TECTONIC EVOLUTION IMPLICATION OF GEOMETRY SHAPE CHARACTERISTICS FOR MANILA TRENCH

Seafloor topography, tectonic characteristics of the Manila trench and the related earthquake focus data were analyzed.Combined with dynamics numerical simulation results for subduction zones, especially Schellart model, the tectonic characteristics of geometry shape and the sharply changing north-south dive angle for the Manila trench were particularly discussed.Study results show that Huangyan seamount chain which was representing the ancient spreading ridge in the South China Sea subducted into the Manila trench,which did not bring serious influence on the geometry shape of the Manila subduction zone, and its geometry shape corresponded with a trench model of medium length (2 000~3 000 km).Mantle flow parallel to the Manila trench caused by trench retreat and slab rollback aggravated the north-south dive angle to change sharply for the Manila trench.