報告書番号

385021

タイトル（和文）

電子スピン共鳴（ＥＳＲ）年代測定法による断層の活動時期の検討－跡津川断層における予備的検討－

タイトル（英文）

PRELIMINARY STUDIES ON THE AGES OF FAULT MOVEMENTS BY ELECTRON SPIN RESONANCE (ESR) DATING METHOD (THE ATOTSUGAWA FAULT, MAKAWA OUTCROP)

概要 （図表や脚注は「報告書全文」に掲載しております）

断層内物質より抽出した石英粒子を用いたＥＳＲ年代測定法による断層の活動年代測定手法の原理の検討と，跡津川断層真川の露頭への適用を試みた。研究成果は次のとおり。１．熱アニーリング実験，三軸圧縮破壊試験，粉砕・すりつぶし試験の結果，石英中の電子の格子欠陥は断層活動時に，解消され，時間の０セットがなされる可能性が強い。２．求まったＥＳＲ年代は，母岩より破砕帯で，角礫化帯より細粒粘土化帯で若い値が求まった。特に主断層面沿いの細粒粘土化帯で１１．９±０．５万年という最も若い値が求まつた。この値は，地質学的に求められた活動年代と矛盾しない。３．ＥＳＲ年代値の破砕帯内における分布，近傍に最近の地熱活動が認められないことから，断層運動により石英中の格子欠陥が解消され時間の０セツトがなされたものと

概要 （英文）

PHYSICOL BASIS OF DATING THE TIME OF FAULTING BY ESR METHOD USING QUARTZ GRAINS SEPARATED FROM THE INTRAFAULT MATERIALS ARE INVESTIGATED AND THIS METHOD ARE APPLIED FOR THE ATOTSUGAWA FAULT, MAKAWA OUTCROP. RESULTS ARE AS FOLLOWS. (1) AS RESULTS OF THERMAL ANNEALING EXPERIMENT, TRI-AXIAL (BREAKING EXPERIMENT, CRUSHING AND GRINDING EXPERIMENT, DEFECTS IN QUARTZ GRAINS SHOULD BE DESTROYED AT THE TIME OF FAULTING AND TIME-ZERO SETTING SHOULD BE OCCURRED AT THAT TIME. (2) ESR AGES OBTAINED FROM THE ATOTSUGAWA FAULT ARE IN FRACTURED ZONE YOUNGER THAN PARENT ROCKS AND IN CLAYEY ZONE YOUNGER THAN BRECCIATED ZONE. PARTICULARLY THE YOUNGEST ESR AGE, 0.119 PLUS OR MINUS 0.005M. G. , IS OBTAINED AT THE CLAYEY ZONE ALONG THE MAIN FAULT PLANE. THIS ESR AGE IS IN GENERAL AGREEMENT WITH THE AGE ESTIMATED FROM THE GEOLOGICAL SURVEYS. (3) JUDGING FROM THE DISTRIBUTION OF ESR AGES IN AND AROUND THE FRACTURED ZONE AND NO RECENT GEOTHERMAL ACTIVITIES ALONG THE FAULT, DEFECTS IN QUARTZ GRAINS SHOULD BE DESTROYED AT THE TIME OF FAULTING AND THETIME ZERO SETTING SHOULD BE OCCURRED AT THAT TIME. CONSEQUENTLY THE ESR AGES OBTAINED AT THE FRACTURED ZONE SHOULD INDICATE THE TIME OF FAULTING AND THE YOUNGEST ESR AGE SHOULD INDICATE THE CAST TIME OF FAULTING.

報告者

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