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Repeating Low-Frequency Earthquakes Near Wrangell Volcano, Alaska

Description: 

The geometry and tectonics near the eastern edge of the Alaska-Aleutian subduction zone are not well constrained. Complications arise here as the Yakutat microplate is colliding into and subducting beneath continental North America at near-Pacific-plate rates. Even more enigmatic is the source of volcanism for the Wrangell volcanic field (WVF), which occurs on the eastern edge of both the subducting Yakutat terrane and the anomalous ~400 km long gap in arc volcanism between the Cook Inlet volcanoes and the WFV. The region is also host to tectonic tremors, which coincide with the edges of the downgoing Yakutat terrane and likely mark slow slip on the subducting interface. Here, we report new tremor observations east of the Yakutat edge that are distinct from the known subduction zone tremor. The activity occurs south of the WVF and about ~100 km from the edge of the previously observed Yakutat tremor. We perform a matched-filter analysis using low-frequency earthquakes (LFEs) embedded within the tremor signal as templates to create a catalog of thousands of LFEs from 2014 – 2022. The 1-5 Hz LFEs occur episodically, with major episodes recurring every several months. We use data from a network of campaign stations operating from 2016-2018 and create phase-weighted stacks to emphasize phase arrivals for subsequent location. Preliminary analysis suggests the events occur ~25 km south of the WVF at depths of ~30 km. Based on the location and episodic nature of the LFEs, we suggest these events are tectonic in nature, and work is ongoing to constrain the fault geometry.

Session: Seismology's Role in Assessing Volcanic Hazard at Multiple Time Scales [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Aaron Wech

Student Presenter: No

Invited Presentation: 

Authors