One of the most tectonically active regions of the world is the Indo-Burma Ranges (IBR) of North-east (NE) India and its surrounding region. It has been considered as a natural laboratory for exploring the geodynamics and kinematics of the subduction system because of the undergoing complex tectonic processes (Gahalaut et al., 2016;Kayal, 2008). The region experienced two greatest earthquakes, the
<p>Subduction zones host some of the greatest megathrust earthquakes in the world. Slow earthquakes have been discovered around the subduction zones of the Pacific rim very close to megathrust earthquakes. Investigating the lithosphere of the slow earthquake area versus non slow-earthquake area in subduction zones is crucial in understanding the role of the internal structure to control slow earthquakes. In this study, we investigate the lithospheric structure of stations in the slow earthquake area and non slow-earthquake areas in Chile using receiver function analysis and inversion method using teleseismic earthquakes. Here we focus on, especially the Vp/Vs ratios from both slow and non-slow earthquake areas, because the Vp/Vs ratio is sensitive to the fluid distribution in the lithosphere; the fluid distribution possibly controls the potential occurrence of slow earthquakes. Additionally, the nature of the slab can also play a crucial factor. The Vp/Vs ratio results across depth shows significantly higher value in the deeper oceanic slab region beneath the stations in the slow earthquake areas with higher contrast at the boundary.</p>
The Gondwana supercontinent was an accretion of several cratons from different landmasses, namely South America, Antarctica, Africa, Madagascar, Australia, and the Indian subcontinent. The splitting of Gondwanaland during the Mesozoic led to the gradual rifting of these different cratons over geologic time. In this study, crustal structures are imaged by modeling receiver functions to understand the differences in the nature of the crust that was once part of Precambrian Gondwanaland. On comparing the overall crustal thickness with the age of the cratons, it was found that average bounds of crustal thickness varied from ~33 to 45 km in the Precambrian cratons of different ages, and composition varied from felsic to intermediate (Vp/Vs≈1.65−1.78). Observations of gradational Moho beneath few stations could indicate the possibility of mafic underplating at some point in their history of formation, growth, or evolution. Even if plate tectonics were dominant in the middle to late Archean, difference in spreading, drifting velocity, and distance travelled by the continents after Gondwana separation possibly led to crustal delamination, and destruction of thick crustal roots of cratons. Other than delamination, the role of episodic cycles of crustal growth is also observed in the pattern of crustal thickness across each division of the Precambrian. This could be due to alternative high and low crustal regeneration process, repeated episodic recycling, and reworking of early crust, supported by previous geodynamical models.
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