The North Canterbury tectonic setting involves the southward propagating margin of easterly strike-slip activity intersecting earlier thrust activity propagating east from the Alpine Fault. The resulting tectonics contain a variety of structures caused by the way these patterns overlap, creating complexities on the regional and individual feature scale. An unpublished map by Jongens et al. (1999) shows the Ashley-Loburn Fault System crossing the plains from the east connected with the Springfield Thrust Fault in the western margins, possibly the southern limit of the east-west trending strikeslip activity. Of note are two hill structures inferred to be affected by this fault system. View Hill to the west, is on the south side of this fault junction, and Starvation Hill further east, was shown lying on the north side of a left stepover restraining bend. During thrust uplift and simple tilting of the View Hill structure, at least two uplift events post date last Pleistocene aggradation accounting for variations in scarp morphology. Broad constraints on fault dip and the age of the displacement surface suggest that slip-rates are in the order of 0.5 mm/year. East from View Hill, the strike-slip fault was originally thought to curve northeast, around the southeast of Starvation Hill. But there is neither evidence of a scarp, nor other clear evidence of surface faulting at Starvation Hill, which poses the question of the extent to which folding may reflect both fault geometry and fault activity. Starvation Hill is a triangular shape, with a series of distinctive smooth, semi-planar surfaces, lapping across both sides of the hill at a range of elevations and gradients. These surfaces are thought to be remnants of old river channels, and are indicative of tilting and upwarping of the hill structure. 3D computer modelling of these surfaces, combined with studies of the cover sequence on the hill, resulted in inferences being drawn as to the location of hinge lines of a dual-hinged anticline and an overview of the tectonic history of the hill. This illustrates the potential to apply topographical and geomorphic studies to the evolution of geometrically complex structures Starvation Hill is interpreted to be the result of two fault-generated folds, one fault trending north, the other, more recent fault, trending east. These two faults are thought to be sequentially developed segments of the original fault zone inferred by Jongens et al. (1999) but with reinterpreted location and mechanism detail. The presence of two faults has resulted in overprinted differential uplift of the structure, which has been significantly degraded, especially in the southwest corner of the hill. The majority of the formation of the northerly trending structure of Starvation Hill is inferred to be pre-Otiran, with uplift of the later east trending structure continuing into the late Pleistocene and Holocene.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaves 119-130). Also available on the World Wide Web.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

xiii, 75 p. : ill. (some col.) / Uplift rates associated with 12 episodic tremor and slip events on the Cascadia Subduction Zone occurring between 1997 and 2010 have been determined from hourly water level records from 4 NOAA tide gauges (Neah Bay, Port Angeles, Port Townsend, and Seattle). Displacements inferred from water levels generally agree with displacements inferred from modeling GPS data. Examination of uplift between events shows an inter-event deformation rate approximately equal in magnitude, with ETS events, on average, releasing strain accumulated between events, suggesting that ETS is consistent with the elastic rebound theory. Additionally, while the GPS record only extends to the late 1990s and the tremor record includes only recent decades for Cascadia, tidal records in the Pacific Northwest and around the world span many decades. Thus, by showing that ETS can be resolved in tidal records we open up the possibility that tidal records could be used to study ETS where other tools are not available. This thesis contains unpublished coauthored material. / Committee in charge: Dr. David A. Schmidt, Chair; Dr. Ray J. Weldon, Advisor; Dr. Dean Livelybrooks, Member

Subduction zone fault processes range from tsunami-generating megathrust events to aseismic creep along the deeper portions of the fault. Episodic tremor and slow slip (ETS) represents the transition between these two regimes, where slip occurs at semi-regular recurrence intervals of months-to-years. These events are also accompanied by low frequency earthquakes, referred to as tremor. The study of ETS in Cascadia has been made possible by the enhancement of large-scale seismic and geodetic networks. In this dissertation, I use a range of geodetic and seismic observations at sub-daily to decadal time scales to investigate the kinematic behavior of individual ETS events, as well as the long-term behavior of the ETS zone and its relationship with the updip seismogenic zone. In Cascadia, current seismic hazard maps use the ETS zone as the downdip limit of rupture during future megathrust events. In Chapter II, I utilize uplift rates derived from 80 years of leveling measurements to explore the possibility that long-term strain accumulation exists near the ETS zone. The uplift rates are consistent with a region of 10-20% locking on the updip side of the ETS zone. The lack of associated topography indicates that the accumulated strain must be released during the megathrust cycle. The correlation of tremor and slip in Cascadia suggests there is an inherent relationship between the two. In Chapter III, I develop a method for using tremor as a proxy for slip to assess the spatial relationship of tremor and slip. I compare predictions of tremor-derived slip models to results from static inversions of GPS offsets by modeling slip based on the density of tremor. These comparisons suggest that the correlation of tremor and slip is variable along strike and along dip. In Chapter IV, I explore how borehole strainmeters can improve our resolution of slip on the plate interface. I incorporate strainmeters into joint, time-dependent kinematic inversions with GPS data. The temporal resolution of strainmeters provides improved constraints when deriving time-dependent slip estimates during slow slip events, allowing us to better image the kinematics of slow slip. This dissertation includes previously published and unpublished material.

Master of Science / Department of Horticulture and Natural Resources / Jason Griffin / Cary L. Rivard / Sweetpotatoes [Ipomoea batatas (L.) Lam.] are nutritious, easily stored and marketed, well-adapted to organic production, and fit large or small farming operations. Commercial production of propagules for sweetpotato, vine cuttings known as slips, is concentrated among a few coastal states. Consequently, growers in the Central United States have limited access to planting material. Considering the crop’s sensitivity to cold climates and the increasing use of high tunnels (HTs) in the region, the implementation of HT production systems could be a viable mechanism for increasing the distribution of sweetpotato nurseries across the US. The goal of this project was to investigate the production of slip propagation beds in HT systems at two research stations in Northeast and South Central Kansas. Trials were conducted in 2016 and 2017 to compare yield and quality of organic slips grown in HTs and the open-field (OF). Additionally, a split-plot design was utilized inside the HT to compare slip yields for three planting densities (45, 65 and 85-seed roots/m²). Slips grown in the two systems (HT and OF) were field-planted to elucidate the impact of the system on subsequent root tuber yields and grade. HT enterprise budgets were developed to determine what the potential economic impact is for growers that wish to implement this system and to identify the appropriate planting density based on cost and return. In 2016, the HT plots produced more slips than in the OF (P < 0.05), and the overall average slip number was 226.7 in the HT and 147.8 in the OF across both years. However, slips grown in the HT had significantly fewer nodes, less foliage, and compactness (P < .001). The field performance study showed slightly greater average marketable storage root yield from slips produced in the OF (P = NS), but the quantity and distribution of graded storage roots were similar between slips grown in the HT and OF treatments. Increased planting density treatment corresponded with greater average slip yield across all harvests, but was only statistically significant during 1st harvest of 2016. The positive correlation between slip yield and planting densities plateaued between 65 and 85-seed roots/m². When using foundation seed roots the optimum profit for enterprise budgets was achieved at the 65-seed root planting density. The use of 25% foundation and 75% on-farm produced seed roots at 85-seed root density generated $1.05/ft² profit in HT—using the more manual cultural practices and equipment of two case studies. The results of these trials suggest that slip production in HTs may provide growers in the Central and Northern regions of the U.S. a viable technology for developing their own sweetpotato propagation schedule, without compromising plant yield or storage root production. When compared to other common HT crop budgets, our data suggest that HT slip production is an economically-viable system for growers who wish to incorporate slip propagation beds into their HT rotations.

Compte tenu de leurs propriétés mécaniques spécifiques extrêmement intéressantes, les alliages de titane sont largement utilisés notamment pour des applications aéronautiques. Une des limitations concerne certains composants critiques des turbomachines pour lesquels un effet « dwell » est parfois constaté. Ce processus survient dans des conditions particulières combinant un chargement cyclique (fatigue) et statique (fluage) à une température proche de l’ambiante et peut conduire à une rupture prématurée. Bien que de nombreuses études aient permis de cerner le problème, son origine physique/mécanique demeure mal comprise.Les travaux réalisés, essentiellement expérimentaux, visent à analyser les mécanismes de déformation et d’endommagement, sous chargement dwell, à différentes échelles et en lien avec la microstructure métallurgique de l’alliage Ti6242 lamellaire considéré. Des configurations particulières de colonies de lamelles que l’on a nommé « plumes » ont été identifiées comme étant à l’origine de la rupture en dwell. Les caractéristiques morphologiques et cristallographiques correspondantes ont été analysées par différents moyens de microscopie optique et électronique. Un outil d’analyse d’images basé sur la transformée de Fourier rapide a été spécifiquement développé afin de repérer et de quantifier ces éléments à l’échelle de la pièce. Au-delà des campagnes d’essais mécaniques mettant en évidence les conséquences de l’effet dwell en termes de durée de vie, des essais in situ sous microscope réalisés en traction, fluage et dwell sur des « micro-éprouvettes » instrumentées ont permis de mieux comprendre les processus élémentaires de déformation associés aux plumes et conduisant à des hétérogénéités des champs de déformation favorables à l’amorçage de fissures. / Thanks to their extremely attractive specific mechanical properties, titanium alloys are widely used, especially for aerospace applications. However, a “dwell-effect” may sometimes be observed, reducing the lifetime of some critical jet engine components. This phenomenon occurs under specific conditions combining cyclic (fatigue) and static (creep) loading at near ambient temperature and can lead to an early failure. Though many studies have investigated this problem, its physical and mechanical origin remains poorly understood.The aim of the present work was to analyse the deformation and damage mechanisms under dwell loading at different scales, and in relation with the microstructure of a fully lamellar Ti6242 alloy. Particular arrangements of colonies, so-called “feather-like structures”, have been identified as the origin of the failure under dwell conditions. Their morphological and crystallographic characteristics have been analysed by various optical and scanning electron microscopy means. A dedicated image analysis tool based on the fast Fourier transform has been developed to localize and quantify the feather-like structures at the scale of a jet engine component. A mechanical testing campaign demonstrated the dwell-effects consequence on the lifetime until failure. Furthermore, tensile, creep and dwell tests have been carried out in situ under the microscope on “microsamples” bearing gauges. They enabled a better understanding of the elementary deformation processes associated to the feather-like structures and how these structures lead to strain field heterogeneities favouring crack initiation.

Cette étude s’est focalisée sur la compréhension des mécanismes de déformation et d’endommagementd’un superalliage à base de Nickel (Udimet 720Li) utilisé pour la confection de disques de turbine hautepression soumis à des sollicitations monotones et cycliques à des températures inférieures à 500 °C.L’amorçage de fissures de fatigue à 20 °C et 465 °C a été systématiquement observé suivant des facettescristallographiques pour différents états métallurgiques. Une étude quantitative des traces de glissementplastique en surface a permis de montrer que cet endommagement est la conséquence d’une nontransmission de la déformation plastique entre grains voisins. Plus précisément, un mécanisme de rotationcristalline localisée au sein de micro-volumes à l’extrémité de bandes de glissement dans le grain voisin aété identifié à l’origine des fissures.Les configurations cristallographiques favorisant ce processus impliquent notamment les relations entresystèmes de glissement de part et d’autre du joint de grains (angle de TWIST), ou encore la présence d’uneprécipitation fine participant au confinement des bandes de glissement. / This study contributes to the understanding of the deformation and damage mechanisms in a Nickelbasedsuperalloy (the Udimet 720Li) used for the manufacturing of aeroengines high pressure turbinedisks submitted to monotonic and cyclic loadings at temperatures below 500 °C under service conditions.Fatigue crack initiation at 20 °C and 465 °C was systematically observed at large crystallographic facetswhatever the microstructure. An extensive quantitative study of the slip activity at the surface showed thatcrack initiation results from a difficult slip transmission between neighbouring grains. In more details, alocalized crystallographic rotation confined in micro-volumes detected at the tip of slip bands interactingwith the grain boundary were identified to trigger crack initiation.The crystallographic configurations favouring such a process are closely related to the TWIST anglebetween active slip systems on each side of the grain boundary and to a dense and fine precipitationconfining the plasticity.Mots-clés

Les bruits automobiles induits par le frottement sont à l’origine de nombreuses plaintes clients et occasionnent des coûts de garantie considérables pour les constructeurs automobiles. Les objectifs de la thèse consistent à comprendre la physique à l’origine de ces bruits et proposer des méthodologies de simulation afin de les éradiquer. Un système générique est tout d’abord étudié. Ce système discret met en jeu un contact entre deux masses et une loi de frottement de Coulomb présentant une discontinuité à vitesse relative nulle. Des calculs de valeurs propres complexes de ce système linéarisé autour de sa position d’équilibre glissant sont menés et montrent la présence d’instabilités par flottement voire par divergence. Les simulations temporelles montrent quant à elles que les non-linéarités de contact permettent de stabiliser les niveaux vibratoires en cas d’instabilité selon quatre régimes distincts. De plus, malgré ses trois degrés de liberté, ce système est capable de reproduire les mécanismes de stick-slip, sprag-slip et couplage modal ainsi que les bruits de crissement, grincement et craquement rencontrés sur les systèmes automobiles. Des études paramétriques sont également présentées et mettent en avant des bifurcations de Hopf ainsi que l’effet déstabilisant potentiellement induit par l’amortissement. Des méthodologies permettant de catégoriser les réponses en termes de bruit et de mécanisme sont par la suite proposées. Les occurrences et risques de ces derniers sont alors analysés et des tendances sont dégagées. Enfin, la relation entre les bruits et les mécanismes est établie. L’attention est ensuite portée sur un système automobile particulier. Afin d’étudier son comportement crissant, les analyses de stabilité et les simulations temporelles sont désormais menées sur des modèles éléments-finis. Les simulations temporelles permettent d’observer l’établissement de vibrations auto-entretenues et d’identifier, parmi tous les modes instables prédits lors des analyses de stabilité, celui qui est réellement à l’origine de l’instabilité. L’effet du coefficient de frottement sur les motifs de coalescence et les cycles limites est également investigué. Le risque de crissement est ensuite évalué pour des conditions d’utilisation variées du système. La méthodologie, basée sur des analyses de stabilité, permet de retrouver les principaux constats expérimentaux obtenus sur banc d’essai. Le rôle des géométries et des matériaux constituant le système est également discuté. Enfin, une solution permettant de réduire de façon significative le risque de crissement est proposée. / Automotive friction-induced noises are the source of many customer complaints and lead to hugewarranty costs for car manufacturers. The objectives of the thesis are to improve the understanding ofthe physics at the origin of these noises and to propose numerical methodologies to eradicate them.A generic system is first investigated. This discrete system includes a contact between two masses anda Coulomb friction law with a discontinuity at zero relative velocity. Calculations of complex eigenvaluesof the linearized system around its sliding equilibrium position are carried out and show the presence offlutter and even divergence instabilities. Time simulations show that contact non-linearities permit tostabilize the vibrational levels in case of instability according to four distinct behaviors. Furthermore,despite its three degrees of freedom, this system is able to reproduce the stick-slip, sprag-slip and modecouplingmechanisms as well as the squeal, squeak and creak noises encountered in automotive systems.Parametric studies are also presented and highlight Hopf bifurcations as well as the destabilizing effectpotentially induced by damping. Methodologies allowing the categorization of the responses in termsof noise and mechanism are then proposed. Occurrences and risks of these noises and mechanismsare thus analyzed and trends are highlighted. The relationship between noises and mechanisms is alsoestablished.A specific automotive system is then considered. In order to study its squeal behavior, stabilityanalysis and time simulations are now carried out on finite element models. Time simulations allowto observe the establishment of self-excited vibrations and to identify, among all the unstable modespredicted by the stability analysis, the one which is actually the source of the instability. The effectof friction on the coalescence patterns and limit cycles is also investigated. The risk of squeal is thenevaluated in different operating conditions. The methodology, based on stability analysis, leads toresults in good agreement with the experimental observations. The role of geometries and materialsconstituting the system is also discussed. Finally, a solution with significantly low risk of squeal isproposed.