トルコの東アナトリア断層がどのように形成されたかの謎を研究者が解明(Researchers unearth the mysteries of how Turkey’s East Anatolian fault formed)

2023-06-29

2023-06-28 ミネソタ大学

A relief map shows the Anatolian plate and its boundaries, with yellow arrows indicating the motion of the plates. Photo credit: Donna Whitney

◆ミネソタ大学の国際チームが初めて、東アナトリア断層の年代と形成過程を正確に特定しました。この断層帯はトルコとシリアで起きた壊滅的な地震の現場であり、地質学者にとっては地域の地震活動と景観形成についての重要な情報源です。
◆研究結果は地質学の専門誌である『Geology』に掲載され、インフラや住宅配置の意思決定に役立つ情報を提供します。アナトリアンプレートの形成に関する議論がありましたが、この研究ではデータを用いて、約500万年前に形成されたと結論付けました。これにより、地域の地震活動や景観形成の理解が深まりました。

＜関連情報＞

プレートの破壊：東アナトリア断層、アナトリアプレート、地殻変動脱出システムの誕生
Breaking plates: Creation of the East Anatolian fault, the Anatolian plate, and a tectonic escape system

Donna L. Whitney;Jonathan R. Delph;Stuart N. Thomson;Susan L. Beck;Gilles Y. Brocard;Michael A. Cosca;Michael H. Darin;Nuretdin Kaymakcı;Maud J.M. Meijers;Aral I. Okay;Bora Rojay;Christian Teyssier;Paul J. Umhoefer
Geology Published:MAY 16, 2023
DOI:https://doi.org/10.1130/G51211.1

Lateral movement of lithospheric fragments along strike-slip faults in response to collision (escape tectonics) has characterized convergent settings since the onset of plate tectonics and is a mechanism for the formation of new plates. The Anatolian plate was created by the sequential connection of strike-slip faults following ≥10 m.y. of distributed deformation that ultimately localized into plate-bounding faults. Thermochronology data and seismic images of lithosphere structure near the East Anatolian fault zone (EAFZ) provide insights into the development of the new plate and escape system. Low-temperature thermochronology ages of rocks in and near the EAFZ are significantly younger than in other fault zones in the region, e.g., apatite (U-Th)/He: 11–1 Ma versus 27–13 Ma. Young apatite (U-Th)/He ages and thermal history modeling record thermal resetting along the EAFZ over the past ~5 m.y. and are interpreted to indicate thermal activity triggered by strike-slip faulting in the EAFZ as it formed as a through-going, lithosphere-scale structure. The mechanism for EAFZ formation may be discerned from S-wave velocity images from the Continental Dynamics–Central Anatolian Tectonics (CD-CAT) seismic experiment. These images indicate that thin but strong Arabian lithospheric mantle extends ~50–150 km north beneath Anatolian crust and would have been located near the present surficial location of the Bitlis-Zagros suture zone (co-located with the EAFZ in our study area) at ca. 5 Ma. Underthrusting of strong Arabian lithosphere facilitated localization of the EAFZ and thus was a fundamental control on the formation of the Anatolian plate and escape system.