Abstract
Structural evidences in the Koshiki Islands and northern Okiwana trough are very important to understand the opening history of the back arc basin. Based on the fault orientation, fault character, cross-cutting relationship and moved direction, NNE-trending fault system of each area is identified as the rifting phase deformation of the Northern Okinawa-trough. The youngest is the northern Okinawa Trough which formed E-W trend sedimentary basin with ENE-trending fault are related in recent stress field of the Kyushu area.
