Joint modelling of Satellite Gravity & Geoid Data in the south Andaman region of Andaman - Sumatra Subduction Zone

The Andaman - Sumatra subduction zone at the north-eastern margin of Indian oceanic plate, is marked by several events of large earthquakes in the recent past. We present 3D lithospheric density structure over a region south of Andaman and north of Sumatra from joint modelling of regional satellite derived gravity and geoid data constraint with all the available geologic and geophysical information. Our results indicate that the dip of subducting slab is gentle in southern part of Nicobar Island and becomes steeper from the northern part of Nicobar towards Andaman Island, suggesting that Indian plate is segmented from north to south as observed in the slip of great Sumatra earthquake of 2004. The subducting plate penetrates up to 160 - 175 km in this region, which coincides with the foci of earthquakes. The presence of Ninety East Ridge to the south of 100N on the subducting plate notably changes the crustal structure.