5. Conclusions

Figure 15. Confined recent depression north of the Tsushima Islands confirmed by seismic profiles. See Figure 2 for line

Figure 16. Neotectonic synthesis around the southwestern Japan arc together with a seismic section (time migration; SN1-4) showing high-angle faults along the trace of the Southern Japan Sea Fault Zone (SJSFZ). EP, NAP, PP, and PSP in the regional inset represent the Eurasian Plate, the North American Plate, the Pacific Plate, and the Philippine Sea Plate,

respectively. The location of the seismic section is also shown in Figure 2.

locations.

96 Tectonics - Problems of Regional Settings

The present seismic study has fully described the following tectonic epochs of the Japan Sea back-arc basin.

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.

The three-dimensional architecture around the southern Japan Sea has been visualized, as shown in Figure 18. A bird's eye view movie of the subsurface structure based on seismic interpretation and high-resolution original figures in this chapter are available from the Osaka Prefecture University Education and Research Archives (OPERA) (http://hdl.handle.

Post-Opening Deformation History of the Japan Sea Back-Arc Basin: Tectonic Processes on an Active Margin…

http://dx.doi.org/10.5772/intechopen.71953

99

The author would like to thank the Ministry of Economy, Trade, and Industry (METI), and the Japan Oil, Gas, and Metals National Corporation (JOGMEC) for permission to publish this

[1] Engebretson DC, Cox A, Gordon RC. Relative motions between oceanic and continental plates in the Pacific Basin. Geological Society of America Special Paper. 1985;206:1-59

[2] Otofuji Y, Hayashida A, Torii M. When was the Japan Sea opened?: Paleomagnetic evidence from Southwest Japan. In: Nasu N, Uyeda S, Kushiro I, Kobayashi K, Kagami H, editors. Formation of Active Ocean Margins. Tokyo: Terra Publishing Co.; 1985. pp. 551-566

[3] Otofuji Y, Matsuda T. Amount of clockwise rotation of Southwest Japan – Fan shape opening of the southwestern part of the Japan Sea. Earth and Planetary Science Letters.

[4] Itoh Y, Uno K, Arato H. Seismic evidence of divergent rifting and subsequent deformation in the southern Japan Sea, and a Cenozoic tectonic synthesis of the eastern Eurasian

[5] Minami A. Distribution and characteristics of the sedimentary basin offshore San-in to Tsushima Island. Journal of the Japanese Association for Petroleum Technology. 1979;44:89-

[6] Tai Y. On the 'Shinji folded zone'. Memoir of Geological Society of Japan. 1973;9:137-146

net/10466/15505).

Author details

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

Graduate School of Science, Osaka Prefecture University, Japan

margin. Journal of Asian Earth Sciences. 2006;27:933-942

96 (in Japanese with English abstract)

(in Japanese with English abstract)

Yasuto Itoh

References

1987;85:289-301

paper.

Acknowledgements


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.

The three-dimensional architecture around the southern Japan Sea has been visualized, as shown in Figure 18. A bird's eye view movie of the subsurface structure based on seismic interpretation and high-resolution original figures in this chapter are available from the Osaka Prefecture University Education and Research Archives (OPERA) (http://hdl.handle. net/10466/15505).
