Subduction tectonics of the Philippines

[2] The region is bounded by subduction zones, where surrounding oceanic plates to the east and west slide towards the centre of the Philippine archipelago.

[3][12][13] The belt is tectonically separated from surrounding plates, and thus regarded as an "independent block" or "microplate" in the Philippines.

[1][6] However, models agreed that the onset of the Philippine Fault was between 2–4 Ma, and that it propagated southwards to the present southern termination at the northeast of Halmahera.

He suggested that the strike-slip fault is responsible for taking up stresses that cannot be accommodated by the subduction systems surrounding the Philippine Mobile Belt.

[1] The hypothesis of shear partitioning mechanism was agreed by Aurelio (2000) by tracking crustal movement using Global Positioning System (GPS) data.

[1] It has been hypothesized that the trench and fault formed in a synchronized manner;[1] both may have propagated southwards since the middle to late Miocene.

[18][12][19] More branching is observed over the northern and southern segments of the fault zone, which implies the Luzon and Mindanao–Moluccas regions are associated with a more complex tectonic setting.

[7][22][2] The Manila Trench results from eastward subduction of the Eurasian plate (Sundaland Block) beneath the western side of the Philippine Mobile Belt.

[23] A thick profile of sediment deposition in the well-developed forearc basin has promoted the formation of an accretionary wedge along the trench during compression.

It results from the subduction of the Eurasian plate beneath the Philippine Mobile Belt along the Manila Trench since the early Miocene.

[24] The collision zone between the Palawan Microcontinental Block and the Philippine Mobile Belt shows a southwestern propagation through time.

The north-trending trench extends from the southeastern Luzon (15˚30’N) to the northeast of Halmahera (2˚N), with a total length of 1,800 km (1,100 mi)[19][16] and a maximum depth of 10,540 metres (6.55 miles).

[27] It is linked to another east-dipping subduction zone to the north in the East Luzon Trough with an east–west trending strike-slip fault.

[1] It is believed that both the trench and fault zone formed together during early Pliocene,[2] and have since propagated southwards in a synchronized manner.

Rock composition along the major volcanic arc is generally of calc-alkaline to tholeiitic magma series.

Dating arc-derived rocks can constrain the timing for trench formation along with the tectonic evolution to within the Cenozoic.

[clarification needed][4] Volcanic arc formation also favors mineral deposits—copper, gold, and nickel mines are found in the Philippines.

This reflects the sequence of accretionary wedge formation along the western side of the Philippine Mobile Belt.

During early Miocene, the Manila Trench was initiated, which is thought to have been caused by the counterclockwise rotation of Luzon which subsequently led to the collision of Palawan Microcontinental Block and the Philippine Mobile Belt.

[12][23] The Philippine Mobile Belt was accreted to the South China Sea Block, forming the Manila Trench.

[35] Another hypothesis is that the Philippine Trench originated near Bicol (around 13˚N) and propagated southwards to its present abrupt termination at northeastern Halmahera (2˚N).

[22] A similar trend is also observed heading northwards from Bicol to the northern termination of East Luzon Trough.

However, as the Philippine Trench is a young subduction system, the majority are shallow earthquakes (less than 30 km[clarification needed]).