高雄壽山外海海床擴張構造之研究

Abstract

台灣西南部，主要構造則轉變為N-S向，例如潮州斷層。台灣南部主要斷層由北向南依序為觸口斷層、新化斷層、旗山斷層、潮州斷層及恆春斷層；旗山斷層呈東北西南走向全長有65公里。旗山斷層運動特性來說，目前有許多不同的看法，其中包含了認為旗山斷層為左移兼具逆移性質、以逆衝為主、以及具右移分量之逆移斷層，其判別的方法是利用岩層被錯移的現象來判定以及GPS的地殼變形測量。若依據本研究實驗所得的高雄壽山外海高解析度水深資料地形圖，有一明顯向左錯移的海床地表特徵；通常在地表的構造容易受到風化傾蝕和人為活動影響而造成破壞，相對於水面下的構造地形較易於保留原樣，因此本研究將利用多音束測深系統所得資料來判斷旗山斷層是否延伸至此及其海床地表特徵的解釋。 本研究在旗山外海進行高解析度多音束測深系統和3.5KHz淺層震測系統施測，想藉由高解析度的水深和震測資料來判斷出受構造運動所造成的地形和底質的變化。研究區域內兩大線性特徵和兩線性特徵之間的三角形沉陷區域的圓弧崩塌，一系列的海床的表面特徵說明了此地是受到強烈拉張作用力的環境；在旗山線性地形的末端(座落在北緯22度33分，東經120度7.5分)出現平行於它的線型的凹陷區，其凹陷的深度最大約有80公尺，推估此地點可能是研究區域受力的端點位置。研究結果發現此區在左移斷層和正斷層相互作用下，橫移伸張在其末端會有凹陷地及正斷層分布。

Major fault from north to south in Southwestern Taiwan order of Chukou fault, Xinhua fault, Chishan fault, Hengchun fault and Chaozhou fault. The NE-SW trending Chishan fault extens 65km. Characteristics of Chishan fault movement is many different opinions. The deformation and kinematics characteristic of the fault was not well documented. For the kinematics characteristics, there is still a debate for the slip motion of the fault although GPS measurements showing a significant right-lateral slip movement. According to this study, the experimental data of underwater topographic map in the offshore of Chishan fault, there is a significant left-lateral on the surface characteristics of the seabed. Therefore, this study will use the multi-beam sonar system data to judge whether to extend and the seafloor characteristic. The study uses the high-resolution multi-beam sonar system and 3.5kHz seismic reflection system on the seafloor off Shoushan, Kaohsiung. By using the multi-beam and seismic data to judge the tectonic changes of seafloor. In the study area, two linear features and triangle depression area explains extensional force in the surrounding. This result shows that interaction between left lateral fault and normal fault and transextension termination can find the listric fault or flower structure in its terminal.