1999年集集地震斷層的活動引起九二一大地震。本研究針對斷層地下構造形貌對地表變形之影響，共設計了六組模型進行二維物理模型實驗，詳細觀察與分析模型構造之變化，並將實驗結果與其他地質、地球物理資料對比，提出合理之定性解釋主要目的在於瞭解集集地震斷層活動特性。其中群組一與二是模擬單傾角斷層活動對地表變形，群組三、四、五與六則模擬雙傾角斷層面活動對地表變形的影響。 群組一與二研究結果顯示，在石岡以南的區域，集集地震斷層呈現單傾角斷層的活動模式，地表變形主要以斷層崖、地表隆起與褶皺等現象；群組三、四、五與六研究結果顯示，在石岡以東的區域，集集地震斷層呈現雙傾角斷層的活動模式，地表變形主要以斷層崖、地表隆起、褶皺與次生斷層等現象。 綜合分析比較本研究結果與其他地質、地球物理資料，可知台灣西部的構造演化模式由東向西發展，呈現一連串的覆瓦狀構造，現今未出露的彰化斷層將有可能會是台灣西部未來的地震斷層之一。 Chi-Chi fault activity derived 921 Taiwan Earthquake in 1999. Six groups of 2-D physical modeling tests have been designed to study the influence of the underground fault structure on surface deformation. Groups 1 and 2 are designed to simulate a single-dip fault activity while Groups 3, 4, 5, and 6 are designed to simulate a duplex-dip fault activity. The main purpose of this study is to propose the qualitative characteristics of the Chi-Chi earthquake fault by correlating the test results with available geological and geophysical data. Chi-Chi earthquake faulting tends to be more like a single-dip fault model in the area to the south of Shihkang Dam as revealed by the test results from Groups 1 and 2; surface deformations are mainly reflected by the presence of fault scarps, surface bulges and folds. In the area to the east of Shihkang Dam, Chi-Chi earthquake faulting shows a double-dip fault model; surface deformations are fault scarps, surface bulges folds and secondary backthrusts as revealed by the test results from Groups 3 to 6. By synthesizing all the test results with available geological and geophysical data, it shows that the mode of the tectonic evolution in Western Taiwan has been developing from east to west as indicated by the distributed series of imbricate structures. And besides, the un-outcropped Changhua fault may be one of the future earthquake faults in Western Taiwan.
