In this research, the seismic observations with sub-km resolution conducted in the hypocenter region of the 2000 Tottori earthquake, which was the first challenging ones in the world, have revealed a very complex shape of fault plane and existence of non-double couple earthquakes for the first time. Geological observations conducted in the same area have clarified that aftershock of this earthquake is caused by the reactivation of faults which have been formed along the major fault strand since the Miocene age. On the Median Tectonic Line fault zone formed in the Late Cretaceous, the detailed architecture has been clarified, and our understanding for the processes and mechanism of strain localization has been advanced. Furthermore, it has been clarified that seismic rupture even occurs in the lower part of crust, which is ductile otherwise, and in the fractured fine-grained rocks further deformation proceeds by grain-size sensitive creep enhanced by metamorphic reactions.