Geodetic observations of very rapid convergence and back-arc extension at the Tonga arc

Bevis, Michael; Taylor, Frederick W.; Schutz, B. E.; Récy, Jacques; Isacks, Bryan L.; Helu, Saimone P.; Singh, Rajendra; Kendrick, Eric; Stowell, James; Taylor, Brian; Calmantli, Stephane

doi:10.1038/374249a0

Cited by 338 publications

(235 citation statements)

References 20 publications

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“…Cox and Engebretson (1985) identified this change of motion to have occurred at 5 Ma visible in a slight bend in the Hawaiian-Emperor seamount chain at that time. Further investigations of geologic settings along almost the entire Pacific plate boundary as well as magnetic anomalies have supported this finding (Bevis et al, 1995;Cande and Stock, 2004;Harbert and Cox, 1989;King, 2000;Oskin et al, 2001;Oskin and Stock, 2003a, b;Wessel and Kroenke, 2000). It has been suggested that the change of plate motion was caused by cessation of southward-directed subduction of the Pacific plate along the northern Melanesian arc which was initiated by the collision of the Ontong Java Plateau (OJP) with the arc (Cox and Engebretson, 1985;Harbert and Cox, 1989;Knesel et al, 2008;Kroenke, 2000, 2007).…”

Section: Introductionmentioning

confidence: 66%

Quantifying the forces needed for the rapid change of Pacific plate motion at 6Ma

Austermann¹,

Ben‐Avraham²,

Bird³

et al. 2011

Earth and Planetary Science Letters

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Editor: Y. Ricard Keywords:Pacific plate motion plate driving forces slab detachment oceanic plateau collision northern Melanesian arc Studies have documented several rapid changes along the Pacific-North American, Pacific-Antarctic and Pacific-Australian plate boundaries in latest Miocene to earliest Pliocene time consistent with a sudden clockwise rotation of Pacific plate velocity relative to hotspots during this period. We test the hypothesis that this change in plate motion was initiated by cessation of subduction along the northern Melanesian arc due to the collision between the arc and the Ontong Java plateau. This hypothesis has long been formulated but never tested quantitatively. We use a geomechanical model of the lithosphere to determine the changes in plate boundary forces that are necessary to obtain the observed change in the Pacific plate motion. Our model results show that the change in motion can be explained by a clockwise rotation of the slab-related (basal-strength) component of plate driving force. The change of slab-related force from a post-6 Ma to a pre-6 Ma setting is perpendicular to the arc and points towards the Australian plate. The force per unit length is in the range of currently accepted values for subduction zones. Since there have been no other relevant changes at subduction zones along the Pacific plate boundary during the latest Miocene, we relate this change in slab-related force to the former southward-dipping Pacific plate slab along the northern Melanesian arc system which is now detached. Our model results suggest that rapid changes in plate motion can be triggered by slab detachment, with consequences for plate boundary processes even at great distances from the event.

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Section: Introductionmentioning

confidence: 66%

Quantifying the forces needed for the rapid change of Pacific plate motion at 6Ma

Austermann¹,

Ben‐Avraham²,

Bird³

et al. 2011

Earth and Planetary Science Letters

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“…These boundary conditions approximate the components of Tonga region plate motions that lie in the plane of the model (parallel to the azimuth of Pacific plate motion). Smaller plate motion components normal to the model plane also exist [Gripp and Gordon, 1990;Bevis et al, 1995] but were ignored in the simple two-dimensional models of this study. Use of more realistic three-dimensional plate motion boundary conditions is the subject of ongoing work [Hall et al, 1999].…”

Section: Viscous Flow Modelsmentioning

confidence: 99%

Modeling anisotropy and plate‐driven flow in the Tonga subduction zone back arc

Fischer¹,

Parmentier²,

Stine³

et al. 2000

J. Geophys. Res.

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Abstract. The goal of this study is to determine whether shear wave splitting observed in subduction zone back arc regions, the Tonga subduction zone in particular, can be quantitatively modeled with flow in the back arc mantle driven by the motions of the subducting slab and the upper back arc plate. We calculated two-dimensional mantle flow models using known Tonga plate motions as boundary conditions and assuming a range of uniform and variable viscosity structures. Shear wave splitting was predicted for the anisotropy due to lattice preferred orientation (LPO) of olivine and orthopyroxene in the flow model finite strain fields. The predicted shear wave splitting provides a good match to the fast directions (parallel to the azimuth of subducting plate motion) and splitting times (0.5-1.5 s) observed in Tonga, both for models where LPO anisotropy develops everywhere above 410 km and for models where LPO anisotropy is confined to regions of relatively high stress. If LPO anisotropy does develop over the entire upper 410 km of the mantle, the strength of anistropy induced by a given amount of shear strain must be relatively weak (-4% for shear strains of 1.5, with a maximum value of-6% for very large strains). The splitting observations are comparably fit by a wide range of different viscosity models. Anisotropy due to melt-filled cracks aligned by stresses in the back arc flow models predicts fast directions roughly normal to observed values and thus cannot alone explain the observed splitting.

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“…GPS velocities (observed, black; model, red), and rotation poles (shown with semicircular red arrows, black ellipses show pole location uncertainties) of Tonga arc (Tong) relative to Australian (Aust) and Pacific (Paci) plates. GPS velocity vectors [Bevis et al, 1995] are shown relative to Australian plate. Black vectors with rates next to them show relative motion in back arc and at the trench (rates are in cm/a, predicted from block model [Wallace et al, 2005]).…”

Section: A22 Present-day Examples Withoutmentioning

confidence: 99%

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

Wallace

Ellis

Mann

2009

Geochem Geophys Geosyst

101

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[1] We review geophysical and geological data from 23 active and ancient plate boundaries to document a compelling spatial and temporal relationship between collision, plate boundary curvature, rapid tectonic rotations, and the occurrence of back-arc rifting. Our observations support a conceptual model where the change from subduction to collision causes rapid fore-arc rotation (when viewed in a reference frame relative to the bounding tectonic plates), leading to marked plate boundary curvature. Our global compilation reveals that most active back-arc rifts are associated with rapidly rotating fore arcs and nearby collisions. Thus, we propose that collision and rapid fore-arc rotations play a major role in the evolution and kinematics of back-arc basins. We conduct numerical modeling to better understand the physical processes behind these observed rapid tectonic rotations at convergent margins. Our results suggest that the presence of an indentor or choke point in the subduction system (e.g., collision) can generate rapid rotation of the fore arc about a nearby pole and lead to back-arc rifting. The rate of fore-arc rotation and back-arc rifting depends on the incoming indentor velocity and can be greatly enhanced by slab rollback and the presence of a low-viscosity back arc. Where viscosity of the back arc is low, fore-arc rotation dominates; where back-arc viscosity is high, the formation of strike-slip faults and tectonic escape dominates. Our observational and model-derived results illustrate that shallow crustal forces produced by the entry of buoyant features into subduction zones are a fundamental mechanism for the generation of fore-arc block rotations, plate boundary curvature, back-arc rift evolution, and tectonic escape in subduction systems. Rollback of the subducting slab within the mantle will certainly enhance the processes we describe but it is not the only driving force. Wallace, L. M., S. Ellis, and P. Mann (2009), Collisional model for rapid fore-arc block rotations, arc curvature, and episodic back-arc rifting in subduction settings, Geochem. Geophys. Geosyst., 10, Q05001,

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Geodetic observations of very rapid convergence and back-arc extension at the Tonga arc

Cited by 338 publications

References 20 publications

Quantifying the forces needed for the rapid change of Pacific plate motion at 6Ma

Quantifying the forces needed for the rapid change of Pacific plate motion at 6Ma

Modeling anisotropy and plate‐driven flow in the Tonga subduction zone back arc

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

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