Abstract
The area in and around Taiwan is dominated by the eastward subduction of the South China Sea along the Manila trench in the south and collision between the North Luzon volcanic arc and the passive Chinese continental margin in the north. The development of this plate boundary is enigmatic however it is likely the rupture and subsequent initiation of subduction was related to the change from extension to compression along structures such as fracture zones inherited from the rifting phase of the South China Sea.

Three E-W wide-angle refraction datasets combined with coincident active source seismic reflection data allow us to develop a new model to describe the origin and evolution of the Gagua Ridge bathymetric feature in the West Philippine Basin. One observation we have been able to make is that the oceanic crust to the east of Gagua Ridge appears to be underthrust to the west beneath the oceanic crust of the Huatung Basin to a depth of 15-20 km. extend east to west across the Gagua Ridge bathymetric feature to reveal deep crustal structure of the easternmost West Philippine Basin. Data were acquired offshore Taiwan as part of the 2009 TAIGER program.