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Date of Award

Spring 2024

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Roland, Emily Carlson

Second Advisor

Caplan-Auerbach, Jacqueline

Third Advisor

Walton, Maureen L.

Abstract

Offshore southeastern Alaska and western Canada, the Queen Charlotte Fault (QCF) separates the Pacific (PA) and North American (NA) plates. Here the plate boundary experiences ~55 mm/yr of dextral slip accompanied by increasing fault obliquity from north to south. Among the historical M>7 earthquakes that have occurred on the QCF, two recent earthquake ruptures in 2012 and 2013 highlight the potential for seismic and tsunami hazard along the margin. Earthquake observations and geophysical imaging following the 2013 Mw7.5 Craig earthquake provided new insight into QCF crustal architecture, but also created new questions about how earthquake rupture dynamics are related to strain localization and detailed margin structure along the central QCF. This thesis uses wide-angle refraction data from a recent margin-scale active source seismic experiment to characterize specific crustal materials bounding the Queen Charlotte Fault. Data collected during the 2021 Transform Obliquity on the Queen Charlotte Fault and Earthquake Study (TOQUES) is used to determine the first crustal-scale 2D seismic P-wave velocity profile crossing the QCF near the epicenter of the 2013 Mw7.5 Craig earthquake. Along this profile, the modeled seismic velocity structure is used to image the expression of the ocean-continental fault zone and probe for the existence of a fault damage zone. The resulting velocity model is considered within the context of anticipated margin deformation associated with strike-slip and convergent plate motions, as well as past earthquake behavior. I find that the central QCF is composed of a narrow, minimally damaged, near-vertical landward-dipping fault separating a down-warped and deformed Pacific plate from the thicker seismically-faster Alexander terrane on the North American side. These interpretations are supported by recent submarine geomorphology, gravity modeling, and seismic experiments aimed at defining this rapidly slipping oceanic-continental transform boundary.

Type

Text

Keywords

Tomography, Queen Charlotte Fault, Strike slip, earthquake, Alaska, Canada, Tectonophysics, Geophysics, Seismology, Alexander Terrane, terranes, faulting, fault zone, P-wave, velocity

Publisher

Western Washington University

OCLC Number

1441178599

Subject – LCSH

Faults (Geology)--Alaska; Faults (Geology)--British Columbia--Haida Gwaii; Strike-slip faults (Geology)--Alaska; Strike-slip faults (Geology)--British Columbia--Haida Gwaii; Fault zones--Alaska; Fault zones--British Columbia--Haida Gwaii; Earthquakes--Alaska; Earthquakes--British Columbia--Haida Gwaii; Earthquake zones--Alaska; Earthquake zones--British Columbia--Haida Gwaii; Seismology--Alaska; Seismology--British Columbia--Haida Gwaii; Geodynamics--Alaska; Geodynamics--British Columbia--Haida Gwaii; Seismic tomography--Alaska, Seismic tomography--British Columbia--Haida Gwaii; Seismic waves--Speed; Seismic traveltime inversion

Geographic Coverage

Haida Gwaii (B.C.); Alaska

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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