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M.Sc. (Geology) / Please refer to full text to view abstract

The role of heterogeneity in two long-range systems is explored with a focus on the interplay of this heterogeneity with the component system interactions. The first will be the heterogeneous Ising model with long-range interactions. Earthquake fault systems under long-range stress transfer with varying types of heterogeneity will be the second system of interest. First I will review the use of the intervention method to determine the time and place of nucleation and extend its use as an indicator for spinodal nucleation. The heterogeneous Ising model with fixed magnetic sites will then be reformulated as a dilute random field Ising model. This reformulation will allow for the application of spinodal nucleation theory to the heterogeneous Ising model by correcting the spinodal field and the critical exponent sigma describing the critical behavior of clusters in spinodal nucleation theory. The applicability of this correction is shown by simulations that determine the cluster scaling of the nucleating droplets near the spinodal. Having obtained a reasonable definition of the saddle point object describing the nucleation droplet, the density profile of the nucleating droplet is measured and deviations from homogeneous spinodal nucleation are found due to the excess amount of sparseness in the nucleating droplet due to the heterogeneity. Earthquake fault systems are then introduced and a connection is shown of two earthquake models. Heterogeneity is introduced in the form of asperities with the intent of modeling the effect of hard rocks on earthquake statistics. The asperities are observed to be a crucial element in explaining the behavior of aftershocks resulting in Omori's law. A second form of heterogeneity is introduced by coupling the Olami-Feder-Christensen model to an invasion percolation model for the purpose of modeling an earthquake fault system undergoing hydraulic fracturing. The ergodicty and event size statistics are explored in this extended model. The robustness of the event size statistics results are explored by allowing for the dissipation parameter in the Olami-Feder-Christensen model to vary.

acase@tulane.edu / Fault growth is often accomplished by linking a series of en echelon faults through relay ramps. A relay ramp is the area between two overlapping fault segments that tilts and deforms as the faults accrue displacement. The structural evolution of breached normal fault relay ramps remains poorly understood because of the difficulty in defining how slip is partitioned between the most basinward fault (known as the outboard fault, which includes the severed fault tip), the overlapping fault (inboard fault), and any ramp-breaching linking faults. Along the Warner Valley fault in south-central Oregon, two relay ramps displaying different fault linkage geometries are lined with a series of pluvial shorelines that record a Pleistocene paleolake regression. The inner edges of these shorelines act as paleo-horizontal datums that have been deformed by fault activity, and are used to measure relative slip variations across the relay ramp bounding faults. By measuring the elevation changes using a 10m digital elevation model (DEM) of shoreline inner edges, I estimate the amount of fault activity on severed fault tips. In order to attribute shoreline deformation to fault activity I identify shoreline elevation anomalies, where deformation exceeds a ± 0.3% window from normalized elevation values; this encompasses my conservative estimates of natural variability in the shoreline geomorphology and the error associated with the data collection. For each ramp-breaching fault style activity is concentrated near the fault linkage site. Even after a ramp is fully breached the severed fault tip temporarily retains some connectivity to the main fault segment. Severed fault tips along a mid-ramp breach tend to be more active than the severed fault tip at a footwall breach. Persistent fault activity along the entire severed fault tip is dependent on the position of the linkage. These results indicate that on the time scale of 104 years after linkage, severed fault tips persist as active structures and accommodate meaningful amounts of strain. / 1 / Christopher Samuel Young

Graduation date: 1981 / Best scan available. Figures in original are black and white photocopies.

Mason, Texas and the surrounding areas have been previously studied and mapped at small scales, showing the large normal faults that cut through the area. Many secondary faults exist close to the large faults, and are not mapped in previous studies because of the small scale of the maps. The large number of faults, when the smaller secondary faults are considered, makes Mason a good place for studying the nature of normal faults in this region and making generalizations about their nature. This thesis examines one of these faults, the McMillan Fault, and the secondary faults in its hanging wall at a large scale, in order to assess the nature of normal faults in the Mason area. The McMillan Ranch in Mason, Texas, was mapped at a scale of 1:7,000 using both traditional and digital mapping methods, to determine the lengths and displacements of each fault, and attempt to determine a length/displacement ratio which can be applied to all normal faults in this area. A single length/displacement ratio was not determined, just as in previous studies. This study determined that the normal faults in the area are planar, high angle normal faults with varying displacement amounts. As a result, observations determined that deformation in the hanging wall of normal faults exceeded the deformation in the footwalls of the same faults. The main fault on the McMillan Ranch is the McMillan Fault, and its shape is determined based upon the orientation of the subsidiary normal faults in its hanging wall. A detailed study of the geology of the McMillan Ranch and the surrounding area, including a geologic history of the area, geologic map and cross section, and stratigraphic descriptions including bed-by-bed descriptions, stratigraphic column, and thin sections of each unit was carried out as a preliminary step to perform analyses of the faults on the ranch. The presence of the McMillan Fault was already known, and the pasture that was chosen for this study was best represented at a scale of 1:7,000. At such a large scale, it was necessary to recognize precisely where in the stratigraphic section the mapper was located, as some subsidiary faults were recognized by beds missing, rather than entire units. The structural data gathered from the field convey the varying natures of faults, even within the same area, and support the conclusion that length alone is not sufficient to predict displacement value on a fault.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 96-97). Also available via the Internet.

The focus of this research is on identification, location, interruption, characterization and overall management of faults in conventional AC distribution systems as well as isolated MVDC power systems. The primary focus in AC distributions systems is on identifying and locating underground cable faults using voltage and current waveforms as the input data. Cable failure process is gradual and is characterized by a series of single-phase sub-cycle incipient faults with high arc voltage. They often go undetected and eventually result in a permanent fault in the same phase. In order to locate such incipient cable faults, a robust yet practical algorithm is developed taking into account the fault arc voltage. The algorithm is implemented in the time-domain and utilizes power quality monitor data to estimate the distance to the fault in terms of the line impedance. It can be applied to locate both sub-cycle as well as permanent faults. The proposed algorithm is evaluated and proved out using field data collected from utility distribution circuits. Furthermore, this algorithm is extended to locate evolving faults on overhead distribution lines. Evolving faults are faults beginning in one phase of a distribution circuit and spreading to another phase after a few cycles. The algorithm is divided into two parts, namely, the single line-to-ground portion of the fault and the line-to-line-to-ground portion of the fault. For the single line-to-ground portion of the fault, the distance to the fault is estimated in terms of the loop or self-reactance between the monitor and the fault. On the other hand, for the line-to-line-to-ground and line-to-line portion of the fault the distance is estimated in terms of the positive-sequence reactance. The secondary focus of fault management in AC distribution systems is on identifying fault cause employing voltage and current waveform data as well as meteorological information. As the first step, unique characteristics of cable faults are examined along with methods to identify such faults with suitable accuracy. These characteristics are also used to distinguish underground cable faults from other overhead distribution line faults. The overhead line faults include tree contact, animal contact and lightning induced faults. Waveform signature analysis, wavelet transforms and arc voltages during the fault event are used for fault cause identification and classification. A statistical based classification methodology to identify fault cause is developed by utilizing promising characteristics. Unlike the AC system infrastructure which is already in place, the DC system considered in this document is that of a notional electric ship. The nature of DC current, with the absence of a current zero as well as the presence of power electronic devices influencing the current behavior, makes interrupting DC fault currents challenging. As a part of this research an innovative DC fault interruption scheme is proposed for rectifier- fed MVDC systems. A fault at the terminals of a phase-controlled rectifier results in a high magnitude current impulse caused by the filter capacitor discharging into the fault resistance. It is proposed to use a series inductor to limit the magnitude of this current impulse. The addition of the inductor results in an underdamped series RLC circuit at the output terminals of the rectifier which causes the fault current to oscillate about zero. Furthermore, it is proposed to utilize a conventional AC circuit breaker to interrupt this fault current by exploiting the zero crossings resulting from the oscillations. Using the proposed scheme for the example case, the peak fault current magnitude as well as the interruption time is significantly reduced. / text

No description available.

Oblique continental collision between the Pacific and Australian Plates in the central South Island of New Zealand (between c. 44 and 46°S) results in distributed reverse faulting. Only a few of these faults have been studied in detail, highlighting a major knowledge deficit in the earthquake behaviour, magnitude potential and contribution to seismic hazard for many faults in this part of the orogen. Three reverse faults are investigated in detail in this thesis: the Moonlight Fault Zone (MFZ), the Fox Peak Fault and the Forest Creek Fault. Geochronologic approaches, including Schmidt hammer exposure-age dating, radiocarbon dating, and optically stimulated luminescence dating, are combined with paleoseismic trenching, fault surface trace mapping, analysis of GPS and LiDAR survey data, and numerical modelling to characterise the rupture behaviour of these faults. A new Schmidt hammer chronofunction based on over 7000 clast analyses is developed that relates rebound value (R-value) to age for river terraces. The rapid, inexpensive, non-destructive, and statistically valid nature of this technique makes it widely applicable for age dating here and globally. I use Schmidt hammer exposure-age dating along with other geochronologic and surveying methods to show that stranded post-last glacial lake shorelines of Lake Wakatipu are undeformed and at a uniform elevation across the MFZ. This indicates an absence of uplift across the MFZ since c. 13 ka and suggests that this fault may be inactive or subject to long periods of interseismic quiescence despite its location in the active orogen. This result also challenges the long-held hypothesis that lake shorelines throughout central NZ are tilted due to isostatic rebound. Three segments of the Fox Peak Fault are identified through field mapping and surveying. Slip rates at over 50 locations along the 36.5 km total length of the fault (c. 1.5 mm yr⁻¹ maximum) co-vary with the bounding range topography and exhibit large gradients near intersecting NW-striking faults. Four paleoseismic trenches were excavated to determine if these segment boundaries represent barriers to earthquake rupture propagation. Evidence of 3-4 earthquakes since c. 16 ka on the two end segments with overlapping age uncertainties indicates that the recurrence interval of the fault is 2000-3000 years. The most recent event (MRE) occurred at c. 2.5 ka. Large single event displacement to length ratios on these segments and a single event scarp on the central segment indicate that while the segment boundaries control on-fault slip gradients, they are not likely to impede through-going ruptures in an earthquake. This is a relatively recent development from the long-term tectonic geomorphology, which is suggestive of range growth on separate faults.