宜蘭平原西側雪山山脈之構造地形分析初探

Primary Study of Morphotectonic Analysis in the Hsuehshan Range of western Yilan Plain, Northeastern Taiwan

李孟綸(Meng-Lun Li)

指導教授 ： 鄧屬予

國立臺灣大學/理學院/地質科學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201801289

摘要

雪山山脈東側與宜蘭平原交界的丘陵地區，在地形上為一明顯的構造線形。前人推斷此地形特徵為活斷層所致，但並未提出明確的地質證據。本研究利用數值地形分析配合影像判釋和野外調查，以探討該丘陵區的裂縫系統及構造特徵。
為求得地形上之裂縫特性，本研究透過日照陰影圖及曲率地圖強化線形特徵，以勾繪該丘陵區的斷層跡線，並利用構造等高線法求得斷層之位態後，再比對曲率地圖以區分斷層滑移屬性。大體而言，本區充斥著短小的斜滑斷層，位態為東北-西南與西北-東南兩走向，其分別向東南傾斜40至50度及向東北或西南傾斜約70度，兩相夾70至90度角。
地形上之斷層跡線亦可在野外確實追蹤，其斷層毀壞帶及核心皆可明確查驗，其核心伴隨有密集的破裂面、斷層角礫岩、斷層泥及斷層擦面。實地量測斷層擦面之位態後，本研究發現其與地形判釋之結果大致相同，其中，有東北-西南向之左斜滑斷層，傾角多陡立，上有向東北傾10至20度的擦線。而西北-東南向的右斜滑斷層，斷層面呈陡立或略向東北傾，擦線向東南傾沒10度。
綜合地形判釋及野外調查結果，可知宜蘭平原西側丘陵地區為一斜滑斷層為主的破碎帶，統整這些裂縫與它們的滑動方向後，可知其反應西北-東南向拉張，與衛星定位系統(GPS)所展現之方向一致，可顯示地形之特徵與後造山期的斜張作用有關。

關鍵字

線形判釋 ； 斜滑斷層 ； 大地應變 ； 活斷層

並列摘要

The northwestern edge of Yilan Plain is marked by a topographic lineament cutting through to the Hsuehshan Range. Previous researchers usually regarded the northwestern edge of Yilan Plain as an active normal fault according to its topography features and associated surface deformation but presented no structural evidence. With combination of Digital Terrain Model analysis, lineament interpretation and field survey, we examine the fracture systems in the area along the eastern edge of the Hsuehshan Range to explore the structural characteristics of the fractures zone.
We first enhanced lineament features from hillshade and curvature thematic maps to extract faulting traces on the eastern Hsuehshan Range. Then, we used structural contours method, in association with the curvature map, to obtain the fault attitude and attribute. The result show that the major fractures are NE-SW oblique-slip faults with dipping angle 55~80゜to the SE and NW-trending vertical oblique-slip faults.
The fault traces found in the field and generally associated with fault breccias, gouges and slickensides. One NE-trending sinistral oblique-slip faults are marked with vertical dipping and slickenlines about 20゜plunging to the NE; whereas another two vertical, NW-striking dextral oblique-slip faults with slickenlines about 10゜plunging to the SE.
In sum, the fractures zone is composed of oblique-slip fractures striking NE-SW and NW-SE. The movements of those fractures, possibly caused by post-collision oblique extension in northeastern Taiwan, are in accordance with the strain patterns deduced from Global Position System records in the study area.

並列關鍵字

interpretation of lineaments ； oblique-slip faults ； ground strain ； active fault

參考文獻

Allmendinger, R. W., Cardozo, N., & Fisher, D. M. (2011). Structural geology algorithms: Vectors and tensors: Cambridge University Press.

Anderson, E. M. (1942). The dynamics of faulting and dyke formation with applications to Britain: Oliver and Boyd.

Angelier, J., Bergerat, F., Hao-Tsu, C., & Teh-Quei, L. (1990). Tectonic analysis and the evolution of a curved collision belt: the Hsüehshan Range, northern Taiwan. Tectonophysics, 183(1-4), 77-96.

Angelier, J., Chang, T.-Y., Hu, J.-C., Chang, C.-P., Siame, L., Lee, J.-C., Deffontaines, B., Chu, H.-T., & Lu, C.-Y. (2009). Does extrusion occur at both tips of the Taiwan collision belt? Insights from active deformation studies in the Ilan Plain and Pingtung Plain regions. Tectonophysics, 466(3), 356-376.

Argialas, D., Mavrantza, O., & Stefouli, M. (2000). Automatic mapping of tectonic lineaments (fault) using methods and techniques of photo interpretation/digital remote sensing and expert systems. THALES Project, 1174(6).