台灣中部三義斷層於后里-豐原地區之近地表地質構造特性研究;The subsurface structure characteristics of Sanyi active fault in the Houli-Fengyuan area, central western Taiwan

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Title:	台灣中部三義斷層於后里-豐原地區之近地表地質構造特性研究;The subsurface structure characteristics of Sanyi active fault in the Houli-Fengyuan area, central western Taiwan
Authors:	謝承恩;Hsieh, Cheng-En
Contributors:	應用地質研究所
Keywords:	三義斷層;逆衝斷層;斷層活動性;無人飛行載具影像測繪;Sanyi fault;thrust fault;fault activities;UAV-mapping
Date:	2017-01-19
Issue Date:	2017-05-05 17:42:52 (UTC+8)
Publisher:	國立中央大學
Abstract:	三義斷層為經濟部中央地質調查所歸類的第一類活動斷層。然而大安溪以南露頭稀少，無連續露頭點判定三義斷層確實位置，因此本研究蒐集豐原市區鑽探資料、地電阻影像，判定三義斷層可能位置以及斷層帶寬度；藉調查大安溪以南，大甲溪南北岸露頭，做為確定三義斷層延伸位置的控制點，並以無人飛行載具搭載高解析度相機，配合高精度測量地面控制點測繪，記錄大甲溪畔三義斷層帶現今樣貌，以利未來研究活動斷層之變形行為；建立地質構造剖面探討后里-豐原地區三義斷層的近地表地質構造特性。本研究修訂豐原地區之三義斷層活動斷層跡，位於地調所版本之西側約500公尺。而三義斷層由南段至北段，層位落差由4600公尺轉為中段3600公尺，最北段三義地區再轉為4700公尺。三義斷層南北段構造特性不同，斷層南段上盤最老之岩層為桂竹林層；北段上盤出露老於桂竹林層之東坑層。根據本研究製做正射化的立面影像，三義斷層於大甲溪之斷層帶寬約500公尺，由至少4條錯移量不等的分支斷層 (F1-F3)以及主斷層組成(F4)組成。F4主斷層出露於大甲溪南岸，為斷層帶的最西側，上盤為桂竹林層之青灰色砂岩，下盤為黃褐色沖積層。F1分支斷層，位於大甲溪北岸峭壁面的最西側高約30公尺處，截切厚約10公尺、沉積年代約為19589 Cal BP之黃褐色砂層。 ;Sanyi fault is an active fault, which has been classified into the first category because of cutting the recent alluvium by Central Geology Survey (CGS), MOEA, Taiwan. However, the nature of sparse outcrops south of the Da-an River shattered the confidence of investigators on determining its southern surface trace. In this study, drilling data, electrical resistivity image (ERI) data and field observations are collated to analyze and determine the locations of the southern Sanyi fault and possible widths of its fault zone. This study document the well-known Sanyi fault outcrop on Dajia River cliff and its surrounding area via the UAV-photogrammetry technique. Also, the benchmark of this site and integrate aforementioned data for locating the Sanyi fault southern trace are exploited in this study. Moreover, the vertical structural profiles across the southern Sanyi fault are constructed to compare with the subsurface geological structures north of the Da-an River displayed by others. The Sanyi fault trace around Fengyuan area modified by this study is shifted about 500 meters west to the one in the CGS’s latest version. The structural profiles across the fault illustrate that the maximum stratigraphic throws increase from 4600 m in the south to 3600 in the central, and 5080 m in the north along the Sanyi fault. The oldest strata exposed in hanging wall belong to late Moicene Kueichulin Fm south of the Da-an River. The strata of Tunkeng Fm, which is older than Kueichulin Fm, has been found in hanging wall north of the Da-an River. The UAV-based mapping result shows that there are at least 3 fault branches (F1-F3) associated with a main fault (F4) within the 500-meter-wide Sanyi fault zone. On the south bank of Dajia River, the F4 is located at the westernmost of the fault zone. Late Miocene strata belong to Kueichulin Fm in the hanging wall of the F4 while Holocene terrace deposits appear in the footwall. The F1 appears in the westernmost of the northern cliff and cuts through a 19589 Cal BP sandy layer with 10 meters thick.
Appears in Collections:	[Graduate Institute of Applied Geology] Electronic Thesis & Dissertation

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