Nine west-northwest-trending faults on the continental margin of Oregon and Washington, between 43° 05'N and 470 20'N latitude, have been mapped using seismic reflection, sidescan sonar, submersibles, and swath bathymetry. Five of these oblique faults are found on both the Juan de Fuca and North American plates, and offset abyssal plain sedimentary units left-laterally from 2.0 to 5.5 km. These five faults extend 8-18 km northwestward from the deformation front. The remaining four faults, found only on the North American plate, are also inferred to have a left-lateral slip sense. The age of the Wecoma fault on the abyssal plain is 600±50 ka, and has an average slip rate of 7-1 0 mm/year. Slip rates of the other four abyssal plain faults are 5.5 ± 2 - 6. 7 ± 3 mm/yr. These faults are active, as indicated by offset of the youngest sedimentary units, surficial fault scarps, offsets of surficial channels, and deep fluid venting. All nine faults have been surveyed on the continental slope using SeaMARC 1A sidescan sonar, and three of them were surveyed with a high-resolution AMS 150 sidescan sonar on the continental shelf off central Oregon. On the continental slope, the faults are expressed as linear, high-angle WNW trending scarps, and WNW trending fault-parallel folds that we interpret as flower structures. Active structures on the shelf include folds trending from NNE to WNW and associated flexural slip thrust faulting; NNW to N trending right-lateral strike-slip faults; and WNW trending left-lateral strike-slip faults. Some of these structures intersect the coast and can be correlated with onshore Quaternary faults and folds, and others are suspected to be deforming the coastal region. These structures may be contributing to the coastal marsh stratigraphic record of co-seismic subsidence events in the Holocene. We postulate that the set of nine WNW trending left-lateral strike-slip faults extend and rotate the forearc clockwise, absorbing most or all of the arc parallel component of plate convergence. The high rate of forearc deformation implies that the Cascadia forearc may lack the rigidity to generate M > 8.2 earthquakes. From a comparison of Cascadia seismogenic zone geometry to data from circum-Pacific great earthquakes of this century, the maximum Cascadia rupture is estimated to be 500 to 600 km in length, with a 150-400 km rupture length in best agreement with historical data. / Graduation date: 1994

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Islands are valuable research systems for evolution and conservation, but most work has focused on oceanic islands. Far less study has occurred on near-shore islands where inter-island and island-mainland dispersal is an important microevolutionary process. Further studies in near-shore systems would aid the expansion of island evolutionary theory and conservation initiatives. In this thesis, I studied populations of Song Sparrows (Melospiza melodia) on near-shore islands along the Pacific coast of North America to examine the causes and consequences of dispersal for microevolutionary and ecological processes. Within an island metapopulation, where inter-island distances ranged from 200m to 2km, male and female immigration rates were influenced by adult density and sex ratio respectively, suggesting that intrasexual territoriality influences immigration. Islands differed in immigration levels, with low immigration and high resident recruitment on more isolated islands. I next examine genetic structuring at a larger spatial scale (0-300km). I found that the scale of genetic structuring within continuously distributed populations was less than 10km, suggesting that Song Sparrows are a sedentary passerine. Regional comparisons revealed that holding geographic distance constant, larger genetic distances occur in areas located at subspecific boundaries or across water barriers. The apparent reduction in dispersal to islands had broad-scale consequences. Across Pacific Coast islands, island populations consistently had lower genetic variation than mainland populations. Small and remote island populations tended to have the lowest genetic variation. From an in situ conservation stance, populations on large, remote islands could be important contributors to intraspecific genetic diversity because of high genetic differentiation. Finally, I link genetic structuring with contemporary dispersal and show that migration rates among the Channel Islands are low, suggesting that these islands are demographically independent. The absence of shared mtDNA haplotypes between extant and extinct populations suggests that inter-island migration was historically low, potentially explaining why the two extirpated islands have not been recolonized. Collectively, my thesis results increase our understanding of the mechanisms of divergence on insular populations by examining factors affecting dispersal, the spatial scale of divergence and estimating the consequences of reduced gene flow on islands for broad-scale patterns of genetic variation, microevolution and demographic stability.

Graduation date: 2006

Graduation date: 1980

Islands are valuable research systems for evolution and conservation, but most work has focused on oceanic islands. Far less study has occurred on near-shore islands where inter-island and island-mainland dispersal is an important microevolutionary process. Further studies in near-shore systems would aid the expansion of island evolutionary theory and conservation initiatives. In this thesis, I studied populations of Song Sparrows (Melospiza melodia) on near-shore islands along the Pacific coast of North America to examine the causes and consequences of dispersal for microevolutionary and ecological processes. Within an island metapopulation, where inter-island distances ranged from 200m to 2km, male and female immigration rates were influenced by adult density and sex ratio respectively, suggesting that intrasexual territoriality influences immigration. Islands differed in immigration levels, with low immigration and high resident recruitment on more isolated islands. I next examine genetic structuring at a larger spatial scale (0-300km). I found that the scale of genetic structuring within continuously distributed populations was less than 10km, suggesting that Song Sparrows are a sedentary passerine. Regional comparisons revealed that holding geographic distance constant, larger genetic distances occur in areas located at subspecific boundaries or across water barriers. The apparent reduction in dispersal to islands had broad-scale consequences. Across Pacific Coast islands, island populations consistently had lower genetic variation than mainland populations. Small and remote island populations tended to have the lowest genetic variation. From an in situ conservation stance, populations on large, remote islands could be important contributors to intraspecific genetic diversity because of high genetic differentiation. Finally, I link genetic structuring with contemporary dispersal and show that migration rates among the Channel Islands are low, suggesting that these islands are demographically independent. The absence of shared mtDNA haplotypes between extant and extinct populations suggests that inter-island migration was historically low, potentially explaining why the two extirpated islands have not been recolonized. Collectively, my thesis results increase our understanding of the mechanisms of divergence on insular populations by examining factors affecting dispersal, the spatial scale of divergence and estimating the consequences of reduced gene flow on islands for broad-scale patterns of genetic variation, microevolution and demographic stability.

Thesis (M.A.)--University of Wisconsin--Madison, 1966. / Title from title screen (viewed July 2, 2008). Includes bibliographical references. Online version of the print original.

Thesis (M.M.A.)--University of Washington, 1997. / Includes bibliographical references (leaves [168]-182).

Thesis (Ph. D. in Anthropology)--Vanderbilt University, May 2010. / Title from title screen. Includes bibliographical references.

Based on Thesis (Ph. D.)--University of California, 1937. / Bibliography: p. [289]-304.