Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures

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dc.contributor.utaustinauthorWalton, Maureen A. L.en_US
dc.contributor.utaustinauthorGulick, Sean P. S.en_US
dc.creatorWalton, Maureen A. L.en_US
dc.creatorGulick, Sean P. S.en_US
dc.creatorHaeussler, Peter J.en_US
dc.creatorRoland, Emily C.en_US
dc.creatorTrehu, Anne M.en_US
dc.date.accessioned2016-10-28T19:51:59Z
dc.date.available2016-10-28T19:51:59Z
dc.date.issued2015-05en_US
dc.description.abstractThe Queen Charlotte fault (QCF) is a dextral transform system located offshore of southeastern Alaska and western Canada, accommodating similar to 4.4 cm/yr of relative motion between the Pacific and North American plates. Oblique convergence along the fault increases southward, and how this convergence is accommodated is still debated. Using seismic reflection data, we interpret offshore basement structure, faulting, and stratigraphy to provide a geological context for two recent earthquakes, an M-w 7.5 strike-slip event near Craig, Alaska, and an M-w 7.8 thrust event near Haida Gwaii, Canada. We map downwarped Pacific oceanic crust near 54 degrees N, between the two rupture zones. Observed downwarping decreases north and south of 54 degrees N, parallel to the strike of the QCF. Bending of the Pacific plate here may have initiated with increased convergence rates due to a plate motion change at similar to 6 Ma. Tectonic reconstruction implies convergence-driven Pacific plate flexure, beginning at 6 Ma south of a 10 degrees bend the QCF (which is currently at 53.2 degrees N) and lasting until the plate translated past the bend by similar to 2 Ma. Normal-faulted approximately late Miocene sediment above the deep flexural depression at 54 degrees N, topped by relatively undeformed Pleistocene and younger sediment, supports this model. Aftershocks of the Haida Gwaii event indicate a normal-faulting stress regime, suggesting present-day plate flexure and underthrusting, which is also consistent with reconstruction of past conditions. We thus favor a Pacific plate underthrusting model to initiate flexure and accommodation space for sediment loading. In addition, mapped structures indicate two possible fault segment boundaries along the QCF at 53.2 degrees N and at 56 degrees N.en_US
dc.description.departmentInstitute for Geophysicsen_US
dc.description.sponsorshipUSGS Earthquake Hazards External Grants Programen_US
dc.description.sponsorshipNational Earthquake Hazards Reduction Programen_US
dc.description.sponsorshipUTIG Ewing/Worzel Fellowshipen_US
dc.identifierdoi:10.15781/T2RB6W49H
dc.identifier.citationWalton, Maureen AL, Sean PS Gulick, Peter J. Haeussler, Emily C. Roland, and Anne M. Tréhu. "Basement and regional structure along strike of the Queen Charlotte Fault in the context of modern and historical earthquake ruptures." Bulletin of the Seismological Society of America, Vol. 105, No. 2B (May., 2015): 1090-1105.en_US
dc.identifier.doi10.1785/0120140174en_US
dc.identifier.issn0037-1106en_US
dc.identifier.urihttp://hdl.handle.net/2152/43271
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialBulletin of the Seismological Society of Americaen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectislands refraction projecten_US
dc.subjectbritish-columbiaen_US
dc.subjectnortheastern pacificen_US
dc.subjectsoutheastern alaskaen_US
dc.subjectfairweather faulten_US
dc.subjecttransition faulten_US
dc.subjecttripleen_US
dc.subjectjunctionen_US
dc.subjectwestern canadaen_US
dc.subjectplate boundaryen_US
dc.subjectnorth-americaen_US
dc.subjectgeochemistry & geophysicsen_US
dc.titleBasement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Rupturesen_US
dc.typeArticleen_US

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