New Definition of Philippine Plate Bound

Journal of the Geological Society of the Philippines

Vol. 64 No. 1 January-December 2009

New Definition of Philippine Plate Boundaries and Implications to the Philippine Mobile Belt 1

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Alfredo Mahar Francisco A. Lagmay , Ma. Luisa G. Tejada , Rolando E. Pena, Mario A. Aurelio , 2 3 3 Brian Davy , Sevillano David , Elmer Billedo 1

National Institute of Geological Sciences, College of Science, University of the Philippines, Diliman, Quezon City 1101, Philippines 2 Geological and Nuclear Science, New Zealand 3 Mines and Geoscience Bureau, J. Fernandez Bldg., MGB Comp. North Ave. Diliman Quezon City

Abstract

The Philippine Mobile Belt (PMB) is a zone of intense deformation and active seismicity between convergent zones bounding the Philippine Archipelago. This zone was first defined by Gervasio (1967) to distinguish the seismically active portion of the Philippine Archipelago from the southwestern region of the Philippines. According to Gervasio, the “mobile belt”, includes North Luzon, South Luzon, West Visayas, Northwest Mindanao, Bicol Region, East Visayas, Zamboanga, Cotabato and the rest of Mindanao with Catanduanes Island representing the east outer zone of the PMB. The aseismic region, on the other hand, is constituted by Palawan and Mindoro. In the plate tectonics framework, the PMB represents a zone of deformation between surrounding major plates, namely: the Philippine Sea, Eurasian (Sunda Block) and Indo-Australian Plates. Only Palawan and Mindoro, the aseismic regions of the Philippines are part of the Eurasian Plate. Based on recent Global Positioning System, gravity, and seismicity data, we reinterpret Philippine Plate boundaries that define the extent of the Philippine Mobile Belt. The eastern section of North Luzon, heretofore described as part of the PMB, moves in a northwest direction with similar velocity as the Philippine Sea Plate. This suggests that the northwestward motion of the Philippine Sea Plate at the eastern margin of Luzon is mainly decoupled along the left-lateral Polilio-Philippine fault zone. The Polilio-Philippine fault is a zone of intense seismicity and is herein regarded as the crustal tear generated by the ongoing collision of the Benham Rise with Luzon starting from 20 Ma. This interpretation considers the eastern section of North Luzon as part of the Philippine Sea Plate and has major implications to the delineation of plate boundaries of the Philippines. Introduction

The Philippine archipelago is a mature island arc that is at present being accreted to the eastern margin of the Eurasian Plate (Sunda Block) (Ben-Avraham, 1978; Hamilton, 1979; McCabe et al., 1982; Holloway, 1982; Karig, 1983; Rangin et al., 1985; Pubellier et al., 1996). It is primarily composed of a complex mixture of oceanic crust, marine sedimentary sequences, arc volcanics, (Rangin et al., 1985; Geary et al., 1988; Encarnacion, 2004; Jr. et al., 2004), and microcontinental fragments rifted from southeast China (Hamilton, 1979; Holloway, 1982; McCabe et al., 1982; Taylor and Hayes, 1983; Encarnacion et al., 1995; Encarnacion and Mukasa, 1997). These terranes formed the Philippine archipelago through plate convergence of the Philippine Sea Plate (western margin of the Pacific Plate domain), Eurasian Plate and the Indo-Australian Plate (Figure 1).

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Figure 1 : A) Map showing the main plates surrounding the Philippine Archipelago. B) Major tectonic features of the Philippines. The gray shaded area is the Philippine Mobile Belt (PMB) of Gervasio (1967). The stippled gray shaded area is the Palawan-Mindoro continental block. AR= Abra River Fault; VA=Vigan Agao Fault; C=Cordilleran Fault; P=Pugo Fault; D=Digdig Fault; LD=Laur D ingalan Fault.

The entire archipelago is bounded by a system of subduction zones, collision zones, and wrench faults. These structures are remnant features of the complex geodynamic history of the island arc as well as structures of ongoing tectonic processes. The actively deforming region of the Philippines is a zone known as the Philippine Mobile Belt or PMB (Figure 1; Gervasio, 1967). This deformed and seismically active region is bounded by subduction zones of opposite polarities. At the eastern border of the Philippines is a west dipping subduction zone known as the Philippine Trench. Generally east-dipping subduction zones on the western margin of the PMB are the Manila, Negros, Sulu, and Cotabato trenches. In between these west and east dipping subduction zones is the approximately 1400 km long left-lateral Philippine Fault (Allen, 1962; Barrier et al., 1991; Aurelio et al., 1991), which straddles the entire length of the PMB. In this region of Southeast Asia, these tectonic structures largely accommodate the stress imparted by the ongoing northwest movement of the Philippine Sea Plate towards Eurasia (Fitch, 1972; Morgan, 1972; Karig, 1975; Seno, 1977; Chase, 1978; Ranken et al., 1984; Huchon, 1986). To the southwest of the PMB is the Palawan-Mindoro block, an aseismic region of continental affinity (Hamilton, 1979; Holloway, 1982). The trenches bounding the eastern and western part of the archipelago are major sites of seismicity (Figure 2). These define the regions where marginal basins surrounding the Philippines are consumed. Geological Society of the Philippines

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The South China Sea, Sulu Se a and the Celebes Sea Basins subduct along the east-dipping Manila, Negros and Cotabato trenches, respectively. The Sulu Trench is another locus where the seafloor of the Sulu Sea is consumed. In the eastern margin of the archipelago, the Philippine Trench is where the Philippine Sea Plate is consumed (Rangin, 1991; Aurelio, 2000).

Figure 2. Plot of seismicity in the Philippines from 1973-2006. Size of circle scaled to magnitude while the scale bar represents depth. Data from USGS Advanced National Seismic System (ANSS) and plotted using Generic Mapping Tools (GMT).

A major collision event between the eastern border of Luzon and the Benham Rise, a large oceanic plateau, (Figure 1) occurred during the Early Miocene (Bautista et al., 2001; Lallemand et al., 1998; Sajona et al., 1997). The collision is a major episode in the evolution of the Philippines well-preserved in the stratigraphic (Karig, 1973; Lewis and Hayes, 1983; Florendo, 1994; Bautista et al., 2001) and structural records (Pinet and Stephan, 1990; Ringenbach et al., 1993), which is supported by new Gravity and GPS (Rangin et al., 1999; Galgana et al., 2007) data. This paper elucidates the consequences of the Benham Rise collision and what the new ge ophysical and GPS data suggest about the demarcation of the PMB boundaries between the Philippine Sea and Eurasian Plates. New Geophysical Data Geophysical Evidence - Gravity Models

The strong 150-180 mgal Bouguer anomaly gradient between the Benham Rise and Luzon marks both an increase in crustal thickness as well as the presence of localized sedimentary basins associated with fossil accretionary prisms and relict subduction zone features that were active during the Oligocene (Lewis and Hayes, 1983). Gravity data modeling for the central Benham Rise show a crustal thickness of Geological Society of the Philippines

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15-18 km (Figure 3D). These values fall at the lower end of the range of crustal thickness expected for a Large Igneous Province (Coffin and Eldholm, 1994). The crust of Benham Rise is significantly thicker than the 6-10 km crustal thickness expected for normal oceanic crust.

Figure 3. Gravity profiles of the Benham Rise region. A) Map of Benham Rise showing gravity profile transects B) Line across the East Luzon Trough, Benham Rise and Molave Spur C) Line 2 across the East Luzon Trough and the Benham Rise D) Line across the Bicol Saddle and Benham Rise. All transects show crustal thicknesses greater than normal oceanic crust.

Beneath the East Luzon Trough, the underlying crustal thickness shown by the 2-D gravity model is 1 2-15 -3 km despite an allowance for approximately 5 km of fossil accreted sediment of density 2.4 gcm on the inner margin (Figure 3B and 3C). Similarly, the northeast trending profile transecting the Bicol saddle (Figure 3D), shows a crustal thickness that is at least 15 km, again despite an allowance for approximately 4 km of overlying accreted sediment. The 2-D models, like the Bouguer anomaly data, imply that the Benham Rise has been accreted beneath Luzon along both its western and southern margins. GPS Data

The first neotectonic model of the Philippines based on combined GPS data, seismicity, topography, and geology (Figure 4) was presented by Rangin et al. (1999). The model proposes smaller plates subdividing the PMB: A Luzon plate in the north, a Visayas plate in the southwest


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Figure 4. A. Distribution of the major tectonic boundaries and active mobile micro blocks in the Philippines. GEODYSSEA sites and their acronyms are shown. Estimated velocity vectors are given in mm yr-1. GPS stations: LA=LAOA, VI=VIRA, PU=PUER, Il=ILOI, ZA=ZAMB, DA=DAVA, TA=TAWA; INF=Infant Fault; Bi=Bicol peninsula; MC=Bacolod Corridor; VPF=Verde Passage Fault; Ta=Tablas island; Pa=Palawan island; Zama=Zamboanga Peninsula; NBT=North Borneo Trench; PF=Philippine Fault; VAW=Vigan Agao Wrench Fault. B. GEODYSSEA GPS vectors with respect to Sundaland (black arrows). From Rangin et al.,1999.

and an “East Philippine Sliver”. Specific Euler vectors computed for these plates, are based on two geodetic stations for the Luzon Plate, and three geodetic stations for the Visayas Plate. The “East Philippine Sliver” contains only one GPS station. The latter is inferred to be stable in its northern part but owing to numerous normal faults that cross-cut this plate in the south, slip rates along the Philippine -1 Fault are collectively reduced from 35 to 22 mm yr along its border with the proposed Visayas Plate. Additional distributed deformation within these proposed plates of the PMB was also noted. Geodetic -1 evidence for 20 mm yr sinistral slip on the Infanta segment of the Philippine fault was cited which consider both sides of this fault to be parts of the Luzon plate. The two control points in the Visayas -1 block which should have equal velocity actually differ by 18 mm yr , and that the Euler rotation best-fit -1 to the three velocity vectors leaves residuals up to 13 mm yr . Rangin et al., 1999 also propose subduction at the aseismic Sulu Trench and the seismically active Cotabato Trench, but show these trenches as terminating in a plate interior, which therefore cannot be rigid (Bird, 2 003).

Because of evidence for high strain rates and differential velocities in each of the proposed small plates -1 (and East Philippine Sliver) at the level of 13-20 mm yr , Bird (2003), found the plate subdivisions proposed by Rangin et al., 1999 too detailed compared with the definitions given for the rest of his global compilation of plate boundaries. Instead, he designated the entire


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Philippine Islands region, except for Palawan as an orogen (Figure 5). This orogen designation approximately corresponds to the Philippine Mobile Belt of Gervasio (1967). In the map presented by Bird (2003) the orogen is presented with a replot of the GPS vectors showing the Manila Trench and a strike-slip connection to the Philippine Trench. Utilizing regional GPS velocities from Luzon, Philippines, with focal mechanism data from the Harvard Centroid Moment Tensor (CMT) Catalog, tectonic deformation in the complex plate boundary zone between the Philippine Sea Plate and Eurasian Plate was estimated by Galgana et al. (2007). In their paper, major tectonic structures that were found to “absorb the plate convergence” include the Manila -1 -1 -1 Trench (20-100 mm yr ) and East Luzon Trough (9-15 mm yr )/Philippine Trench (29-34 mm yr ), which accommodate eastward and westward subduction beneath Luzon, respectively; the left-lateral strike-1 slip Philippine Fault (20-40 mm yr ), and its northward extensions, the Northern Cordillera Fault (17-37 -1 -1 mm yr ), and the Digdig Fault (17-27 mm yr ). Their analysis further suggests that much of the Philippine Fault and associated splays are locked to partly coupled, while the Manila and Philippine trenches appear to be poorly coupled. Luzon is best characterized as a tectonically active plate boundary zone, comprising six mobile elastic tectonic blocks between two active subduction zones. The Philippine Fault and associated intra-arc faults accommodate much of the trench parallel component of relative plate motion (Galgana et al., 2007). Figure 5. The Philippines orogen (black outline with crosshatching) surrounds the Philippine Sea (PS) - Eurasian Plate (Sunda Plate) convergent plate boundary (heavy colored lines). Important active faults plotted with heavy dashed lines: Philippine trench Pt, Manila trench Mt, Negros trench Nt, Sulu trench St, Cotabato trench Ct, Philippine fault Pf. Geodetic velocities from Rangin et al., 1999 are plotted relative to SU. Boundary types are: CCB continental convergent boundary, CTF continental transform fault, CRB continental rift boundary, OSR oceanic spreading ridge, OTF oceanic transform fault, OCB oceanic convergent boundary, SUB subduction zone. From Bird, 2003.


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Kinematic models derived from geodetic data modeled by Galgana and others (2007) predicts coupling between Luzon and the Philippine Sea Plate (Figure 6). Similar vectors in the eastern portion of the North Luzon block (CAG1 and CAG2 modelled blocks) and the Benham Rise-West Philippine Basin suggest they are moving as a single unit. The smaller magnitude northwest directed vector in the western part of the North Luzon Block (ILOC block) may be due to decoupling along the Digdig Fault. Seismicity Data

Seismicity maps in the region of the Benham Rise show a locus of epicenters that border its western and southern margins. Along the East Luzon Trough are predominantly shallow earthquake hypocenters (see Figure 2) no more than 100 km deep. These earthquakes are characterized by focal mechanism solutions typical of faults with thrust and strike-slip motion (Figure 7). Although the thrust motion can be associated with subduction, the distribution pattern of the hypocenters is not a distinct Benioff Zone (Figure 8). These strike-slip and thrust faults may also be interpreted as due to the presence of active tectonic structures east of Luzon and not necessarily that of an active subduction zone. The interpretation as to whether it is a subduction zone or a zone of seismicity associated with active thrust and strike-slip faults or even restrained subduction (Bautista et al., 2001) is important in its classification as a major plate boundary of the Philippines. In the context of an already accreted Benham Rise determined from the interpretation of new Gravity data presented in this work, combined GPS and seismic data suggest that the region of the East Luzon Trough is not a major active plate boundary. Despite persistent seismicity in the region, there is no significant differential movement between northeast Luzon and the Philippine Sea Plate near the Benham Rise. The active seismicity and highly coupled nature of northeast Luzon and the Philippine Sea Plate (Benham Rise Region) is quite unusual for a convergent (subduction) plate boundary especially considering the fact that the Philippine Sea Plate east of Luzon is moving northwestward at a high velocity. It appears that bulk of the northwestward motion of the Philippine Sea Plate in the area east of Luzon is mainly accommodated in the southern margin of the Benham Rise, where a linear pattern of seismicity within the Bicol Shelf connects the Philippine Trench with the Polilio-Philippine (LaurDingalan) Fault (Figure 7). This tectonic structure characterised by left-lateral strike-slip focal mechanism solutions is interpreted as a “crustal tear” developed by the collision of the Benham Rise with Luzon since 20 Ma. The crustal tear is well defined up to the Pugo Fault and becomes undefined as it enters the South China Sea because of scattered seismicity in the area. Because of the collision of the Benham Rise with Northern Luzon, the eastern section of Northern Luzon moves as an integral part of the Philippine Sea Plate. Its boundary with the PMB is defined by seismicity data to correspond with the east-west trending Polilio-Philippine Fault. The western extension of this left-lateral fault possibly connects with the Manila Trench as proposed by Bird (2003).


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Figure 6. Relative motions with respect to Central Luzon (CLUZ) of the Philippine crustal blocks after Galgana et al., 2007. GPS stations and vectors shown only in or adjacent to the ILOC, CAG1 and CAG2 blocks. Note the different scales for the measure vector (blue and model vector (black).

Figure 7 . Map of the eastern border of Luzon showing the bathymetry of the Benham Rise. Plots of the epicenters and focal mechanism solution data (from the Advanced National Seismic System and Harvard Centroid Moment Tensor archive) show seismic activity at the trenches surrounding the west and southwest portions of the Plateau. The dashed line is the trace of the tear produced by the NW collision of the Benham Rise with eastern Luzon.


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Figure 8 . Earthquake hypocenters within 20 km from lines A- A’ and B-B’ (see figure 7) projected into the cross-sectional plane of the transect lines. The hypocenters are mostly shallow focus no more than 100 km deep and do not constitute a well-defined Benioff zone.

Boundary of the Eurasian Plate (Sunda Block) and Philippine Sea Plate

Based on the interpretation of geophysical data on the Benham Rise and North Luzon, the boundary between the Eurasian Plate, Philippine Sea Plate and the Philippine Mobile Belt is modified. The new boundary is similar to the plate boundary map of Bird (2003) but without the continuation of the PolilioPhilippine Fault crustal tear into the Manila Trench, an idea which necessitates further verification. Descriptions of the plate boundaries in the Philippines are presented in this section. Philippine Sea Plate and Eurasian Plate boundary

The Eurasian and Philippine Sea Plate boundary starts from the north along the Nankai-Ryukyu Trench and follows the Longitudinal Valley Fault along the coast of Taiwan and ends at the junction of the Manila Trench and Polilio-Philippine Fault zone (Figure 9). The PMB is located west of the PolilioPhilippine Fault zone, squeezed between the Philippine Trench and the Manila, Negros and Cotabato Trenches. The northwestward movement of the Philippine Sea Plate is accommodated by subduction along the Philippine Trench and strike-slip motion of the Polilio-Philippine Fault zone. Stress imparted by motion of the Philippine Sea Plate in the northern part of Luzon is accommodated by the active left-lateral


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Philippine Fault distributed along the Laur-Dingalan, Pugo, Vigan-Aggao, Abra River and Digdig fault segments (Figure 9). Philippine Sea Plate and Philippine Mobile Belt Boundary

The Philippine Trench and the Polilio-Philippine Fault marks the boundary between the Philippine Sea Plate and the PMB. Stress induced by motion of the Philippine Sea Plate is ac commodated by subduction along this trench and by shear partitioning along the Philippine Fault Zone (Barrier et al., 1991) from south of Mindanao up to Laur-Dingalan, Luzon, where the Philippine Fault meets the Polilio-Philippine Fault (Figure 9). Eurasian Plate Philippine Mobile Belt Boundary

The Eurasian Plate, PMB boundary extends from the junction of the Manila Trench and Polilio-Philippine Fault zone to the Negros and Cotabato Trenches at 4 latitude (Figure 9). The Manila Trench disappears southward where continental blocks of the southeastern Eurasian Plate margin have accreted to the arc rocks of the Philippine Mobile Belt (Sarewitz and Karig, 1986). These continental blocks are now interpreted to be accreted to the Philippine archipelago in the areas of Palawan (Encarnacion et al., 1995), West Mindoro (Holloway, 1982), Northwest Panay and Romblon Island (Hamilton, 1979; Taylor and Hayes, 1983). Active subduction along the Manila and Negros Trenches are mainly induced by movement of the Philippine Sea Plate. ◦

Conclusions

The Philippine Mobile Belt (PMB) is a zone of intense deformation and active seismicity between convergent zones bounding the Philippine Archipelago. First defined by Gervasio (1967) to distinguish the seismic portion of the Philippine Archipelago from the southwestern region of the Philippines, the PMB has constantly been cited in the literature on Philippine tectonics. Evolving from an era prior to the development of Plate Tectonics, the PMB is now understood as a zone of decoupling from surrounding major plates. Interpretation of new geophysical data redefines the boundaries of the PMB relative to the Philippine Sea, Eurasian and Indo-Australian plates. The eastern section of North Luzon, previously considered as part of the PMB is considered as integrated with the Philippine Sea Plate. The boundary between the PMB and the Philippine Sea Plate represents a crustal tear caused by the collision of the Benham Rise with Luzon and is defined by the left-lateral Polilio-Philippine Fault. The crustal tear continues to the Pugo segment of the Philippine Fault where stress imparted by motion of the Philippine Sea Plate in the northern part of Luzon is accommodated by the active left-lateral Philippine Fault distributed along the Laur-Dingalan, Pugo, Vigan-Aggao, Abra River and Digdig fault segments. Thus, the extent of the PMB as originally defined by Gervasio (1967) is reduced. In this interpretation, the PMB now only includes the western section of North Luzon, South Luzon, West Visayas, Northwest Mindanao, Bicol Region, East Visayas, Zamboanga, Cotabato and the rest of Mindanao with Catanduanes Island representing the eastern outer zone of the PMB.


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Figure 9. Plate boundaries surrounding the Philippine Mobile Belt. In this revised tectonic map, the Philippine Mobile Belt does not include the eastern portion of North Luzon.


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References Allen, C., 1962. Circum-Pacific faulting in the Philippines-Taiwan region. Journal of Geophysical Research, 67, 12, 4795 –4812. Aurelio, M., 2000. Tectonics of the Philippines revisited. Journal of the Geological Society of the Philippines , 55, 119 –184. Aurelio, M., Barrier, E., Rangin, C., and Muller, C., 1991. The Philippine Fault in the late Cenozoic evolution of the Bondoc-Masbate N. Leyte area, Central Philippines. Journal of Southeast Asian Earth Sciences. Barrier, E., Huchon, P., and Aurelio, M., 1991. Philippine Fault: a key to Philippine kinematics. Geology , 19, 32 –25. Bautista, B., Bautista, M., Oike, K., Wu, F., and Punongbayan, R., 2001. A new insight into the geometry of subducting slabs in northern Luzon, Philippines. Tectonophysics, 339, 279 –310. Ben-Avraham, Z., 1978. The evolution of marginal basins and adjacent shelves in east and Southeast Asia. Tectonophysics, 45, 269 –288. Bird, P., 2003. An update digital model of plate boundaries. Geochemistry Geophysics Geosystems, 4, 3, 1027. Chase, C., 1978. Extension behind island arcs and motions relative to hot spots. Journal of Geophysical Research, 83, NB11, 5385 –5387. Coffin, M. and Eldholm, O., 1994. Large igneous provinces: crustal structure, dimensions, and external consequences. Reviews in Geophysics, 32, 1 –36. Encarnacion, J., 2004. Multiple ophiolite generation preserved in the northern Philippines and the growth of an island complex. Tectonophysics, 392, 103 –130. Encarnacion, J., Essene, E., Mukasa, S., and Hall, C., 1995. High pressure and temperature subophiolitic kyanite garnet amphibolites generated during initiation of mid-Tertiary subduction. Journal of Petrology , 36, 1481 –1503. Encarnacion, J. and Mukasa, S., 1997. Age and Geochemistry of an ”anorogenic” crustal melt and implications for the origin of I-type granites. Lithos, 42, 1 –13.

Fitch, T., 1972. Plate convergence, transcurrent faulting and internal deformation adjacent to southeast Asia and western Pacific. Journal of Geophysical Research, 77, 4432 –4460. Florendo, F., 1994. Tertiary arc rifting in northern Luzon, Philippines. Tectonics,13, 2, 623 –640. Galgana, G., Hamburger, M., McCaffrey, R., Corpuz, E., and Chen, Q., 2007. Analysis of crustal deformation in Luzon, Philippines using geodetic observations and earthquake focal mechanism. Tectonophysics. Doi:10.1016/j.tecto.2006.12.001. Geary, E., Kay, R., Reynolds, J., and Kay, S., 1988. Geochemistry of the mafic rocks from the Coto Block, Zambales ophiolite, Philippines: trace element evidence for two stages of crustal growth. Tectonophysics, 168, 43 –63. 20


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Gervasio, F., 1967. Age and nature of orogenesis in the Philippines. Tectonophysics, 4, 1, 379 –402. Hamilton, W., 1979. Tectonics of the Indonesian Region. U.S. Geological Survey Professional Paper , 1078. Holloway, N., 1982. The stratigraphic and tectonic relationship of Reed Bank, north Palawan and Mindoro to the Asian mainland and its significance in the evolution of the South China Sea. Association of American Petroleum Geologists Bulletin, 66, 1357 –1383. Huchon, P., 1986. Comment on the ”Kinematics of the Philippine Sea Plate. Tectonics, 5, 1, 165 –168.

R. T., Maury, Jr., R., G.P.Y. Yumul, G. P. J., Polve, M., Cotton, J., Dimalanta, C., and Olaguera, F., 2004. Subduction-related magmatic imprint of most Philippine ophiolites: Implications on the early geodynamic evolution of the Philippine archipelago. Bulletin Societe Geologie France, 175, 443 –460. Karig, D., 1973. Plate convergence between the Philippines and the Ryukyu Islands. Marine Geology , 14, 153 – 168. Karig, D., 1975. Basin genesis in the Philippine Sea. In Initial Report of DSDP 31 , 857 –879. U.S. Government Printing Office. Karig, D., 1983. Accreted terranes in the northern part of the Philippine archipelago. Tectonics, 2, 21, 1 –236. Lallemand, S., Popoff, M., Cadet, J., Bader, A., Pubellier, M., Rangin, C., and Deffontaines, B., 1998. Genetic relations between the central and southern Philippine Trench and the Sangihe Trench. Journal of Geophysical Research, 103, B1, 933 –950. Lewis, S. and Hayes, D., 1983. The tectonics of northward propagating subduction along eastern Luzon, Philippine islands. In D. Hayes, ed., The tectonic and Geologic Evolution of the Southeast Asian Seas and Islands, AGU Monograph, volume 27, 57 –78. American Geophysical Union. McCabe, R., Almasco, J., and Diegor, W., 1982. Geologic and paleomagnetic evidence for a possible Miocene collision in western Panay, Central Philippines. Geology , 10, 325 –329. Morgan, W., 1972. Plate motions and deep mantle convection. Geological Society of America Memoir , 132, 7 –22. Pinet, N. and Stephan, J., 1990. The Philippine wrench fault system in the Ilocos foothills, northwestern Luzon, Philippines. Tectonophysics, 183,207 –224. Pubellier, M., Quebral, R., Aurelio, M., and Rangin, C., 1996. Docking and post-docking escape tectonics in the southern Philippines. Geological Society Special Publications. Rangin, C., 1991. The Philippine Mobile Belt: A complex plate boundary. Journal of Southeast Asian Earth Sciences, 6, 209 –220. Rangin, C., Pichon, X. L., Mazzotti, S., Pubellier, M., Chamot-Rooke, N., Aurelio, M., Walpersdorf, A., and Quebral, R., 1999. Plate convergence measured by GPS across the Sundaland Philippine Sea plate deformed boundary: The Philippines and eastern Indonesia. Geophysical Journal International .


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Rangin, C., Stephan, J., and Muller, C., 1985. Middle Oligocene oceanic crust of the South China Sea jammed into the Mindoro Collision Zone (Philippines). Geology , 13, 425 –428. Ranken, B., Caldwell, R., and Karig, D., 1984. Kinematics of the Philippine Sea Plate. Tectonics, 3, 5, 555 –575. Ringenbach, J., Pinet, N., Stephan, J., and Delteil, J., 1993. Structural variety and tectonic evolution of the strike-slip basins related to the Philippines fault system, northern Luzon, Philippines. Tectonics. Sajona, F., Bellon, H., Maury, R., Pubellier, M., Quebral, R., Cotten, J., Bayon, F., Pagado, E., and Cotten, J., 1997. Tertiary and Quaternary magmatism in Mindanao and Leyte (Philippines: geochronology, geochemistry and tectonic setting. Journal of Asian Earth Sciences, 15, 2-3, 121 –153. Sarewitz, D. and Karig, D., 1986. Geologic evolution of Western Mindoro Island and the Mindoro Suture Zone, Philippines. Journal of Southeast Asian Earth Sciences, 1, 2, 117 –141. Seno, T., 1977. The instantaneous rotation vector of the Philippine Sea Plate in relation to the Eurasian Plate. Tectonophysics, 42, 209 –226. Taylor, B. and Hayes, D., 1983. Origin and history of the South China Sea Basin. In The tectonic and geologic evolution of Southeast Asian sea and island: Part 2 A.G.U. Monograph , volume 27, 23 –56. American Geophysical Union. 22

Key words: Philippine Mobile Belt, Benham Rise, Philippine Tectonics, Philippine Trench, Philippine Fault, Manila Trench

Corresponding author. Email address: [email protected] (A.M.F. Lagmay1).


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New Definition of Philippine Plate Bound

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