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.