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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/5474

    Title: 斗六丘陵桐樹湖斷層地下構造研究;A Study of subsurface structures in the Touliu terrace of Tongsuhu fault
    Authors: 劉耕源;Gang-Yang Liu
    Contributors: 地球物理研究所
    Keywords: 活動斷層;桐樹湖斷層;斗六地區;Tongsuhu fault;Touliu terrace
    Date: 2004-06-14
    Issue Date: 2009-09-22 09:54:46 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 中台灣地區沿著西部麓山帶之外帶的西緣,即北從后里台地、南到嘉義丘陵西緣之間,一般認為有一系列的南北向之活動斷層分布,其中在濁水溪以南的斗六丘陵、及其西緣之桐樹湖斷層,為本研究之目標。雖然地調所活動斷層圖上,並未將桐樹湖斷層列入,但作為彰化斷層南延之「驥尾」,亦值得關心。本研究測區範圍北從濁水溪南岸,南至古坑桶頭一線,西起斗六丘陵的邊緣,東則到竹山丘陵,約10x10公里,在此範圍佈出60餘條測線,其中有些為成對之交叉測線,用以偵測地下地層之構造變化。 前人研究中,桐樹湖斷層被認為是一條樞紐斷層(Hsiao,1971),在上新世晚期之前為正斷層,使北港陸台以緩慢的斜坡向東傾沒,但新期造山運動開始後,此樞紐斷層轉為斷坡(ramp)(Suppe and Namson,1979),成為一埋於地下之「盲斷層」,致使內林背斜以不對稱之高角度逆衝於其上方。比起北方之彰化斷層(造成之地層傾角在10至35度),桐樹湖斷層之高角度地層變化極為特殊(30至50度)。本研究結果,雖然在斗六丘陵西緣之所有測線剖面上,均未發現斷層錯動地層之痕跡,但發現地下構造變化充分反映盲斷層產生之「斷層延展褶皺」(fault-propagation-fold)。本研究獲得以下幾點結論: (1)八卦背斜確實南延到內林背斜,彰化斷層與桐樹湖斷層應有所關聯,而南北兩構造在濁水溪南岸附近相連,造成觸口台地、坪頂埔台地與竹山地區地下地層低角度東傾。 (2)桐樹湖斷層埋於地下2公里左右,在上新世晚期時為深部樞紐斷層,但新期造山運動後來轉為一斷坡,而以斷層彎曲褶皺的形式抬起上方之內林背斜。 (3)內林背斜之背斜軸在南北都發生往西偏移情況,整個內林背斜構造以梅林至圳頭坑之間為核心(構造最高),向北向東伸展而出。往北即濁水溪南岸地區發展成一單斜,往南則背斜漸趨對稱,且變寬變緩。 (4)東西向左移之古坑斷層稍為影響到桐樹湖斷層系統,但影響程度不大。內林背斜系統可能繼續往南延伸至小梅背斜。 (5)從地表地形與地下構造迴異的情況來看,桐樹湖斷層所造成的內林背斜的地形,已被河流大量的侵蝕。故桐樹湖斷層有其構造上之意義,但因已不活動,失去活動斷層之特性。 The Tongsuhu fault is located at the western border of the Touliu terrace west-central Taiwan. The fault could be a southern extension of the Changhua fault (the Pakua terrace). These faults are considered as a series of thrust faults developing along the most western edge of the deformation front of Taiwan’s western foothills. Although the Tongsuhu, fault is not on the active fault list of Central Geologic Survey, recently due to the construction of the Hushan Dam, the activity level of this fault is under re-evaluation. In this study, we use the seismic reflection method map the underground structures around the fault. It is found that most of seismic sections are composed of highly bending layers, but do no show any trace of fault offsets. The fault-bend-fold model, proposed by Suppe and Namson (1979), is accepted to explain such structural variations. The current topographic features hardly agree with underground structure distributions. The Tongsuhu fault, tough, is a blind thrust, its possibility to be an active fault could be low.
    Appears in Collections:[地球物理研究所] 博碩士論文

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