[J05-1] Crustal dynamics: Multidisciplinary approach to seismogenesis I

[J05-1-04] Effects of Postseismic Stress Redistribution of the 2011 Tohoku Earthquake on Fault Activities

^○Yan Hu¹, Roland Burgmann², Naoki Uchida³, Brent Delbridge², Kelin Wang⁴ (1.University of Science and Technology of China, 2.University of California Berkeley, 3.Tohoku University, 4.Geological Survey of Canada)

The postseismic deformation and seismicity following the 2011 Mw9.0 Tohoku-Oki earthquake have been recorded at unprecedented spatial-temporal resolution. Taking advantage of these observations, we have refined our published three-dimensional (3D) viscoelastic finite element models to study the evolution of the stress field following the 2011 earthquake. The model incorporates the first-order 3D structural heterogeneity in NE Japan which includes the subduction of the Pacific and Philippine Sea plates, and the laterally-heterogeneous and depth-layered rheological structure of the upper mantle. We assume that the upper mantle is characterized by a bi-viscous Burgers rheology. Our preferred model well reproduces the first-order pattern of the five-year GPS observations of the postseismic crustal deformation in both horizontal and vertical directions. We calculate postseismic Coulomb stress perturbations (CSP) on published known crustal faults as well as over nodal planes of earthquakes from focal mechanism data. Overall, thrust faults tend to undergo stress decrease after the 2011 earthquake while normal and strike-slip faults tend to undergo stress increase. After the 2011 mainshock, events in the forearc and near the rupture region of the subducting slab underwent generally CSP decrease, while the events downdip of the 2011 rupture experienced generally CSP increase. The outer rise of the Pacific plate underwent CSP increase.