Velocity structure of the Queen Charlotte Fault across the 2013 Mw 7.5 Craig earthquake region

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.