Crustal Stress in Continental Alaska and the Yukon
Description:
The crustal stress field controls active fault orientations and the style of deformation. In continental Alaska, ponderous topographic relief, complex interactions between the lithosphere and subducting material, and a mosaic of inherited terrane boundaries may all exert strong influences on crustal stress and deformation. To map the state of stress in continental Alaska, we compile regional moment tensors from earthquakes in the North American Plate and then conduct formal stress inversions and forward modeling of frictional fault slip potential. While the availability of data vary across the state, both first-order patterns active across thousands of km and second-order anomalies spanning a few hundred km are resolved. Overall, horizontal maximum compression directions fan roughly radially about the Yakutat Microplate, from ENE-WSW in the Seward Peninsula and western Alaska and Brooks Ranges, to SSE-NNW in the central Alaska and Brooks Ranges, N–S in the Yukon Flats Basin, and NE–SW in the Wrangell, St. Elias, Ogilvie, and Mackenzie Mountains. The radial orientations are sustained across multiple independent stress provinces for up to 1000 km inland from the microplate. Consistent with models of indenter tectonics, however, the relative magnitude of horizontal compression decreases with distance from the Yakutat indenter: Evenly mixed reverse-oblique faulting in the Alaska, Wrangell, and St. Elias Ranges transitions to strike-slip between the Denali and Kaltag Faults, and strike-slip with secondary extension in the western Brooks Range, Seward Peninsula, and southwestern Alaska. Superposed ~15° variations in stress directions and small differences in faulting styles between stress provinces may be due to glacial rebound and other isostatic adjustments, gravitational potential energy variations, or mantle processes.
Session: Crustal Deformation and Seismic Hazard in Western Canada, Cascadia and Alaska [Poster]
Type: Poster
Date: 4/20/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Will Levandowski
Student Presenter: No
Invited Presentation:
Authors
Will Levandowski Presenting Author Corresponding Author bouldergeophysics@gmail.com Tetra Tech, Inc. |
Jamey Turner jturner@bgcengineering.ca BGC Engineering Inc. |
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Crustal Stress in Continental Alaska and the Yukon
Category
Crustal Deformation and Seismic Hazard in Western Canada, Cascadia and Alaska