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Kelin Wang - One of the best experts on this subject based on the ideXlab platform.
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deformation cycles of Subduction earthquakes in a viscoelastic earth
Nature, 2012Co-Authors: Kelin Wang, Yan Hu, Jiangheng HeAbstract:Subduction zones produce the largest earthquakes. Over the past two decades, space geodesy has revolutionized our view of crustal deformation between consecutive earthquakes. The short time span of modern measurements necessitates comparative studies of Subduction zones that are at different stages of the deformation cycle. Piecing together geodetic ‘snapshots’ from different Subduction zones leads to a unifying picture in which the deformation is controlled by both the short-term (years) and long-term (decades and centuries) viscous behaviour of the mantle. Traditional views based on elastic models, such as coseismic deformation being a mirror image of interseismic deformation, are being thoroughly revised. ‘Snapshots’ of Subduction zones using space geodesy reveal that the viscous behaviour of the mantle controls crustal deformation, requiring the revision of traditional ‘elastic’ models for earthquake risk assessment. Space geodesy — the use of satellites to monitor Earth — has revolutionized our view of crustal deformation between consecutive earthquakes. However, the brevity of such measurements means that studies must be done by comparing multiple Subduction zones at different stages of the earthquake cycle. By piecing together geodetic 'snapshots' from the Sumatra, Chile and Cascadia Subduction zones, this Review presents a unifying picture in which deformation is controlled by the viscous behaviour of the mantle in both the short term (years) and the long term (decades to centuries).
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Effects of fluid circulation in subducting crust on Nankai margin seismogenic zone temperatures
Geology, 2008Co-Authors: Glenn A. Spinelli, Kelin WangAbstract:Vigorous fl uid circulation maintained in newly subducted ocean crust signifi cantly affects Subduction zone temperatures on the Nankai margin, Japan. The shallow part of the igneous ocean crust is pervasively fractured and thus highly permeable, allowing vigorous hydro thermal circulation. This circulation has been recognized as an important control on the thermal budget and evolution of ocean crust worldwide. However, existing Subduction zone thermal models either do not include hydrothermal circulation in ocean crust or assume that it abruptly stops upon Subduction. Here we use a conductive proxy to incorporate the thermal effects of high Nusselt number fl uid circulation in subducting crust into a Subduction zone thermal model. Hydrothermal circulation reduces temperatures in the seismogenic zone of the Nankai margin plate boundary fault by ~20 °C at the updip limit of seismicity and ~100 °C at the downdip limit. With improved thermal models for Subduction zones that include the effects of hydrothermal circulation in subducting crust, estimates of metamorphic reaction progress and interpretations of fault zone processes on various margins may need to be revisited.
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thermal regime of the southwest japan Subduction zone effects of age history of the subducting plate
Tectonophysics, 1995Co-Authors: Kelin Wang, R. D. Hyndman, Makoto YamanoAbstract:Abstract During a mid-Miocene (at about 15 Ma) tectonic reorganization, an ocean spreading ridge perpendicular to the strike of the Nankai Trough Subduction zone stopped spreading. Since that time there has been Subduction of the cooling fossil spreading ridge. In the present study, we have developed a time-dependent thermal Subduction model for this region using the finite-element method. There are good seismological and geological constraints for the plate geometry and for the Subduction history of the past 15 Ma. Boundary conditions are specified so that the oceanic plate subducting at the Nankai Trough becomes cooler as it gets older. The model results agree with the present heat-flow trend that decreases landward, and explain the paleothermal regime of high mid-Miocene temperatures inferred from land geological studies. The tectonics of the region prior to 15 Ma has some uncertainties. Assuming Subduction of an active spreading ridge or an 80-Ma-old lithosphere prior to 15 Ma give the same results for the present thermal regime of the seaward portion of the forearc but different results for the most landward region (> 250 km). The thermal history of the forearc since 15 Ma can be summarized as a rapid warming period as a consequence of ridge Subduction, followed by a cooling trend to the present as a result of the aging of the subducting plate. The results illustrate the thermal consequences of one type of ridge Subduction. They also demonstrate that the thermal regime of a Subduction zone depends critically on the age history of the subducting oceanic lithosphere, especially if it is young, as well as such parameters as the subducting plate dip angle and thickness of insulating sediments on the incoming oceanic crust. This dependence is especially important when the thermal regime is used to constrain the seismogenic behaviour of the Subduction thrust fault.
Glenn A. Spinelli - One of the best experts on this subject based on the ideXlab platform.
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Thermal effects of fluid circulation in the basement aquifer of subducting ocean crust
Journal of Geophysical Research-Solid Earth, 2009Co-Authors: Thomas Kummer, Glenn A. SpinelliAbstract:Most thermal models of Subduction zones assume no advection of heat by fluid flow because slow flow through underthrusting sediment, the plate boundary fault zone, and margin wedge likely transports only a minor amount of heat. We model coupled fluid and heat transport in a Subduction zone and show that hydrothermal circulation in subducting basaltic basement rocks can greatly influence Subduction zone temperatures. Fractured basaltic basement is several orders of magnitude more permeable than a typical plate boundary fault zone or marine sediments, allowing fluid circulation to redistribute and extract heat from a Subduction zone. Fluid circulation within the basement aquifer suppresses temperatures along the subducting slab relative to cases with no fluid transport. Heat is extracted from under the margin wedge and transported into the ocean crust near the trench. This circulation has a large effect on Subduction zone temperatures when topographic wavelength-dominated convection occurs (>5 times the critical Rayleigh number). With the exception of very cold Subduction zones (i.e., those with very fast convergence or very small taper) topographic wavelength-dominated convection occurs with aquifer permeability >= 10(-11) m(2) (in the range typically determined for upper ocean crust), suggesting such fluid circulation may be important in many Subduction zones. Because fluid circulation more effectively transports heat in warmer systems, hydrothermal circulation moderates the effects of convergence rate as a control on Subduction zone temperatures.
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Effects of fluid circulation in subducting crust on Nankai margin seismogenic zone temperatures
Geology, 2008Co-Authors: Glenn A. Spinelli, Kelin WangAbstract:Vigorous fl uid circulation maintained in newly subducted ocean crust signifi cantly affects Subduction zone temperatures on the Nankai margin, Japan. The shallow part of the igneous ocean crust is pervasively fractured and thus highly permeable, allowing vigorous hydro thermal circulation. This circulation has been recognized as an important control on the thermal budget and evolution of ocean crust worldwide. However, existing Subduction zone thermal models either do not include hydrothermal circulation in ocean crust or assume that it abruptly stops upon Subduction. Here we use a conductive proxy to incorporate the thermal effects of high Nusselt number fl uid circulation in subducting crust into a Subduction zone thermal model. Hydrothermal circulation reduces temperatures in the seismogenic zone of the Nankai margin plate boundary fault by ~20 °C at the updip limit of seismicity and ~100 °C at the downdip limit. With improved thermal models for Subduction zones that include the effects of hydrothermal circulation in subducting crust, estimates of metamorphic reaction progress and interpretations of fault zone processes on various margins may need to be revisited.
Federico Rossetti - One of the best experts on this subject based on the ideXlab platform.
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history of Subduction and back arc extension in the central mediterranean
Geophysical Journal International, 2001Co-Authors: Claudio Faccenna, Thorsten W Becker, Francesco Pio Lucente, Laurent Jolivet, Federico RossettiAbstract:SUMMARY Geological and geophysical constraints to reconstruct the evolution of the Central Mediterranean Subduction zone are presented. Geological observations such as upper plate stratigraphy, HP–LT metamorphic assemblages, foredeep/trench stratigraphy, arc volcanism and the back-arc extension process are used to define the infant stage of the Subduction zone and its latest, back-arc phase. Based on this data set, the time dependence of the amount of subducted material in comparison with the tomographic images of the upper mantle along two cross-sections from the northern Apennines and from Calabria to the Gulf of Lyon can be derived. Further, the reconstruction is used to unravel the main evolutionary trends of the Subduction process. Results of this analysis indicate that (1) Subduction in the Central Mediterranean is as old as 80 Myr, (2) the slab descended slowly into the mantle during the first 20–30 Myr (Subduction speeds were probably less than 1 cm year x1 ), (3) Subduction accelerated afterwards, producing arc volcanism and back-arc extension and (4) the slab reached the 660 km transition zone after 60–70 Myr. This time-dependent scenario, where a slow initiation is followed by a roughly exponential increase in the Subduction speed, can be modelled by equating the viscous dissipation per unit length due to the bending of oceanic lithosphere to the rate of change of potential energy by slab pull. Finally, the third stage is controlled by the interaction between the slab and the 660 km transition zone. In the southern region, this results in an important re-shaping of the slab and intermittent pulses of back-arc extension. In the northern region, the decrease in the trench retreat can be explained by the entrance of light continental material at the trench.
Andrea Argnani - One of the best experts on this subject based on the ideXlab platform.
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Plate motion and the evolution of Alpine Corsica and Northern Apennines
Tectonophysics, 2012Co-Authors: Andrea ArgnaniAbstract:The polarity of Subduction in the Corsica-Northern Apennine system is a long-debated issue. Models adopting an original W-dipping Subduction and models preferring a flip in the polarity of Subduction, from E-dipping to W-dipping present inconsistencies that are mainly due to the 2D approach. A new proposal is presented, using Late Cretaceous to Present-Day kinematic reconstructions of the Central Mediterranean. A wide oceanic embayment is required to the west of the Adriatic Promontory, to account for the Oligocene-Present calcalkaline volcanism and back-arc extension. This implies that the continental collision that originated the Alps s.s. could not continue SW-ward of Adria. The change in Subduction polarity, going from the Alps, to the Apennines, is taken as on original feature since the beginning of convergence. Kinematic reconstructions show that the point where Subduction polarity changes moved N-ward along the plate boundary, from Late Cretaceous to Eocene. As a result, areas that previously experienced the continental collision of the Adriatic Promontory were subsequently affected by the oceanic Subduction of the Tethyan embayment. This sequence of events caused the collapse of Alpine Corsica and led to the opening of the Balearic back-arc basin.A similar kinematic evolution is ongoing in Taiwan, where the N-ward Subduction of the Philippine Sea plate is progressively substituting the E-ward Subduction of the Eurasian plate, causing the collapse of the orogen in northern Taiwan.The slivers of continental basement rocks that are encased within the uppermost nappe in Corsica have been interpreted as remnants of a microplate that collided with Corsica. Plate kinematics offers an alternative explanation, with these basement rocks being derived from the colliding Adriatic promontory during Paleocene-Eocene; the promontory then passed away laterally, allowing the juxtaposition of the Alpine belt of Corsica with the early Apennines. © 2012 Elsevier B.V.
Marty Grove - One of the best experts on this subject based on the ideXlab platform.
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late paleozoic tectonic history of the ertix fault in the chinese altai and its implications for the development of the central asian orogenic system
Geological Society of America Bulletin, 2007Co-Authors: Stephanie M Briggs, Craig E Manning, Zhengle Chen, Xiaofeng Wang, Marty GroveAbstract:The Central Asian Orogenic System (CAOS) is one of the largest Phanerozoic accretionary orogens in the world and may represent a signifi cant site of continental growth. Its origin has been explained by two competing models: syn-Subduction strikeslip duplication of a single (>1000 km) long-lived arc (ca. 630‐360 Ma) or collision of multiple arcs and micro-continents. Central to the debate are the relative roles of syn-Subduction strike-slip faulting versus thrusting. In both models, the Ertix fault fi gures prominently, either as a roof fault of a large strike-slip duplex system developed during oceanic Subduction or as a suture of arc-continent or continent-continent collision. In order to differentiate between the above models, we conducted fi eld mapping, detailed kinematic analysis, and geochronological dating of the Ertix fault zone in the Chinese Altai. Our work indicates that the fault is a crustal-scale thrust that was active in the Permian. Its hanging wall records two pulses of magmatism ca. 450 Ma and ca. 280 Ma and experienced peak pressure and temperature of 6.2‐7.7 kbar and 560‐ 670 °C. Our geologic observations, together with the existing geologic information, favor a tectonic model that involves two episodes of Subduction below the Altai arc: fi rst, in the Ordovician, along a south-dipping Subduction zone; and second, in the late Carboniferous and early Permian along northdipping Subduction of the Junggar ocean. It was during the latter event that a melange complex was underplated below the older Ordovician arc, metamorphosed at lower crustal depths, and then exhumed to the upper crust along the south-directed Ertix thrust zone.
