Quasi-static simulation of seismic cycle of great inter-plate earthquakes following a friction law in laterally heterogeneous viscoelastic medium under gravitation -FEM approach-

Recent simulation studies based on the friction law derived from laboratory experiments have successfully modeled seismic cycles of great inter-plate earthquakes in a half-space homogeneous elastic medium. However, the lateral heterogeneities in the medium and the viscoelastic properties under gravitation, which would seriously affect the simulation of seismic cycles, have not yet been examined in the previous studies. We consider the quasi-static simulation, and discuss the problems in extending the simulation in a simple elastic medium to that in a laterally heterogeneous viscoelastic medium under gravitation using Finite Element Method(FEM) with an example of 2-D modeling of seismic cycles in northeast Japan where the subduction of the Pacific plate causes the great inter-plate earthquakes. Before the introduction of complicated friction law, we examine a simple friction case, where an artificial seismic cycle, with a given constant friction in a locked portion during an interseismic period of 100 years and zero friction during the coseismic and postseismic period of 1 year, is considered. We compare this simple friction case with the rateand statedependent friction case both in a pure elastic medium and in a viscoelastic medium under gravitation.