Tectonic tremor in South-Central Alaska

Abstract:

The geometry of the eastern end of the Alaska-Aleutian subduction zone is complicated by inclusion of the Yakutat microplate, which also slips beneath continental North America at near Pacific Plate rates. Here, I perform a search for tectonic tremor to identify slow plate boundary slip by scanning continuous waveforms from 2007-2015 from all available seismic data in south-central Alaska. Using envelope cross-correlation, I detect and locate ~12,000 tectonic tremor epicenters that are confined along-strike to the edges of the tomographically imaged Yakutat terrane, and extend ~80 km east of the inferred Pacific Plate edge marked by Wadati-Benioff zone seismicity. I interpret tremor to mark slow, semi-continuous slip occurring at the interface between the Yakutat and North American plates, which continues beyond the eastern edge of the Pacific Plate. In this model, the Yakutat terrane is welded to the underlying Pacific Plate in the west, but extends past the eastern terminus of the subducting Pacific Plate.