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Tomotaka Iwata - One of the best experts on this subject based on the ideXlab platform.
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source rupture process of the 2011 ibaraki oki japan earthquake mw 7 9 estimated from the joint inversion of strong motion and gps data relationship with Seamount and Philippine Sea Plate
Geophysical Research Letters, 2013Co-Authors: Hisahiko Kubo, Kimiyuki Asano, Tomotaka IwataAbstract:[1] The source-rupture process of the 2011 Ibaraki-oki earthquake was estimated from the joint inversion of the strong-motion and global positioning system (GPS) data. The estimated seismic moment and maximum slip are 7.8 × 1020 Nm (Mw 7.9) and 6.3 m, respectively. The total rupture duration is approximately 30 s. The derived source model has one large slip area, which is surrounded by the subducted Seamount and the northeastern edge of the Philippine Sea Plate. From this model, we concluded that the rupture propagation of the 2011 Ibaraki-oki earthquake was stopped by the Seamount and the Philippine Sea Plate. We also showed the possibility of the rupture of this event being the reactivation of the preexisting asperity of an event that occurred in 1923.
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Source‐rupture process of the 2011 Ibaraki‐oki, Japan, earthquake (Mw 7.9) estimated from the joint inversion of strong‐motion and GPS Data: Relationship with Seamount and Philippine Sea Plate
Geophysical Research Letters, 2013Co-Authors: Hisahiko Kubo, Kimiyuki Asano, Tomotaka IwataAbstract:[1] The source-rupture process of the 2011 Ibaraki-oki earthquake was estimated from the joint inversion of the strong-motion and global positioning system (GPS) data. The estimated seismic moment and maximum slip are 7.8 × 1020 Nm (Mw 7.9) and 6.3 m, respectively. The total rupture duration is approximately 30 s. The derived source model has one large slip area, which is surrounded by the subducted Seamount and the northeastern edge of the Philippine Sea Plate. From this model, we concluded that the rupture propagation of the 2011 Ibaraki-oki earthquake was stopped by the Seamount and the Philippine Sea Plate. We also showed the possibility of the rupture of this event being the reactivation of the preexisting asperity of an event that occurred in 1923.
Shu-kun Hsu - One of the best experts on this subject based on the ideXlab platform.
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Plate tearing in the northwestern corner of the subducting Philippine Sea Plate
Journal of Asian Earth Sciences, 2013Co-Authors: Jing-yi Lin, Chao-shing Lee, Shu-kun Hsu, Jean-claude Sibuet, Chin-wei LiangAbstract:The Philippine Sea Plate (PHS) simultaneously subducts northwestward and collides eastward with the Eurasian Plate (EU) in northeast Taiwan. These two tectonic events induce high seismic activity, which makes northeastern Taiwan one of the most seismically active zones in the world. To understand the mechanical processes at work, we used existing geophysical data and the aftershocks recorded following a recent large strike-slip event occurring within the PHS oceanic crust. During this event, a NW–SE trending left-lateral sub-parallel to the PHS/EU convergence vector was active. As a consequence of the collision/subduction Plate geometry, we show that the lithosphere of the northwestern corner of the PHS has been torn in a NW–SE orientation. This tectonic feature is associated with an abrupt tectonic stress boundary and could generate large intra-Plate earthquakes.
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Strike-slip intraPlate earthquakes in the Western Philippine Sea Plate
Tectonophysics, 2013Co-Authors: Jing-yi Lin, Yen-fu Chen, Chao-shing Lee, Shu-kun Hsu, Chin-wei Liang, Yi-chin Lin, Hsin-sung HsiehAbstract:Abstract On 26 April 2010, a strike-slip earthquake (Mw 6.5) occurred in the Western Philippine Sea Plate. We deployed 14 ocean-bottom seismometers to record the corresponding aftershocks to acquire information regarding these intraPlate events. Our results show that the aftershocks were located along two linear features that intersect with an angle of approximately 120° and are considered a conjugate fault set. The P axis of the mainshock focal mechanism is consistent with the compressive stress direction induced by the arc–continent collision occurring in eastern Taiwan. The pre-existing oceanic fracture zones and tectonic fabrics do not appear to be reactivated based on the distinct rupture directions determined from the relocated aftershocks. However, the abrupt halt of the aftershocks at the border of the fracture zone suggests that pre-existing weak zones could act as a barrier to rupture propagation. Moreover, most large earthquakes have occurred near fracture zones, indicating that the pre-existing weakness may favor the generation of earthquakes compared to the other portion of the oceanic Plate due to the relatively low rock strength of this zone.
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Evidence for Early Cretaceous oceanic crust trapped in the Philippine Sea Plate
Earth and Planetary Science Letters, 2000Co-Authors: Anne Deschamps, Shu-kun Hsu, Patrick Monié, Serge Lallemand, K.y. YehAbstract:Abstract The Huatung Basin is a small oceanic basin located east of Taiwan. Previous age estimates from magnetic lineation studies indicated an Eocene age for the basin, and formation from the Central Basin Spreading Center of the West Philippine Basin during the last phase of spreading in Middle Eocene. New Ar/Ar ages obtained on gabbros dredged on oceanic basement highs of the Huatung Basin are Early Cretaceous. These old ages are consistent with Early Cretaceous ages determined on radiolarian assemblages from Lanyu Island (Luzon Arc). We have performed magnetic anomalies modeling for an Early Cretaceous oceanic crust. Our results are in good agreement with new Ar/Ar ages determinations. The best fit is indeed obtained with an opening of the Huatung Basin during the Early Cretaceous from 131 to 119 Ma, with a half spreading rate varying between 25 and 30 mm/yr. The spreading center appears to be located south of the actual basin. The abnormal depth (5500 m instead of 5900 m) and thickness (∼12 km instead of 6 km) of the crust beneath the basin indicate that there was probably an excess supply of magma during its formation. We propose that the basin is a fragment of the former ‘proto-south China Sea’ or possibly the ‘New Guinea Basin’ that has been trapped by the Philippine Sea Plate.
Jason R. Ali - One of the best experts on this subject based on the ideXlab platform.
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Philippine Sea Plate motion history: Eocene-Recent record from ODP Site 1201, central West Philippine Basin
Earth and Planetary Science Letters, 2015Co-Authors: Carl Richter, Jason R. AliAbstract:Abstract Ocean Drilling Program Site 1201 (19°17.8′N, 135°5.9′E) was drilled in the West Philippine Basin, about 100 km west of the inactive Palau-Kyushu Ridge and 450 km north of the extinct “Central Basin Fault” spreading center. A 509-m long Eocene to Miocene sedimentary sequence overlying middle Eocene (Chron C21n, ∼ 47 Ma ) basalts was recovered. Using paleomagnetism, this site provides an excellent opportunity to deduce the paleolatitude and motion history of the central Philippine Sea Plate throughout the last 45–50 m.y. Although Plate motion models for the Philippine Sea Plate are now fairly well established, data gaps exist both in time and geographical spread. The sediments at Site 1201 consist of a lower sequence of volcaniclastic turbidites sourced from the Palau-Kyushu Ridge and an upper succession of late Oligocene to early Pliocene red deep-Sea clays. Paleolatitudes derived from the sedimentary sequence support the model of northward movement of the Plate since the Eocene. Analysis of 37 basaltic basement samples indicates that this part of the Plate lay ∼ 7.1 ° ( + 5.4 ° , − 5.2 ° ) S in the middle Eocene. The rate of movement shows slowing of the Plate between 50 and 20 Ma, with a minimum of Plate movement at 20 Ma. An attempt to extract a rotational component of the Plate using the present-day field overprint from the azimuthally unoriented drill cores suggests a clockwise motion compatible with existing models.
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north luzon and the Philippine Sea Plate motion model insights following paleomagnetic structural and age dating investigations
Journal of Geophysical Research, 2007Co-Authors: Karlo L. Queaño, Jason R. Ali, John Milsom, Jonathan C Aitchison, Manuel PubellierAbstract:Results of one of the most comprehensive paleomagnetic and supporting geological programs ever carried out in offshore SE Asia on North Luzon, northern Philippines, are reported. Six new results, based on 66 sites, are reported from a total collection of 243 individual sites. Declinations in the data subset are sometimes scattered, likely reflecting combinations of major Plate and local rotations in both clockwise and counterclockwise directions, and thus have a somewhat limited value for tectonic modeling. The inclination data are, however, much more valuable and can be best explained if North Luzon traveled as part of the Philippine Sea Plate for most of its history, a scenario which is compatible with the known geology of the eastern Philippines and broader region. In the proposed model, for all of its Eocene-Pliocene history, North Luzon is placed on the western edge of the Philippine Sea Plate, effectively always just to the west of the site where the Benham Plateau formed ~40 Ma. The paleomagnetic data indicate a substantial northward migration of the area since the start of the Neogene, with an earlier interval stretching back to at least the mid-Early Cretaceous when this part of the Plate occupied equatorial latitudes. Post-15 Ma motion of the Plate has involved the indentation of the Palawan microcontinental block into the western side of the Philippine Archipelago. Deformations induced by this process offer the most likely explanation for the scattered declinations observed in North Luzon and areas a short distance to the south.
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Palaeomagnetic data from a mesozoic Philippine Sea Plate ophiolite on Obi Island, Eastern Indonesia
Journal of Asian Earth Sciences, 2001Co-Authors: Jason R. Ali, Robert Hall, Simon BakerAbstract:Abstract Palaeomagnetic data are presented from part of the Halmahera ophiolite exposed on Obi Island, eastern Indonesia. Until the late Neogene, Obi formed part of the southern Philippine Sea Plate; it is now isolated from that Plate and is located between fault strands in the left-lateral Sorong Fault Zone. Two areas were sampled: the first area comprised two sites from a microgabbro and a third site in a thin intruding dyke, and the second area yielded one site from a sheeted dyke suite. The mean in situ direction for the two areas is D=216.1°, I=23.3° , where the angular separation is 34.7°. Rotating the mean directions back to the palaeo-vertical clusters the vectors, so that D=219.4°, I=12.1°, where the angular separation is 20.1°. This clustering, together with other lines of palaeomagnetic evidence, suggests that the magnetisation is primary. The ophiolite is Mesozoic, and most likely formed in the Jurassic. This information, together with recently published palaeomagnetic data from nearby Upper Cretaceous Philippine Sea Plate formations, suggest that the oldest parts of the Philippine Sea Plate were situated close to the equator in the western Pacific in the middle Mesozoic.
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Evolution of the boundary between the Philippine Sea Plate and Australia: palaeomagnetic evidence from eastern Indonesia
Tectonophysics, 1995Co-Authors: Jason R. Ali, Robert HallAbstract:Abstract The boundary between the Philippine Sea and Australian Plates is the left-lateral Sorong Fault system of eastern Indonesia. Until recently, modelling this boundary for the period before about 5 Ma was difficult; the Tertiary motion of the Philippine Sea Plate was uncertain and palaeomagnetic data from areas adjacent to the fault were lacking. Recent geological and palaeomagnetic studies of the area north of the Sorong Fault have elucidated the Tertiary motion history of the Philippine Sea Plate, providing a reference for examining movements within the fault system. We report new palaeomagnetic data from within the Sorong Fault Zone, from the islands of Taliabu and Obi. Taliabu is part of the Sula Platform and is considered to be derived from Australia. Pelagic limestones from the Upper Cretaceous Tanamu Formation of Taliabu yielded a direction of D = 329.1°, I = −34.9° implying counter-clockwise rotation and a formation latitude of 19 ± 5°S. Sula and Misool are postulated to be part of a single microcontinent which had a different Late Cretaceous-mid-Tertiary movement history from Australia. The Sula Platform was transported to its present position by movement along the Sorong Fault system in the Late Miocene. Obi includes rocks of Philippine Sea and Australian origin; all the new sites are in rocks of Philippine Sea Plate origin. Since the Early Neogene the Philippine Sea Plate, which includes all islands north of the Sorong Fault, has rotated 40° clockwise and moved 10–15° northwards. Philippine Sea Plate rocks within the Sorong Fault Zone record similar latitude shifts, but different rotations. In north Obi, the Upper Oligocene Anggai River Formation and the Middle Miocene Woi Formation record ∼ 60° and ∼ 30° counter-clockwise rotations, respectively. The sense of rotation is consistent with motion within a left-lateral fault system, with the Philippine Sea and Australian Plates providing the shear couple. In contrast, the Woi Formation in southeast Obi records 15–20° clockwise rotation; this area is separated from the zone of counter-clockwise movement in north Obi by a strand of the Sorong Fault. Arc volcaniclastic rocks from the Upper Cretaceous Leleobasso Formation of northwest Obi have a primary magnetisation with a mean direction of D = 357.1°, I = −21.9°. These rocks formed at ∼ 11°N or ∼ 11°S, depending on the interpreted rotation history, and indicate a Pacific rather than Indian Ocean origin. A volcanic arc at the southern edge of the Philippine Sea Plate collided with eastern New Guinea at ∼ 25 Ma. The Philippine Sea-Australia Plate boundary then changed from subduction to strike-slip, as the Philippine Sea Plate began its Neogene rotation, initiating the Sorong Fault system. We suggest that many of the arc fragments in the New Guinea orogenic belt originated in the southern Philippine Sea Plate arc which has subsequently been dismembered by strike-slip faulting.
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Origin and motion history of the Philippine Sea Plate
Tectonophysics, 1995Co-Authors: Robert Hall, Jason R. Ali, Charles D. Anderson, Simon BakerAbstract:Abstract The Philippine Sea Plate is the one major Plate whose Tertiary motion is poorly constrained and whose origin is problematical. Its southern boundary is the Sorong Fault system which is part of a major left-lateral fault system at the northern margin of the Australian Plate. The southern part of the Plate in eastern Indonesia has been neglected in most syntheses but includes some of the oldest rocks within the Plate which are separated from remnant arcs of the Daito Ridge province of the northern Philippine Sea by the West Philippine Central Basin. The east Indonesian islands of the Halmahera-Waigeo region contain a good Mesozoic and Tertiary stratigraphic record indicating a long arc history for the southern part of the Plate. New palaeomagnetic data from these islands define two sub-areas: an area forming part of the Philippine Sea Plate north of the Sorong Fault, and an area within the Sorong Fault system. The area north of the fault records a long-term clockwise rotation history whereas that within the fault zone records local rotations interpreted as due to deformation at the Plate edge. Rocks of Philippine Sea Plate origin within both areas record similar latitudinal shifts. The rotation of the area north of the Sorong Fault is considered to represent the motion of the southern part of the Philippine Sea Plate. The new data indicate large Tertiary clockwise rotations similar to earlier suggestions for other parts of the Plate but record a discontinuous and more complex motion history than previously suggested. For the southern part of the Plate there was 40° rotation with northward translation between 0 and 25 Ma, no significant rotation between 25 and 40 Ma, and there was 50° rotation with southward translation between 40 and 50 Ma. We show that the new palaeomagnetic data form part of a single set with earlier palaeomagnetic data from elsewhere in the Plate. The translation history of the southern part of the Plate in eastern Indonesia can be reconciled with northward motions recorded elsewhere and can be used to determine rotation poles for the Plate (15°N, 160°E for the interval 5–25 Ma, and 10°N, 150°E for the interval 40–50 Ma). Reconstructions based on these poles predict that at ∼ 45 Ma the Palau-Kyushu Ridge had a WNW-ESE orientation which is very different from that postulated by many models used to explain the widespread boninite volcanism in the Izu-Bonin-Marians forearc at this time. The long arc history of the southern part of the Plate and the reconstructions based on the rotation poles calculated from the palaeomagnetic data favour an origin for the West Philippine Basin by spreading in a backarc basin.
Kantaro Fujioka - One of the best experts on this subject based on the ideXlab platform.
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a trapped Philippine Sea Plate origin for morb from the inner slope of the izu bonin trench
Earth and Planetary Science Letters, 1999Co-Authors: Susan M. Debari, Brian Taylor, K.j. Spencer, Kantaro FujiokaAbstract:Basement outcrops sampled by submersible and dredge from the inner slope of the Izu^Bonin trench at 32‡N and 6200^6700 m water depth have a distinct mid-ocean ridge basalt (MORB) chemistry unlike any other rocks previously sampled in the Izu^Bonin arc. They are low K tholeiites with moderate TiO2 (0.7^1.8 wt%), extremely low Ba (1.5^7 parts per million), low Ba/La (1.2^3) and are depleted in light rare-earth elements. These samples could represent either an accreted piece of subducting Pacific Plate or a trapped remnant of Philippine Sea Plate on which the Izu^Bonin arc was built. Although their major and trace element chemistry do not help to distinguish their source, the Sr, Nd and Pb isotopes clearly support a Philippine Sea Plate origin. The isotopic signature of the inner trench slope samples matches that of Philippine Sea Plate lavas, with 87 Sr/ 86 Sr = 0.70321^0.70373, 143 Nd/ 144 Nd = 0.513057^0.513077 and 206 Pb/ 204 Pb = 18.2^18.5. The samples have elevated 207 Pb/ 204 Pb (15.3^15.5) and 208 Pb/ 204 Pb (38.0^38.2) values compared to the Northern Hemisphere reference line (NHRL) and their isotopic signature is distinct from the Mesozoic Pacific MORB being subducted. These are the first samples of trapped Philippine Sea oceanic crust discovered in the Izu^ Bonin^Mariana arc. They require that models for the formation of intra-oceanic arc crust account for pre-existing oceanic crust and that estimates of arc magma production rates are lowered accordingly. fl 1999 Elsevier Science B.V. All rights reserved.
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A trapped Philippine Sea Plate origin for MORB from the inner slope of the Izu^Bonin trench
Earth and Planetary Science Letters, 1999Co-Authors: Susan M. Debari, Brian Taylor, K.j. Spencer, Kantaro FujiokaAbstract:Basement outcrops sampled by submersible and dredge from the inner slope of the Izu^Bonin trench at 32‡N and 6200^6700 m water depth have a distinct mid-ocean ridge basalt (MORB) chemistry unlike any other rocks previously sampled in the Izu^Bonin arc. They are low K tholeiites with moderate TiO2 (0.7^1.8 wt%), extremely low Ba (1.5^7 parts per million), low Ba/La (1.2^3) and are depleted in light rare-earth elements. These samples could represent either an accreted piece of subducting Pacific Plate or a trapped remnant of Philippine Sea Plate on which the Izu^Bonin arc was built. Although their major and trace element chemistry do not help to distinguish their source, the Sr, Nd and Pb isotopes clearly support a Philippine Sea Plate origin. The isotopic signature of the inner trench slope samples matches that of Philippine Sea Plate lavas, with 87 Sr/ 86 Sr = 0.70321^0.70373, 143 Nd/ 144 Nd = 0.513057^0.513077 and 206 Pb/ 204 Pb = 18.2^18.5. The samples have elevated 207 Pb/ 204 Pb (15.3^15.5) and 208 Pb/ 204 Pb (38.0^38.2) values compared to the Northern Hemisphere reference line (NHRL) and their isotopic signature is distinct from the Mesozoic Pacific MORB being subducted. These are the first samples of trapped Philippine Sea oceanic crust discovered in the Izu^ Bonin^Mariana arc. They require that models for the formation of intra-oceanic arc crust account for pre-existing oceanic crust and that estimates of arc magma production rates are lowered accordingly. fl 1999 Elsevier Science B.V. All rights reserved.
Jing-yi Lin - One of the best experts on this subject based on the ideXlab platform.
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Plate tearing in the northwestern corner of the subducting Philippine Sea Plate
Journal of Asian Earth Sciences, 2013Co-Authors: Jing-yi Lin, Chao-shing Lee, Shu-kun Hsu, Jean-claude Sibuet, Chin-wei LiangAbstract:The Philippine Sea Plate (PHS) simultaneously subducts northwestward and collides eastward with the Eurasian Plate (EU) in northeast Taiwan. These two tectonic events induce high seismic activity, which makes northeastern Taiwan one of the most seismically active zones in the world. To understand the mechanical processes at work, we used existing geophysical data and the aftershocks recorded following a recent large strike-slip event occurring within the PHS oceanic crust. During this event, a NW–SE trending left-lateral sub-parallel to the PHS/EU convergence vector was active. As a consequence of the collision/subduction Plate geometry, we show that the lithosphere of the northwestern corner of the PHS has been torn in a NW–SE orientation. This tectonic feature is associated with an abrupt tectonic stress boundary and could generate large intra-Plate earthquakes.
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Strike-slip intraPlate earthquakes in the Western Philippine Sea Plate
Tectonophysics, 2013Co-Authors: Jing-yi Lin, Yen-fu Chen, Chao-shing Lee, Shu-kun Hsu, Chin-wei Liang, Yi-chin Lin, Hsin-sung HsiehAbstract:Abstract On 26 April 2010, a strike-slip earthquake (Mw 6.5) occurred in the Western Philippine Sea Plate. We deployed 14 ocean-bottom seismometers to record the corresponding aftershocks to acquire information regarding these intraPlate events. Our results show that the aftershocks were located along two linear features that intersect with an angle of approximately 120° and are considered a conjugate fault set. The P axis of the mainshock focal mechanism is consistent with the compressive stress direction induced by the arc–continent collision occurring in eastern Taiwan. The pre-existing oceanic fracture zones and tectonic fabrics do not appear to be reactivated based on the distinct rupture directions determined from the relocated aftershocks. However, the abrupt halt of the aftershocks at the border of the fracture zone suggests that pre-existing weak zones could act as a barrier to rupture propagation. Moreover, most large earthquakes have occurred near fracture zones, indicating that the pre-existing weakness may favor the generation of earthquakes compared to the other portion of the oceanic Plate due to the relatively low rock strength of this zone.