Distributed normal faulting and relatively low heat flow conditions during early rifting in the southern Okinawa Trough
14 affiliations
- 1Geological Survey of Japan, AIST
- 2Earthquake Research Institute, The University of Tokyo
- 3Marine Core Research Institute, Kochi University
- 4Japan Agency for Marine-Earth Science and Technology
- 5Atmosphere and Ocean Research Institute, The University of Tokyo
- 6Akita University
- 7University of Toyama
- 8University of the Ryukyus
- 9Kyoto University
- 10Kochi University
- 11Chiba University
- 12Marine Works Japan Ltd.
- 13Nippon Marine Enterprises, Ltd.
- 14MOL Marine & Engineering Co., Ltd.
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.
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BibTeX
@article{otsubo2026distributed,
title = {{Distributed normal faulting and relatively low heat flow conditions during early rifting in the southern Okinawa Trough}},
author = {Makoto Otsubo and Masataka Kinoshita and Minoru Ikehara and Ryuta Arai and Ayanori Misawa and Hiroaki Koge and Katsura Kameo and Chiori Tamura and Ryoji Toda and Stephen P. Obrochta and Takanori Kagoshima and Tomohiro Toki and Daisuke Kuwano and Seiya Fujishima and Akane Yamamoto and Natsuki Nomura and Aya Osanai and Keita Kono and Issui Ikuma and Chika Onai and Yusei Miyamoto and Yuka Taira and Yu Miyagi and Soma Sato and Michelle M. Nishimoto and Yukihiko Nakano and Hikaru Iwamaru and Yu Suzuki},
journal = {Progress in Earth and Planetary Science},
year = {2026},
month = oct,
doi = {10.1186/s40645-026-00854-3},
url = {https://doi.org/10.1186/s40645-026-00854-3},
note = {CC BY},
}
RIS
TY - JOUR
TI - Distributed normal faulting and relatively low heat flow conditions during early rifting in the southern Okinawa Trough
AU - Makoto Otsubo
AU - Masataka Kinoshita
AU - Minoru Ikehara
AU - Ryuta Arai
AU - Ayanori Misawa
AU - Hiroaki Koge
AU - Katsura Kameo
AU - Chiori Tamura
AU - Ryoji Toda
AU - Stephen P. Obrochta
AU - Takanori Kagoshima
AU - Tomohiro Toki
AU - Daisuke Kuwano
AU - Seiya Fujishima
AU - Akane Yamamoto
AU - Natsuki Nomura
AU - Aya Osanai
AU - Keita Kono
AU - Issui Ikuma
AU - Chika Onai
AU - Yusei Miyamoto
AU - Yuka Taira
AU - Yu Miyagi
AU - Soma Sato
AU - Michelle M. Nishimoto
AU - Yukihiko Nakano
AU - Hikaru Iwamaru
AU - Yu Suzuki
PY - 2026
DA - 2026/10/25
JO - Progress in Earth and Planetary Science
DO - 10.1186/s40645-026-00854-3
UR - https://doi.org/10.1186/s40645-026-00854-3
AB - 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.
SN - 2197-4284
ER -