Temperature distribution for interplate seismic events in the southcentral Alaska subduction zone based on 3-D thermomechanical modeling

In the southcentral Alaska subduction zone, the Pacific plate and an oceanic plateau, known as the Yakutat terrane, are subducting at a convergence rate of similar to 4.7 cm/yr in the direction of N21.5 degrees W with respect to the current North American plate. We constructed a 3-D thermomechanical model to simulate the simultaneous subduction of the Pacific plate and Yakutat terrane. In the numerical simulation, the oceanic plate subducts along a 3-D geometry model obtained from the seismic data, with a spatiotemporally changing convergence rate that was provided based on the past plate motion model. Under these conditions, we obtained the time-dependent temperature and mantle flow velocity fields from 18 Ma to the present. As a result, we discovered that the interplate temperature for the source region of the 1964 Alaska earthquake with a coseismic slip larger than 2 m was estimated to be 155-323 degrees C at depths of approximately 10-20 km. We also estimated the temperature for the slip area with cumulative slip larger than 5 cm of the northeastern 2009-2013 long-term slow slip event (L-SSE) and the southwestern 2010-2012 L-SSE to be 337-570 degrees C and 300-381 degrees C, respectively. In the southcentral Alaska subduction zone, the temperature at the boundary between the downdip of the seismogenic zone and the updip of the L-SSEs is estimated to be approximately 350 degrees C, which is consistent with the temperature at the transition from frictional instability to stability at the plate boundary proposed in previous studies.