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Geologic Evolution of the Denali Fault System and Associated Crustal Structure

Description: 

The Denali fault is an active right-lateral continental strike-slip fault that transects the North American Cordillera from northern British Columbia to the Bering Sea shelf. Along the ~1,100 km on-land section of the fault, the strike changes by over 100º and as a result the fault system complexity changes along strike, ranging from a multi-stranded fault with a well-defined locus of master faults in southwestern Yukon to a highly localized master strand bordered by splay thrust systems through central Alaska, then to a multi-stranded fault system in western Alaska. The structural evolution of the Denali fault as a major continental fault system that has accommodated hundreds of kilometers of displacement implies that the fault is a significant geophysical feature. However, the complex and diverse geology surrounding the fault and variability in geologic and geophysical data resolution related to the difficulty of access cause the perceived geophysical signature of the fault to be spatially variable.

Here, we aim to review the geologic evolution of the Denali fault system by blending new advancements with established ideas that have held up over time. We integrate the regional geologic framework with a series of new P-receiver function (PRF) profiles that cross the Denali Fault. The new PRF profiles use all available data (1999-2022) from both temporary and permanent broadband seismometers available from the IRIS DMC to image the crust. These data include the seven recently deployed ICED array stations that targeted the eastern Alaska Range and adjacent section of the Denali Fault that had previously been under-resolved by the TA and other deployments. Geophysical information from this section of the fault corroborates the geologic observations indicating that the Denali fault is a primary lithospheric-scale boundary, with some sections that clearly indicate a step across the Moho. However, in the west some sections of the fault there is no clear evidence in the PRFs of a change in crustal thickness.

Session: Crustal Deformation and Seismic Hazard in Western Canada, Cascadia and Alaska

Type: Oral

Date: 4/20/2023

Presentation Time: 08:30 AM (local time)

Presenting Author: Meghan S. Miller

Student Presenter: No

Invited Presentation: 

Authors