe of the body extends into the Horseshoe Abyssal Plain. This lobe is interpreted as being a cumulative mass wasting feature, formed by the gravity-driven downslope transport of large allochthonous masses as debris flows and slides and slumps, encouraged by a regional gradient and a pre-existing trough in the Horseshoe Abyssal Plain. The total volume of sediments involved was of the order of 72 000 km 3 , and the time of emplacement has been estimated as being Tortonian on the basis of seismic correlation with core data at DSDP site 135. This chaotic unit has formed a series of longitudinal diapiric ridges in the northern Gulf of Cadiz, which have been interpreted to act as a transport system for gas generated in the lower slope area to migrate to the upper slope where gas-related features are seen. Gas hydrates are present beneath the lower continental slope, as inferred from a bottom-simulating reflection on seismic reflection profiles.
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Sainz-Maza, Aparicio Sergio. "Caracterización gravimétrica de zonas de rift en islas volcánicas oceánicas : aplicación a las islas de Tenerife y el Hierro." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/461592.

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Los sistemas de rift en configuraciones volcánicas, se encuentran relacionadas con crecimiento de grandes edificios volcánicos y se definen como áreas de la corteza sometidas a esfuerzos extensivos que generan fracturas en forma de fisuras a través de las cuales se emite lava. Los grupos de fisuras delinean los sistemas de rift. Tradicionalmente, los sistemas de rift han sido considerados áreas de la superficie terrestre que actúan a modo de conductos profundos que enlazan las zonas de generación del magma en el manto y corteza inferior con la superficie terrestre, canalizando y controlando el ascenso de los magmas de manera directa. Algunos estudios recientes basados en datos geológicos, geofísicos y paleomagnéticos cuestionan dicho enraizamiento profundo, considerando por el contrario un origen más superficial. Dicho origen estaría asociado tanto a la tectónica regional como a procesos locales relacionados con las variaciones en la carga gravitatoria durante el proceso de desarrollo de los edificios volcánicos. Con el objetivo de contribuir al conocimiento de estos sistemas hemos elegido estudiar los sistemas de rift de Tenerife y El Hierro, ambas situadas en el Archipiélago Canario. Ambas, ofrecen la oportunidad de llevar a cabo un estudio de este tipo a la vista de sus características superficiales. Morfológicamente, estas islas presentan lo que en apariencia serían tres zonas de rift cada una, también denominadas «dorsales». En superficie, ambas islas muestran una disposición similar de su volcanismo basáltico a lo largo de estás dorsales, habiéndose propuesto tradicionalmente una configuración de triple rift en cada isla. Con el fin de obtener una imagen interna de los sistemas de rift tanto en Tenerife como en el Hierro, se desarrollaron modelos tridimensionales de contrastes de densidad del subsuelo. Estos modelos fueron obtenidos mediante la aplicación de un algoritmo genético de inversión gravimétrica que emplea como parámetros de entrada los datos de las anomalías gravimétricas. Dichas anomalías fueron calculadas a través del análisis de una gran cantidad de datos de gravedad terrestre provenientes de distintas fuentes de datos, incluidos datos recogidos expresamente para la densificación de valores de gravedad en las áreas de estudio. Son estos modelos finales, los que hemos empleado como la base sobre la que argumentar las posteriores discusiones. El modelo obtenido para la isla de El Hierro, apunta en este caso, a que los sistemas de rift, son estructuras poco enraizadas, las cuales estarían originadas a pocos kilómetros de la superficie, siendo su configuración controlada por una combinación de la tectónica regional y por procesos extensivos tanto de carga como de inestabilidades gravitatorias. Estas estructuras, serían utilizadas para facilitar el transporte lateral del magma una vez que este alcanzara los niveles más superficiales de la corteza. El modelo tridimensional obtenido para la dorsal noroeste de la isla de Tenerife, sugiere una estructura análoga a la anterior, un origen superficial de estos sistemas de rift. En cambio, la comparación entre los modelos correspondientes a la estructura bajo dicha dorsal y la estructura del subsuelo correspondiente a la parte sur de la isla, señala claras diferencias entre ambas. Esto señala a que el origen de ambas es distinto y, por tanto, el modelo volcánico de la parte sur de la isla estaría más en correspondencia con un campo volcánico monogenético que con una configuración típica de rift, como ya había sido sugerido en trabajos previos.
Rift systems in oceanic volcanic areas are related to the growth of large volcanic buildings and are defined as areas of the crust subjected to extensive stresses that generate fractures in the form of fissures through which lava is emitted. The groups of cracks delineate rift systems. Traditionally, they have been considered deep structures acting as conduits that connect the areas of magma generation in the mantle with the earth's surface, controlling the magma rise in a way direct. Some recent studies based on geological, geophysical and paleomagnetic data question this deep rooting, considering instead a shallower origin. This origin would be associated with both regional tectonics and local processes related to variations in the gravitational load during the development process of volcanic buildings. In order to increase the knowledge of these systems we have studied the rift systems of Tenerife and El Hierro, both located in the Canarian Archipelago. Both, offer the opportunity to carry out a study of this type in view of its surface characteristics. Morphologically, these islands present three potential zones of rift, also denominated "dorsales". In surface, both islands show a similar arrangement of their basaltic volcanism along these “dorsales”, having traditionally been proposed a triple rift configuration in each island. We built an internal image of the Tenerife and El Hierro rift systems based in 3D models of subsoil density contrasts. These models were obtained by the application of an inversion genetic algorithm based on gravity data which uses as input parameters gravimetric anomalies. These models are the basis on which we will develop the subsequent discussions. The model obtained for the El Hierro Island, the rift systems are poorly rooted structures. They would have a shallower origin. Moreover, the three-dimensional model obtained for the north- western ridge of the island of Tenerife suggests a structure similar to the previous one, a superficial origin of these rift systems. In contrast, the comparison between the models corresponding to the structure under the “dorsal” and the subsurface structure corresponding to the southern part of the island, shows clear differences between the two. This indicates that the origin of both is different and, therefore, the volcanic model of the southern part of the island would be more in correspondence with a monogenetic volcanic field than with a typical configuration of rift, as already had been suggested in previous works.
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47

Leftwich, Timothy E. "Geophysical investigations of the crustal structure and evolution of Mars." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1147893346.

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48

Matthews, Jonathan. "The Quaternicionic structure of the Equation of Geophysical fluid Dynamics." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494783.

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49

Matthews, Jonathan. "The Quaternionic structure of the Equations of Geophysical fluid Dynamics." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494800.

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50

Ates, Abdullah. "Geophysical investigations into the deep structure of the Bristol area." Thesis, University of Bristol, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333977.

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