Key Points:
- We present receiver function imaging from a dense three-component
nodal array deployment on Kodiak Island above the subducting Pacific
Plate.
- A clear slab Moho conversion is found but, in contrast to the Kenai
Peninsula, there is no evidence of a low-velocity layer atop the slab.
- The 1964 Great Alaska Earthquake ruptured across structural segments
with heterogeneous plate interface properties.
We conduct a high-resolution teleseismic receiver function investigation
of the subducting plate interface within the Alaskan forearc beneath
Kodiak Island using data collected as part of the Alaska Amphibious
Community Seismic Experiment in 2019. The Kodiak node array consisted of
398 nodal geophones deployed at ~200 m spacing on
northeastern Kodiak Island within the southern asperity of the 1964
Mw9.2 Great Alaska earthquake. Receiver function images at frequencies
of 1.2 and 2.4 Hz show a coherent, slightly dipping velocity increase at
~30-40 km depth consistent with the expected slab Moho.
In contrast to studies within the northern asperity of the 1964 rupture,
we find no evidence for a prominent low-velocity layer above the slab
Moho thick enough to be resolved by upgoing P-to-S conversions. These
results support evidence from seismicity and geodetic strain suggesting
that the 1964 rupture connected northern (Kenai) and southern (Kodiak)
asperities with different plate interface properties.