Materials Science and Seismological Approaches to Understanding Seismogenic Processes Earthquake Dynamic Rupture and Stress Field around the Fault

We have examined the effects of stress applied to a fault system on the dynamic rupture process of earthquakes. First, we investigated a feasibility of estimating the stress field from final slip distribution during an earthquake. The result of a numerical simulation suggests that principal stress directions can be estimated within an error of 5 degrees but stress ratio could not be well resolved. Then, a dynamic rupture process of the 2000 western Tottori earthquake (Mw6.6) was modeled assuming a tri-axial homogeneous stress field. The result was that the maximum principal stress direction of N105°E was the easiest for the rupture to propagate. This is mainly due to the initial shear stress distribution on the fault. This principal stress direction is consistent with that estimated by a stress tensor inversion of aftershock moment tensors of this earthquake. These results suggest a possibility to obtain a stress field applied to the fault by analyzing slip distributions of past earthquakes.