2026-10-21 産業技術総合研究所
沖縄トラフ南部域の正断層と地殻熱流量によるリフト形成の概略図
＜関連情報＞
- https://www.aist.go.jp/aist_j/press_release/pr2026/pr20261021/pr20261021.html
- https://link.springer.com/article/10.1186/s40645-026-00854-3
南沖縄トラフの初期リフト形成期における、分布した正断層と比較的低い熱流量条件 Distributed normal faulting and relatively low heat flow conditions during early rifting in the southern Okinawa Trough
Makoto Otsubo, Masataka Kinoshita, Minoru Ikehara, Ryuta Arai, Ayanori Misawa, Hiroaki Koge, Katsura Kameo, Chiori Tamura, Ryoji Toda, Stephen P. Obrochta, Takanori Kagoshima, Tomohiro Toki, Daisuke Kuwano, Seiya Fujishima, Akane Yamamoto, Natsuki Nomura, Aya Osanai, Keita Kono, Issui Ikuma, Chika Onai, Yusei Miyamoto, Yuka Taira, Yu Miyagi, Soma Sato, … Yu Suzuki
Progress in Earth and Planetary Science Published:21 October 2026
DOI:https://doi.org/10.1186/s40645-026-00854-3
Abstract
The southern Okinawa Trough provides an opportunity to investigate the early stage of back-arc rifting before the onset of oceanic spreading. We examined the Yaeyama and Yonaguni Rifts using multichannel seismic reflection data, swath bathymetry, heat flow measurements, and geomagnetic observations. The seismic profiles reveal widespread seafloor-cutting normal faults and thick trough-fill sediments in both rift segments. In the Yaeyama Rift, a localized acoustically transparent body is identified beneath the rift axis and may represent a shallow intrusive feature. However, higher-resolution seismic data or additional geophysical constraints would be required to confirm its origin. Heat flow values are generally low (40–63 mW/m2) except for one localized anomaly, consistent with previous observations of subdued heat flow in the southern Okinawa Trough. The geomagnetic data do not indicate extensive shallow volcanic construction, although localized magnetized bodies (e.g., small intrusive or volcanic units) may be present. These observations suggest that early rifting in the southern Okinawa Trough is dominated by distributed normal faulting under thermally subdued conditions and with only limited evidence for substantial magmatic contribution, with possible localized magmatic activity in the Yaeyama Rift. Our results provide structural and thermal constraints on the diversity of early-stage rifting processes in continental back-arc basins.
