Insights into strain-partitioning along a continental-oceanic transform from comprehensive marine seismic imaging of the Queen Charlotte Fault, offshore western Canada and southeast Alaska
Abstract
The Transform Obliquity along the Queen Charlotte Fault and Earthquake Study (TOQUES) addresses two fundamental questions: 1) How is transpressive strain accommodated and partitioned at transform plate boundaries? and 2) What are the primary physical conditions controlling deformation and seismogenesis along an oceanic-continental strike-slip fault? The Queen Charlotte Fault (QCF) is a transform plate boundary offshore Canada and southeast Alaska that accommodates >50 mm/yr of dextral strike-slip motion between the Pacific (PAC) and North America (NA) plates. The fault displays systematic changes in fault obliquity and PAC plate age along-strike and hosted large earthquakes in 2012 and 2013: the M7.8 Haida Gwaii thrust event and the M7.5 Craig strike-slip earthquake, respectively. Current understanding of how these variations affect seismicity, crustal-scale deformation, and lithospheric structure and dynamics is severely limited due to lack of instrumentation and modern seismic imaging. The TOQUES project, a comprehensive active-passive marine seismology campaign conducted in 2021-2022, systematically samples a ~450 km-long portion of the fault that captures the transition from potential underthrusting and wrench tectonics to pure strike-slip motion. New long-offset crustal-scale multichannel seismic reflection data collected aboard the R/V Marcus G. Langseth reveals fault zone architecture along the QCF and provides insight into the relationship between the QCF and off-fault structures on the PAC plate. Coincident wide-angle reflection/refraction profiles recorded on a temporary ocean bottom seismometer array deployed by the CCGS Tully will provide rheological constraints for understanding earthquake rupture behavior and will investigate the extent of potential PAC underthrusting along the southern QCF. A longer-term broadband ocean bottom seismometer array will characterize seismicity with the 2013 rupture zone. Each dataset will provide essential constraints for detailed structural imaging and seismicity characterization. Taken together, these new data will offer insight into how strike-slip and compressive strain are accommodated and partitioned over geologic timescales.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.T52C..02W