報告書番号

384017

タイトル（和文）

中央構造線と跡津川断層の分布性状と活動性－地表調査と断層内物質分析による総合検討－

タイトル（英文）

STUDY ON DISTRIBUTION AND ACTIVITY OF MEDIANTECHTONIC LINE AND ATOTSUGAWA FAULT -SURFACE FEATURE AND PROPERTY OF INTRAFAULT MATERIAL-

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究は断層活動性の調査・評価法を確立するための一環として，既往の調査研究に示された若干の著名な大規模「活断層」について詳細な地表調査による断層露頭の解析，並びに当所で開発した断層内物質分析法により，各断層の分布，性状および活動性の解明を行なった。その結果，１）地表調査により，各々の断層は連続した一本の断層となっているのではなく複数本の断層および破砕帯からなることが明らかとなった。２）断層の活動時期はその分布地域により異る。３）断層内物質を用いた断層活動性検討手法が有効である。４）断層変位計による断層変位計測の結果，昭和５２～５６年の間各々の断層の動きは認められなかった。今後これらの手法を多数の地点において実施し，断層活動特性評価手法の確立をはかりたい。

概要 （英文）

INVESTIGATION OF FAULT OUTCROP AND ANALYSIS OF INTRAFAULT MATERIALS WERE PERFORMED TO ELUCIDATE ACTIVITY AND DISTRIBUTION OF FAULTS WITHIN THE MEDIAN TECTONIC LINE(MTL) IN EASTERN SHIKOKU ISLAND AND WESTERN KII PENINSULA AND WITHIN THE ATOTSUGAWA FAULT(ATF)IN CENTRAL JAPAN. THE MTL AND ATF, RESPECTIVELY, ARE NOT COMPOSED OF ONE CONTINUOUS FAULT, BUT CONSIST MAINLY OF SEVERAL DISTINCTIVE FAULTS MOVING AT DIFFERENT PERIODS. INTRAFAULT MATERIALS WERE EXAMIND ON THIER GRAIN-SIZE DISTRIBUTION, MINERALOGY AND SURFACE TEXTURES OF QUARTZ GRAINS. ASSUMING THAT THE GRAIN-SIZE DISTRIBUTION BECOMES FINER WITH TIME AFTER FAULT MOTION. FAULTS IN THE NORTH SIDE OF THE MTL IN KII PENINSULAAND FAULTS WITHIN THE ATF MOVED AT RELATIVELY YOUNGER AGE THAN THOSE WITHIN THE MTL. SURFACE TEXTURE OF QUARTZ GRAINS IN THE INTRAFAULT MATERIAL ARE CLASSIFIED INTO 6 GROUPS, CORESPONDING TO THE AGE AFTER EACH FAULT MOTION. AND IT HAS BEEN CLEARED THAT, THE NORTH SIDE FAULT OF MTL AND SOME FAULT IN ATF SHOWS THE YOUNGER AGE THAN OTHERS BY THE CLASSIFICATION OF QUARTZ GRAINS. FAULT ACTIVITY FROM THE PROPERTIES OF INTRAFAULT MATERIALS ARE IN GOOD AGREEMENT WITH THAT FROM FAULT OUTCROP INVESTIGATION. THIS INDICATES THAT THE PROPERTIES OF INTRAFAULT MATERIALS ARE OF SIGNIFICANCE IN EVALUATING FAULT ACTIVITY. FAULT DISPLACEMENT METERS DEVISED IN OUR INSTITUTE WERE INSERTED INTO FAULT SURFACES AT FAULT OUTCROPS TO MEASURE FAULT DISPLACEMENT. THE MEASUREMENT SHOWS THAT EACH FAULT IN THE MTL AND ATF DID NOT MOVE DURING THE MEASUREMENT PERIOD FROM 1977 TO 1981.

報告者

キーワード