Article,
Dynamic rupture of the 2011 Mw 9.0 Tohoku-Oki earthquake: Roles of a possible subducting seamount
Journal of Geophysical Research, 117 (B5): B05311+ (May 22, 2012)
DOI: 10.1029/2011JB009124
Abstract
Using a hybrid MPI/OpenMP parallel finite element method for spontaneous
rupture and seismic wave propagation simulations, we investigate
features in rupture propagation, slip distribution, seismic radiation,
and seafloor deformation of the 2011 Mw 9.0 Tohoku-Oki earthquake
to gain physical insights into the event. With simplified shallow
dipping (10degree sign) planar fault geometry, 1D velocity structure,
and a slip-weakening friction law, we primarily investigate initial
stress and strength conditions that can produce rupture and seismic
radiation characteristics of the event revealed by kinematic inversions,
and seafloor displacements observed near the epicenter. By a large
suite of numerical experiments aided by parallel computing on modern
supercomputers, we find that a seamount of a dimension of \~70
km by 23 km just up-dip of the hypocenter on the subducting plane,
parameterized by higher static friction, lower pore-fluid pressure,
and higher initial stress than surrounding regions, may play a dominant
role in the 2011 event. Its high strength stalls up-dip rupture for
tens of seconds, and its high stress drop generates large slip. Its
failure drives the rupture to propagate into the shallow portion
that is likely velocity-strengthening, resulting in significant slip
near the trench within a limited area. However, the preferred model
suggests that the largest slip in the event occurs near the hypocenter.
High-strength patches along the down-dip portion of the subducting
plane are most effective among several possible factors in generating
high-frequency seismic radiations, suggesting the initial strength
distribution there is very heterogeneous.
