地学雑誌 | Journal of Geography (Chigaku Zasshi)

2015 Vol.124 No.5

Collision between the Ogasawara Plateau and the Izu―Ogasawara Arc

Japan’s continental shelf survey has revealed that the Ogasawara Plateau is colliding with the Izu-Ogasawara Arc and accreting to it （Ohara et al., 2015）. The Japan Arc is considered to have developed through the collision and accretion of bathymetric highs （e.g., Taira, 2001）; here, an ongoing continental growth process is observed. The collision between the Ogasawara Plateau and the Izu-Ogasawara forearc causes shoaling of the axis of the Izu-Ogasawara Trench. The depth of the axis at the collision point is 3450 m, 〜6000 m shallower than the deepest point within the Izu-Ogasawara Trench. This collision process caused numerous lineaments interpreted as faults in the western part of the Ogasawara Plateau, and tectonic emplacement of the Hahajima Seamount （HS） at the forearc just in front of the collision point. The Commission on the Limits of the Continental Shelf （CLCS） recognized the accretion of the Ogasawara Plateau to the Izu-Ogasawara Arc, and concluded in the recommendation to Japan that the western part of the Ogasawara Plateau is considered to be a “submarine elevation” in the sense of Article 76, paragraph 6 of the United Nations Convention on the Law of the Sea （UNCLOS）. In other words, the western part of the Ogasawara Plateau is considered to be a natural prolongation of Japan’s landmass on the Izu-Ogasawara Arc, including Chichi-jima and Haha-jima Islands.

（Yasuhiko OHARA, Yukihiro KATO and Akira NISHIMURA）

Special Issue: Japan’s Continental Shelf Survey and Its Contributions to Ocean Floor Geoscience

Overview of the Special Issue “Japan's Continental Shelf Survey and Its Contributions to Ocean Floor Geoscience”

Yasuhiko OHARA, Yukihiro KATO, Akira NISHIMURA and Tsutomu NAKAZAWA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 675.

DOI:10.5026/jgeography.124.675

Preface for the Special Issue “Japan’s Continental Shelf Survey and Its Contributions to Ocean Floor Geoscience”

Yasuhiko OHARA, Yukihiro KATO, Akira NISHIMURA and Tsutomu NAKAZAWA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 681.

DOI:10.5026/jgeography.124.681

Geoscientific Characteristics of the Seafloor of the Southern Ocean of Japan Revealed by Japan's Continental Shelf Survey（Review Article）

Yasuhiko OHARA, Yukihiro KATO, Tsuyoshi YOSHIDA and Akira NISHIMURA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 687.

DOI:10.5026/jgeography.124.687

Role of Detailed Bathymetric Information in Ocean Geosciences: Challenge of the Continental Shelf Delimitation Survey of Japan（Original Article）

Kiyoyuki KISIMOTO, Tsuyoshi YOSHIDA, Yasuhiko OHARA and Makoto YUASA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 711.

DOI:10.5026/jgeography.124.711

Magnetic Anomalies in the Philippine Sea: Implications for Regional Tectonics（Original Article）

Kyoko OKINO

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 729.

DOI:10.5026/jgeography.124.729

Crustal Density Structure in the Western Pacific Area Derived from Gravity Modeling Using the Results of Seismic Crustal Structure Surveys（Original Article）

Takemi ISHIHARA and Yukari FUJIOKA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 749.

DOI:10.5026/jgeography.124.749

Basin Genesis and Magmatism in the Philippine Sea（Review Article）

Osamu ISHIZUKA, Yasuhiko OHARA and Makoto YUASA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 773.

DOI:10.5026/jgeography.124.773

Large-scale Seismic Experiments Conducted by Japan Coast Guard in the Northwestern Pacific Plate and the Philippine Sea Plate（Review Article）

Kentaro KANEDA, Azusa NISHIZAWA and Mitsuhiro OIKAWA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 787.

DOI:10.5026/jgeography.124.787

Velocity Structure of the Izu-Ogasawara Island Arc（Review Article）

Narumi TAKAHASHI, Shuichi KODAIRA, Takeshi SATO, Mikiya YAMASHITA, Yuka KAIHO, Seiichi MIURA, Tetsuo NO, Kaoru TAKIZAWA, Naoto NOGUCHI, Norio SHIMOMURA and Yoshiyuki KANEDA

Journal of Geography (Chigaku Zasshi), 2015, 124(5), 813.

DOI:10.5026/jgeography.124.813