Overview of Current Tectonics in the Philippines Region
Building Blocks
Understanding the tectonic configuration in the Philippines region necessitates a clear vision of the plates, basins and terranes involved, and their mutual relationships. What follows is a concise summation of each component. For more on the geologic character of these "building blocks" visit the section of this website Plates and Geology.
The Philippine "Accreted Terrane"
This terms refers to the landmass which comprises the nation of the Philippines, seen in Figure 1, at the left of the diagram. It is also referred to as the Philippine Mobile Belt by some workers (e.g. Yumul et al., 2002). Aurelio et al. (2013) summarizes the geology of this landmass succinctly as being comprised of volcanic arcs, ophiolite belts and sedimentary successions derived from a long history of rifting, subduction and continental-arc collision. The Philippine accreted terrane overrides both the subduction of the South China Sea along the Manila trench to the west and the Philippine Sea Plate (PSP) along the Philippine Trench to the east (Hall et al., 1995). The terranes northernmost margin sees the transition from subduction to a collisional regime, which is examined in more detail below. The sinistral strike-slip Philippine Fault Zone cuts length-wise through the Philippine accreted terrane, accommodating the lateral stress component of the obliquely subducted slabs (Aurelio et al., 2000). |
The Philippine Sea Plate (PSP)
The PSP refers to the slab of oceanic lithosphere east of the Philippine accreted terrane (Hall et al., 1995). To the south, the PSP is bounded by the sinistral Sorong Fault along the northernmost margin of Australia (Hall et al., 1995). The complex geometry of the PSP near Taiwan is discussed in the case study below, which invokes slab tearing to accommodate the observed motions (Zheng et al., 2013). To the east, the PSP overrides the Pacific Plate, along the Mariana Trench (Hall et al., 1995). In the west, the PSP subducts beneath the Philippine accreted terrane except at the Manila Trench (Pacanovsky et al., 1999). Pacanovsky et al. (1999) used finite-element modelling to investigate the stress field on the PSP. Their results suggest that the Taiwan-Luzon area of the PSP has a stress field consistent with collisional forces. Furthermore, Pacanovsky et al.'s (1999) model was used to delineate the relative importance of trench pull (derived from convergence rate and slab dip, among other factors) and trench suction (derived from asthenospheric counter-flow) for the PSP. Their model best fits the observed stress field on the PSP with trench suction being 10% that of trench pull. |
The South China Sea
The South China Sea is an "Atlantic-Type" Marginal basin (Taylor & Hayes, 1983). It near the margin of the Eurasian Plate, and is actively being subducted beneath the Philippine accreted terrane along the Manila Trench. To the north, near Taiwan, the basin has been completely subducted, and now the continental margin of the Eurasian Plate is involved in continental-arc collision. The South China Sea is bordered north and south by passive continental margins (Taylor & Hayes, 1983). There is currently north-south spreading along an east-trending spreading center (evidence by the fracture patterns), as well as an inactive SW trending relict spreading ridge in the basin (Taylor & Hayes, 1983). The South China Sea basin is subdivided into separate east and west subbasins. Taylor & Hayes (1983) suggest that the development of the South China Sea basin was not related to back-arc spreading from subduction at the Manila Trench, and rather is derived from a complex history of strike-slip faulting, rotation, and seafloor spreading that initiated in the Oligocene. |
The Sunda Plate
The Sunda Plate lies west of the Philippine accreted terrane, and is bordered to the south-west by subduction on the Sunda Arc, Java Trench and the Timor Trough, which in all cases it acts to override the Indo-Australian Plate (Socquet et al., 2006). To the east, the Sunda Plate is subducted along the Manila Trench (Socquet et al., 2006). The South China Sea basin is considered a part of the Sunda Plate (Socquet et al., 2006). The Sunda Plate is involved in a T-T-F (Trench-Trench-Fault) triple junction with the Australian Plate and the PSP near its southern margin (Socquet et al., 2006). The motion along the strike-slip fault is sinistral, accommodating the westward motion of the PSP (Socquet et al., 2006). |
The Caroline Plate
The Caroline Plate is a small plate south and east of the PSP (See Figure 3). It includes the East and West Caroline Basins (Bird, 2003). Prior to Bird's (2003) paper, the Caroline was often treated as part of the Pacific Plate in global tectonic models. This leads to ambiguity in some of the literature as to the plate's exact definition. It is bordered by the PSP to the west along the Ayu and Pala Trenches (Bird, 2003). In general, the Caroline Plate's boundary with the Pacific Plate is variable across its length, and varies between sinistral transform and convergent (Bird, 2003). |
The Eurasian Plate
The evolution of the Eurasian Plate is discussed in some detail on the page Tectonic History. Often, other smaller adjacent plates to the Eurasian Plate with similar relative motions are modeled as one. As shown in Figure 5, the Eurasian Plate is extremely large, and the details of its tectonics are beyond the scope of this website. Along the Ryukyu Trench, the Eurasian Plate overrides the PSP (See Figure 5). The boundary between the Sunda Plate and the Eurasian Plate is noted to not be uniformly stable and is subject to active deformation (Bird, 2003). |
Celebes Sea
The Celebes Sea is a basin to the west of the Philippine plate. It is hypothesized that at the time it was formed, the Celebes Sea spreading ridge and the West Philippine Sea spreading ridge were the same ridge which became separated after clockwise rotation of the Philippine Plate (see "Outstanding Questions" section for more information on rotation of the Philippine Plate). (Nichols & Hall, 1999) |
The Palawan Microcontinental Block This term refers to the continental sliver separated from the Eurasian Plate by north-south spreading in the South China Sea that began in the mid Oligocene, evidence by magnetic anomalies (Holloway, 1981). This spreading resulted in the collision of the North Palawan Block with the Philippine Archipelago (Holloway, 1981). A plausible cross section through this collisional environment is shown below in Figure 12. The Sulu Sea
The Sulu Sea is a marginal basin, split into sub-basins by the Sulu Ridge (NW and SE, as shown in Figure 6). Hutchison (1992) models the Sulu Sea as marginal basin formed in an intra-arc rift, due to the subduction along the northern margin of the Celebes Sea (indicated as the Sulu Trench in Figure 6). |
Case Studies of Regional Tectonics
Continental-Arc Collision and an Unusual Slab Geometry (Taiwan)
To the north of the Philippines, the Philippines Sea plate and the Eurasian plate meet in the island of Taiwan. In southeastern Taiwan, the Eurasian plate is subducting under the Philippine Sea “slab” (fig. 7). Even though the Eurasian plate lithosphere is more buoyant than the oceanic crust, it can be subducted because it is being dragged down by the adjacent, subducting South China Sea. On the other hand, in northeastern Taiwan, the Philippine Sea “slab” is subducting under the Eurasian plate along the Ryukyu trench. This results in a funky configuration that is accommodated by a slab tear, where hot asthenosphere upwelling occurs (fig. 8).
On the west side, it appears that Taiwan is colliding with the South China Shelf (easternmost portion of the Eurasian plate). This is an example of arc-continent collision, in which the arc will eventually be accreted into the Eurasian plate.
To the north of the Philippines, the Philippines Sea plate and the Eurasian plate meet in the island of Taiwan. In southeastern Taiwan, the Eurasian plate is subducting under the Philippine Sea “slab” (fig. 7). Even though the Eurasian plate lithosphere is more buoyant than the oceanic crust, it can be subducted because it is being dragged down by the adjacent, subducting South China Sea. On the other hand, in northeastern Taiwan, the Philippine Sea “slab” is subducting under the Eurasian plate along the Ryukyu trench. This results in a funky configuration that is accommodated by a slab tear, where hot asthenosphere upwelling occurs (fig. 8).
On the west side, it appears that Taiwan is colliding with the South China Shelf (easternmost portion of the Eurasian plate). This is an example of arc-continent collision, in which the arc will eventually be accreted into the Eurasian plate.
IBM Arc System The eastern margin of the Philippine Sea Plate is 2800 km long, from Tokyo, Japan to Guam, United States. This plate boundary consists of the Pacific plate subducting under the Philippine Sea plate. This intra-oceanic convergent margin has been thoroughly studied since it is very well exposed and its geologic history is very well preserved. Also, it hosts the deepest point in the Earth, the Challenger Deep at 11 km depth. The Izu-Bonin-Mariana (IBM) arc system consists of the Izu, Bonin, and Mariana segments. The Izu and Bonin segments are separated by the Sofugan Tectonic Line and the Mariana segment is separated from the Bonin segment at the northern end of the Mariana Trough (fig. 9). The Mariana segment consists of
|
The evolution of the convergent boundary is preserved in the fore-arc and is interpreted in Figure 10.
|
Geometry of Subduction Beneath the Philippine Accreted Terrane (Mobile Belt)
In the "Building Blocks" section above, it was noted that there is "double subduction" along the Philippine accreted terrane. This complex geometry is not fully understood. Observed plate velocities for the PSP necessitate oblique subduction, the lateral component of which is accommodated by motion along the sinistral Philippine Fault Zone (Aurelio, 2000). But what is the geometry of these subducted slabs? Yumul et al.'s (2003) generalized tectonic schematic, shown in Figure 12, gives the current interpretation of this region. In this figure, the subduction of the Celebes Sea basin beneath the Philippine Accreted Terrane, and the subduction of the PSP are shown. Yumul et al. (2003) do not speculate on the future of these subducted slabs. The authors of this website speculate that continued subduction of these two slabs will inevitably lead to a "space problem" which requires both slabs to dip very steeply to avoid collision, or a drastic change in the geometry of the system. The effect of asthenospheric flow on these mutually subducting slabs is not clear, and should be a subject of future research. |
References Cited:
Aurelio, M.A., Pena, R.E., Taguibao, K.J.L (2013). Sculpting the Philippine archipelago since the cretaceous through rifting, oceanic spreading, subduction, obduction, collision, and strike-slip faulting: Contribution to IGMA5000. Journal of Asian Earth Sciences. V. 72. Pp. 102 – 107. Doi: 10.1016/j.jseaes.2012.10.007.
Aurelio, M.A. (2000). Shear partitioning in the Philippines: Constraints from Philippine Fault and global positioning system data. Island Arc. V. 9. I. 4. Pp. 584 - 597. Doi: 10.1046/j.1440-1738.2000.00304.x.
Bautista, B.C., Bautista, M.L.P., Oike, K., Wu, F.T., Punongbayan, R.S. (2001). A new insight on the geometry of subducting slabs in northern Luzon, Philippines. Tectonophysics. V. 339. I. 3-4. Pp. 279-310. Doi: 10.1016/S0040-1951(01)00120-2.
Bird, P. (2003). An updated digital model of plate boundaries. Geochemistry, Geophysics, Geosystems. V.4. No. 3. Doi: 10.1029/2001GC000252.
Hall, R., Ali, J.R., Anderson, C.D., Baker, S.J. (1995). Tectonophysics. V. 251. Pp. 229 - 250. Doi: 10.1016/0040-1951(95)00038-0.
Holloway, N.H. (1981). The North Palawan Block, Philippines: its relation to the Asian Mainland, and its role in the evolution of the South China Sea. Geol. Soc. Malaysia Bulletin. V. 14. Pp. 19 - 58.
Huang, J., Zhao, D. (2006) High-resolution mantle tomography of China and surrounding regions. Journal of Geophysical Research. V. 11. Doi:10.1029/2005JB004066.
Hussong D. M., S. Uyeda, R. Knapp, H. Ellis, S. Kling, and J. Natland (1981), Deep Sea Drilling Project Leg 60: Cruise Objectives, Principal Results, and Explanatory Notes. Initial Report on Deep Sea Drill Project 60: p. 3–28.
Hutchison, C.S. (1992). The Southeast Sulu Sea, a Neogene marginal basin with outcropping extensions in Sabah. Geol. Soc. Malaysia, Bulletin. V.32. Pp. 89 - 108.
Iidaka, T., Iwasaki, T., Takeda, T., Moriya, T., Kumakawa, I., Kurashimo, E., Kawamura, T., Yamazaki, F., Koike, K., Aoki, G. (2003). Configuration of subducting Philippine Sea plate and crustal structure in the central Japan region. Geophysical Research Letters. V. 30. No. 5. Doi: 10.1029/2002GL016517.
Iris. Magnitude 7.6 Earthquake - Phillipine Island Region. Accessed at: https://www.iris.edu/hq/files/programs/education_and_outreach/retm/tm_120831_philippines/120831_philippines.pdf. Accessed on: April 5th, 2017.
Nichols, G., & Hall, R. (January 01, 1999). History of the Celebes Sea Basin based on its stratigraphic and sedimentological record. Journal of Asian Earth Sciences, 17, 1, 47-59.
Pacanovsky, K.M., Davis, D.M. (1999). Intraplate stresses and the plate-driving forces in the Philippine Sea Plate. Journal of Geophysical Research. V. 104. No. B1. Pp. 1095 – 1110. Doi: 10.1029/98JB02845.
Stern, R. J., Fouch, M. J., & Klemperer, S. L. (2003). An overview of the Izu‐Bonin‐Mariana subduction factory. Inside the subduction factory, 175-222.
Socquet, A. Simons, W., Vigny, C., McCaffrey, R. Subarya, C., Sarsito, D., Ambrosius, B., Spakman, W. (2006). Microblock rotations and fault coupling in SE Asia triple junction (Sulawesi, Indonesia) from GPS and earthquake slip vector data. Journal of Geophysical Research. V. 111. Doi: 10.1029/2005JB003963.
Taylor, B., Hayer, D.E. (1983). Origin and History of the South China Sea Basin. American Geophysical Union: Geophysical Monograph Series. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands: Part 2. V. 27. Doi: 10.1029/GM027p0023.
Yumul, G.P., Dimalanta, C.B., Maglambayan, V.B., Marquez, E.J. (2008). Tectonic setting of a composite terrane: A review of the Philippine island arc system. Geosciences Journal. V. 12. I. 1. Pp. 7-17. Doi: 10.1007/s12303-008-0002-0.
Yumul, G. P., Dimalanta, C. B., Tamayo, R. A., & Maury, R. C. (2003). Collision, subduction and accretion events in the Philippines: a synthesis. Island Arc, 12(2), 77-91.
Zheng, H. W., Gao, R., Li, T. D., Li, Q. S., & He, R. Z. (2013). Collisional tectonics between the Eurasian and Philippine Sea plates from tomography evidences in Southeast China. Tectonophysics, 606, 14-23.
Aurelio, M.A., Pena, R.E., Taguibao, K.J.L (2013). Sculpting the Philippine archipelago since the cretaceous through rifting, oceanic spreading, subduction, obduction, collision, and strike-slip faulting: Contribution to IGMA5000. Journal of Asian Earth Sciences. V. 72. Pp. 102 – 107. Doi: 10.1016/j.jseaes.2012.10.007.
Aurelio, M.A. (2000). Shear partitioning in the Philippines: Constraints from Philippine Fault and global positioning system data. Island Arc. V. 9. I. 4. Pp. 584 - 597. Doi: 10.1046/j.1440-1738.2000.00304.x.
Bautista, B.C., Bautista, M.L.P., Oike, K., Wu, F.T., Punongbayan, R.S. (2001). A new insight on the geometry of subducting slabs in northern Luzon, Philippines. Tectonophysics. V. 339. I. 3-4. Pp. 279-310. Doi: 10.1016/S0040-1951(01)00120-2.
Bird, P. (2003). An updated digital model of plate boundaries. Geochemistry, Geophysics, Geosystems. V.4. No. 3. Doi: 10.1029/2001GC000252.
Hall, R., Ali, J.R., Anderson, C.D., Baker, S.J. (1995). Tectonophysics. V. 251. Pp. 229 - 250. Doi: 10.1016/0040-1951(95)00038-0.
Holloway, N.H. (1981). The North Palawan Block, Philippines: its relation to the Asian Mainland, and its role in the evolution of the South China Sea. Geol. Soc. Malaysia Bulletin. V. 14. Pp. 19 - 58.
Huang, J., Zhao, D. (2006) High-resolution mantle tomography of China and surrounding regions. Journal of Geophysical Research. V. 11. Doi:10.1029/2005JB004066.
Hussong D. M., S. Uyeda, R. Knapp, H. Ellis, S. Kling, and J. Natland (1981), Deep Sea Drilling Project Leg 60: Cruise Objectives, Principal Results, and Explanatory Notes. Initial Report on Deep Sea Drill Project 60: p. 3–28.
Hutchison, C.S. (1992). The Southeast Sulu Sea, a Neogene marginal basin with outcropping extensions in Sabah. Geol. Soc. Malaysia, Bulletin. V.32. Pp. 89 - 108.
Iidaka, T., Iwasaki, T., Takeda, T., Moriya, T., Kumakawa, I., Kurashimo, E., Kawamura, T., Yamazaki, F., Koike, K., Aoki, G. (2003). Configuration of subducting Philippine Sea plate and crustal structure in the central Japan region. Geophysical Research Letters. V. 30. No. 5. Doi: 10.1029/2002GL016517.
Iris. Magnitude 7.6 Earthquake - Phillipine Island Region. Accessed at: https://www.iris.edu/hq/files/programs/education_and_outreach/retm/tm_120831_philippines/120831_philippines.pdf. Accessed on: April 5th, 2017.
Nichols, G., & Hall, R. (January 01, 1999). History of the Celebes Sea Basin based on its stratigraphic and sedimentological record. Journal of Asian Earth Sciences, 17, 1, 47-59.
Pacanovsky, K.M., Davis, D.M. (1999). Intraplate stresses and the plate-driving forces in the Philippine Sea Plate. Journal of Geophysical Research. V. 104. No. B1. Pp. 1095 – 1110. Doi: 10.1029/98JB02845.
Stern, R. J., Fouch, M. J., & Klemperer, S. L. (2003). An overview of the Izu‐Bonin‐Mariana subduction factory. Inside the subduction factory, 175-222.
Socquet, A. Simons, W., Vigny, C., McCaffrey, R. Subarya, C., Sarsito, D., Ambrosius, B., Spakman, W. (2006). Microblock rotations and fault coupling in SE Asia triple junction (Sulawesi, Indonesia) from GPS and earthquake slip vector data. Journal of Geophysical Research. V. 111. Doi: 10.1029/2005JB003963.
Taylor, B., Hayer, D.E. (1983). Origin and History of the South China Sea Basin. American Geophysical Union: Geophysical Monograph Series. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands: Part 2. V. 27. Doi: 10.1029/GM027p0023.
Yumul, G.P., Dimalanta, C.B., Maglambayan, V.B., Marquez, E.J. (2008). Tectonic setting of a composite terrane: A review of the Philippine island arc system. Geosciences Journal. V. 12. I. 1. Pp. 7-17. Doi: 10.1007/s12303-008-0002-0.
Yumul, G. P., Dimalanta, C. B., Tamayo, R. A., & Maury, R. C. (2003). Collision, subduction and accretion events in the Philippines: a synthesis. Island Arc, 12(2), 77-91.
Zheng, H. W., Gao, R., Li, T. D., Li, Q. S., & He, R. Z. (2013). Collisional tectonics between the Eurasian and Philippine Sea plates from tomography evidences in Southeast China. Tectonophysics, 606, 14-23.