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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Off-fault Damage Associated with a Localized Bend in the North Branch San Gabriel Fault, California

Becker, Andrew 1987- 14 March 2013 (has links)
Structures within very large displacement, mature fault zones, such as the North Branch San Gabriel Fault (NBSGF), are the product of a complex combination of processes. Off-fault damage within a damage zone and first-order geometric asperities, such as bends and steps, are thought to affect earthquake rupture propagation and energy radiation, but the effects are not completely understood. We hypothesize that the rate of accumulation of new damage decreases as fault maturity increases, and damage magnitude saturates in very large displacement faults. Nonetheless, geometric irregularities in the fault surface may modify damage zone characteristics. Accordingly, we seek to investigate the orientation, kinematics, and density of features at a range of scales within the damage zone adjacent to an abrupt 13 degree bend over 425 m in the NBSGF in order to constrain the relative role of the initiation of new damage versus the reactivation of preexisting damage adjacent to a bend. Field investigation and microstructural study focused on structural domains before, within, and after the fault bend on both sides of the fault. Subsidiary fault fabrics are similar in all domains outside the bend, which suggests a steady state fracture density and orientation distribution is established on the straight segments before and after the bend. The density of fractures within and outside the bend is similar; however, subsidiary fault orientations and kinematics are different within the bend relative to the straight segments. These observations are best explained by relatively low rates of damage generation relative to rates of fault reactivation during the later stages of faulting on the NBSGF, and that damage zone kinematics is reset as the host rock moves into the bend and again upon exiting the bend. Consequently, significant energy released during earthquake unloading can be dissipated by reactivation and slip on existing fractures in the damage zone, particularly adjacent to mesoscale faults. Thus, areas of heightened reactivation of damage, such as adjacent to geometric irregularities in the fault surface, could affect earthquake rupture dynamics.
2

Predicting the spatial distribution of stoats, ship rats and weasels in a beech forest setting using GIS

Lough, Hamish January 2006 (has links)
Using trap data the Hawdon, Poulter and South Branch valleys, a spatial distribution model was created for Stoats (Mustela erminea), Ship Rats (Rattus rattus) and Weasels (Mustela nivalis) in the North Branch of the Hurunui River. Ten spatial attributes were analysed in this thesis as potential spatial predictors of Stoats, Ship rats or Weasels; four of which were distance related measurements (distance from ecotonal edge, distance from river, distance from river tributary and distance from trapping edge); three were climate based variables (mean maximum temperature, mean minimum temperature and mean precipitation) and three were topographical based variables (elevation, aspect and slope). Relationships that existed between each spatial attribute and the number of Stoats, Ship Rats and Weasels caught were quantified by comparing the significance of the mean trapping rate with each spatial attribute and expressed spatially as maps in a Geographical Information System (GIS). Results from this thesis found elevation, aspect and distance from ecotonal edge as potential spatial predictors of Stoat populations. Elevation and aspect were found to be potential predictors of Ship rat and Weasel populations. GIS is able to predict the spatial distribution of pest species to a similar (or better) level compared to more formal associative models. The potential of GIS is however, restrained by the same limitations associated with these models. By using a larger trapping data set and identifying a number of social interactions between Stoats, Ship Rats and Weasels, one can improve the accuracy of spatially modelling each species within a Beech forest environment. Therefore, improve our understanding how landscapes influence the distribution of each pest species.
3

Predicting the spatial distribution of stoats, ship rats and weasels in a beech forest setting using GIS

Lough, Hamish January 2006 (has links)
Using trap data the Hawdon, Poulter and South Branch valleys, a spatial distribution model was created for Stoats (Mustela erminea), Ship Rats (Rattus rattus) and Weasels (Mustela nivalis) in the North Branch of the Hurunui River. Ten spatial attributes were analysed in this thesis as potential spatial predictors of Stoats, Ship rats or Weasels; four of which were distance related measurements (distance from ecotonal edge, distance from river, distance from river tributary and distance from trapping edge); three were climate based variables (mean maximum temperature, mean minimum temperature and mean precipitation) and three were topographical based variables (elevation, aspect and slope). Relationships that existed between each spatial attribute and the number of Stoats, Ship Rats and Weasels caught were quantified by comparing the significance of the mean trapping rate with each spatial attribute and expressed spatially as maps in a Geographical Information System (GIS). Results from this thesis found elevation, aspect and distance from ecotonal edge as potential spatial predictors of Stoat populations. Elevation and aspect were found to be potential predictors of Ship rat and Weasel populations. GIS is able to predict the spatial distribution of pest species to a similar (or better) level compared to more formal associative models. The potential of GIS is however, restrained by the same limitations associated with these models. By using a larger trapping data set and identifying a number of social interactions between Stoats, Ship Rats and Weasels, one can improve the accuracy of spatially modelling each species within a Beech forest environment. Therefore, improve our understanding how landscapes influence the distribution of each pest species.

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