China
Africa
Explore chapters and articles related to this topic
Introduction
Published in Hector Estrada, Luke S. Lee, Introduction to Earthquake Engineering, 2017
This theory, however, does not fully explain all phenomena associated with lithospheric plate movement. The current view is that plate movement is driven by additional forces, known as ridge push and slab pull, which also derive their energy from the dissipation of heat from the earth’s core through convection currents (this theory is still being debated). These forces are generated at the mid-oceanic ridge (divergent zones) and at the subduction zones. At the divergent zones, lava cools at the surface creating new oceanic ridge; as this new material moves away from the divergent zones, it continues to cool, becoming denser. At the other end of the plate, the oceanic lithosphere becomes even denser with age as it continues to cool and thicken. This causes the lithospheric plate to tilt toward the subduction zones, like an unbalanced boat in water. The mid-oceanic ridge then rises above the rest of the seafloor, and as the new material rises to the top of the ridge, gravity pulls it down; this is called ridge push. Also, the greater density of old oceanic lithosphere at the subduction zones, relative to the underlying asthenosphere, allows gravity to pull these rocks (known as slabs) down into the mantle. This is believed to be the source of the driving force for the majority of plate movement.
Petrological and isotopic data from Eocene granites in the Luocang area, South Lhasa terrane, Tibet: implications for the India–Eurasia collision
Published in Australian Journal of Earth Sciences, 2021
J.-G. Gao, F. Ding, J.-Q. Lin, Q.-H. Zhu, Y. Sun, X.-G. Xie
Granitic rocks (47 Ma) in the Siborongqu area in the eastern South Lhasa terrane have been attributed to Neo-Tethys oceanic plate breakoff and considered the product of a crust–mantle mixed source (Li et al., 2019). A similar conclusion has been given for quartz monzonite (ca 51 Ma) of the Qiangmucuoge area in the eastern Lhasa terrane (Su et al., 2020). The large-scale ca 50 Ma magmatic event of the Lhasa terrane has generally been considered the product of breakoff of the Neo-Tethys oceanic plate and the resulting asthenospheric upwelling could have lasted several million years (ca 53–47 Ma) (van de Zedde & Wortel, 2001). Breakoff of the Neo-Tethys oceanic slab resulted in instantaneous loss of slab pull and continuing subduction of Indian lithosphere would have been at a low angle (Hou, Mo et al., 2006: Hou, Zhao et al., 2006).
Subduction geometry controls on dynamic topography: implications for the Jurassic Surat Basin
Published in Australian Journal of Earth Sciences, 2019
T. Smith, V. Bianchi, F. A. Capitanio
During subduction, changes in the geometry of subducting slabs, likely associated with mantle-depth slab tears, could alter mantle flow and thus upper plate tractions. For instance, slab tearing occurs when the velocity of the subducting slab varies along strike, leading to the formation of large strike-slip faults perpendicular to the subduction trench (Gasparon, Rosenbaum, Wijbrans, & Manetti, 2009; Rosenbaum, Gasparon, Lucente, Peccerillo, & Miller, 2008). Slab detachment occurs when the downward slab-pull forces of subduction and upward slab buoyancy overcome the internal strength of the subducting slab, leading to strike-parallel faulting and eventual detachment (Argnani, 2009; Rosenbaum et al., 2008). Variations in this process wherein a partially detached slab sinks, generate a torque that alters the uplift regime (Capitanio, 2014).
An XFEM Model for Seismic Activity in Indian Plate
Published in Journal of Earthquake Engineering, 2018
S. Jayalakshmi, S. T. G. Raghukanth, B. N. Rao
The slab pull force acts at the subduction zone along the Indo-Burmese and the Andaman arc. Several authors have empirically related slab pull force and ridge push force due to the lack of understanding of the causative agents [Scholz and Campos, 1995]. Previously, the models developed by Jayalakshmi and Raghukanth [2015] studied the effect of only ridge push force on Indian Plate. However, these models did not consider the effect of slab pull on the eastern subduction zone of the plate. For the slab pull force, there are no well-established expressions due to numerous uncertainties. However, this force acts on the eastern edge of the plate and plays an important role in the stress field in Indian Plate. From our previous study [Jayalakshmi and Raghukanth, 2016], the magnitude of slab pull force varied between 0.5 FRP and FSP = 10FRP to run several models and obtain a good comparison of average deformation of the plate with the available GPS data. Thus, by trial and error, the values of FSP are obtained as 2FRP along Indo-Burmese and 2/3 FRP along Andaman arc.