以反射震測法研究木屐寮斷層及其附近構造

Investigating the Muchiliao Fault and Nearby Structures by Seismic Reflection Method

王宏霖(Hung-Lin Wang)

指導教授 ： 王乾盈

國立中央大學/地球科學學院/地球物理研究所/碩士(2006年)

摘要

論文名稱：以反射震測法研究木屐寮斷層及其附近構造 頁數:134頁 校所組別：國立中央大學 地球物理研究所 畢業時間及提要別：九十四學年度第二學期 碩士學位論文提要 研究生：王宏霖 指導教授：王乾盈博士 論文提要內容： 木屐寮斷層位於白河附近之嘉義丘陵的西緣，地形上具有明顯的線形特徵，但地表上缺乏直接的地層錯動證據，是否為活動斷層尚有爭議。本研究利用淺層反射震測法研究木屐寮斷層，認為木屐寮斷層受板塊擠壓應力與白河古構造高區(本文暫稱為白河古脊)阻擋的影響，兼具關子嶺背斜西翼軸面、地層彎拱上抬及垂直軸面擠壓的特性。在不同位置的地質條件下，具有不同的特徵： 研究區域內之八掌溪流域為北港基盤高區緊接續之南側，本身即為東西向橫梗構造之一部分，變形較為不易，故構造發展程度不如南方關子嶺背斜構造，淺部地層也因此發展成較為開闊且平緩的構造系統，本文稱之為「嘉義平緩區」。此區地層呈現平緩單斜，南北分隔木屐寮斷層與九芎坑斷層，而木屐寮斷層僅發育於牛稠埔高地至六重溪之間，長約12公里，其中崎內國小至木屐寮村由於應力集中的因素，為木屐寮斷層擠壓變形最劇烈的區域，斷層西側岩層近乎水平，但東側岩層劇烈抬升，急速彎曲導致軸部破壞，產生斷裂及小幅錯開，甚至延伸至地表，部分剖面顯示地層為「一面沉積一面變形」的「生長構造(growth structure)」，顯示木屐寮斷層於更新世?期以來持續受到相當強烈的擠壓應力，具有高度活動性。 木屐寮斷層雖然沒有明顯的斷層錯距，卻是一個相當重要的「活動構造」，受橫向構造的影響，極有可能發展成為兼具走滑的逆衝斷層。該活動構造已具有活動斷層之特徵，其活動性不宜低估。

關鍵字

木屐寮斷層 ； 反射震測法 ； 關仔嶺背斜

並列摘要

Investigating the Muchiliao Fault and Nearby Structures by
Seismic Reflection Method

Hung-Lin Wang

ABSTRACT

The Muchiliao fault lies near Pai-Ho town and follows the western border of Chia-I hills. The fault has obvious lineation pattern in topography, but there still lack geologic evidences to support its existence. The fault is ranked as a ‘suspect’ fault in the Chinese Geologic Survey''s (CGS) active fault list. This research uses the seismic reflection method to study the Muchiliao fault including the location and the configuration of the fault. The possible mechanism of the fault’s evolution is also under investigation.
The Muchiliao fault is formed as a result of the tectonic pushing against the Bai-Ho structural high. The Kuantzuling anticline is the main structural rise of the area and the Muchiliao fault is at the bending axis of its western wing. North of the fault, the variation of the structural strata are relatively gentle, forming the Chia-I structural flat area. This flat area separates the ChiuChungkeng fault at the north and the Muchiliao fault at the south.
The general shape of the Muchiliao fault appears as a disturbance along the bending axis when the layers are bent to become the western wing of the Kuantzuling anticline. The fault, 12 km long, can be divided into the northern and southern parts. At the northern part, the fault suffers great distortion. The structural strata bend significantly with apparent breakages and/or movement along the bending axis. The breakages may have extent to the surface. We also observe interesting ‘growth folding’ around the Muchiliao fault, which shows up as that the layer dipping angles vary at different depths. At the southern part, the layer bending becomes smoother without obvious offsets, in fact, a syncline shape appears at the expected fault places.
Although the Muchiliao fault does not have great fault slips, the structural disturbance it causes might be significant. It can be assigned as an ‘active fold’ in the respect of ‘active fault’ consideration. This active structure may have characteristics of active faults, and its importance should not be underestimated.

並列關鍵字

Kuantzuling anticline ； Seismic Reflection Method ； Muchiliao fault

參考文獻

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參 考 文 獻