1999年在台灣中部發生的車籠埔斷層活動觸發921集集大地震，斷層線近乎南北向延伸，由南端之桶頭，往北延展至卓蘭，在地表造成長度約100公里的地表破裂帶。此地震斷層在北端豐原附近呈現1至2公里寬的破裂帶，斷層轉為東西走向，向東延伸約4公里至內灣後再轉為東北向。 本研究以薄皮逆衝理論為基礎，參考相關研究資料，設計傾斜之模擬活脫面，進行車籠埔斷層以及鄰近之雙冬斷層、水裡坑斷層與梨山斷層之物理模型研究。原始物理模型之設計係考慮台灣西部麓山帶地下3~6公里深處，存在一低角度之滑脫面，並將車籠埔斷層、雙冬斷層、水裡坑斷層與梨山斷層在地下視為與滑脫面相交。本實驗分為兩群組，車籠埔斷層群組與孕震帶斷層群組，分別探討單一斷層的變形機制與斷層組的關係。 二維物理模型實驗有助於瞭解斷層各部位之變形機制。實驗結果顯示，受到來自台灣東南方的板塊聚合壓縮作用，台灣西部在基底滑脫面以上的地層持續累積能量，岩層沿著既有的斷層或其他弱面破裂，造成地震的發生與地表的變形。且地表變形與基底滑脫面和斷層傾角之大小密切相關。綜合車籠埔斷層群組實驗結果，以滑脫面傾角為8度，且斷層傾角為30度之模型試驗最能滿足實際觀測之相關地質與地球物理資料。綜合孕震帶斷層群組實驗結果，台灣地層的分佈主要是越向西，則地層年代越新，顯示逆衝斷層作用係由東向西逐漸遷移發展。台灣西部前緣斷層帶，呈現蜿蜒彎曲的形狀，原因可能是由於各段斷層不等時不等量的逆衝位移所導致，前緣斷層帶表示台灣造山作用至今之變形範圍，與活斷層作用亦有非常密切的關聯。 921 Chi-Chi earthquake has been triggered by Chelungpu faulting in 1999. The fault line extends approximately 100 km from Tongtou to Cholan in a nearly NS direction. Chelungpu fault, also known as Chi-Chi earthquake fault, shows a fracture zone with a width of 1 to 2 km at Fongyuan and turns to EW direction with a 4-km extension to Neiwan with a further NE extension. By referring to the thin-skinned model and the available data, this study carried out physical modeling tests to modify the activity of Chelungpu fault. The initial models of the tests were designed to slide on an inclined plane by considering a low-angle décollement exists in a depth of 3 to 6 km under the Western Foothill region of Taiwan. The main purpose of the study is to the understanding of the deformation mechanism under plate collision in the study region. The modified Chelungpu fault is connected to the décollement to the depth in the study. The tests are tentatively divided into tow groups, the Chelungpu fault group; and the seismogenic zone group. The test results of Chelungpu fault group show that rock body overlying the décollement in central Taiwan accumulate plate collision energy in a SE-NW direction, and the rock body deforms and breaks along the existing plane of weakness when its inherent strength is overcome. Surface deformation is intimately related to both the dip angles of the fault plane and décollement. Test results of the model with angles of 8o and 30o for the modified décollement and the fault plane respectively match most satisfactorily with the available geologic and geophysical data. By combining the test results from the seismogenic zone group, it shows that faulting system distributed in central Taiwan in en echelon form. And the ages of the fault activities become younger and younger from east to west.
