Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 228-244).

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Geodetic observations provide kinematic constraints on the behavior of tectonically active fault systems. Estimates of earthquake cycle activity derived from these constraints may depend on modeling assumptions and/or regularization of a geodetic inverse problem, which is often poorly conditioned. Common model assumptions may affect kinematic solutions and conclusions about physical properties of faults and fault zones. For example, within a geometrically complex fault system, parameterization of nearby faults may affect slip estimates on an individual fault. In addition, fault slip models are often regularized by assuming that slip varies smoothly in space, which may artificially smear slip estimates beyond physical boundaries. As an alternative to smooth regularization, the applied mathematics field of compressed sensing provides a suite of methods for recovering sparse solutions. Applied to GPS observations of the 2011 Tohoku earthquake, compressed sensing algorithms enable imaging of spatially localized slip during and following the earthquake, and identification of a sharp boundary between coseismic and postseismic slip. Similar algorithms recover quantized solutions and may be applied to models of plate boundary deformation. Beginning with a dense array of tectonic micro-plates bounded by mapped faults in North America, these methods can be used to detect coherent motions of groups of micro-plates behaving as larger active blocks, effectively quantifying the complexity of North America plate boundary deformation. By improving our ability to identify and compare kinematic constraints on earthquake cycle processes, we are able to characterize the spectrum of earthquake cycle behaviors and gain a deeper understanding of earthquake phenomenology and physics. / Earth and Planetary Sciences

Field study at seven Scottish sites has resulted in the following evidence for late- and post-glacial earthquakes and fault movements. a) Glen Roy, western Highlands: Earthquake-induced deformation structures are observed in 10,000 year-old lake deposits, and can be related to a surface fault rupture and several landslides. The deformation structures have been mapped over an area of 100 sq. km and display most intense deformation in a central area, with decreasing degrees of deformation in peripheral zones. This zonation is interpreted in terms of varying intensities of ground-shaking during a major earthquake. The field data indicate a magnitude 6.25 event. b) Kinloch Hourn, western Highlands: A prominent, 14-km long fault displays evidence for recurrent movement. A magnitude 5.5-6.0 event occurred between 3500 and 2400 years ago, and unquantified movement has occurred since then. c Firth of Lorn (west coast): Levelling survey, at two sites, indicates several vertical displacements of up to 3m, of a 10,000 year old raised shoreline. d) Lismore (west coast): Lateral fault displacements of c. 0.5m have disrupted present rock and soil morphology and indicate movement in the last few thousand years. e Tayside, eastern Scotland: Two sites display soft-sediment deformation structures in late-glacial sands and silts. The structures are interpreted as the result of (unquantified) earthquake ground-shaking. This field evidence is collectively evaluated in terms of crustal stress, earthquake recurrence and present-day earthquake hazard. Earthquakes as large as magnitude 7 are thought to have occurred but were probably triggered by glacial rebound stesses. Earthquakes upto magnitude 6 have certainly occurred, some as recently as 3000 years ago, and are likely to recur. Present-day surface fault displacements of up to 0.1m are considered likely on fractures favourably orientated with respect to the present-day stress field.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

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This study explores the impact post-earthquake images from Christchurch, New Zealand inserted into a task requiring sustained attention or vigilance have on performance, selfreports of task-focus, and cerebra activity using functional near-infrared spectroscopy (fNIRS). The images represent the current state of Christchurch; a city struggling to recover from devastating earthquakes that peaked in February, 2011, killing 185 people, injuring hundreds more and causing widespread and massive damage to infrastructure, land and building in the region. Crowdsourcing was used to gather a series of positive and negative photos from greater Christchurch to be employed in the subsequent experiment. Seventy-one Christchurch resident participants (51 women, 20 men) then took part in a vigilance task with the sourced images embedded to assess possible cognitive disruptions. Participants were randomly assigned to one of three conditions: embedded positive pictures, embedded negative pictures, or embedded scrambled image controls. Task performance was assessed with signal detection theory metrics of sensitivity A’ and β’’. Individuals viewing the positive images, relating to progress, rebuild, or aesthetic aspects within the city, were overall more conservative or less willing to respond than those in the other conditions. In addition, positive condition individuals reported lower task focus, when compared to those in the control condition. However, indicators of cerebral activity (fNIRS) did not differ significantly between the experimental groups. These results combined, suggest that mind wandering events may be being generated when exposed to positive post-earthquake images. This finding fits with recent research which indicates that mind-wandering or day dreaming tends to be positive and future oriented. While positive recovery images may initiate internal thoughts, this could actually prove problematic in contexts in which external attention is required. While the actual environment, of course, needs to recover, support agencies may want to be careful with employing positive recovery imagery in contexts where people actually should be paying attention to something else, like operating a vehicle or machinery.

The last 10 years has seen a renewed interest in the behaviour of unreinforced masonry panels under earthquake loading. Research on full scale structures requires massive, expensive test equipment, is time consuming and costly in manpower. Full scale testing therefore, has been limited to specific, very narrow investigations. Modelling at a reduced scale offers immense savings with wider possible fields of study. The first stage of the author's work was aimed therefore at developing prototype materials for 1: 4 scale models, and establishing their fundamental mechanical properties. A complete description of the material properties should provide all the parameters for numerical and analytical predictions and for static and dynamic testing of prototype replicas at the small scale. The parameters investigated in the static testing phase included compressive, tensile and shear strength, Young's modulus and Poisson's ratio, shear modulus and brick-mortar interface bond among others. The second stage involved the development of a shaking table and the investigation of six low-aspect, confined, infill panels subjected to sinusoidal cyclic loading. The study investigated their dynamic behaviour and energy dissipation capacity with progressive damage. Parametric studies were conducted with respect to the brick, mortar and masonry strength. The damage was photographically documented and the cracking propagation is detailed from the initial stages up to collapse. Classic full scale cracking patterns and failure modes were observed which gave the author considerable confidence in the model results. Shear-ductile failures were recorded for panels confined by low axial compressive forces which seems in part to contradict some current opinion, but reference is also given to similar findings published recently in scientific journals. The final component of the work was concerned with a numerical assessment using a commercially available finite element program incorporating a non-linear concrete constitutive material model. This numerical model was fine-tuned by using the previously obtained experimental data to simulate cracking patterns of small masonry specimens under static load.

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