海底下の巨大断層の電磁イメージング～トルコ国マルマラ海海底下の北アナトリア断層の構造を解明～

2026-01-09 東京科学大学

図. トルコ国マルマラ海海底下の北アナトリア断層の3次元比抵抗構造図。暖色系が流体に富む変形域、寒色系が流体に乏しい固着域を表す。（Kaya et al., 2025）

＜関連情報＞

• https://www.isct.ac.jp/ja/news/gg9ud4k7tjwg
• https://www.isct.ac.jp/plugins/cms/component_download_file.php?type=2&pageId=&contentsId=1&contentsDataId=3004&prevId=&key=ed1371cc19ddafe7b5f1e64f6dc8df51.pdf
• https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G52995.1/722052/3-D-electromagnetic-imaging-of-highly-deformed

マルマラ海の下にある北アナトリア断層の大きく変形した流体に富む弱層と固着部分の3次元電磁画像化
3-D electromagnetic imaging of highly deformed fluid-rich weak zones and locked section of the North Anatolian fault beneath the Marmara Sea

Tülay Kaya-Eken;Yasuo Ogawa;Yoshiya Usui;Takafumi Kasaya;M. Kemal Tunçer;Yoshimori Honkura;Naoto Oshiman;Masaki Matsushima;Weerachai Siripunvaraporn
Geology  Published:December 08, 2025
DOI:https://doi.org/10.1130/G52995.1

Reliable knowledge of the crustal properties beneath the North Anatolian fault (NAF), seismically silent for more than 250 years beneath the Marmara Sea (MS), is crucial for understanding seismic hazard and mitigating the potential for disaster on an enormous scale. In the present work, the first three-dimensional inverse modeling performed on a magnetotelluric dataset of the MS has unveiled localized weak and locked fault segments along this shear deformation zone. Low-resistivity regions along the northern branch of the NAF beneath the Central and Çınarcık-Imralı basins are likely attributed to the presence of fluids, which may represent a fault zone conductor in a fractured zone and can explain the densely populated microseismicity. These low-resistivity anomalies surrounded by higher resistivity structures imply that the segmented, multi-branched NAF system extends beneath the MS, following the Intra-Pontide suture zone. The resistive anomalies, between the Central and Çınarcık basins, along with those at the western and eastern extremities of the MS, presumably signify regions of stress accumulation, shedding light on the ongoing processes of fault mechanics at play in this critical region.