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1
Marotta, A. M., F. Restelli, A. Bollino, A. Regorda, and R. Sabadini. "The static and time-dependent signature of ocean–continent and ocean–ocean subduction: the case studies of Sumatra and Mariana complexes." Geophysical Journal International 221, no. 2 (January 16, 2020): 788–825. http://dx.doi.org/10.1093/gji/ggaa029.
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SUMMARY The anomalous density structure at subduction zones, both in the wedge and in the upper mantle, is analysed to shed light on the processes that are responsible for the characteristic gravity fingerprints of two types of subduction: ocean–continent and ocean–ocean. Our modelling is then performed within the frame of the EIGEN-6C4 gravitational disturbance pattern of two subductions representative of the above two types, the Sumatra and Mariana complexes, finally enabling the different characteristics of the two patterns to be observed and understood on a physical basis, including some small-scale details. A 2-D viscous modelling perpendicular to the trench accounts for the effects on the gravity pattern caused by a wide range of parameters in terms of convergence velocity, subduction dip angle and lateral variability of the crustal thickness of the overriding plate, as well as compositional differentiation, phase changes and hydration of the mantle. Plate coupling, modelled within a new scheme where the relative velocity at the plate contact results self-consistently from the thermomechanical evolution of the system, is shown to have an important impact on the gravity signature. Beyond the already understood general bipolar fingerprint of subduction, perpendicular to the trench, we obtain the density and gravity signatures of the processes occurring within the wedge and mantle that are responsible for the two different gravity patterns. To be compliant with the geodetic EIGEN-6C4 gravitational disturbance and to compare our predictions with the gravity at Sumatra and Mariana, we define a model normal Earth. Although the peak-to-peak gravitational disturbance is comparable for the two types of subductions, approximately 250 mGal, from both observations and modelling, encompassing the highest positive maximum on the overriding plates and the negative minimum on the trench, the trough is wider for the ocean–ocean subduction: approximately 300 km compared to approximately 180 km for the ocean–continent subduction. Furthermore, the gravitational disturbance pattern is more symmetric for the ocean–ocean subduction compared to the ocean–continent subduction in terms of the amplitudes of the two positive maxima over the overriding and subducting plates. Their difference is, for the ocean–ocean type, approximately one half of the ocean–continent one. These different characteristics of the two types of subductions are exploited herein in terms of the different crustal thicknesses of the overriding plate and of the different dynamics in the wedge and in the mantle for the two types of subduction, in close agreement with the gravity data.
2
Lynner, Colton. "Anisotropy-revealed change in hydration along the Alaska subduction zone." Geology 49, no. 9 (June 3, 2021): 1122–25. http://dx.doi.org/10.1130/g48860.1.
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Abstract Megathrust earthquake behavior in subduction zones is controlled by a variety of factors including the hydration state of the subducting slab. Increased hydration reduces the occur-rence of great, damaging earthquakes by diminishing the strength of the material along the interface between tectonic plates. Understanding variations in hydration in subductions zones is necessary for properly assessing the overall hazard posed by each region. Fortunately, seismic anisotropy is strongly dependent upon hydration of the subducting crust and litho-sphere. I present shear-wave splitting measurements that illuminate changes in anisotropy, and therefore hydration, of the subducting Pacific plate beneath the Alaska subduction zone (northern Pacific Ocean). Variations in shear-wave splitting directly correlate to changes in the behavior of great, megathrust earthquakes. My measurements show that the Shumagin seismic gap is characterized by a hydrated subducting slab, explaining the long-term lack of great earthquakes. Observations in the immediately adjacent Semidi segment, which experiences great events regularly, indicate a far less hydrated slab. These results are driven by the preferential alignment of paleo-spreading fabrics of the Pacific plate. Where fabrics are more closely aligned with the orientation of the trench, outer-rise faulting and plate hydration is enhanced. These results highlight the importance of changes in preexisting slab structures and subsequent hydration in the production of great, damaging earthquakes.
3
Suchoy, Lior, Saskia Goes, Benjamin Maunder, Fanny Garel, and Rhodri Davies. "Effects of basal drag on subduction dynamics from 2D numerical models." Solid Earth 12, no. 1 (January 20, 2021): 79–93. http://dx.doi.org/10.5194/se-12-79-2021.
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Abstract. Subducting slabs are an important driver of plate motions, yet the relative importance of different forces in governing subduction motions and styles remains incompletely understood. Basal drag has been proposed to be a minor contributor to subduction forcing because of the lack of correlation between plate size and velocity in observed and reconstructed plate motions. Furthermore, in single subduction system models, low basal drag leads to subduction behaviour most consistent with the observation that trench migration velocities are generally low compared to convergence velocities. By contrast, analytical calculations and global mantle flow models indicate basal drag can be substantial. In this study, we revisit this problem by examining the drag at the base of the lithosphere, for a single subduction system, in 2D models with a free trench and composite non-linear rheology. We compare the behaviour of short and long plates for a range of asthenospheric and lithospheric rheologies. We reproduce results from previous modelling studies, including low ratios of trench over plate motions. However, we also find that any combination of asthenosphere and lithosphere viscosity that produces Earth-like subduction behaviour leads to a correlation of velocities with plate size, due to the role of basal drag. By examining Cenozoic plate motion reconstructions, we find that slab age and plate size are positively correlated: higher slab pull for older plates tends to be offset by higher basal drag below these larger plates. This, in part, explains the lack of plate velocity–size correlation in observations, despite the important role of basal drag in the subduction force balance.
4
Schellart, W. P., and V. Strak. "Geodynamic models of short-lived, long-lived and periodic flat slab subduction." Geophysical Journal International 226, no. 3 (April 1, 2021): 1517–41. http://dx.doi.org/10.1093/gji/ggab126.
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SUMMARY Flat slab subduction has been ascribed to a variety of causes, including subduction of buoyant ridges/plateaus and forced trench retreat. The former, however, has irregular spatial correlations with flat slabs, while the latter has required external forcing in geodynamic subduction models, which might be insufficient or absent in nature. In this paper, we present buoyancy-driven numerical geodynamic models and aim to investigate flat slab subduction in the absence of external forcing as well as test the influence of overriding plate strength, subducting plate thickness, inclusion/exclusion of an oceanic plateau and lower mantle viscosity on flat slab formation and its evolution. Flat slab subduction is reproduced during normal oceanic subduction in the absence of ridge/plateau subduction and without externally forced plate motion. Subduction of a plateau-like feature, in this buoyancy-driven setting, enhances slab steepening. In models that produce flat slab subduction, it only commences after a prolonged period of slab dip angle reduction during lower mantle slab penetration. The flat slab is supported by mantle wedge suction, vertical compressive stresses at the base of the slab and upper mantle slab buckling stresses. Our models demonstrate three modes of flat slab subduction, namely short-lived (transient) flat slab subduction, long-lived flat slab subduction and periodic flat slab subduction, which occur for different model parameter combinations. Most models demonstrate slab folding at the 660 km discontinuity, which produces periodic changes in the upper mantle slab dip angle. With relatively high overriding plate strength or large subducting plate thickness, such folding results in periodic changes in the dip angle of the flat slab segment, which can lead to periodic flat slab subduction, providing a potential explanation for periodic arc migration. Flat slab subduction ends due to the local overriding plate shortening and thickening it produces, which forces mantle wedge opening and a reduction in mantle wedge suction. As overriding plate strength controls the shortening rate, it has a strong control on the duration of flat slab subduction, which increases with increasing strength. For the weakest overriding plate, flat slab subduction is short-lived and lasts only 6 Myr, while for the strongest overriding plate flat slab subduction is long-lived and exceeds 75 Myr. Progressive overriding plate shortening during flat slab subduction might explain why flat slab subduction terminated in the Eocene in western North America and in the Jurassic in South China.
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Kirdyashkin, A. A., A. G. Kirdyashkin, V. E. Distanov, and I. N. Gladkov. "ON HEAT SOURCE IN SUBDUCTION ZONE." Geodynamics & Tectonophysics 12, no. 3 (September 17, 2021): 471–84. http://dx.doi.org/10.5800/gt-2021-12-3-0534.
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The subduction of an oceanic plate is studied as the motion of a high-viscosity Newtonian fluid. The subducting plate spreads along the 670-km depth boundary under the influence of oppositely directed horizontal forces. These forces are due to oppositely directed horizontal temperature gradients. We consider the flow structure and heat transfer in the layer that includes both the oceanic lithosphere and the crust and moves underneath a continent. The heat flow is estimated at the contact between the subducting plate and the surrounding mantle in the continental limb of the subduction zone. Our study results show that the crustal layer of the subducting plate can melt and a thermochemical plume can form at the 670-km boundary. Our model of a thermochemical plume in the subduction zone shows the following: (1) formation of a plume conduit in the crustal layer of the subducting plate; (2) formation of a primary magmatic chamber in the area wherein the melting rate equals the rate of subduction; (3) origination of a vertical plume conduit from the primary chamber melting through the continent; (4) plume eruption through the crustal layer to the surface, i.e. formation of a volcano. Our experiments are aimed to model the plume conduit melting in an inclined flat layer above a local heat source. The melt flow structure in the plume conduit is described. Laboratory modeling have revealed that the mechanisms of melt eruption from the plume conduit differ depending on whether a gas cushion is present or absent at the plume roof.
6
Boutelier, D., and O. Oncken. "3-D thermo-mechanical laboratory modelling of plate-tectonics." Solid Earth Discussions 3, no. 1 (February 18, 2011): 105–47. http://dx.doi.org/10.5194/sed-3-105-2011.
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Abstract. We present an experimental apparatus for 3-D thermo-mechanical analogue modelling of plate-tectonics processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic with softening analogue materials, is submitted to a constant temperature gradient producing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry). Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and changed because of the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.
7
Arcay, D. "Dynamics of interplate domain in subduction zones: influence of rheological parameters and subducting plate age." Solid Earth 3, no. 2 (December 21, 2012): 467–88. http://dx.doi.org/10.5194/se-3-467-2012.
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Abstract. The properties of the subduction interplate domain are likely to affect not only the seismogenic potential of the subduction area but also the overall subduction process, as it influences its viability. Numerical simulations are performed to model the long-term equilibrium state of the subduction interplate when the diving lithosphere interacts with both the overriding plate and the surrounding convective mantle. The thermomechanical model combines a non-Newtonian viscous rheology and a pseudo-brittle rheology. Rock strength here depends on depth, temperature and stress, for both oceanic crust and mantle rocks. I study the evolution through time of, on one hand, the brittle-ductile transition (BDT) depth, zBDT, and, on the other hand, of the kinematic decoupling depth, zdec, simulated along the subduction interplate. The results show that both a high friction and a low ductile strength at the asthenospheric wedge tip shallow zBDT. The influence of the weak material activation energy is of second order but not negligible. zBDT becomes dependent on the ductile strength increase with depth (activation volume) if the BDT occurs at the interplate decoupling depth. Regarding the interplate decoupling depth, it is shallowed (1) significantly if mantle viscosity at asthenospheric wedge tip is low, (2) if the difference in mantle and interplate activation energy is weak, and (3) if the activation volume is increased. Very low friction coefficients and/or low asthenospheric viscosities promote zBDT = zdec. I then present how the subducting lithosphere age affects the brittle-ductile transition depth and the kinematic decoupling depth in this model. Simulations show that a rheological model in which the respective activation energies of mantle and interplate material are too close hinders the mechanical decoupling at the down-dip extent of the interplate, and eventually jams the subduction process during incipient subduction of a young (20-Myr-old) and soft lithosphere under a thick upper plate. Finally, both the BDT depth and the decoupling depth are a function of the subducting plate age, but are not influenced in the same fashion: cool and old subducting plates deepen the BDT but shallow the interplate decoupling depth. Even if BDT and kinematic decoupling are intrinsically related to different mechanisms of deformation, this work shows that they are able to interact closely. Comparison between modelling results and observations suggests a minimum friction coefficient of 0.045 for the interplate plane, even 0.069 in some cases, to model realistic BDT depths. The modelled zdec is a bit deeper than suggested by geophysical observations. Eventually, the better way to improve the adjustment to observations may rely on a moderate to strong asthenosphere viscosity reduction in the metasomatised mantle wedge.
8
Guillaume, B., L. Husson, F. Funiciello, and C. Faccenna. "The dynamics of laterally variable subductions: laboratory models applied to the Hellenides." Solid Earth 4, no. 2 (July 10, 2013): 179–200. http://dx.doi.org/10.5194/se-4-179-2013.
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Abstract. We designed three-dimensional dynamically self-consistent laboratory models of subduction to analyse the relationships between overriding plate deformation and subduction dynamics in the upper mantle. We investigated the effects of the subduction of a lithosphere of laterally variable buoyancy on the temporal evolution of trench kinematics and shape, horizontal flow at the top of the asthenosphere, dynamic topography and deformation of the overriding plate. Two subducting units, which correspond to a negatively buoyant oceanic plate and positively buoyant continental one, are juxtaposed via a trench-perpendicular interface (analogue to a tear fault) that is either fully-coupled or shear-stress free. Differential rates of trench retreat, in excess of 6 cm yr−1 between the two units, trigger a more vigorous mantle flow above the oceanic slab unit than above the continental slab unit. The resulting asymmetrical sublithospheric flow shears the overriding plate in front of the tear fault, and deformation gradually switches from extension to transtension through time. The consistency between our models results and geological observations suggests that the Late Cenozoic deformation of the Aegean domain, including the formation of the North Aegean Trough and Central Hellenic Shear zone, results from the spatial variations in the buoyancy of the subducting lithosphere. In particular, the lateral changes of the subduction regime caused by the Early Pliocene subduction of the old oceanic Ionian plate redesigned mantle flow and excited an increasingly vigorous dextral shear underneath the overriding plate. The models suggest that it is the inception of the Kefalonia Fault that caused the transition between an extension dominated tectonic regime to transtension, in the North Aegean, Mainland Greece and Peloponnese. The subduction of the tear fault may also have helped the propagation of the North Anatolian Fault into the Aegean domain.
9
Boutelier, D., and O. Oncken. "3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments." Solid Earth 2, no. 1 (May 24, 2011): 35–51. http://dx.doi.org/10.5194/se-2-35-2011.
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Abstract. We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry). Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.
10
Arcay, D. "Dynamics of interplate domain in subduction zones: influence of rheological parameters and subducting plate age." Solid Earth Discussions 4, no. 2 (July 20, 2012): 943–92. http://dx.doi.org/10.5194/sed-4-943-2012.
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Abstract. The properties of the subduction interplate domain are likely to affect not only the seismogenic potential of the subduction area but also the overall subduction process, as it influences its viability. Numerical simulations are performed to model the long-term equilibrium state of the subduction interplate when the diving lithosphere interacts with both the overriding plate and the surrounding convective mantle. The thermomechanical model combines a non-Newtonian viscous rheology and a pseudo-brittle rheology. Rock strength here depends on depth, temperature and stress, for both oceanic crust and mantle rocks. I study the evolution through time of, on one hand, the kinematic decoupling depth, zdec and, on the other hand, of the brittle-ductile transition (BDT) depth, zBDT, simulated along the subduction interplate. The results reveal that zBDT mainly depends on the friction coefficient characterising the interplate channel and on the viscosity at the lithosphere-asthenosphere boundary. The influence of the weak material activation energy is of second order but not negligible. zBDT becomes dependent on the ductile strength increase with depth (activation volume) if the BDT occurs at the interplate deocupling depth. Regarding the interplate decoupling depth, it is basically a function of (1) mantle viscosity at asthenospheric wedge tip, (2) difference in mantle and interplate activation anergy, and (3) activation volume. Specific conditions yielding zBDT = zdec are discussed. I then present how the subducting lithosphere age affects the brittle-ductile transition depth and the kinematic decoupling depth in this model. Simulations show that a rheological model in which the respective activation energies of mantle and interplate material are too close impedes strain localization during incipient subduction of a young (20 Myr old) and soft lithosphere under a thick upper plate. Finally, both the BDT depth and the decoupling depth are a function of the subducting plate age, but are not influenced in the same fashion: cool and old subducting plates deepen the BDT but shallow the interplate decoupling depth. Even if BDT and kinematic decoupling are instrinsically related to different mechanisms of deformation, this work shows that they are able to interact closely.
11
Zhou, Xin, Zhong-Hai Li, Taras V. Gerya, and Robert J. Stern. "Lateral propagation–induced subduction initiation at passive continental margins controlled by preexisting lithospheric weakness." Science Advances 6, no. 10 (March 2020): eaaz1048. http://dx.doi.org/10.1126/sciadv.aaz1048.
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Understanding the conditions for forming new subduction zones at passive continental margins is important for understanding plate tectonics and the Wilson cycle. Previous models of subduction initiation (SI) at passive margins generally ignore effects due to the lateral transition from oceanic to continental lithosphere. Here, we use three-dimensional numerical models to study the possibility of propagating convergent plate margins from preexisting intraoceanic subduction zones along passive margins [subduction propagation (SP)]. Three possible regimes are achieved: (i) subducting slab tearing along a STEP fault, (ii) lateral propagation–induced SI at passive margin, and (iii) aborted SI with slab break-off. Passive margin SP requires a significant preexisting lithospheric weakness and a strong slab pull from neighboring subduction zones. The Atlantic passive margin to the north of Lesser Antilles could experience SP if it has a notable lithospheric weakness. In contrast, the Scotia subduction zone in the Southern Atlantic will most likely not propagate laterally.
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Sun, Weidong. "The initiation of plate subduction." Solid Earth Sciences 2, no. 4 (December 2017): 89–90. http://dx.doi.org/10.1016/j.sesci.2017.10.001.
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Van Houtte, Chris, Stephen Bannister, Caroline Holden, Sandra Bourguignon, and Graeme McVerry. "The New Zealand Strong Motion Database." Bulletin of the New Zealand Society for Earthquake Engineering 50, no. 1 (March 31, 2017): 1–20. http://dx.doi.org/10.5459/bnzsee.50.1.1-20.
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This article summarises work that has been undertaken to compile the New Zealand Strong Motion Database, which is intended to be a significant resource for both researchers and practitioners. The database contains 276 New Zealand earthquakes that were recorded by strong motion instruments from GeoNet and earlier network operators. The events have moment magnitudes ranging from 3.5 to 7.8. A total of 134 of these events (49%) have been classified as occurring in the overlying crust, with 33 events (12%) located on the Fiordland subduction interface and 7 on the Hikurangi subduction interface (3%). 8 events (3%) are deemed to have occurred within the subducting Australian Plate at the Fiordland subduction zone, and 94 events (34%) within the subducting Pacific Plate on the Hikurangi subduction zone. There are a total of 4,148 uniformly-processed recordings associated with these earthquakes, from which acceleration, velocity and displacement time-series, Fourier amplitude spectra of acceleration, and acceleration response spectra have been computed. 598 recordings from the New Zealand database are identified as being suitable for future use in time-domain analyses of structural response. All data are publicly available at http://info.geonet.org.nz/x/TQAdAQ.
14
Nettesheim, Matthias, Todd A. Ehlers, David M. Whipp, and Alexander Koptev. "The influence of upper-plate advance and erosion on overriding plate deformation in orogen syntaxes." Solid Earth 9, no. 6 (November 5, 2018): 1207–24. http://dx.doi.org/10.5194/se-9-1207-2018.
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Abstract. Focused, rapid exhumation of rocks is observed at some orogen syntaxes, but the driving mechanisms remain poorly understood and contested. In this study, we use a fully coupled thermomechanical numerical model to investigate the effect of upper-plate advance and different erosion scenarios on overriding plate deformation. The subducting slab in the model is curved in 3-D, analogous to the indenter geometry observed in seismic studies. We find that the amount of upper-plate advance toward the trench dramatically changes the orientation of major shear zones in the upper plate and the location of rock uplift. Shear along the subduction interface facilitates the formation of a basal detachment situated above the indenter, causing localized rock uplift there. We conclude that the change in orientation and dip angle set by the indenter geometry creates a region of localized uplift as long as subduction of the down-going plate is active. Switching from flat (total) erosion to more realistic fluvial erosion using a landscape evolution model leads to variations in rock uplift at the scale of large catchments. In this case, deepest exhumation again occurs above the indenter apex, but tectonic uplift is modulated on even smaller scales by lithostatic pressure from the overburden of the growing orogen. Highest rock uplift can occur when a strong tectonic uplift field spatially coincides with large erosion potential. This implies that both the geometry of the subducting plate and the geomorphic and climatic conditions are important for the creation of focused, rapid exhumation.
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Guillaume, B., L. Husson, F. Funiciello, and C. Faccenna. "The dynamics of laterally variable subductions: laboratory models applied to the Hellenides." Solid Earth Discussions 5, no. 1 (April 9, 2013): 315–63. http://dx.doi.org/10.5194/sed-5-315-2013.
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Abstract. We design three-dimensional dynamically self-consistent laboratory models of subduction to analyze the relationships between overriding plate deformation and subduction dynamics in the upper mantle. We investigate the effects of the subduction of a lithosphere of laterally variable buoyancy on the temporal evolution of trench kinematics and shape, horizontal flow at the top of the asthenosphere, dynamic topography and deformation of the overriding plate. The interface between the two units, analogue to a trench-perpendicular tear fault between a negatively buoyant oceanic plate and positively buoyant continental one, is either fully-coupled or shear-stress free. Differential rates of trench retreat, in excess of 6 cm yr−1 between the two units, trigger a more vigorous mantle flow above the oceanic slab unit than above the continental slab unit. The resulting asymmetrical sublithospheric flow shears the overriding plate in front of the tear fault, and deformation gradually switches from extension to transtension through time. The consistency between our models results and geological observations suggests that the Late Cenozoic deformation of the Aegean domain, including the formation of the North Aegean Trough and Central Hellenic Shear zone, results from the spatial variations in the buoyancy of the subducting lithosphere. In particular, the lateral changes of the subduction regime caused by the Early Pliocene subduction of the old oceanic Ionian plate redesigned mantle flow and excited an increasingly vigorous dextral shear underneath the overriding plate. The models suggest that it is the inception of the Kefalonia Fault that caused the transition between an extension dominated tectonic regime to transtension, in the North Aegean, Mainland Greece and Peloponnese. The subduction of the tear fault may also have helped the propagation of the North Anatolian Fault into the Aegean domain.
16
O'Neill, Craig, Simon Turner, and Tracy Rushmer. "The inception of plate tectonics: a record of failure." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2132 (October 2018): 20170414. http://dx.doi.org/10.1098/rsta.2017.0414.
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The development of plate tectonics from a pre-plate tectonics regime requires both the initiation of subduction and the development of nascent subduction zones into long-lived contiguous features. Subduction itself has been shown to be sensitive to system parameters such as thermal state and the specific rheology. While generally it has been shown that cold-interior high-Rayleigh-number convection (such as on the Earth today) favours plates and subduction, due to the ability of the interior stresses to couple with the lid, a given system may or may not have plate tectonics depending on its initial conditions. This has led to the idea that there is a strong history dependence to tectonic evolution—and the details of tectonic transitions, including whether they even occur, may depend on the early history of a planet. However, intrinsic convective stresses are not the only dynamic drivers of early planetary evolution. Early planetary geological evolution is dominated by volcanic processes and impacting. These have rarely been considered in thermal evolution models. Recent models exploring the details of plate tectonic initiation have explored the effect of strong thermal plumes or large impacts on surface tectonism, and found that these ‘primary drivers’ can initiate subduction, and, in some cases, over-ride the initial state of the planet. The corollary of this, of course, is that, in the absence of such ongoing drivers, existing or incipient subduction systems under early Earth conditions might fail. The only detailed planetary record we have of this development comes from Earth, and is restricted by the limited geological record of its earliest history. Many recent estimates have suggested an origin of plate tectonics at approximately 3.0 Ga, inferring a monotonically increasing transition from pre-plates, through subduction initiation, to continuous subduction and a modern plate tectonic regime around that time. However, both numerical modelling and the geological record itself suggest a strong nonlinearity in the dynamics of the transition, and it has been noted that the early history of Archaean greenstone belts and trondhjemite–tonalite–granodiorite record many instances of failed subduction. Here, we explore the history of subduction failure on the early Earth, and couple these with insights from numerical models of the geodynamic regime at the time. This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics'.
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Prytkov, A. S., and N. F. Vasilenko. "The March 25, 2020 MW 7.5 Paramushir earthquake." Geosystems of Transition Zones 5, no. 2 (2021): 113–27. http://dx.doi.org/10.30730/gtrz.2021.5.2.113-120.121-127.
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The strong earthquake with moment magnitude Mw = 7.5 occurred on March 25, 2020, in the North Kurils to the southeast of the Paramushir Island. The hypocenter of the earthquake was located under the oceanic rise of deep-sea trench in the subducting Pacific lithospheric plate. This earthquake has been the strongest seismic event since 1900 for an area about 800 km long of the outer rise of the trench. It also was the strongest earthquake for the 300-kilometer long area of the Kuril-Kamchatka subduction zone adjacent to the epicenter. The article summarizes the data on the Paramushir earthquake. Tectonic position of the earthquake, source parameters, features of the aftershock process development, as well as coseismic displacement of the nearest continuous GNSS station are considered. The performed analysis did not allow us to clearly determine the rupture plane in the source. Nevertheless, the study of the features of the outer-rise earthquake is a matter of scientific interest, since the stress state of the bending area of the subducting Pacific lithospheric plate reflects the interplate interaction in the subduction zone.
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Wang, Xu, Peimin Zhu, Timothy M. Kusky, Na Zhao, Xiaoyong Li, and Zhensheng Wang. "Dynamic cause of marginal lithospheric thinning and implications for craton destruction: a comparison of the North China, Superior, and Yilgarn cratons." Canadian Journal of Earth Sciences 53, no. 11 (November 2016): 1121–41. http://dx.doi.org/10.1139/cjes-2015-0110.
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We present a comparative tectonic analysis of the North China Craton (NCC), which has lost parts of its root, with the Yilgarn and Superior cratons, which preserve their roots. We compare the geophysical structure and tectonic histories of these cratons to search for reasons why some cratons lose their roots, while others retain them. Based on the comparison and analysis of geological, geophysical, and geochemical data, it is clear that the lithospheric thinning beneath craton margins is a common phenomenon, which may be caused by convergence between plates. However, craton destruction is not always accompanied by lithospheric thinning, except for cratons that suffered subduction and collision from multiple sides. The Western Block (also known as the Ordos Block) of the NCC, Yilgarn and Superior cratons have not experienced craton destruction; the common ground among them is that they are surrounded by weak zones (e.g., mobile belts or orogens) that sheltered the cratons from deformation, which contributes greatly to the long-term stability of the craton. Subduction polarity controlled the water released by the subducting plate, and if subducting plates dip underneath the craton, they release water that hydroweakens the overlying mantle, and makes it easy for delamination or sub-continental lithospheric mantle erosion to take place in the interior of the craton. Thus, subduction polarity during convergence events is an important element in determing whether a craton retains or loses its root.
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Butterworth, N. P., R. D. Müller, L. Quevedo, J. M. O'Connor, K. Hoernle, and G. Morra. "Pacific plate slab pull and intraplate deformation in the early Cenozoic." Solid Earth 5, no. 2 (August 6, 2014): 757–77. http://dx.doi.org/10.5194/se-5-757-2014.
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Abstract. Large tectonic plates are known to be susceptible to internal deformation, leading to a~range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motion directions, and cannot be responsible for the Hawaiian–Emperor bend (HEB), confirming previous interpretations that the 47 Ma HEB does not primarily reflect an absolute plate motion event.
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Butterworth, N. P., R. D. Müller, L. Quevedo, J. M.O'Connor, K. Hoernle, and G. Morra. "Pacific Plate slab pull and intraplate deformation in the early Cenozoic." Solid Earth Discussions 6, no. 1 (January 14, 2014): 145–90. http://dx.doi.org/10.5194/sed-6-145-2014.
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Abstract. Large tectonic plates are known to be susceptible to internal deformation, leading to a range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific Plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its north-western perimeter, causing lithospheric extension along pre-existing weaknesses. Large scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau, and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians Volcanic Ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motions, and cannot be responsible for the Hawaii-Emperor Bend (HEB), confirming previous interpretations that the 47 Ma HEB does not reflect an absolute plate motion event.
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Kelemen, Peter B., and Craig E. Manning. "Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up." Proceedings of the National Academy of Sciences 112, no. 30 (June 5, 2015): E3997—E4006. http://dx.doi.org/10.1073/pnas.1507889112.
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Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5–10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory.
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Petersen, Robert I., Dave R. Stegman, and Paul J. Tackley. "The subduction dichotomy of strong plates and weak slabs." Solid Earth 8, no. 2 (March 24, 2017): 339–50. http://dx.doi.org/10.5194/se-8-339-2017.
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Abstract. A key element of plate tectonics on Earth is that the lithosphere is subducting into the mantle. Subduction results from forces that bend and pull the lithosphere into the interior of the Earth. Once subducted, lithospheric slabs are further modified by dynamic forces in the mantle, and their sinking is inhibited by the increase in viscosity of the lower mantle. These forces are resisted by the material strength of the lithosphere. Using geodynamic models, we investigate several subduction models, wherein we control material strength by setting a maximum viscosity for the surface plates and the subducted slabs independently. We find that models characterized by a dichotomy of lithosphere strengths produce a spectrum of results that are comparable to interpretations of observations of subduction on Earth. These models have strong lithospheric plates at the surface, which promotes Earth-like single-sided subduction. At the same time, these models have weakened lithospheric subducted slabs which can more easily bend to either lie flat or fold into a slab pile atop the lower mantle, reproducing the spectrum of slab morphologies that have been interpreted from images of seismic tomography.
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Brown, Michael, Tim Johnson, and Nicholas J. Gardiner. "Plate Tectonics and the Archean Earth." Annual Review of Earth and Planetary Sciences 48, no. 1 (May 30, 2020): 291–320. http://dx.doi.org/10.1146/annurev-earth-081619-052705.
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If we accept that a critical condition for plate tectonics is the creation and maintenance of a global network of narrow boundaries separating multiple plates, then to argue for plate tectonics during the Archean requires more than a local record of subduction. A case is made for plate tectonics back to the early Paleoproterozoic, when a cycle of breakup and collision led to formation of the supercontinent Columbia, and bimodal metamorphism is registered globally. Before this, less preserved crust and survivorship bias become greater concerns, and the geological record may yield only a lower limit on the emergence of plate tectonics. Higher mantle temperature in the Archean precluded or limited stable subduction, requiring a transition to plate tectonics from another tectonic mode. This transition is recorded by changes in geochemical proxies and interpreted based on numerical modeling. Improved understanding of the secular evolution of temperature and water in the mantle is a key target for future research. ▪ Higher mantle temperature in the Archean precluded or limited stable subduction, requiring a transition to plate tectonics from another tectonic mode. ▪ Plate tectonics can be demonstrated on Earth since the early Paleoproterozoic (since c. 2.2 Ga), but before the Proterozoic Earth's tectonic mode remains ambiguous. ▪ The Mesoarchean to early Paleoproterozoic (3.2–2.3 Ga) represents a period of transition from an early tectonic mode (stagnant or sluggish lid) to plate tectonics. ▪ The development of a global network of narrow boundaries separating multiple plates could have been kick-started by plume-induced subduction.
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Geersen, Jacob, Andrea Festa, and Francesca Remitti. "Structural constraints on the subduction of mass-transport deposits in convergent margins." Geological Society, London, Special Publications 500, no. 1 (December 19, 2019): 115–28. http://dx.doi.org/10.1144/sp500-2019-174.
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AbstractThe subduction of large and heterogeneous mass-transport deposits (MTDs) is discussed to modify the structure and physical state of the plate boundary and therewith exert an influence on seismicity in convergent margins. Understanding which subduction-zone architectures and structural boundary conditions favour the subduction of MTDs, primarily deposited in oceanic trenches, is therefore highly significant. We use bathymetric and seismic reflection data from modern convergent margins to show that a large landslide volume and long runout, in concert with thin trench sediments, increase the chances for an MTD to become subducted. In regions where the plate boundary develops within the upper plate or at its base (non-accretionary margins), and in little-sedimented trenches (sediment thickness <2 km), an MTD has the highest potential to become subducted, particularly when characterized by a long runout. On the contrary, in the case of a heavily sedimented trench (sediment thickness >4 km) and short runout, an MTD will only be subducted if the thickness of subducting sediments is higher than the thickness of sediments under the MTD. The results allow identification of convergent margins where MTDs are preferentially subducted and thus potentially alter plate-boundary seismicity.
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Obara, Kazushige, and Takuya Nishimura. "Main Results from the Program Promotion Panel for Subduction-Zone Earthquakes." Journal of Disaster Research 15, no. 2 (March 20, 2020): 87–95. http://dx.doi.org/10.20965/jdr.2020.p0087.
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Understanding the occurrence mechanism of subduction zone earthquakes scientifically is intrinsically important for not only forecast of future subduction earthquakes but also disaster mitigation for strong ground motion and tsunami accompanied by large earthquakes. The Program Promotion Panel for Subduction-zone earthquakes mainly focused on interplate megathrust earthquakes in the subduction zones and the research activity included collection and classification of historical data on earthquake phenomena, clarifying the current earthquake phenomena and occurrence environment of earthquake sources, modelling earthquake phenomena, forecast of further earthquake activity based on monitoring crustal activity and precursory phenomena, and development of observation and analysis technique. Moreover, we studied the occurrence mechanism of intraslab earthquakes within the subducting oceanic plate. Five-year observational research program actually produced enormous results for deep understanding of subduction zone earthquakes phenomena, especially in terms of slow earthquakes, infrequent huge earthquakes, and intraslab earthquakes. This paper mainly introduces results from researches on these phenomena in subduction zones.
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Saprygin, S. M., and V. N. Soloviev. "Pacific plate subduction in 1978‒1981." Geosystems of Transition Zones 1, no. 1 (2017): 49–57. http://dx.doi.org/10.30730/2541-8912.2017.1.1.049-057.
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Sharples, W., M. A. Jadamec, L. N. Moresi, and F. A. Capitanio. "Overriding plate controls on subduction evolution." Journal of Geophysical Research: Solid Earth 119, no. 8 (August 2014): 6684–704. http://dx.doi.org/10.1002/2014jb011163.
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Behr, Whitney M., and Thorsten W. Becker. "Sediment control on subduction plate speeds." Earth and Planetary Science Letters 502 (November 2018): 166–73. http://dx.doi.org/10.1016/j.epsl.2018.08.057.
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Liu, He, Renqiang Liao, Lipeng Zhang, Congying Li, and Weidong Sun. "Plate subduction, oxygen fugacity, and mineralization." Journal of Oceanology and Limnology 38, no. 1 (July 13, 2019): 64–74. http://dx.doi.org/10.1007/s00343-019-8339-y.
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Zheng, Yong-Fei, and Yi-Xiang Chen. "Continental versus oceanic subduction zones." National Science Review 3, no. 4 (August 11, 2016): 495–519. http://dx.doi.org/10.1093/nsr/nww049.
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Abstract Subduction zones are tectonic expressions of convergent plate margins, where crustal rocks descend into and interact with the overlying mantle wedge. They are the geodynamic system that produces mafic arc volcanics above oceanic subduction zones but high- to ultrahigh-pressure metamorphic rocks in continental subduction zones. While the metamorphic rocks provide petrological records of orogenic processes when descending crustal rocks undergo dehydration and anataxis at forearc to subarc depths beneath the mantle wedge, the arc volcanics provide geochemical records of the mass transfer from the subducting slab to the mantle wedge in this period though the mantle wedge becomes partially melted at a later time. Whereas the mantle wedge overlying the subducting oceanic slab is of asthenospheric origin, that overlying the descending continental slab is of lithospheric origin, being ancient beneath cratons but juvenile beneath marginal arcs. In either case, the mantle wedge base is cooled down during the slab–wedge coupled subduction. Metamorphic dehydration is prominent during subduction of crustal rocks, giving rise to aqueous solutions that are enriched in fluid-mobile incompatible elements. Once the subducting slab is decoupled from the mantle wedge, the slab–mantle interface is heated by lateral incursion of the asthenospheric mantle to allow dehydration melting of rocks in the descending slab surface and the metasomatized mantle wedge base, respectively. Therefore, the tectonic regime of subduction zones changes in both time and space with respect to their structures, inputs, processes and products. Ophiolites record the tectonic conversion from seafloor spreading to oceanic subduction beneath continental margin, whereas ultrahigh-temperature metamorphic events mark the tectonic conversion from compression to extension in orogens.
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Warren, C. J. "Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms." Solid Earth 4, no. 1 (February 13, 2013): 75–92. http://dx.doi.org/10.5194/se-4-75-2013.
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Abstract. The formation and exhumation of high and ultra-high-pressure, (U)HP, rocks of crustal origin appears to be ubiquitous during Phanerozoic plate subduction and continental collision events. Exhumation of (U)HP material has been shown in some orogens to have occurred only once, during a single short-lived event; in other cases exhumation appears to have occurred multiple discrete times or during a single, long-lived, protracted event. It is becoming increasingly clear that no single exhumation mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. Subduction zone style and internal force balance change in both time and space, responding to changes in width, steepness, composition of subducting material and velocity of subduction. In order for continental crust, which is relatively buoyant compared to the mantle even when metamorphosed to (U)HP assemblages, to be subducted to (U)HP conditions, it must remain attached to a stronger and denser substrate. Buoyancy and external tectonic forces drive exhumation, although the changing spatial and temporal dominance of different driving forces still remains unclear. Exhumation may involve whole-scale detachment of the terrane from the subducting slab followed by exhumation within a subduction channel (perhaps during continued subduction) or a reversal in motion of the entire plate (eduction) following the removal of a lower part of the subducting slab. Weakening mechanisms that may be responsible for the detachment of deeply subducted crust from its stronger, denser substrate include strain weakening, hydration, melting, grain size reduction and the development of foliation. These may act locally to form narrow high-strain shear zones separating stronger, less-strained crust or may act on the bulk of the subducted material, allowing whole-scale flow. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Future research directions include identifying temporal and spatial changes in exhumation mechanisms within different tectonic environments, and determining the factors that influence those changes.
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Mikumo, Takeshi, Shri Krishna Singh, and Miguel A. Santoyo. "A possible stress interaction between large thrust and normal faulting earthquakes in the Mexican subduction zone." Bulletin of the Seismological Society of America 89, no. 6 (December 1, 1999): 1418–27. http://dx.doi.org/10.1785/bssa0890061418.
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Abstract A large, nearly vertical, normal-faulting earthquake (Mw = 7.1) took place in 1997 in the subducting Cocos plate just beneath the ruptured fault zone of the 1985 Michoacan, Mexico, earthquake (Mw = 8.1). We investigate the possibility of stress interaction between the two large events through a 3D analysis of coseismic-stress change that was due to the first event, taking into consideration the postseismic change and the dynamic rupture process of the second event. In the middle portion of the subducting plate at depths below 30 km, the calculated coseismic increase in the vertical-shear stress and in the Coulomb-failure stress beneath the high stress-drop zones of the 1985 earthquake is in the order of 0.4 to 0.8 MPa. It was also found that the 1997 earthquake took place in the zone of maximum coseismic-stress increase. Possible postseismic-stress changes due to the subduction process or to the loading of the overriding continental lithosphere and from aseismic slip would enhance the coseismic-stress change and hence the possibility of occurrence of a normal-faulting earthquake in the subducting plate. The dynamic rupture pattern of the 1997 event seems to be consistent with the inferred stress interactions.
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Scholl, David W., and Roland von Huene. "Subduction zone recycling processes and the rock record of crustal suture zonesThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent." Canadian Journal of Earth Sciences 47, no. 5 (May 2010): 633–54. http://dx.doi.org/10.1139/e09-061.
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Offshore observations at modern ocean-margin subduction zones (OMSZs) reveal that bodies of accreted material are commonly volumetrically small or missing, that crustal thinning and subsidence (3–5 km) has occurred, and that most trench axes lie close (5–30 km) to the seaward tapering edge of coastal basement rock. Onshore mapping commonly documents missing or only narrow terranes of former forearc rock and the inboard migration of the arc magmatic front. These observations are evidence that subduction is accompanied by the removal of sediment and crustal material from the submerged forearc by the kindred tectonic processes, respectively, of sediment subduction and subduction erosion. Subduction erosion truncates the margin (migrates the trench inboard) at ∼2.5 km/Ma. Onshore observations at ancient crust-suturing subduction zones (CSSZs) imply that collisional suturing is accompanied by sediment subduction and truncation of both upper and lower plates. During a protracted period of suturing (20–50 million years), a 100–200 km wide (or wider) band of the seaward edge of each plate can be removed subductively. Truncation of the upper plate is effected by subduction erosion, and that of the lower plate by the necking and break-off of its subducted edge. The average linear rate of crustal loss for each plate is estimated at ∼1.5 km/Ma, or ∼3 km/Ma combined. Because significant crustal loss occurs before and during tectonic fusing of colliding crustal blocks, structures and rock bodies that might be expected to record a former OMSZ and the formation of a CSSZ may be absent, unimpressively small, or preserved only as exhumed masses of once deeply subducted material.
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Farrar, Edward, and John M. Dixon. "Ridge subduction: kinematics and implications for the nature of mantle upwelling." Canadian Journal of Earth Sciences 30, no. 5 (May 1, 1993): 893–907. http://dx.doi.org/10.1139/e93-074.
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Ridge subduction follows the approach of an oceanic spreading centre towards a trench and subduction of the leading oceanic plate beneath the overriding plate. There are four possible kinematic scenarios: (1) welding of the trailing and overriding plates (e.g., Aluk–Antarctic Ridge beneath Antarctica); (2) slower subduction of the trailing plate (e.g., Nazca–Antarctic Ridge beneath Chile and Pacific–Izanagi Ridge beneath Japan); (3) transform motion between the trailing and overriding plates (e.g., San Andreas Transform); or (4) divergence between the overriding and trailing plates (e.g., Pacific – North America). In case 4, the divergence may be accommodated in two ways: the overriding plate may be stretched (e.g., Basin and Range Province extension, which has brought the continental margin into collinearity (and, therefore, transform motion) with the Pacific – North America relative motion); or divergence may occur at the continental margin and be manifest as a change in rate and direction of sea-floor spreading because the pair of spreading plates changes (e.g., from Pacific–Farallon to Pacific – North America), spawning a secondary spreading centre (i.e., Gorda – Juan de Fuca – Explorer ridge system) that migrates away from the overriding plate.Mantle upwelling associated with sea-floor spreading ridges is widely regarded as a passive consequence, rather than an active cause, of plate divergence. Geological and geophysical phenomena attendant to ridge–trench interaction suggest that regardless of the kinematic relations among the three plates, a thermal anomaly formerly associated with the ridge migrates beneath the overriding plate. The persistence of this thermal anomaly demonstrates that active mantle upwelling may continue for tens of millions of years after ridge subduction. Thus, regardless of whether the mantle upwelling was active or passive at its origin, it becomes active if the spreading continues for sufficient time and, thus, must contribute to the driving mechanism of plate tectonics.
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Bessat, Annelore, Thibault Duretz, György Hetényi, Sébastien Pilet, and Stefan M. Schmalholz. "Stress and deformation mechanisms at a subduction zone: insights from 2-D thermomechanical numerical modelling." Geophysical Journal International 221, no. 3 (February 21, 2020): 1605–25. http://dx.doi.org/10.1093/gji/ggaa092.
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SUMMARY Numerous processes such as metamorphic reactions, fluid and melt transfer and earthquakes occur at a subducting zone, but are still incompletely understood. These processes are affected, or even controlled, by the magnitude and distribution of stress and deformation mechanism. To eventually understand subduction zone processes, we quantify here stresses and deformation mechanisms in and around a subducting lithosphere, surrounded by asthenosphere and overlain by an overriding plate. We use 2-D thermomechanical numerical simulations based on the finite difference and marker-in-cell method and consider a 3200 km wide and 660 km deep numerical domain with a resolution of 1 km by 1 km. We apply a combined visco-elasto-plastic deformation behaviour using a linear combination of diffusion creep, dislocation creep and Peierls creep for the viscous deformation. We consider two end-member subduction scenarios: forced and free subduction. In the forced scenario, horizontal velocities are applied to the lateral boundaries of the plates during the entire simulation. In the free scenario, we set the horizontal boundary velocities to zero once the subducted slab is long enough to generate a slab pull force large enough to maintain subduction without horizontal boundary velocities. A slab pull of at least 1.8 TN m–1 is required to continue subduction in the free scenario. We also quantify along-profile variations of gravitational potential energy (GPE). We evaluate the contributions of topography and density variations to GPE variations across a subduction system. The GPE variations indicate large-scale horizontal compressive forces around the trench region and extension forces on both sides of the trench region. Corresponding vertically averaged differential stresses are between 120 and 170 MPa. Furthermore, we calculate the distribution of the dominant deformation mechanisms. Elastoplastic deformation is the dominant mechanism in the upper region of the lithosphere and subducting slab (from ca. 5 to 60 km depth from the top of the slab). Viscous deformation dominates in the lower region of the lithosphere and in the asthenosphere. Considering elasticity in the calculations has an important impact on the magnitude and distribution of deviatoric stress; hence, simulations with increased shear modulus, in order to reduce elasticity, exhibit considerably different stress fields. Limiting absolute stress magnitudes by decreasing the internal friction angle causes slab detachment so that slab pull cannot be transmitted anymore to the horizontal lithosphere. Applying different boundary conditions shows that forced subduction simulations are stronger affected by the applied boundary conditions than free subduction simulations. We also compare our modelled topography and gravity anomaly with natural data of seafloor bathymetry and free-air gravity anomalies across the Mariana trench. Elasticity and deviatoric stress magnitudes of several hundreds of MPa are required to best fit the natural data. This agreement suggests that the modelled flexural behaviour and density field are compatible with natural data. Moreover, we discuss potential applications of our results to the depth of faulting in a subducting plate and to the generation of petit-spot volcanoes.
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Sodoudi, F., A. Bruestle, T. Meier, R. Kind, and W. Friederich. "New constraints on the geometry of the subducting African plate and the overriding Aegean plate obtained from P receiver functions and seismicity." Solid Earth Discussions 5, no. 1 (April 16, 2013): 427–61. http://dx.doi.org/10.5194/sed-5-427-2013.
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Abstract. New combined P receiver functions and seismicity data obtained from the EGELADOS network employing 65 stations within the Aegean constrained new information on the geometry of the Hellenic subduction zone. The dense network and large dataset enabled us to accurately estimate the Moho of the continental Aegean plate across the whole area. Presence of a negative contrast at the Moho boundary indicating the serpentinized mantle wedge above the subducting African plate was clearly seen along the entire forearc. Furthermore, low seismicity was observed within the serpentinized mantle wedge. We found a relatively thick continental crust (30–43 km) with a maximum thickness of about 48 km beneath the Peloponnesus Peninsula, whereas a thinner crust of about 27–30 km was observed beneath western Turkey. The crust of the overriding plate is thinning beneath the southern and central Aegean (Moho depth 23–27 km). Moreover, P receiver functions significantly imaged the subducted African Moho as a strong converted phase down to a depth of 180 km. However, the converted Moho phase appears to be weak for the deeper parts of the African plate suggesting reduced dehydration and nearly complete phase transitions of crustal material into denser phases. We show the subducting African crust along 8 profiles covering the whole southern and central Aegean. Seismicity of the western Hellenic subduction zone was taken from the relocated EHB-ISC catalogue, whereas for the eastern Hellenic subduction zone, we used the catalogues of manually picked hypocenter locations of temporary networks within the Aegean. P receiver function profiles significantly revealed in good agreement with the seismicity a low dip angle slab segment down to 200 km depth in the west. Even though, the African slab seems to be steeper in the eastern Aegean and can be followed down to 300 km depth implying lower temperatures and delayed dehydration towards larger depths in the eastern slab segment. Our results showed that the transition between the western and eastern slab segments is located beneath the southeastern Aegean crossing eastern Crete and the Karpathos basin. High resolution P receiver functions also clearly resolved the top of a strong low velocity zone (LVZ) at about 60 km depth. This LVZ is interpreted as asthenosphere below the Aegean continental lithosphere and above the subducting slab. Thus the Aegean mantle lithosphere seems to be 30–40 km thick, which means that its thickness increased again since the removal of the mantle lithosphere about 15 to 35 Ma ago.
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Whittaker, A., M. H. P. Bott, and G. D. Waghorn. "Stresses and plate boundary forces associated with subduction plate margins." Journal of Geophysical Research 97, B8 (1992): 11933. http://dx.doi.org/10.1029/91jb00148.
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Shi, Huiyan, Tonglin Li, Rui Sun, Gongbo Zhang, Rongzhe Zhang, and Xinze Kang. "Insights from the P Wave Travel Time Tomography in the Upper Mantle Beneath the Central Philippines." Remote Sensing 13, no. 13 (June 23, 2021): 2449. http://dx.doi.org/10.3390/rs13132449.
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In this paper, we present a high resolution 3-D tomographic model of the upper mantle obtained from a large number of teleseismic travel time data from the ISC in the central Philippines. There are 2921 teleseismic events and 32,224 useful relative travel time residuals picked to compute the velocity structure in the upper mantle, which was recorded by 87 receivers and satisfied the requirements of teleseismic tomography. Crustal correction was conducted to these data before inversion. The fast-marching method (FMM) and a subspace method were adopted in the forward step and inversion step, respectively. The present tomographic model clearly images steeply subducting high velocity anomalies along the Manila trench in the South China Sea (SCS), which reveals a gradual changing of the subduction angle and a gradual shallowing of the subduction depth from the north to the south. It is speculated that the change in its subduction depth and angle indicates the cessation of the SCS spreading from the north to the south, which also implies that the northern part of the SCS opened earlier than the southern part. Subduction of the Philippine Sea (PS) plate is exhibited between 14° N and 9° N, with its subduction direction changing from westward to eastward near 13° N. In the range of 11° N–9° N, the subduction of the Sulu Sea (SS) lies on the west side of PS plate. It is notable that obvious high velocity anomalies are imaged in the mantle transition zone (MTZ) between 14° N and 9° N, which are identified as the proto-SCS (PSCS) slabs and paleo-Pacific (PP) plate. It extends the location of the paleo-suture of PSCS-PP eastward from Borneo to the Philippines, which should be considered in studying the mechanism of the SCS and the tectonic evolution in SE Asia.
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Noda, Atsushi, Hiroaki Koge, Yasuhiro Yamada, Ayumu Miyakawa, and Juichiro Ashi. "Subduction of trench-fill sediments beneath an accretionary wedge: Insights from sandbox analogue experiments." Geosphere 16, no. 4 (June 17, 2020): 953–68. http://dx.doi.org/10.1130/ges02212.1.
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Abstract Sandy trench-fill sediments at accretionary margins are commonly scraped off at the frontal wedge and rarely subducted to the depth of high-pressure (HP) metamorphism. However, some ancient exhumed accretionary complexes are associated with high-pressure–low-temperature (HP-LT) metamorphic rocks, such as psammitic schists, which are derived from sandy trench-fill sediments. This study used sandbox analogue experiments to investigate the role of seafloor topography in the transport of trench-fill sediments to depth during subduction. We conducted two different types of experiments, with or without a rigid topographic high (representing a seamount). We used an undeformable backstop that was unfixed to the side wall of the apparatus to allow a seamount to be subducted beneath the overriding plate. In experiments without a seamount, progressive thickening of the accretionary wedge pushed the backstop down, leading to a stepping down of the décollement, narrowing of the subduction channel, and underplating of the wedge with subducting sediment. In contrast, in experiments with a topographic high, the subduction of the topographic high raised the backstop, leading to a stepping up of the décollement and widening of the subduction channel. These results suggest that the subduction of stiff topographic relief beneath an inflexible overriding plate might enable trench-fill sediments to be deeply subducted and to become the protoliths of HP-LT metamorphic rocks.
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Goes, Saskia, Roberto Agrusta, Jeroen van Hunen, and Fanny Garel. "Subduction-transition zone interaction: A review." Geosphere 13, no. 3 (June 1, 2017): 644–64. http://dx.doi.org/10.1130/ges01476.1.
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Abstract As subducting plates reach the base of the upper mantle, some appear to flatten and stagnate, while others seemingly go through unimpeded. This variable resistance to slab sinking has been proposed to affect long-term thermal and chemical mantle circulation. A review of observational constraints and dynamic models highlights that neither the increase in viscosity between upper and lower mantle (likely by a factor 20–50) nor the coincident endothermic phase transition in the main mantle silicates (with a likely Clapeyron slope of –1 to –2 MPa/K) suffice to stagnate slabs. However, together the two provide enough resistance to temporarily stagnate subducting plates, if they subduct accompanied by significant trench retreat. Older, stronger plates are more capable of inducing trench retreat, explaining why backarc spreading and flat slabs tend to be associated with old-plate subduction. Slab viscosities that are ∼2 orders of magnitude higher than background mantle (effective yield stresses of 100–300 MPa) lead to similar styles of deformation as those revealed by seismic tomography and slab earthquakes. None of the current transition-zone slabs seem to have stagnated there more than 60 m.y. Since modeled slab destabilization takes more than 100 m.y., lower-mantle entry is apparently usually triggered (e.g., by changes in plate buoyancy). Many of the complex morphologies of lower-mantle slabs can be the result of sinking and subsequent deformation of originally stagnated slabs, which can retain flat morphologies in the top of the lower mantle, fold as they sink deeper, and eventually form bulky shapes in the deep mantle.
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Lyu, Tianyang, Zhiyuan Zhu, and Benjun Wu. "Subducting slab morphology and mantle transition zone upwelling in double-slab subduction models with inward-dipping directions." Geophysical Journal International 218, no. 3 (June 14, 2019): 2089–105. http://dx.doi.org/10.1093/gji/ggz268.
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SUMMARY Lithospheric plates on the Earth's surface interact with each other, producing distinctive structures comprising two descending slabs. Double-slab subduction with inward-dipping directions represents an important multiplate system that is not yet well understood. This paper presents 2-D numerical models that investigate the dynamic process of double-slab subduction with inward dipping, focussing on slab geometry and mantle transition zone upwelling flow. This unique double-slab configuration limits trench motion and causes steep downward slab movement, thus forming fold piles in the lower mantle and driving upward mantle flow between the slabs. The model results show the effects of lithospheric plate properties and lower-mantle viscosity on subducting plate kinematics, overriding plate stress and upward mantle flow beneath the overriding plate. Appropriate lower-mantle strength (such as an upper–lower mantle viscosity increase with a factor of 200) allows slabs to penetrate into the lower mantle with periodical buckling. While varying the length and thickness of a long overriding plate (≥2500) does not have a substantial effect on slab geometry, its viscosity has a marked impact on slab evolution and mantle flow pattern. When the overriding plate is strong, slabs exhibit an overturned geometry and hesitate to fold. Mantle transition zone upwelling velocity depends on the speed of descending slabs. The downward velocity of slabs with a large negative buoyancy (caused by thickness or density) is very fast, inducing a significant transition zone upwelling flow. A stiff slab slowly descends into the deep mantle, causing a small upward flow in the transition zone. In addition, the temporal variation of mantle upwelling velocity shows strong correlation with the evolution of slab folding geometry. In the double subduction system with inward-dipping directions, the mantle transition zone upwelling exhibits oscillatory rise with time. During the backward-folding stage, upwelling velocity reaches its local maximum. Our results provide new insights into the deep mantle source of intraplate volcanism in a three-plate interaction system such as the Southeast Asia region.
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De Franco, Roberta, Rob Govers, and Rinus Wortel. "Numerical comparison of different convergent plate contacts: subduction channel and subduction fault." Geophysical Journal International 171, no. 1 (October 2007): 435–50. http://dx.doi.org/10.1111/j.1365-246x.2006.03498.x.
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Cramer, Chris H., and Eric Jambo. "Impact of a Larger Fore‐Arc Region on Earthquake Ground Motions in South‐Central Alaska Including the 2018 M 7.1 Anchorage Inslab Earthquake." Seismological Research Letters 91, no. 1 (December 11, 2019): 174–82. http://dx.doi.org/10.1785/0220190183.
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Abstract The thermal state of the crust and mantle in subduction zones is controlled by the depth of the subducting plate. With low‐angle subduction, like at the eastern end of the Alaska subduction zone, the less attenuating fore‐arc is extended farther from the trench and can effect ground motions in addition to source and site effects. Recent crustal and subduction earthquakes in south‐central Alaska, including the 2018 M 7.1 Anchorage event, demonstrate these effects. Inslab earthquake waves in the subducting plate can propagate up the slab to the fore‐arc region with less attenuation, causing an increase in observed ground motions. Long‐period ground motions from the 2018 M 7.1 Anchorage earthquake are significantly higher than predicted ground motions from current subduction ground‐motion models within 50–100 km of the epicenter. At short periods, ground motions show reduced amplitudes due to nonlinear sediment effects in the Anchorage area, reducing the damage potential of the earthquake. At long periods, ground motions are little affected by sediment nonlinearity and remain higher than expected. The duration of shaking was too short for widespread liquefaction effects, unlike during the 1964 M 9.2 earthquake. Other historical earthquakes have produced similar increases in ground motions in the Cook Inlet and Kenai Peninsula region. At both short and long periods, ground motions from the 2016 Iniskin M 7.1 inslab earthquake are higher than expected in the Cook Inlet region. The 2015 Redoubt M 6.3 inslab earthquake also shows increased ground motions in the Cook Inlet region at all periods. Crustal Q estimates from Lg waves show less attenuation in south‐central Alaska at longer periods. In the larger south‐central Alaska region crustal Q(f)=336f0.34 compared to Q(f)=217f0.84 for all of Alaska with most of the decrease in attenuation at frequencies below 2 Hz.
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Plunder, Alexis, Cédric Thieulot, and Douwe J. J. van Hinsbergen. "The effect of obliquity on temperature in subduction zones: insights from 3-D numerical modeling." Solid Earth 9, no. 3 (June 14, 2018): 759–76. http://dx.doi.org/10.5194/se-9-759-2018.
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Abstract. The geotherm in subduction zones is thought to vary as a function of the subduction rate and the age of the subducting lithosphere. Along a single subduction zone the rate of subduction may strongly vary due to changes in the angle between the trench and the plate convergence vector, i.e., the subduction obliquity, due to trench curvature. We currently observe such curvature in, e.g., the Marianas, Chile and Aleutian trenches. Recently, strong along-strike variations in subduction obliquity were proposed to have caused a major temperature contrast between Cretaceous geological records of western and central Turkey. We test here whether first-order temperature variation in a subduction zone may be caused by variation in the trench geometry using simple thermo-kinematic finite-element 3-D numerical models. We prescribe the trench geometry by means of a simple mathematical function and compute the mantle flow in the mantle wedge by solving the equation of mass and momentum conservation. We then solve the energy conservation equation until steady state is reached. We analyze the results (i) in terms of mantle wedge flow with emphasis on the trench-parallel component and (ii) in terms of temperature along the plate interface by means of maps and the depth–temperature path at the interface. In our experiments, the effect of the trench curvature on the geotherm is substantial. A small obliquity yields a small but not negligible trench-parallel mantle flow, leading to differences of 30 °C along-strike of the model. Advected heat causes such temperature variations (linked to the magnitude of the trench-parallel component of velocity). With increasing obliquity, the trench-parallel component of the velocity consequently increases and the temperature variation reaches 200 °C along-strike. Finally, we discuss the implication of our simulations for the ubiquitous oblique systems that are observed on Earth and the limitations of our modeling approach. Lateral variations in plate sinking rate associated with curvature will further enhance this temperature contrast. We conclude that the synchronous metamorphic temperature contrast between central and western Turkey may well have resulted from reconstructed major variations in subduction obliquity.
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Stockmal, G. S., S. P. Colman-Sadd, C. E. Keen, S. J. O'Brien, and G. Quinlan. "Collision along an irregular margin: a regional plate tectonic interpretation of the Canadian Appalachians." Canadian Journal of Earth Sciences 24, no. 6 (June 1, 1987): 1098–107. http://dx.doi.org/10.1139/e87-107.
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An idealized plate tectonic model for the pre-Carboniferous development of the Canadian Appalachians explains the 400 km dextral offset of tectonostratigraphic zones from Quebec and northern New Brunswick to Newfoundland and the up to 600 km offset of oppositely verging belts of Acadian deformation from the Gaspé Peninsula to eastern Newfoundland. It is proposed that these offsets, which occur at the St. Lawrence promontory, result from the collision of an irregular North American passive continental margin with island arc and continental crust to the east, along an east-dipping subduction zone. The line of subduction is assumed to have been linear and the subducting slab to have maintained its mechanical integrity during collision. A "jigsaw fit" of the opposite sides of the Iapetus Ocean is made unnecessary by invoking lithospheric delamination and tectonic wedging during the Acadian orogeny in Newfoundland. The model is consistent with surface geology and recent deep seismic reflection observations from north of Newfoundland.
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LiPeng, ZHANG, LI He, and WANG Kun. "Plate subduction and porphyry Cu-Au mineralization." Acta Petrologica Sinica 36, no. 1 (2020): 113–24. http://dx.doi.org/10.18654/1000-0569/2020.01.12.
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Dominguez, S., S. E. Lallemand, J. Malavieille, and R. von Huene. "Upper plate deformation associated with seamount subduction." Tectonophysics 293, no. 3-4 (August 1998): 207–24. http://dx.doi.org/10.1016/s0040-1951(98)00086-9.
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Peral, Mireia, Ágnes Király, Sergio Zlotnik, Francesca Funiciello, Manel Fernàndez, Claudio Faccenna, and Jaume Vergés. "Opposite Subduction Polarity in Adjacent Plate Segments." Tectonics 37, no. 9 (September 2018): 3285–302. http://dx.doi.org/10.1029/2017tc004896.
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Chertova, M. V., W. Spakman, A. P. van den Berg, and D. J. J. van Hinsbergen. "Absolute plate motions and regional subduction evolution." Geochemistry, Geophysics, Geosystems 15, no. 10 (October 2014): 3780–92. http://dx.doi.org/10.1002/2014gc005494.
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Gutiérrez-Alonso, Gabriel, Javier Fernández-Suárez, Arlo B. Weil, J. Brendan Murphy, R. Damian Nance, Fernando Corfú, and Stephen T. Johnston. "Self-subduction of the Pangaean global plate." Nature Geoscience 1, no. 8 (July 6, 2008): 549–53. http://dx.doi.org/10.1038/ngeo250.
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