台灣東部的花東縱谷位於歐亞大陸板塊及菲律賓海板塊隱沒的縫合帶及弧陸碰撞帶上，地震活動相當活躍，地表變形也相當明顯，根據前人研究顯示，位於縱谷兩側分別有兩個重要的斷層系統，分別是西側的中央山脈斷層及東側的花東縱谷斷層，但因縱谷中堆積厚層的沉積物，使得地下斷層構造難以被追縱與描繪，因此有許多不同的構造模型被提出。為了解縱谷中複雜的地震活動與斷層的關係，本研究以雙震盪震源車為震源，於花東縱谷北段規劃7條反射震測測線(壽豐到瑞穗)，結果顯示壽豐至光復之震測剖面，能夠觀察到連續且向東傾斜的地層，深度可達約2 公里，僅在光復地區可看見嶺頂斷層之錯動，大體上呈現一沉積盆地之形貌，而在瑞穗區域的震測剖面中，則是以褶皺為主的震測相，若以褶皺軸方向推估應力來源為東北-西南向，與菲律賓海板塊的運動方向有關。根據變化如此劇烈的震測相，於花東縱谷北段中，地下構造越往北方延伸，其受到的變形程度越低，沉積層序越趨於穩定。;The Longitudinal Valley (LV) is the suture zone of the Eurasian and Philippine Sea plates in eastern Taiwan, which results in high seismicity and significantly crustal deformation in this area. Based on previous studies, two main thrust fault systems, the Longitudinal Valley fault and the Central Range fault, have been suggested to distribute on the east side and on the west side of the LV, respectively. However, due to thick sediments covered beneath the LV, the fault geometry and the subsurface structure are difficult to be traced. Therefore, several conceptual models have been proposed for the deformation of the LV with few constraints on the geophysical data beneath it. In this study, in order to investigate the subsurface structure of the LV, we used two Mini-vibrators as sources to conduct seismic reflection survey in the northern part of the LV (from Rueishui to Shoufeng). There are 7 seismic profiles in this region and, in general, the signals from the reflectors can be down to 2-3 km depths. As a result, the subsurface structures change dramatically from Rueishui to Kuangfu. From Rueyshui to Shoufeng, continuous strata dipping to the east are observed. The results could imply the complicated tectonic history in the northern part of the LV.
