Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap ...

• Main Author: Chuang, Yuling Lindsay
• Format: Text
• Language: English
• Published: University of British Columbia 2018
• Subjects: Yakutat; Alaska
• Online Access: https://dx.doi.org/10.14288/1.0363105; https://doi.library.ubc.ca/10.14288/1.0363105

Tectonic tremors in Alaska (USA) are associated with subduction of the Yakutat plateau, but their origins are unclear due to lack of depth constraints. We have processed tremor recordings to extract low-frequency earthquakes (LFEs), and generated a set of six LFE waveform templates via iterative network matched filtering and stacking. The timing of impulsive P (compressional) wave and S (shear) wave arrivals on template waveforms places LFEs at 40–58 km depth, near the upper envelope of intraslab seismicity and immediately updip of increased levels of intraslab seismicity. S waves at near-epicentral distances display polarities consistent with shear slip on the plate boundary. We compare characteristics of LFEs, seismicity, and tectonic structures in central Alaska with those in warm subduction zones, and propose a new model for the region’s unusual intraslab seismicity and the enigmatic Denali volcanic gap (i.e., an area of no volcanism where expected). We argue that fluids in the Yakutat plate are confined ...