Myanmar-Andaman-Sumatra subduction margin revisited: Insights of arc-specific deformations

Change of stress patterns during 2004 MW 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

“…The critical plate convergence obliquity and the shallowest dip of the subducting Indo‐Australian Plate near Sumatra (McCaffrey, ) started increasing towards the north near 7°N latitude (fig. 5 of Khan et al, ), reaching a maximum near 14°N latitude. The Sagaing and Sumatra fault systems connected through the Andaman Sea spreading ridge in the back‐arc area accounted for the SSE‐ to SE‐directed movement of the different crustal blocks of the overriding plate.…”

“…The tectonic processes evolved near the central part were possibly affected by the geometry of the margin and the velocity of the converging Indo‐Australian and Asian plates (Chakraborty & Khan, ; Khan & Chakraborty, ). The varying nature of plate convergence velocity, changes in arc geometry, and the variation of penetration depth (Khan et al, ; Khan & Chakraborty, ; Maung, ) along this margin corroborate the observation. We propose that the northern part of the study area was affected by the Eastern Himalaya, and the effect was not so powerful towards the south because of the merging of NER, Andaman Trench, and Sumatra Trench around 10°N latitude; the inherited stress from the Indo‐Australian Plate motion was dominat near the Sumatra segment, and caused several great earthquakes in this area (Figure ).…”

“…Royer and Gordon () demarcated the zone as a diffused triple junction (DTJ) between the Indian, Australian, and Capricorn plates, which is located over the central part of NER near ~10°S. The sharp changes in dips of the subducting oceanic lithosphere near Central Sumatra (Widiyantoro & van der Hilst, ) and the Andaman regions (Khan et al, ) lead to complex deformation and tectonic segmentation of the subducting and overriding plates in this area (Kumar, Srijayanthi, & Ravi Kumar, ).…”

“…Occurrences of the historical earthquakes with magnitude more than 8.0 show concentration near the Sumatra segment, with a few events of magnitude less than 8.0 near the Nicobar–South Andaman segment (Chlieh et al, ; Lay et al, ; Newcomb & McCann, ). The curvature of the margin gradually changes past the Andaman area towards the north, with corresponding changes in seismotectonics of the subducting and overriding plates (Khan, Shamim, Mohanty, Kumar, & Banerjee, ; Maung, ). The anomalous stress accumulation as well as deformation processes operating prior to the occurrence of the 2004 mega‐event had received less attention for this region; most of the studies were mainly confined to the evolution chronology of different tectonic features.…”

Crustal Configuration and Seismic Stability of the Eastern Indian Shield and Adjoining Regions: Insights for Incidents of Great Earthquakes in the Nepal-Bihar-Sikkim Himalaya

“…The area is bounded by the Eastern Ghats mobile belt on the south and the Himalayan foothills on the north. The Gangetic alluvium and the FIGURE 1 | Regional map (reconstructed after Khan et al, 2017b;Valdiya and Sanwal, 2017;Altenbernd et al, 2020) showing the location of the study area (rectangular block demarcated by red dashed line). Abbreviations: AC, Aravalli Craton; BKC, Bundelkhand Craton; CITZ, Central India Tectonic Zone; EGB, Eastern Ghats Belt; CP, Chhotanagpur Plateau; SC, Singhbhum Craton, BC, Bastar Craton; DC, Dharwar Craton; SGT, Southern Granulite Terrain; MG, Mahanadi Graben; GG, Godavari Graben; SM, Shillong Massif; IMR, Indo-Myanmar Range; GR, Ganga River; UGB, Upper Gangetic Basin; LGB, Lower Gangetic Basin; BR, Brahmaputra River.…”