Basement faulted structure in the South Okinawa Trough and vicinity

Basement faults in EW, NEE and NE direction are situated along outstendittg tectonic line, most of which are tensionalfracture. Huge basement faults mainly formed and controlled basic tectonic framework of each main tectonic belt and development of tectonics of different feature. The formation of the basement faults is associated with tensional movement of the Okinawa trough-resulted from rising of the mantle stream of the back-arc and the revolving-tensional tilt of the are system toward the trench axis. Most of basement faults in NW,NNW and NW direction are tensional strike-slip fault. They cut the main tectonic zone, forming and controlling the different geophysical and tectonic characteristics of the second tectonic blocks. Miyako fracture zone is a very active zone in a long time, which is the result of stress adjustment of crust by the action of horizontal stress from Philippine Sea direction.