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Geodynamic Modeling of Flat Slab Subduction Driving Microplate Tectonics in Alaska

Description: 

The Aleutian-Alaska subduction zone (AAS) forms the northern boundary of the Pacific Ring of Fire, a tectono-physiographic term for the collection of subduction zones that outwardly flank the eastern, northern, and western perimeters of the Pacific Ocean. The AAS is characterized by ocean-ocean subduction in the west (Aleutian segment) and by ocean-continent subduction in the east (Alaska segment). We present high-resolution, 3D visco-plastic models of the Alaska subduction zone that examine the effect of laterally variable plate coupling on the 3D dynamic feedback between the upper- and down-going plates. In particular, the models examine the role of localized increased plate coupling in the flat slab region on the microplate motion of the portion of south-central Alaska located both above the flat slab and south of the Denali fault, hereafter referred to as the southern Alaska microplate (SAK). The results show a variably coupled subduction interface and weak Denali fault shear zone produce higher plateness for the SAK and a better fit to observed variability in long-term slip rates along the length of the Denali Fault shear zone. Further, by incorporating a 3D tectonic configuration, the models show the SAK (not the North American plate (NAM)) overlies the flat slab segment of the subduction zone. Given that the 1964 Great Alaska earthquake epicenter occurs where SAK (not NAM) is the upper plate, the models suggest a large-scale tectonic framework for this event wherein the SAK plays a key role; namely, the tectonic regime of southern Alaska is analogous to that of oblique flat slab subduction driving large-scale motion of the SAK, with the Great Alaska earthquake situated in this domain of restricted escape. This implies that the long-term tectonics of the Denali fault shear zone and flat slab subduction interface are interconnected through the motion of the intervening SAK. Therefore, treating these features as interconnected may be important for future hazard assessment modeling in Alaska.

Session: From Geodynamics to Earthquake Rupture, Models That Cross Time- and Length-Scales [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Margarete

Student Presenter: No

Invited Presentation: 

Authors