SEAFLOOR DEFORMATION ACROSS THE MINDORO COLLISION ZONE (MCZ) AND VERDE ISLAND PASSAGE FAULT ZONE (VIPFZ), PHILIPPINES

Marine geohazard surveys conducted for an offshore gas pipeline route crossed two major, active fault zones offshore Mindoro Island. Bathymetric charts and computer renderings of seafloor data provide a detailed image of associated seafloor deformation. The MCZ is the southern extension of the Manila Trench, where continental crust of the South China Sea is subducted beneath continental crust of Mindoro Island. The active collision zone off the southern end of Mindoro Island is 25 km west of the previously inferred trace. At this location the subducted plate is being arched, and tension fractures and extensional faults are present. Transpressional folding and thrust faulting are evident in the overriding plate, reflecting oblique convergence. The VIPFZ is a major left-lateral fault zone between Luzon and Mindoro Island. Numerous pull-aparts, pressure ridges, volcanic vents, and volcanic islands (including Verde Island itself) occur along the VIPFZ. The VIPFZ appears to be offset by the historically active Aglubang fault west of Verde Island.