一直以來，台灣南部外海海域被認為台灣周遭海域具有較低地震潛勢地區域，但從1900年至今所記錄到規模大於7的地震分布發現，為數不少事件是集中在台灣東南部呂宋島弧和它鄰近的海洋板塊內發生的。在這之中有幾個歷史地震在文獻記載中皆有造成明顯的災害，例如: 1936年8月22日恆春外海東方規模7.3、1959年8月15日恆春東南方規模7.1和1996年9月5日恆春與蘭嶼間規模7.07地震。其中，1959年震央位於鵝鑾鼻東南方50公里處，芮氏地震規模7.1，震源深度20公里的地震更是使恆春鎮東南方和西南方受到高度4到5公尺海嘯侵襲，並造成許多人員傷亡。但由於這些地體構造區位於海域，地質與地球物理資料的取得非常困難，限制了相關研究的進行，使得一般對於此區的地質構造和孕震機制等瞭解不足。為了解決以上研究及地震災害預警相關問題，本計畫希望以位於台灣南部外海海域馬尼拉隱沒系統相關構造為研究區域，藉由臨時海底地震網的設置來做此區域地震特性的研究和觀察。藉由研究這些構造區的地震特性來了解此地區大地震產生的機制，並希望能藉此對於地震的潛勢和危害來做較合理的估計。 ;The southern Taiwan offshore area has been considered to have a low seismic potential in for a long time now. However, based on the historical record from 1900 to the present for the earthquakes with magnitude larger than 7, we observed several events occurred along the Luzon Arc and in its vicinity, around the southern Taiwan. Among them, several earthquakes have caused significant disasters and have been recorded in the literature, for example, the 1936/8/22 ML 7.3 earthquake in the eastern offshore Hengchuen, the 1959/8/15 ML 7.1 earthquake in the SE offshore Hengchuen and the 1996/9/5 magnitude 7.07 earthquake between Hengchuen and Lanyu. In addition, the 1959 Hengchuen earthquake, with an epicenter of about 20 km deep, has induced tsunamis in the southeast and southwest Hengchuen Town area with a wave height of 4 to 5 m and caused many casualties. However, located in the marine area, the acquisition of geological and geophysical data of these area is very difficult, which limits the progress of related research and makes the understanding of the geological structure and the seismogenic mechanism of this area generally insufficient. In order to solve the above mentioned issues, this project aims to study the Manila subduction system by using a temporary ocean bottom seismometer network. By studying the seismic characteristics of these tectonic zones, we attempt to obtain more understanding about the mechanism of the occurrence of large earthquakes, and hope to make a reasonable estimate of the seismic potential and hazards of the southern Taiwan area.
