Burma plate motion

Abstract

Plate motion in the Indo‐Burmese Arc‐Andaman‐Sumatra region of Burma plate is poorly resolved. This is mainly due to lack of relevant data and complex tectonics of the region. We analyze (1) azimuths of coseismic displacements due to the 2004 Sumatra‐Andaman and 2005 Nias earthquakes; (2) estimates of interseismic deformation in the Indo‐Burmese Arc, Andaman, Sumatra, and Sagaing Fault regions (all based on GPS measurements); (3) long‐term plate motion rates across Sumatra Fault System, Sagaing Fault, and Andaman Sea from geomorphological and other geophysical studies, and (4) the earthquake focal mechanisms in the region. We suggest that the SSW motion of Sunda plate with respect to Indian plate may be partitioned into the dextral strike‐slip motion across the Sagaing Fault in the north and Sumatra Fault System in south in the back‐arc region, and the arc‐normal motion across the Sumatra subduction zone, which becomes oblique in Andaman and southern Indo‐Burmese Arc region and dextral in the northern Indo‐Burmese Arc region of the fore arc. Under the rigid plate approximation, we estimate a pole for India‐Burma plate pair at 27 ± 1°N, 82 ± 1.1°E with an angular velocity of 0.845 ± 0.12°/Ma and for Burma‐Sunda at 22.3 ± 1.1°N, 109.3 ± 2.5°E with an angular velocity of 0.67 ± 0.12°/Ma. Thus the plate motion in the northern and southern regions of Burma plate, namely, the Indo‐Burmese Arc and Andaman‐Sumatra Arc, may be explained by a single pole and does not require a boundary between the two.