Thermal regime and petrologic metamorphism in Alaska: Implications for subduction interface and wedge earthquakes

Characterized by repeated large earthquakes, slow slips, and tectonic
tremors with their simultaneous release of large amounts of energy, the
unstable subduction interface beneath Alaska presents a chance to
understand the composite dynamic transition from deep to shallow
subduction channel where these enigmatic fault slips and seismic events
occur. The complex subducted slab morphology associated with the
frequent occurrence of various types of faulting behaviors in Alaska is
poorly understood. Our result shows that the subduction of the Pacific
plate and the subsequent release of large amounts of fluid likely
contribute to the repeated fast and slow earthquakes there, as evidenced
by the petrological metamorphic transition in the incoming plate. The
offshore Alaska seismogenic zone, as well as the slow earthquakes
identified near the Upper Cook Inlet, compare well with the distribution
of slab dehydration slivers, including large destructive earthquakes that
have occurred in Alaska. The fluid upwelling from dewatered oceanic crust
and the continental wedge serpentinizing is probably related to various
transportation pathways controlled by dip angle and upwell in the
predominant direction following the subduction channel or veins in the
overriding lithosphere.