https://scholars.lib.ntu.edu.tw/handle/123456789/37535
標題: | 台灣地震地質研究-台灣西南部活斷層研究─台灣西南部活斷層的大地構造分析 | 作者: | 鄧屬予 | 關鍵字: | 活動斷層;地震;構造地質;大地構造;西南台灣;Southwestern Taiwan;Active Fault;Earthquake;structural geology;Tectonics | 公開日期: | 2005 | 出版社: | 臺北市:國立臺灣大學地質科學系暨研究所 | 摘要: | 台灣西南部橫跨碰撞造山帶和相鄰的前陸地區。前陸地區以正斷層為主, 潛伏在雲嘉平原的地下。斷層面的走向大抵在東北東-西南西到東-西向之間, 傾斜多向南。斷層截切深部中新統以下的地層,有些則可向上貫穿上新-更新統 而接近地表。造山帶則以逆斷層和逆衝斷層為主,多出露於地表。斷層面的走 向大多呈北北東-南南西,傾角陡緩不一,但多數向東南傾斜。斷層的間距則有 由西向東減少的趨勢。 前 陸地區的正斷層是大陸邊緣張裂活動的產物,主要形成於中新世晚期, 上新世以來已停止活動。在目前西北-東南向的擠壓作用下,有些正斷層已反轉 成逆斷層或平移斷層。造山帶內的逆斷層系統是碰撞擠壓作用的產物,正由東 向西不斷發展。在山脈的前緣,由於垂直向的壓力較小,橫向的壓力相對較 大,因此所造成的軸差應力最大,利於逆斷層的滑動。在山脈的後方,山脈的 荷重使得垂直壓力逐步增加,軸差應力隨之減小,因此不利用逆斷層的發展。 整體而言,台灣西南部最活躍的斷層應位於變形前緣的附近,在前陸地區外緣 和造山帶內部的斷層活動性相對較低。 就 現有的測量資料看來,台灣西南部地表變形率最大的地方是在造山帶變 形前緣的兩側。許多截切地表及晚第四紀地層的大斷層,如觸口、白河、九芎 林等,以及歷史文獻所記載的災害性大地震,幾乎全發生於此。而近代儀器紀 錄也顯示本區不但地震頻繁,而且多為壓縮型的地震。這些現象都說明了變形 前緣是台灣西南部最主要的斷層活動區。 Southwestern Taiwan comprises part of the collision orogen and its neighboring foreland area. The foreland area is characterized by an array of NEE to E-trending, south-dipping normal faults buried beneath the Yun-Chia plain. The collision orogen is marked by imbricated NNE-trending, east-dipping thrusts and overthrusts that are either exposed on the surface or buried in the subsurface. Normal faults of the foreland formed mainly in the late Miocene as a result of crustal extension in the China continental margin that has ceased to be active since the Pliocene. Presently these normal faults are undergoing NW-directed compression and some have been reactivated as reverse or strike-slip faults. The thrusts of the collision orogen are the product of the E-W compression, which continues pushing the orogenic pile to deform internally. The deformation front of the orogen, where the gravitational force induced by the orogenic pile is the smallest and the devitoric stress greatest, is the area most prone to thrusting and, hence, is the area of highest potential for active faulting. Based on available geodetic data, the area near the deformation front of the collision orogen has the greatest strain rate in southwestern Taiwan. Numerous late Quaternary faults, including some causing disasters in the historical records, are located in that area. Recent instrumental records also show that earthquakes of compressional mechanisms are distributed near the deformation front. All these phenomena seem to indicate that faults near the deformation front are the most active in southwestern Taiwan. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/11870 | 其他識別: | 932119M002012 | Rights: | 國立臺灣大學地質科學系暨研究所 |
顯示於: | 地質科學系 |
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932119M002012.pdf | 135.32 kB | Adobe PDF | 檢視/開啟 |
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