臺南盆地位處於北港高區南側至南海海盆北部，自新生代以來即開始張裂，盆地內保存了臺灣自白堊紀基盤以來區域構造演化沉積紀錄。前人研究認為臺南 盆地的北側邊界為義竹斷層，然而由於資料的缺乏，義竹斷層往西側的延伸、活動性及臺南盆地的空間分佈及其演化歷史並不清楚。因此本研究於臺南盆地西側及周邊區域蒐集28條海域反射震測資料，其中包含傳統大能量的空氣鎗震測系統以及高解析電火花震測系統資料，經過資料處理綜合分析後，除重新建構臺南盆地演化史外，並同時探討淺部沉積構造及斷層活動性。另外，本研究引自鄰近地區前人研究的鑽井資料進行震測相位特徵及年代比對，其中共判斷出九層層序地層介面，時間橫跨33百萬年至1.8萬年前的末次冰盛期侵蝕面。其中本研究發現義竹斷層很可能自33.9百萬年前即開始發育，空間上於東經118度45分左右即無法維持大斷距的邊界斷層特徵，轉而變成數條小斷距的義竹斷裂帶，並至少可往西延伸至東經118度左右，因此義竹斷裂帶全長至少有300公里長，若完全破裂很可能導致大規模地震。此外，臺南盆地也依義竹斷層不同的斷裂類型在16百萬年後可分成東臺南盆地：2至4公里厚的沉積物，及西臺南盆地：僅有1至2公里厚沉積物，此可能顯示東臺南盆地受南海張裂停止後之後其張裂作用影響較為劇烈。 ;The Tainan Basin is situated in between Beigang basement high and northern South China Sea basin. It is started to rift since early Cenozoic time which preserves geological and sedimentary evidence of the tectonic evolution of the Tainan basin. Previous studies suggested the Yichu fault serves as a northern boundary fault of the Tainan basin. However, due to lack of multi-channel seismic data in particular west portion of the Tainan basin, Yichu fault western prolongation, activities and spatial distribution and evolution of the Tainan basin are unclear. Therefore, we collected 18 multi-channel seismic profiles which include deep penetration seismic data and near seafloor high resolution sparker seismic data. After data processing and integrated analyses, a modified tectonic evolution of the Tainan basin is proposed and sedimentary structures and fault activities near seafloor are also discussed. In addition, we have tied seismic interfaces to nearby previous well logging studies which identified nine sedimentary sequence boundaries in between 33 Ma and 1.8 ka. The result shows that the Yichu fault is probably initiated since 33.9 Ma, western prolongation toward 118。45’E losing large vertical offset boundary fault characteristics rather produced several small offset faults becoming Yichu fault zone. The whole 300 kilometers long Yichu fault zone can be prolongated toward 118。E at least which could probably develop big magnitude earthquake in the future. Furthermore, the Tainan basin can be sub-divided into two sections: east Tainan basin containing 1.5-2.5 thick sediments and west Tainan basin rather preserving thinner 1.2-1.4 kilometers thick sediments, which may suggest post-spreading of the South China Sea basin rifting episode occurred at eastern Tainan basin. It is worthy to investigate this rifting episode in the future.
