6 Conclusions
We analyzed teleseismic P waves from 398 autonomous three-component 5-Hz nodal geophones on Kodiak Island as part of the Alaska Amphibious Community Seismic Experiment. We calculated RFs with a Gaussian value of 2.5 (~1.2 Hz) and a Gaussian value of 5.0 (~2.4 Hz). The lower frequency (1.2 Hz) RFs were comparable to RFs from near-collocated broadband seismometers, and the higher frequency (2.4 Hz) RFs image produced more details. In both low and high frequency images, there is a coherent, SE to NW dipping positive phase at the expected slab Moho depth but no observable negative arrival to indicate phase conversions at the oceanic crust. To help explain the observed RFs, we calculated synthetic RFs from 1-D models. These synthetic tests suggest that the overriding forearc material and Pacific oceanic crust have nearly identical seismic velocities and densities. We conclude that the 1964 Great Alaska Earthquake ruptured beyond the extent of the low-velocity shear zone observed in the Kenai asperity into a structural setting beneath Kodiak Island with little seismic contrast across the plate boundary interface.