Active subduction and strain partitioning in western Myanmar revealed by a dense new GPS velocity field

Abstract:

The tectonics of the Burma microplate in Myanmar and its interaction with the Indian plate to the west and the Eurasian and Sunda plates to the east remain a subject of controversy, in part due to a lack of geodetic observations across the majority of the active faults. By resurveying GPS benchmarks installed in 2000-2003, we acquired a dense set of new geodetic velocities spanning central and western Myanmar, from 15 – 23 ºN and 93 – 98 ºE. In combination with new survey monuments and continuous GNSS sites, we report a total of more than 80 new velocities. These data were collected in collaboration with governmental and academic institutions in Myanmar (the Department of Meteorology and Hydrology, the Myanmar Survey Department, and the Myanmar Earthquake Committee), and the results more than triple the total number of available geodetic velocities in the country.

For the first time, our results confirm geodetically the occurrence of active convergence along the central Rakhine coast in a manner consistent with active subduction and kinematic coupling of the megathrust, at a rate of 15 – 20 mm/yr. The data also establish a constant strike-slip rate of 20 – 23 mm/yr along the full length of the Sagaing fault. We examine several proposed models for the partitioning of strike-slip and thrust motion across the Indo-Burman ranges and the Myanmar central basin, and find that a relatively small set of active faults can explain the data well. In the future, better geodetic coverage will allow us to validate and expand these results, particularly along the southwestern coast and within the Ayeyarwaddy delta.