台湾-吕宋岛双火山弧的构造意义

TECTONIC IMPLICATIONS OF THE DOUBLE ISLAND ARC BETWEEN TAIWAN AND LUZON

扼要评介了国内外关于台湾-吕宋岛双火山弧在南海沿马尼拉海沟俯冲的动力学过程和俯冲板块深部形态等方面研究的成果;认为目前的动力学模式还不够完善,没有能够对台湾-吕宋岛双火山弧中存在的第四纪火山间断做出合理的解释,为此引入“板片窗”概念,对已经提出的动力学模式进行了修改;并统计1964～2006年发生于菲律宾地区的地震震中位置,认为存在于菲律宾群岛17°～19°N之间的深源地震稀疏带和存在于14°～15°N之间的喇叭状地震稀疏带是地震作用对于南海板片窗构造存在的反映;结合研究区域已有应力场研究资料,认为俯冲的南海亚板块中板片窗两侧俯冲倾角的差异,应该是造成俯冲带内应力分布出现分带现象的原因之一。

In this paper some brief comments were made on the research achievements of geodynamic process of the South China Sea subducted through the Manila Trench and the geometry of the subducted slab based on research results on the double island arc between Taiwan and Luzon. It is regarded by the authors that the proposed geodynamic modes are not complete, as the modes fail to make a satisfactory explanation to the gap of Quaternary volcanoes existing between Mt. Cagua and Baguio. Modification has been made on the latest proposed geodynamic mode by employing the concept of slab window. An earthquake catalog covering the period from 1964 to 2006 has been collected, and we believe that the low frequency of deep earthquake events in the area between latitude 17°N and 19°N as well as in the adjacent area between the 14° - 15°N latitude of the Philippine Archipelago in the shape of horn are reflection of the existing slab-window beneath the Philippine Archipelago. Analytical results of the stress state in the slab of South China Sea plate suggest that the differences in dips of the two parts of the subducting South China Sea plate beside the deduced slab window can help to decipher the variety of the stress state in intraslab stress field of the subducting South China Sea plate.