10:45 AM - 11:00 AM
[SCG61-19] Modeling strain concentration and mountain building processes in central Japan considering heterogeneous rheological structure
Keywords:Central Japan, Strain concentration zone, Mountain building, Finite element method, Nonlinear viscoelasticity , Plasticity based on Mohr-Coulomb criterion
Based on dense geothermal gradient data from Hi-net (Matsumoto et al., 2007) and the Geological Survey of Japan (Tanaka et al., 2004), we develop a thermal structure. We also consider a thick sedimentary layer where the friction coefficient is low based on the J-SHIS deep subsurface structure (NIED). Numerical results show that under the compressional tectonic setting, mountains are reproduced along high geothermal gradient regions. We can reproduce the Hida mountain range, Chikuma mountain, Echigo mountain range, and others, where a geothermal anomaly exists. Our model can also reproduce strain concentration in the Hida region. Furthermore, we can reproduce a strain concentration zone by setting the frictional coefficient to be low in the basement of the Niigata region.
However, the model cannot reproduce the strain concentration zone in the Atotsugawa and Kinki regions where strike slip faulting is dominant; therefore, we consider the boundary condition that yields the stress state of the strike-slip faulting and the effect of water distribution or rheology of partial melting based on seismic velocity anomalies (Nakajima and Hasegawa, 2007). We can reproduce strain concentration along the seismic velocity anomalies. Our results suggest that the Niigata-Kobe strain concentration zone is developed by several factors: thermal anomaly, pre-existing rift structure, and the presence of fluid and partial melting in the crust and the upper mantle.