Contribution of post-critical reflections to ground motions from mega-thrust events in the Cascadia subduction zone
| dc.contributor.author | McNeill, Andrew Floyd | |
| dc.contributor.supervisor | Spence, George D. | |
| dc.contributor.supervisor | Rogers, Garry Colin | |
| dc.date.accessioned | 2009-11-18T22:09:50Z | |
| dc.date.available | 2009-11-18T22:09:50Z | |
| dc.date.copyright | 2005 | en |
| dc.date.issued | 2009-11-18T22:09:50Z | |
| dc.degree.department | School of Earth and Ocean Sciences | en |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | In this study the contribution of post-critical reflections at the oceanic Moho to ground motions from mega-thrust events in the Cascadia subduction zone is examined. The hypothesis to be tested is that the Moho post-critical reflection is a primary component of the S-wave-field at large epicentral distances from a subduction zone thrust earthquake. Pseudo 3-D modeling using P-SV pseudo-spectral synthetic seismograms and ray tracing amplitude calculations are employed. Double couple line sources are initiated within a structural model for the Cascadia subduction zone that incorporates an updated Juan de Fuca slab geometry. Areas in which the oceanic Moho post-critical reflection is a primary component of the seismic wave-field are defined as a function of landward extent of rupture for the next mega-thrust event. For rupture extending landward of the down-dip limit of the seismogenic zone, Moho post-critical reflections create a broad maximum in peak ground motions at locations that fall within the Pacific Northwest urban corridor [Portland, Seattle. Vancouver. Victoria]. At these locations, ground motions from sources with dominant frequencies between 1 Hz and 3 Hz can be a factor up to 1.5 greater than those modeled in the absence of the oceanic Moho post-critical reflection. A second maximum is associated with the presence of forearc mantle serpentinization, which affords a route for post-critical reflections at the oceanic Moho to escape upwards toward the Earth's surface rather than being trapped in the oceanic crust wave-guide. The forearc mantle wedge acts to concentrate seismic energy within a narrow region at locations, just landward of major population centers. | en |
| dc.identifier.uri | http://hdl.handle.net/1828/1872 | |
| dc.language | English | eng |
| dc.language.iso | en | en |
| dc.rights | Available to the World Wide Web | en |
| dc.subject | earthquakes | en |
| dc.subject | Pacific Northwest | en |
| dc.subject | Japan | en |
| dc.subject.lcsh | UVic Subject Index::Sciences and Engineering::Earth and Ocean Sciences | en |
| dc.title | Contribution of post-critical reflections to ground motions from mega-thrust events in the Cascadia subduction zone | en |
| dc.type | Thesis | en |