[S-SS07] 地震発生の物理・断層のレオロジー

[SSS07-P11] An evaluation of the combined effect of slab geometry and plate convergence on the normal traction along subduction zones.

*Pierre Romanet¹、Tatsuhiko Saito¹、Eiichi Fukuyama^1,2 (1.Earthquake and Tsunami Research Division, NIED, Tsukuba, Ibaraki, Japan、2.Graduate School of Engineering, Kyoto University, Kyoto, Japan)

キーワード：Stress, Fault geometry, observation

Understanding where the most devastating megathrust events take place is a long standing question in seismology. Many studies have pointed out that the geometry could be a part of the answer, as it has a strong effect on the dynamics of earthquake in modeling, and that many observations point at geometrical complexity in region where the dynamic of the earthquake was changing. To link the geometry and the plate velocity, we calculated the elastic normal traction rate due to plate velocity projected onto the slab geometry along major subduction zones.

Noticeable features are that some of the biggest earthquake that happened in recent history seem to be located in relatively high normal traction portion of the subduction plate (the Mw 9.1 Tohoku earthquake, the Mw 9.1 2004 Sumatra Earthquake and the 1994, Mw 9.2 Great Alaska Earthquake). However, this observation also suffers from exceptions from the South of Chile (the 1960, Mw 9.5 Valdivia earthquake and the 2010, Mw 8.8 Maule earthquake). Although it is still speculative, the normal traction change also provides a plausible explanation for the tremor gap observed in Nankai region, where the no tremors are reported in the region of high normal traction rate.

This work is a first attempt to explain how the combine effect of slab geometry and plate velocity modifies the stress field on the slab along subduction zone.