台灣東部利稻池上地區深部電性構造; The deep electrical structures of Litao-Chihshang area, eastern Taiwan

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Title:	台灣東部利稻池上地區深部電性構造;The deep electrical structures of Litao-Chihshang area, eastern Taiwan
Authors:	徐煥銘;Huan-Ming Hsu
Contributors:	地球物理研究所
Keywords:	花東縱谷;池上斷層;大地電磁法;Magnetotellurics
Date:	2006-06-28
Issue Date:	2009-09-22 09:54:39 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究論文係利用大地電磁法(Magnetotellurics，MT)探測台灣東部縱谷南段，探討該地區深部地層之電性構造。池上斷層位於縱谷斷層南段，是花東縱谷中地表變形最明顯的斷層之一，而池上斷層每年以二公分至三公分潛移，短短約十公里寬度卻吸收近三分之一板塊聚合速率，會聚了相當部分的地殼變形量。測區位於台東縣，西起利稻沿著新武呂溪橫跨卑南溪河床，東至池上錦園海岸山脈止共二十三個測站點，長約三十公里的東西向剖線。初始觀測資料做一系列的資料處理，包含統計分析、訊號濾波等，並利用各種參數判斷資料品質與維度關係。最後應用二維逆推技術，得到最佳擬合的地下電性構造剖面，並加以分析與解釋。二維MT剖面顯示、剖面之電阻率異常分佈頗不均勻，大致可區分為50歐姆?米以下的低電阻異常與500歐姆?米以上的高電阻異常： 1. 剖面西側之中央山脈地區，利稻、霧鹿、及新武等地，淺部2公里處呈現低電阻異常，可與地表之斷層或溫泉露頭相比對；而深部2公里至10公里則呈現高電阻異常，反應中央山脈地區深部的岩層。 2. 花東縱谷地區之淺部（約0.5 Km）呈現低電阻，屬於沖積層及河階台地；深部（約4 Km 以下）又呈現低電阻，可能係海洋板塊地殼之反應。 3. 剖面東側之海岸山脈地區則屬低電阻區，可與地表之利吉混同層比對，該層由地表延伸至地下深部10公里。 Abstract In this study, Magnetotellurics (MT) was used to survey the southern Longitudinal Valley of east of Taiwan, where the famous Chi-Shang fault lies. This valley, about 10 km in width, with 2-3 cm/y of creep, absorbed nearly 1/3 convergent strain of the two plate between Philippine Sea Plates and the Eurasia plate. The survey area is in the Taitung county. There are 23 MT soundings form a W-E profile of about 30 km in length. Initially, the observed MT data was made a series of data processing , including FFT, statistical analysis , and signal filter, etc., so as to decide and select the good quality data for inversion. Then 2D-NLCG inversion was applied to obtain the best fitting of the underground electrical structure profile for further analysis and explanation The 2D electric image of the profile shows that the distributions of the resistivity anomalies are uneven. However, we can distinguish the low resistivity anomaly and the high resistivity anomaly by using the resistivities of lower than 50 ohm-m and higher than 500 ohm-m, respectively, in this area: 1. In the Central Mountain Range, the west of the profile, e.g., locations of Li-Dao, Wu-Lu and Shin-Wu, low resistivity anomalies display at the shallow part of depth of about 2 km, where are well correlated with the surface faults and hot springs; whereas to the high resistivity anomaly display at depth from 2 to 10 km, reflecting the hard rocks of the Central Range. 2. In the Longitudinal Valley, the central of the profile, at the shallow part (about 0.5 km) shows low resistivity anomaly, indicating alluvial or talus; moreover, as depth increase to more than 4 km, a large low resistivity anomaly displays, possibly reflecting the intrusion of the eastern oceanic crust. 3. In the Coast Range, the east of the profile, the low resistivity anomaly correlated well with the surface melange, which extend from the surface to the depth of 10 km by our MT results.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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