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2019 Fiscal Year Final Research Report

Crustal extension and shortening in the forearm region of the Northeast Japan arc since Miocene time

Research Project

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Project/Area Number 17K14404
Research Category

Grant-in-Aid for Young Scientists (B)

Allocation TypeMulti-year Fund
Research Field Geology
Research InstitutionTohoku University

Principal Investigator

Okada Shinsuke  東北大学, 災害科学国際研究所, 助教 (50626182)

Project Period (FY) 2017-04-01 – 2020-03-31
Keywords地下構造 / 反転テクトニクス / 水平短縮 / 伸張変形
Outline of Final Research Achievements

In this study, we quantified the crustal extension and shortening across the fault of Southern Sendai Plain since Miocene time. The existing seismic profile, gravity data and the result of CSAMT (Controlled Source Audio-frequency Magneto-Telluric) survey which we conducted in this study were used to understand the subsurface geological structure of the causative active fault and its western extensional structure. Based on this geological structure, we estimated the amount of the shortening. The result show that a horizontal shortening of ca. 460 m has occurred around the Southern part of Sendai Plain since Pliocene time. The extension in the Miocene was estimated to be at least 400 m.

Free Research Field

変動地形学

Academic Significance and Societal Importance of the Research Achievements

東北日本弧は,中新世の日本海拡大に伴って伸張変形を受けており,その後,鮮新世からは短縮変形に変化した。東北日本弧に分布する活断層は,中新世の伸張変形時に形成された正断層が,鮮新世以降に逆断層として再活動している場合も多い。本研究では,仙台平野南部の伏在活断層において地下構造を把握し,中新世の伸張量と鮮新世以降の地殻短縮量を見積もった。活断層の地下構造を把握することは,発生する地震の規模の推定や強震動の推定にも重要な情報となる。また,地質学的な時間スケールにおいて島弧地殻に蓄積される歪みを理解することは,地震発生のポテンシャルを評価することにもつながる。

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Published: 2021-02-19  

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