Introduction — Burma Plate
The Burma plate is a minor tectonic block in Southeast Asia, variably treated as an independent microplate or, for some tectonic syntheses, as part of the broader Eurasian plate. It carries the Andaman and Nicobar islands and northwestern Sumatra, which together form the Andaman–Nicobar–Sumatra island arc that separates the Andaman Sea from the open Indian Ocean. Along its eastern margin the plate meets the Sunda plate on a roughly north–south trending transform that functions as a marginal seafloor‑spreading centre; progressive generation of new oceanic crust here has driven the south‑to‑north opening of the Andaman Sea and laterally displaced the island arc away from mainland Asia since about 4 Ma. On the western side the much larger India plate converges with and subducts beneath the Burma block, creating the Sunda Trench. Situated between the convergent India plate and the Sunda/Eurasian domain, the Burma microplate therefore acts as an intermediary tectonic unit whose transform and subduction boundaries have controlled the region’s island‑arc morphology, marginal‑basin development and plate‑margin geometry.
Tectonic history
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The tectonic evolution of the Burma plate began with the Eocene northward impingement of the Indo‑Australian plate against Eurasia (~50–55 Ma), a collision that triggered Himalayan orogeny and wholesale reconfiguration of regional plate boundaries. India’s relatively rapid northward translation—averaging about 16 cm/yr—was accompanied by a counterclockwise rotation, so that convergence along its eastern margin became markedly oblique; this change in convergence geometry governed deformation in the Burma–Andaman–Malay corridor.
Along that eastern margin, subduction was juxtaposed with strike‑slip motion on major transform faults, a kinematic regime that induced a clockwise flexure of the Sunda arc and altered the arc–trench system including the Western Sunda Arc. Progressive faulting by the late Oligocene (ca. 32 Ma) facilitated mechanical separation of crustal fragments from the Eurasian margin: discrete Burma and Sunda microplates emerged as tectonic blocks that effectively detached from the parent plate.
Continued underthrusting of India beneath the Burma block, coupled with episodic transform displacement, produced backarc extension and the establishment of a seafloor‑spreading center behind the arc. This extensional phase developed into the Andaman Sea basin, with active spreading and basin widening well advanced by the mid‑Pliocene (~3–4 Ma). The sequence of continental collision, plate fragmentation (including partitioning of Indian, Australian and related plates), oblique convergence, transform faulting, arc bending, microplate formation, subduction and backarc spreading provides the mechanistic framework for the current high levels of tectonism and seismicity along the Western Sunda Arc–Trench system.
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Recent tectonic activity
On 26 December 2004 a megathrust rupture on the convergent boundary between the Burma Plate and the subducting Indian Plate produced the 2004 Indian Ocean earthquake, with moment magnitude estimated at 9.1–9.3 Mw. Thrust faulting propagated along more than 1,600 km of the plate interface, representing an unusually long segment of synchronous slip on this margin. The coseismic deformation included both vertical and horizontal offsets of the seafloor—vertical uplift locally reached about 5 m while lateral displacements were as large as ~11 m—generated during a rapid rupture episode lasting roughly seven minutes. This abrupt seabed motion transmitted energy efficiently into the overlying water column and produced trans‑oceanic tsunami waves that struck coastlines around the Indian Ocean. The resulting loss of life and damage were enormous (estimates of fatalities are on the order of 229,800), illustrating the extreme hazard posed by large megathrust events where continental/arc blocks such as the Burma Plate interact with oceanic plates.