利用海底地震儀資料研究南台灣隱沒構造

Abstract

沿著馬尼拉海溝, 南中國海盆, 也就是歐亞板塊上的海洋性板塊, 隱沒至菲律賓海板塊底下。馬尼拉海溝北段結束在南台灣, 往東傾的隱沒帶, 因為歐亞板塊大陸性邊緣與呂宋島弧碰撞而無法繼續隱沒, 而形成台灣的造山帶。在南臺灣這個大陸性與海洋性板塊的交界帶, 隱沒的構造因為缺乏外海觀測資料的關係, 尚未完全明朗。在本篇論文, 我們使用了從 2009 年至 2011 年兩期佈放於北呂宋海槽附近的海底地震儀資料, 聯合中央氣象局的即時觀測網資料形成陸聯網, 進行地震重定位。我們選用了規模大於二以上的地震, 重定位過後, 其分佈更與地殼以及隱沒板塊接近。並利用此聯合陸上及海上的資料組進行逆推, 以得到此區域的一維平均速度模型。在重定位以及一維平均速度模型逆推皆使用可將測站置於任意一層的高程修正, 以讓一維平均速度模型收斂。

Along the Manila trench the oceanic part of the Eurasian plate, i.e., the South China Sea (SCS) basin,is subducting eastward under the Philippine Sea plate. The Manila trench terminates in the north offshore southern Taiwan, where the subduction is impeded by the collision between the Luzon arc and the Eurasian continental margin which have built the Taiwan orogeny. The subduction zone structure at the ocean-continent junction south of Taiwan is so far unknown because of the lack of in-situ sampling. We have conducted OBS experiments in this region during 2009-2011, and conbined it with CWBSN as onshore-offshore network. Events with M > 2 were relocated to better delineate the crustal and slab structure. We carried out inversion for Vp. In relocation and 1D model inversion, we used height correction which can put station into any layer of velocity model to converge in 1D model inversion.