The lack of accretionary prism at the Philippine Trench is suggestive of young origin correlating to an early second stage of development (2–4 Ma) with the central PFZ proposed to have developed between 2.7 and 3.8 Ma. The first stage began at ~10 Ma when the northern segments of the PFZ developed due to the convergence of the China Sea Crust underneath the nearby Manila Trench. The formation of the PFZ was a result of two stages. These two tectonic features thus correlate to a similar time of development. Approximately 30% of the oblique motion is accommodated by the PFZ, while the remaining proportions are displaced along with other regional tectonic features as the Philippine Sea Plate currently subducts below the Philippine archipelago at a rate of 6–8 cm/year. Two vector components accommodate the oblique motion one vector perpendicular to the converging Philippine Trench and one vector parallel to the PFZ. In the Philippine Sea, the subducting Philippine Sea Plate's oblique motion resulted in the Philippine trench and the PFZ back-arc fault system. It is proposed that the Philippine Trench and PFZ represent a ‘shear partitioning’ mechanism, where the oblique physical motions of subduction at the convergent zone resulted in the development of the major strike-slip fault. The fault experiences a slip rate of approximately 2-2.5 cm/year. The fault's current activity can be observed in Holocene sandstone outcrops on the Mati and Davao Oriental islands. These horsetail faults are indicative of the lateral propagation and further development of the PFZ. The northern and southern extensions of the PFZ are characterized by branching faults due to brittle terminations. It extends from Davao Gulf in the south, bisects the Caraga region at the Agusan River basin, crosses to Leyte and Masbate islands, and traverses Quezon province in eastern Luzon before passing through Nueva Ecija up to the Ilocos region in northwest Luzon. This left-lateral strike-slip fault extends NW-SE (N30 – 40 W), accommodating the subducting Philippine Sea Plate's lateral oblique motion to the Philippine Trench. The Philippine Fault Zone (PFZ) extends 1200 km across the Philippine archipelago behind the Philippine Trench's convergent boundary and the subduction of the Philippine Sea Plate. A complete understanding can be gained by viewing the faults in the Philippines as an inter-related Philippine Fault System. All faults in the Philippines are inter-related by the Philippine Mobile Belt's tectonic forces or its tectonic-induced volcanism. These tectonic plates have compressed and lifted parts of the Philippines, causing extensive faulting, primarily on a north–south axis. The Philippine Mobile Belt is compressed on the west by the Eurasian Plate and two arms of the Sunda Plate, and on the east by the Philippine Sea Plate. The strips generally run north-south, and fault lines usually demarcate the zones of convergence. These terranes are long and narrow like the Zambales ophiolites, which are at least 400 km long and 50 km wide. The Philippine Mobile Belt is composed of a large number of accretionary blocks and terranes.
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