八卦山背斜集水區地形計測指標於活動構造意義之探討

The Study on Active Tectonic Meaning of Geomorphic Indices of Watershed in Pakuashan Anticline

孫稜翔(Leng-Hsiang Sun) ； 蔡衡(Heng Tsai)

《地理研究》 49期 (2008/11) Pp. 123-141

https://doi.org/10.6234/JGR.2008.49.06

摘要

本研究嘗試以集水區之地形計測指標探討八卦山背斜集水區地形特徵上之分區及該分區於活動構造上之意義，所採用之指標有面積高度積分、集水區不對稱性、一級河之河道坡度、及水系密度、河流頻率（之後轉換為河流頻率密度比）、細長比、崎嶇數等。研究結果顯示，七項地形計測指標於因素分析後，以一級河之河道坡度、水系密度、河流頻率密度比、崎嶇數等四項最具代表性，其後再以此四項指標利用集群分析將八卦山背斜之125個集水區分為I、II、III三區，並推測背斜北段之區域I及區域II其分區主為反應集水區底岩岩性之差別，而西翼南段區域III與區域I之分區則主為反應地表抬升速率之差異。此外西翼中段有一計測值相對較小區，推測應為「八卦轉換斷層帶」通過八卦山背斜所致。

關鍵字

八卦山背斜 ； 地形計測指標 ； 八卦轉換斷層帶

並列摘要

This study attempts to identify topographic subareas of Pakuashan Anticline by calculating geomorphic indices of watersheds to interpret their tectonic meanings. Seven indices, including hypsometric integral, drainage asymmetry factor, first-order channel gradient, drainage density, stream frequency (were transformed to frequency-density ratio), elongation ratio, and ruggedness number, have been used in this study.First-order channel gradient, drainage density, stream frequency-density ratio (F/D1.8129), and ruggedness number are selected based on factor analysis. According to this result, cluster analysis is applied to identify 125 watersheds on Pakuashan Anticline and dissects this area into three subareas. Subarea I and II mainly highlight the differences in lithology of bedrock; while subarea III and I mainly stress the differences in uplift rate of surface. There is an area with lower geomorphic indices than those of surrounding subareas in central part of western Pakuashan Anticline. It is inferred that this might be due to that Pakua Transfer Fault Zone passes through Pakuashan Anticline.

並列關鍵字

Pakuashan Anticline ； geomorphic index ； Pakua Transfer Fault Zone (PTFZ)

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