Delineation of the Nootka fault zone and structure of the shallow subducted southern Explorer plate as revealed by the Seafloor Earthquake Array Japan Canada Cascadia Experiment (SeaJade)

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dc.contributor.authorHutchinson, Jesse
dc.contributor.supervisorKao, Honn
dc.contributor.supervisorSpence, George D.
dc.date.accessioned2020-05-25T20:15:29Z
dc.date.available2020-05-25T20:15:29Z
dc.date.copyright2020en_US
dc.date.issued2020-05-25
dc.degree.departmentSchool of Earth and Ocean Sciences
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractAt the northern extent of the Cascadia subduction zone, the subducting Explorer and Juan de Fuca plates interact across a translational deformation zone, known as the Nootka fault zone. The Seafloor Earthquake Array Japan-Canada Cascadia Experiment (SeaJade) was designed to study this region. In two parts (SeaJade I and II, deployed from July – September 2010 and January – September 2014), seismic data from the SeaJade project has led to several important discoveries. Hypocenter distributions from SeaJade I and II indicate primary and secondary conjugate faults within the Nootka fault zone. Converted phase analysis and jointly determined seismic tomography with double-difference relocated hypocenters provide evidence to several velocity-contrasting interfaces seaward of the Cascadia subduction front at depths of ~4-6 km, ~6-9 km, ~11-14 km, and ~14-18 km, which have been interpreted as the top of the oceanic crust, upper/lower crust boundary, oceanic Moho, and the base of the highly fractured and seawater/mineral enriched veins within oceanic mantle. During SeaJade II, a MW 6.4 mainshock and subsequent aftershocks, known as the Nootka Sequence, highlighted a previously unidentified fault within the subducted Explorer plate. This fault reflects the geometry of the subducting plate, showing downward bending of the plate toward the northwest. This plate bend can be attributed to negative buoyancy from margin parallel mantle flow induced by intraslab tearing further northwest. Seismic tomography reinforces the conclusions drawn from the Nootka Sequence hypocenter distribution. Earthquakes from the entire SeaJade II catalogue reveal possible rotated paleo-faults, identifying the former extent of the Nootka fault zone from ~3.5 Ma.en_US
dc.description.scholarlevelGraduateen_US
dc.identifier.bibliographicCitationHutchinson, J., H. Kao, G. Spence, K. Obana, K. Wang, and S. Kodaira, 2019, Seismic Characteristics of the Nootka Fault Zone: Results from the Seafloor Earthquake Array Japan–Canada Cascadia Experiment (SeaJade), Bull. Seismol. Soc. Am., doi: 10.1785/0120190008.en_US
dc.identifier.urihttp://hdl.handle.net/1828/11768
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectSeismic tomographyen_US
dc.subjectHypocenter relocationen_US
dc.subjectCascadia subduction zoneen_US
dc.subjectNootka fault zoneen_US
dc.subjectExplorer plateen_US
dc.subjectPlate deformationen_US
dc.subjectMegathrusten_US
dc.subjectJuan de fuca plateen_US
dc.subjectFocal mechanismsen_US
dc.subjectStrike-slip evolutionen_US
dc.subjectConverted phase depth distributionen_US
dc.subjectMoment tensor solutionsen_US
dc.subjectSeaJadeen_US
dc.subjectOcean bottom seismometersen_US
dc.titleDelineation of the Nootka fault zone and structure of the shallow subducted southern Explorer plate as revealed by the Seafloor Earthquake Array Japan Canada Cascadia Experiment (SeaJade)en_US
dc.typeThesisen_US

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