Author details

Yasuto Itoh

1. The Oligo-Miocene back-arc opening of the southern Japan Sea was governed by a divergent rift system. The southwestern Japan block drifted southward and rotated clockwise as a result of differential effective spreading rates determined by the rift geometry.

2. The Japan Sea back-arc region appears to have synchronously suffered North-South strong contraction during a short period of the latest Miocene. Resumed convergence of the Philippine Sea Plate was responsible for the regional tectonic event because frequent igneous intrusions within the upper Miocene series on the shelf are suggestive of revital-

3. Confined and complicated deformation on the back-arc shelf during the Quaternary is related to the dextral wrench deformation of southwest Japan and the eventual arcparallel crustal breakup along the back-arc region. Recent highly oblique subduction of

Figure 18. Bird's eye topographic vista (from southwest) around the southern Japan Sea (top) and the subsurface structural architecture (bottom). See Figure 2 for seismic line locations. Although the total accommodations shown on the seismic data (bottom) of the northern and western back-arc of southwest Japan are in the same level, the present study integrating structural and stratigraphic knowledge has revealed that the shelf to the east of the Tsushima Islands was built

up in a short period reflecting intensive post-opening deformation events since the Miocene.

ized arc volcanism linked to dehydration of the subducted slab.

98 Tectonics - Problems of Regional Settings

the Philippine Sea Plate provoked the prevailing shear stress.

Address all correspondence to: itoh@p.s.osakafu-u.ac.jp

Graduate School of Science, Osaka Prefecture University, Japan
