Tectonic tremor observations across Alaska

Abstract

Tectonic tremor is a semicontinuous, low-frequency seismic signal associated with stable fault motion at major plate boundaries worldwide. In subduction zones, tremor often coincides with geodetic transients that indicate discrete slow slip on the subducting plate interface. Because tremor epicenters offer better spatial and temporal resolution than geodetic inversions of slip, detecting tremor can provide important constraints on plate interface properties, coupling, and dynamics. But in Alaska, challenges abound. The geographic scale of the Alaska–Aleutian subduction zone, the limited land available for instruments in the Aleutian Islands, and the messy nature of the tremor signal itself inhibit efforts to uniformly catalog tremor. Here, I present an overview of such efforts and what can and cannot be inferred from where tremor has been observed. Reliable tremor observations are confined to south-central Alaska in conjunction with the subducting Yakutat microplate, and one section of the eastern Aleutian Islands near Unalaska, with scant evidence of tremor elsewhere. Unique fault interface conditions may explain why tremor is limited to these regions, but most null results are not robust, and the limited observations preclude any large-scale interpretations.