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A tectonic Plate Motion Model (PMM) is essential for geodetic applications, while contributing to the understanding of geodynamic processes affecting the Earth's surface. We introduce a PMM derived from the horizontal velocities of 518 sites extracted from the ITRF2020 solution. These sites were chosen away from plate boundaries, Glacial Isostatic Adjustment regions, and other deforming zones. Unlike the ITRF2014‐PMM, which showed no significant Origin Rate Bias (ORB), velocities used to determine the ITRF2020‐PMM exhibit a statistically significant ORB (0.74 ± 0.09 mm/yr along the Z‐component). Users are advised to add the estimated ORB to the horizontal velocities predicted by the ITRF2020‐PMM rotation poles for full consistency with the ITRF2020. However, the predicted vertical velocities resulting from the addition of the ORB should be discarded. The overall precision with which the ITRF2020 velocity field is represented by the rigid ITRF2020‐PMM is at the level of 0.25 mm/yr WRMS. Plain Language Summary The Earth's surface is divided in large and small tectonic plates, which evolve and move slowly over time, resulting in lateral displacements of the ground surface typically of the order of a few cm/yr. Because of the relative motion between tectonic plates, plate boundaries can be either divergent (when two plates move away from each other), convergent (when two plates collide) or transform (when two plates slide past each other). Plate motion models are used to quantify the relative motions of the plates with respect to each other, and are determined using geological data or observations collected by space geodesy instruments distributed over different plates at the Earth's surface. In the latter case, space geodesy observations from the four space geodetic techniques covering more than 40 years of data are analyzed to estimate the long‐term displacements (or velocities) of each instrument in a well defined and self‐consistent global reference frame. The derived velocity field is then used to estimate a comprehensive plate motion model (PMM). This article presents a PMM for 13 tectonic plates based on a subset of the velocity field from the recently released International Terrestrial Reference Frame 2020 (ITRF2020); see https://itrf.ign.fr/en/solutions/ITRF2020. Key Points We derive a plate motion model for 13 tectonic plates from the ITRF2020 horizontal velocity field Built under the rigid‐plate motion hypothesis, the model represents the ITRF2020 velocity field with a precision of 0.25 mm/yr WRMS The residual velocities would show a global northward motion if a translation rate was not included in the inversion model

Reconstructions of motions of the Nazca, South American, and Indian plates record short‐duration (≲10 Myr) variations in angular velocity, which enable a vector‐based test of the hypothesis that mountain uplift can cause changes in plate motion. Reductions in velocity of Nazca and South America between ∼12 and 6 Ma coincide with a phase of rapid surface uplift in the Central Andes. Decrease in the rate of India's convergence with Eurasia between ∼20 and 10 Ma corresponds to an increase in gravitational potential energy per unit area (GPE) within Tibet, marked by a transition from crustal thickening to thinning. The vectorial test shows that, in each case, the only change in driving force capable of balancing the change in basal drag is an increased resistance along the convergent boundary to the plate. Changes in GPE associated with mountain uplift provide a calibration for basal drags on plates. Basal tractions of ∼0.1–1 MPa provide resisting forces comparable in magnitude to driving forces from GPE variation in ocean lithosphere. The rapid change in motion of the Indian plate between about 48 and 41 Ma is explained by the juxtaposition of the Indian continent against the Andean‐type margin of the Transhimalaya and reduction in driving force due to loss of the slab. The net slab driving force lost was ∼2–4 TN m−1, in agreement with previous studies suggesting that forces resisting slabs' penetration into the mantle largely offset their negative buoyancy. Key Points Calculation of forces required to cause rapid changes in plate motion test the hypothesis that some stem from increase in gravitational potential energy (GPE) of mountains Rapid decreases in velocity of Nazca, South American, and Indian plates require increases in resistance at their convergent boundaries Geological evidence shows that the Miocene decreases in velocity were contemporaneous with increases in GPE of the Andes and Tibet

Plate tectonics describes the horizontal motions of lithospheric plates, the Earth’s outer shell, and interactions among them across the Earth’s surface. Since the establishment of the theory of plate tectonics about half a century ago, considerable debates have remained regarding the driving forces for plate motion. The early “Bottom up” view, i.e., the converting mantle-driven mechanism, states that mantle plumes originating from the core-mantle boundary act at the base of plates, accelerating continental breakup and driving plate motion. Toward the present, however, the “Top down” idea is more widely accepted, according to which the negative buoyancy of oceanic plates is the dominant driving force for plate motion, and the subducting slabs control surface tectonics and mantle convection. In this regard, plate tectonics is also known as subduction tectonics. “Top down”tectonics has received wide supports from numerous geological and geophysical observations. On the other hand, recent studies indicate that the acceleration/deceleration of individual plates over the million-year timescale may reflect the effects of mantle plumes. It is also suggested that surface uplift and subsidence within stable cratonic areas are correlated with plume-related magmatic activities over the hundred-million-year timescale. On the global scale, the cyclical supercontinent assembly and breakup seem to be coupled with superplume activities during the past two billion years. These correlations over various spatial and temporal scales indicate the close relationship and intensive interactions between plate tectonics and plume tectonics throughout the history of the Earth and the considerable influence of plumes on plate motion. Indeed, we can acquire a comprehensive understanding of the driving forces for plate motion and operation mechanism of the Earth’s dynamic system only through joint analyses and integrated studies on plate tectonics and plume tectonics.

With a small fraction of marginal subduction zones, the driving mechanism for the North American plate motion is in debate. We construct global mantle flow models simultaneously constrained by geoid and plate motions to investigate the driving forces for the North American plate motion. By comparing the model with only near‐field subducting slabs and that with global subducting slabs, we find that the contribution to the motion of the North American plate from the near‐field Aleutian, central American, and Caribbean slabs is small. In contrast, other far‐field slabs, primarily the major segments around western Pacific subduction margins, provide the dominant large‐scale driving forces for the North American plate motion. The coupling between far‐field slabs and the North American plate suggests a new form of active plate interactions within the global self‐organizing plate tectonic system. We further evaluate the extremely slow seismic velocity anomalies associated with the shallow partial melt around the southwestern North America. Interpreting these negative seismic shear‐velocity anomalies as purely thermal origin generates considerably excessive resistance to the North American plate motion. A significantly reduced velocity‐to‐density scaling for these negative seismic shear‐velocity anomalies must be incorporated into the construction of the buoyancy field to predict the North American plate motion. We also examine the importance of lower mantle buoyancy including the ancient descending Kula‐Farallon plates and the active upwelling below the Pacific margin of the North American plate. Lower mantle buoyancy primarily affects the amplitudes, as opposed to the patterns of both North American and global plate motions. Key Points The motion of North American plate cannot be fully attributed to the near‐field Aleutian, central American, and Caribbean slabs Large‐scale mantle flow induced by far‐field slabs provides important driving forces for North American plate Assuming shallow slow seismic velocity around southwestern North America as purely thermal origin overly resists North American plate motion

A mantle thermal plume may be tilted, deflected, or even split-up by mantle lateral flows (mantle wind) during its ascent, which in turn changes the spatial distribution of various geological-magmatic responses, such as magmatic activity in the overriding plate and hotspot tracks on the surface, affecting the reliability of the constraints on absolute plate motion history. Previous research on tilted mantle plumes has focused mainly on the lower/whole mantle regions. Whether mantle plumes formed in whole/layered mantle convection suffer lateral tilt in the upper mantle, and how this affects the magmatic activity along the surface hotspot track as well as the plume-related tectonic processes, are important scientific issues in mantle thermal-plume dynamics and plate tectonics theory. This study introduces a thermal Stokes-fluid-dynamics numerical model (in ASPECT software) and pyrolite parameters constrained by mineral physics data, and quantitatively analyzes the tilted/deflected morphology of upper-mantle plumes and the concomitant surface-hotspot location-evolution characteristics under the combined effects of overriding-plate-motion driven flow (Couette) and upper mantle counter-flow (Poiseuille). We find that this composite upper-mantle wind can lead to (1) Plume head-and-upper-conduit horizontal motion in the opposite direction of the overriding plate motion and also with respect to the conduit roots, such that the magmatic spacing is increased; (2) Near-periodic split-up and ascent of a laterally-moving plume conduit, whose split-up/ascent period depends mainly on the thermo-chemical buoyancy of the plume itself; and (3) Under specific conditions of thermo-chemical buoyancy of a main “parent” plume interacting with upper mantle winds, two secondary “child” plumes hundreds of kilometers apart can sprout and ascend sequentially/sub-simultaneously through the upper mantle in a very short period of time (2–4 Myr). The resulting oscillating/jumping behavior of hotspot locations along the overriding plate motion direction can be used to explain the observations on some of Earth’s igneous provinces and hotspot tracks (for example, the Kerguelen hotspot) and related-tectonics, that: (i) younger hotspot-magmatic-tectonic regions can superimpose-to and situate-amidst older ones (surface-hotspot-motion or plume-deflection distances greater than overriding-plate-motion distances, with magmatism separated closely in space but largely in time), and (ii) plume-related magmatism can be widely separated in space but closely in time or age (near-simultaneous ascent of two distant “child” plumes from the same “parent” mantle-plume conduit). Our study suggests that the complex dynamic environment within the upper mantle should be considered when constraining absolute plate motions by the moving-hotspot-reference-frame, especially when these hotspots are located near mid-ocean ridges and/or subduction zones.

—The geodynamics of Northern Eurasia has been analyzed based on repeated coordinate solutions for GNSS stations throughout the Russian Federation territory from 2015 to the present. Two sources of data were used for this purpose: observations at the stations of the Russian Fundamental Astro-Geodetic Network (FAGN) and stations of the International GNSS Service (IGS) with permanent satellite tracking. This data set allowed one to estimate correctness of the block kinematics of the Eurasian plate in three tectonic plate motion models: NUVEL-1A, NNR-MORVEL-56, and ITRF2014. The analysis of the misfits between the observed and model velocities has shown that these misfits have a systematic component in the vicinity of the East European Platform, which differs for each of three models. In addition to analyzing the block kinematics of the Eurasian Plate, we also evaluated its internal stability. For this purpose, we calculated the areal deformations of Northern Eurasia using the finite element method. To this end, the processing results of two original datasets were complemented by the results for the observation data from the global dataset of the Nevada Geodetic Laboratory. Besides interplate boundary deformations, which are consistent with existing ideas of the geodynamics of Northern Eurasia, the strain field analysis also revealed intraplate deformations distributed consistently with the configuration of the Northern Eurasia cratons.

Although an average westward rotation of the Earth's lithosphere is indicated by global analyses of surface features tied to the deep mantle (e.g., hot spot tracks), the rate of lithospheric drift is uncertain despite its importance to global geodynamics. We use a global viscous flow model to predict asthenospheric anisotropy computed from linear combinations of mantle flow fields driven by relative plate motions, mantle density heterogeneity, and westward lithosphere rotation. By comparing predictions of lattice preferred orientation to asthenospheric anisotropy in oceanic regions inferred from SKS splitting observations and surface wave tomography, we constrain absolute upper mantle viscosity (to 0.5–1.0 × 1021 Pa s, consistent with other constraints) simultaneously with net rotation rate and the decrease in the viscosity of the asthenosphere relative to that of the upper mantle. For an asthenosphere 10 times less viscous than the upper mantle, we find that global net rotation must be <0.26°/Myr (<60% of net rotation in the HS3 (Pacific hot spot) reference frame); larger viscosity drops amplify asthenospheric shear associated with net rotation and thus require slower net rotation to fit observed anisotropy. The magnitude of westward net rotation is consistent with lithospheric drift relative to Indo‐Atlantic hot spots but is slower than drift in the Pacific hot spot frame (HS3 ≈ 0.44°/Myr). The latter may instead express net rotation relative to the deep mantle beneath the Pacific plate, which is moving rapidly eastward in our models.

NNR‐MORVEL56, which is a set of angular velocities of 56 plates relative to the unique reference frame in which there is no net rotation of the lithosphere, is determined. The relative angular velocities of 25 plates constitute the MORVEL set of geologically current relative plate angular velocities; the relative angular velocities of the other 31 plates are adapted from Bird (2003). NNR‐MORVEL, a set of angular velocities of the 25 MORVEL plates relative to the no‐net rotation reference frame, is also determined. Incorporating the 31 plates from Bird (2003), which constitute 2.8% of Earth's surface, changes the angular velocities of the MORVEL plates in the no‐net‐rotation frame only insignificantly, but provides a more complete description of globally distributed deformation and strain rate. NNR‐MORVEL56 differs significantly from, and improves upon, NNR‐NUVEL1A, our prior set of angular velocities of the plates relative to the no‐net‐rotation reference frame, partly due to differences in angular velocity at two essential links of the MORVEL plate circuit, Antarctica‐Pacific and Nubia‐Antarctica, and partly due to differences in the angular velocities of the Philippine Sea, Nazca, and Cocos plates relative to the Pacific plate. For example, the NNR‐MORVEL56 Pacific angular velocity differs from the NNR‐NUVEL1A angular velocity by a vector of length 0.039 ± 0.011° a−1 (95% confidence limits), resulting in a root‐mean‐square difference in velocity of 2.8 mm a−1. All 56 plates in NNR‐MORVEL56 move significantly relative to the no‐net‐rotation reference frame with rotation rates ranging from 0.107° a−1 to 51.569° a−1. Key Points 31 plates are added to MORVEL to describe geologically current plate motion The no‐net‐rotation frame for these plates, NNR‐MORVEL56, is determined NNR‐MORVEL56 differs significantly from NNR‐NUVEL1A and other realizations

Insight into the evolution of Philippine Sea‐South China Sea (SCS) plate motions helps reveal the driving mechanisms of the long‐term tectonic complexity in Southeast Asia. Here, based on the integration of the most recent geological and seismic data, we present a new plate reconstruction model for this region characterized by back‐arc extension and subduction since the Eocene. We suggest that the western boundary of the Philippine Sea Plate was a constant sinistral strike‐slip fault at 55–22 Ma with a clockwise self‐rotation. The connection between the SCS and Shikoku Ridges possibly initiates at 30 Ma, when their spreading times overlapped indicating an affinitive origin and magma source. Regional‐scale geodynamic simulations interfaced with our reconstructed plate motion indicate that the seismic high‐velocity body under the SCS is likely to be the leading edge of the Pacific Slab. Plain Language Summary Since 55 million years ago, East Asia has been going through a complex plate recombination. Several quantitative plate motion models have been published, but there remain several irrationalities, for example, a footwall plate was moving away from the trench. We established a new model for the Philippine Sea‐South China Sea (SCS) region as an improvement. Our model provides a smooth movement of the Philippine Sea Plate (PSP) from the equatorial zone to its present position, with a clockwise rotation. Based on it, we deduce: (a) the western boundary of the PSP was a sinistral strike‐slip fault; (b) the spreading ridges in SCS and Shikoku Basin were connected at 30 Ma; (c) the stagnant slab under the SCS is a part of the subducting Pacific Slab. Key Points A new plate reconstruction model of Philippine Sea‐South China Sea (SCS) region since 55 Ma by integrating the latest geological geophysical data The western boundary of the Philippine Sea Plate was a constant sinistral strike‐slip fault at 55–22 Ma The geodynamic model indicates the seismic high‐velocity body under the SCS likely to be the leading edge of the Pacific Slab

This work focuses on using the power of a collapsing bubble in ice breaking. We experimentally validated the possibility and investigated the mechanism of ice breaking with a single collapsing bubble, where the bubble was generated by underwater electric discharge and collapsed at various distances under ice plates with different thicknesses. Characteristics of the ice fracturing, bubble jets and shock waves emitted during the collapse of the bubble were captured. The pattern of the ice fracturing is related to the ice thickness and the bubble–ice distance. Fractures develop from the top of the ice plate, i.e. the ice–air interface, and this is attributed to the tension caused by the reflection of the shock waves at the interface. Such fracturing is lessened when the thickness of the ice plate or the bubble–ice distance increases. Fractures may also form from the bottom of the ice plate upon the shock wave incidence when the bubble–ice distance is sufficiently small. The ice plate motion and its effect on the bubble behaviour were analysed. The ice plate motion results in higher jet speed and greater elongation of the bubble shape along the vertical direction. It also causes the bubble initiated close to the ice plate to split and emit multiple shock waves at the end of the collapse. The findings suggest that collapsing bubbles can be used as a brand new way of ice breaking.