← Back to Sessions

WITHDRAWN Upper Plate Structure in the Alaska Subduction Zone Across the 2020 and 2021 Ruptures From 2D Wide-Angle Seismic Data

Description: 

WITHDRAWN The rigidity and permeability of the overriding continental plate are proposed to influence megathrust behavior in many subduction zones. Here we use 2D wide-angle seismic data acquired in 2011 to evaluate upper plate controls on megathrust behavior across the Semidi and Shumagin sectors of the subduction zone off the Alaska Peninsula. The Semidi segment is strongly locked and regularly ruptures in great (M>8) megathrust earthquakes, such as the M8.2 in 2021. The Shumagin segment is weakly coupled and appears to host regular M7.x events, such as the M7.8 in 2020, but has not hosted a M>8 in at least ~170 years. We present 2D P-wave seismic velocity models across these segments obtained from joint reflection and refraction tomographic inversion. Model uncertainty was estimated using a Monte Carlo approach. The resulting P-wave velocity models display large-scale velocity variations in the overriding plate that are interpreted to represent the extent of the accretionary prism and accreted crustal terranes that form the overriding plate: the Prince William and Chugach terranes. In the Semidi segment, recently recognized shallow slow slip and afterslip appear to be focused beneath the accretionary prism and younger, lower velocity Prince William Terrane while rupture in the 2021 earthquake is concentrated below the higher velocity Chugach terrane. In the Shumagin Gap, slip in the 2020 earthquake straddles the Moho of the overriding plate. Correlations between the downdip extent and style of slip events and overriding plate structure suggest an upper plate influence on megathrust behavior here.

Session: Structure and Behavior of the Alaska-Aleutian Subduction Zone [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Anne

Student Presenter: No

Invited Presentation: 

Authors