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Subduction Zone Interface Structure within the Southern MW9.2 1964 Great Alaska Earthquake Asperity: Constraints from Receiver Functions Across a Spatially Dense Node Array
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  • Evans Awere Onyango,
  • Lindsay L. Worthington,
  • Brandon Schmandt,
  • Geoffrey A. Abers
Evans Awere Onyango
University of New Mexico, University of New Mexico

Corresponding Author:[email protected]

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Lindsay L. Worthington
University of New Mexico, University of New Mexico
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Brandon Schmandt
University of New Mexico, University of New Mexico
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Geoffrey A. Abers
Cornell University, Cornell University
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Abstract

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 ~200-300 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.