A three-dimensional density model of north Andaman subduction zone

R. Yadav, V.M. Tiwari

We present a three-dimensional (3D) density model of northern Andaman subduction zone (10°–15°N) con- structed through joint modelling of satellite free-air gravity and geoid anomalies with constraints from previous studies. This novel modelling approach utilizes geoid and gravity anomalies simultaneously to better resolve the structure of inadequately known part of the subduction zone. The density model suggests:

.      A contrasting situation of subducting Indian plate, mapped up to a depth of ∼180 km in the southern part, and almost missing in the north of the study region.

.      Dip of the Benioff zone and the width of the accretionary prism decreases from south to north. 

.      Nature of the overriding plate varies from oceanic to semi-continental towards the north. 

Moho depth is relatively higher under the seamounts and 90°E ridge. The change in the subduction geometry is probably due to the subducting aseismic ridge, difference in the sediment influx and variation in the convergence rates. The absence of the subducting slab in the north is probably caused due to tearing between northern Andaman in the south and Burmese Arc in the north.


Map of study area and a three dimensional view of north Andaman subduction zone

Journal of Geodynamics 129 (2019) 247-261