1 Introduction
Understanding plate interface structure and subduction geometries can illuminate slip mechanisms, earthquake rupture behavior and shallow subduction zone processes. Because most global forearc regions are submerged, they are commonly studied via marine seismic methods, which, thus far, precludes dense-array natural source seismic imaging. Therefore, well-exposed forearcs such as Kodiak Island provide rare opportunities to study subduction zone and plate interface structure within the shallow forearc using a dense seismic array. Here, we use three-component node array data acquired in 2019 across northeastern Kodiak Island as part of the Alaska Amphibious Community Seismic Experiment (AACSE) to compute Ps teleseismic receiver functions (RFs) to better understand the nature of the plate interface in the rupture area of the 1964 Mw9.2 Great Alaska earthquake.
The Alaska-Aleutian subduction zone has hosted more M>8 earthquakes than any other system globally and offers opportunities to explore relationships between megathrust slip phenomena, seismicity, deformation and forearc structure. The Kodiak node array (Fig. 1) lies within the southern rupture area of the 1964 Mw9.2 Great Alaska earthquake, the second largest earthquake ever recorded (Kanamori, 1977, Fig. 1a). Coseismic slip and ground shaking from this event created damage across a 600-800 km section of the Alaskan margin and triggered local and far-field tsunami. Previous work investigating static deformation, seismic waves, and tsunami propagation revealed two major coseismic slip asperities: the Kenai asperity in the north and the Kodiak asperity in the south (Christensen & Beck, 1994; Ichinose et al., 2007; Johnson et al., 1996; Suito & Freymueller, 2009; Fig. 1a). Differences in rupture behavior, locking and recurrence interval between these two regions suggest major differences in subduction and interface properties within south-central Alaska.