Kinematics and dynamics of the Pamir, Central Asia: Quantifying surface deformation and force balance in an intracontinental subduction zone

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. In natural cases, evidence of advancing margins has been recognized in continental collision zones such as India-Eurasia and Arabia-Eurasia. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In our 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the slab starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the advancing mode is favoured and, in part, provided by the intrinsic force balance of continental collision. We suggest that the advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. These processes are responsible for the migration of the subduction zone by triggering small-scale convection cells in the mantle that, in turn, drag the plates. The amount of advance ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

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Dating and morphostratigraphy of uplifted marine terraces in the Makran subduction zone (Iran)

10.5194/esurf-2018-78 ◽

2018 ◽

Author(s):

Raphaël Normand ◽

Guy Simpson ◽

Frédéric Herman ◽

Rabiul Haque Biswas ◽

Abbas Bahroudi ◽

...

Keyword(s):

Subduction Zone ◽

Surface Deformation ◽

Late Quaternary ◽

Makran Subduction Zone ◽

Megathrust Earthquakes ◽

Surface Uplift ◽

Marine Terraces ◽

Uplift Rates ◽

Tectonically Active ◽

East West

Abstract. The western part of the Makran subduction zone (Iran) has not experienced a great megathrust earthquake in recent human history, yet, the presence of emerged marine terraces along the coast indicates that the margin has been tectonically active during at least the late Quaternary. To better understand the surface deformation of this region, we mapped the terraces sequences of seven localities along the Iranian Makran. Additionnaly, we performed radiocarbon, 230Th/U and optically stimulated luminescence (OSL) dating of the layers of marine sediments deposited on top of the terraces. This enabled us to correlate the terraces regionally and to assign them to different Quaternary sea level highstands. Our results show east-west variations in surface uplift rates mostly between 0.05 and 1.2 mm y−1. We detected a region of anomalously high uplift rate, where two MIS 3 terraces are emerged, yet we are uncertain how to insert these results in a geologically coherent context. Although it is presently not clear whether the uplift of the terraces is linked with the occurrence of large megathrust earthquakes, our results highlight heterogeneous accumulation of deformation in the overriding plate.

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Numerical models of trench migration in continental collision zones

Solid Earth Discussions ◽

10.5194/sed-4-429-2012 ◽

2012 ◽

Vol 4 (1) ◽

pp. 429-458 ◽

Cited By ~ 2

Author(s):

V. Magni ◽

J. van Hunen ◽

F. Funiciello ◽

C. Faccenna

Keyword(s):

Subduction Zone ◽

Plate Tectonics ◽

Numerical Models ◽

Continental Collision ◽

Force Balance ◽

Dip Angle ◽

External Forces ◽

Stress Dependent ◽

Subduction System ◽

Intrinsic Feature

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the trench starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the trench advancing is favoured and, in part provided by, the intrinsic force balance of continental collision. We suggest that the trench advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. The amount of trench advancing ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

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Subduction zone seismo-dynamics: how to bridge the gap between long-term subduction dynamics and megathrust seismicity?

10.5194/egusphere-egu21-2322 ◽

2021 ◽

Author(s):

Adam Beall ◽

Fabio A. Capitanio ◽

Ake Fagereng ◽

Ylona van Dinther

Keyword(s):

Stress State ◽

Subduction Zone ◽

Subduction Zones ◽

Large Scale ◽

Large Earthquake ◽

Force Balance ◽

Mantle Flow ◽

Plate Interface ◽

Plate Motions

<p>The largest and most devastating earthquakes on Earth occur along subduction zones. Here, long-term plate motions are accommodated in cycles of strain accumulation and release. Episodic strain release occurs by mechanisms ranging from rapid earthquakes to slow-slip and quasi-static creep along the plate interface. Slip styles can vary between and within subduction zones, though it is unclear what controls margin-scale variability. Current approaches to seismo-tectonics primarily relate the stress state and seismogenesis at subduction margins to interface material properties and plate kinematics, constrained by recorded seismic slip, GPS motions and integrated strain. At larger spatio-temporal scales, significant progress has been made towards the understanding of subduction dynamics and emerging self-consistent plate motions, tectonics and stress coupling at plate margins. The margin stress state is ultimately linked to the force balance arising from interactions between the slab, mantle flow and upper plate. These mantle and lithosphere dynamics are thus expected to govern the tectonic regimes under which seismicity occurs. It remains unclear how these longer- and shorter-term perspectives can be reconciled. We review the aspects of large-scale subduction dynamics that control tectonic loading at plate margins, discuss possible influences on the stress state of the plate interface, and summarise recent advances in integrating the earthquake cycle and large-scale dynamics. It is plausible that variations in large-scale subduction dynamics could systematically influence seismicity, though it remains unclear to what degree this interplay occurs directly through the plate interface stress state and/or indirectly, corresponding to variation of other subduction zone characteristics. While further constraints of the geodynamic controls on the nature of the plate interface and their incorporation into probabilistic earthquake models is required, their ongoing development holds promise for an improved understanding of the global variation of large earthquake occurrence and their associated risk.</p>

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Ultramafic Cumulates of Oceanic Affinity in an Intracontinental Subduction Zone

Ultrahigh-Pressure Metamorphism ◽

10.1016/b978-0-12-385144-4.00012-6 ◽

2011 ◽

pp. 399-439 ◽

Cited By ~ 1

Author(s):

Jan C.M. De Hoog ◽

Marian Janák ◽

Mirijam Vrabec ◽

Keiko H. Hattori

Keyword(s):

Subduction Zone ◽

Intracontinental Subduction ◽

Ultramafic Cumulates

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D�j� Vu: Understanding Subduction Zones’ Cycle of Seismicity

Eos ◽

10.1029/2019eo124943 ◽

2019 ◽

Vol 100 ◽

Author(s):

Terri Cook

Keyword(s):

Subduction Zone ◽

Subduction Zones ◽

Surface Deformation ◽

Geodetic Data ◽

Seismic Cycle ◽

Data Set ◽

Nankai Subduction Zone

A unique geodetic data set from Japan’s Nankai subduction zone offers an unparalleled opportunity to study surface deformation spanning almost an entire seismic cycle.

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Structural and seismic evidence for intracontinental subduction in the Peter the First Range, Central Asia

Geological Society of America Bulletin ◽

10.1130/0016-7606(1992)104<0397:sasefi>2.3.co;2 ◽

1992 ◽

Vol 104 (4) ◽

pp. 397-408 ◽

Cited By ~ 80

Author(s):

MICHAEL W. HAMBURGER ◽

DANIEL R. SAREWITZ ◽

TERRY L. PAVLIS ◽

GYORGI A. POPANDOPULO

Keyword(s):

Central Asia ◽

Intracontinental Subduction

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Soap-Thickener Induced Local Pressure Fluctuations in a Grease-Lubricated Elastohydrodynamic Point Contact

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1243/pime_proc_1994_208_370_02 ◽

1994 ◽

Vol 208 (3) ◽

pp. 191-198 ◽

Cited By ~ 33

Author(s):

H Åström ◽

C H Venner

Keyword(s):

Film Thickness ◽

Surface Deformation ◽

Pressure Fluctuations ◽

Point Contact ◽

Rheological Behaviour ◽

Force Balance ◽

Experimental Investigations ◽

Local Pressure ◽

Lubricated Contact ◽

Insight Into

In several experimental investigations of grease-lubricated elastohydrodynamic (EHD) contacts indications of soap-thickener formations that enter the contact area have been reported, for example by Kageyama et al. (1), Cann and co-workers (2-4) and Åström and co-workers (5, 6). While passing through a contact such soap-thickener lumps significantly disturb the film thickness by locally increasing the surface deformation. These film-thickness fluctuations must be accompanied by pressure fluctuations, knowledge of which is essential to increase insight in the phenomena determining service life and emitted noise of grease-lubricated contacts. In this paper the authors present a combined experimental/numerical approach to generate insight into such pressure fluctuations. From a fringe pattern obtained with optical interferometry (ball-on-disc apparatus) a film-thickness map is created employing image analysis. This map serves as input to a numerical algorithm for the calculation of the pressure from force balance and elastic deformation theory. Consequently, no assumptions about the rheological behaviour of grease can be made. The method was first tested out on an oil-lubricated contact. This test gave essential insight into the accuracy of the method proposed here and in the magnitude of surface texture induced pressure fluctuations. Subsequently the approach was successfully used to estimate the pressure variations resulting from soap-thickener formations in a grease-lubricated contact (between the same ball and disc).

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Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms

Solid Earth ◽

10.5194/se-4-75-2013 ◽

2013 ◽

Vol 4 (1) ◽

pp. 75-92 ◽

Cited By ~ 59

Author(s):

C. J. Warren

Keyword(s):

High Pressure ◽

Subduction Zone ◽

Driving Forces ◽

Shear Zones ◽

Internal Force ◽

Force Balance ◽

Future Research ◽

Time And Space ◽

Ultra High Pressure ◽

Subducting Slab

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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