Investigating Plate Interface Structure and Potential Splay Fault Geometry in the Southern Mw 9.2 1964 Great Alaska Earthquake Rupture Area Using a Dense Node Array
Description:
The 1964 Mw 9.2 Great Alaska Earthquake is the largest earthquake ever recorded in North America. The Alaska-Aleutian megathrust produces some of the world's most devastating earthquakes, which makes it an excellent setting for studying the nature of subduction zones in terms of seismicity, rupture mechanisms, and structural heterogeneity. Preliminary studies have shown that the 1964 Great Alaska earthquake rupture area is divided into two major segments: the northern (Kenai) asperity and southern (Kodiak) asperity.
The Kodiak nodal array was deployed along a ~60 km road system on Kodiak Island during the 2018-2019 Alaska Amphibious Community Seismic Experiment (AACSE). These three-component 5 Hz geophones were deployed for 25 days between mid-May and mid-June, recording at 500 Hz with an average station spacing of ~200 m, enabling a spatially dense seismic data acquisition for high-resolution imaging and microseismic event detection. Recent imaging studies using teleseismic sources suggest that, unlike the Kenai rupture zone, the Kodiak segment lacks a low-velocity zone above the plate interface. This difference in interface structure implies a variation in rupture behavior between the two asperities, with a low impedance contrast across the plate interface beneath Kodiak Island. The 1964 Great Alaska earthquake is known to be associated with major splay faulting, generating a near-field tsunami. Recent fault mapping offshore Kodiak suggests that the newly identified Ugak fault was the most probable source of local tsunamis on Kodiak island in 1964. Here, we leverage the higher frequency content of local earthquake sources to further investigate splay faulting and plate interface structure within the Kodiak asperity. Current results using four events show a coherent plate interface beneath the Kodiak array; we further aim to delineate potential splay fault geometry along the bounding interface.
Session: Subduction Zone Structure From Trench to Arc [Poster]
Type: Poster
Date: 4/19/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Joshua O. Osasona
Student Presenter: Yes
Invited Presentation:
Authors
Joshua Osasona Presenting Author Corresponding Author josasona@unm.edu University of New Mexico |
Lindsay Worthington lworthington@unm.edu University of New Mexico |
Grace Barcheck grace.barcheck@cornell.edu Cornell University |
Geoffrey Abers abers@cornell.edu Cornell University |
Kiara Daly kad278@cornell.edu Cornell University |
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Investigating Plate Interface Structure and Potential Splay Fault Geometry in the Southern Mw 9.2 1964 Great Alaska Earthquake Rupture Area Using a Dense Node Array
Category
Subduction Zone Structure From Trench to Arc