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Evolution of Subsidiary Faults Associated With the Migration of the Mount Mckinley Restraining Bend, Denali Fault, Alaska

Description: 

The model of a migrating Mount McKinley restraining bend (MMRB) is established based on patterns of active faulting, topography, glaciers, and low-T thermochronology, but the connection between this migration and the patterns of local seismicity, and longer-term geomorphic markers is unclear. Previous analyses of Kantishna Cluster seismicity show that these earthquakes do not approximate discrete fault planes, yet correspond broadly with known active structures. We seek to derive a model of crustal deformation evolution associated with the MMRB that incorporates major regional geologic and geophysical phenomena. To constrain this model, we present new constraints on the rates and distribution of active faulting and combine this with the record of shallow seismicity and new geophysical observations. New results from terrestrial cosmogenic nuclide and luminescence dating of offset landforms, improved fault trace mapping and offset measurement from higher resolution topographic data, and new thermochronologic constraints refine our understanding of the extent, magnitude, and style of active faulting through the MMRB. We propose that the sub-clusters of low-magnitude seismicity with the Kantishna Cluster reflect individual ‘process zones’ of distributed fracturing and faulting associated with the development and propagation of faults outward from the migrating restraining bend. The geophysically-imaged sub-horizontal detachment beneath the Kantishna Hills occurs in a region exhibiting a longer record of distal deformation north of the MMRB as demonstrated by the uplift of the Kantishna Hills anticline. As cumulative uplift of the Kantishna Hills anticline decreases to the west, both the seismicity and the northern extent of active deformation abruptly step closer to the Denali fault. This concentration of deformation between the Hines Creek and Denali faults appears to reflect a shorter period of time interacting with the restraining bend and a lack of development of a deeper detachment to transfer strain into the foreland.

Session: Cordilleran Strike-Slip Faults as Seismogenic and Seismological Features - I

Type: Oral

Date: 5/2/2024

Presentation Time: 04:45 PM (local time)

Presenting Author: Sean

Student Presenter: No

Invited Presentation: 

Authors