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Forearc Seismic Structure at the Alaska Peninsula Revealed From AACSE Receiver Functions

Description: 

The Alaska Amphibious Community Seismic Experiment (AACSE) deployed 75 ocean-bottom seismometers (OBS) and 30 land stations across a 700 km × 250 km region along the Alaska Peninsula portion of the Alaska-Aleutian subduction zone. Including permanent seismic networks, over 130 stations are available for analysis. This region encompasses the Shumagin, Semidi, and Kodiak segments, defined by their along-strike variability in coupling, seismicity, and megathrust rupture, as well as a history of terrane accretion in the overriding North American plate, and uneven plate fabric orientation on the incoming Pacific plate. Here, we use receiver function (RF) analysis of teleseismic earthquakes to provide novel constraints on the seismic velocity structure of the subducting plate, overriding plate, and plate interface offshore.

We calculate RFs for 141 teleseismic events (M≥6.0, distance 30°–100°) using time-domain iterative deconvolution. We visually identify arrivals that are likely due to either the overriding or subducting plate Moho, or plate interface based on comparisons of their arrival times to expectations from regional models. Furthermore, similarity of RFs between proximal stations supports interpretations that these arrivals indicate crustal structure, even in traditionally noisy offshore areas. A primary challenge for OBS-derived RFs is contamination by complex reverberations from the water column and sediment layers. Our study area ranges from sites near the trench with varying thickness of unconsolidated sediment atop basement crust, to the forearc shelf composed of thicker accreted material that has more gradational increases in velocity with depth, spanning depths from ~100–5000 m. Understanding the effects of these varying site structures on RFs still is relatively underexplored. Thus, we investigate the predicted reverberations of these expected structures, and explore the reverberation waveform inversion method of Kim et al. (2024) to mitigate these effects, and recover the underlying crustal signal. We expect this approach to yield new, high-resolution constraints on the forearc seismic structure.

Session: Linking Subduction Zone Processes and Cascading Hazards in Alaska, Cascadia, Chile and Beyond [Poster]

Type: Poster

Date: 4/16/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Ivan P. Rojas Churkovic

Student Presenter: Yes

Invited Presentation: 

Poster Number: 131

Authors