The Andaman–Nicobar–Sumatra subduction margin, with a well-developed Benioff zone down to ~ 200 km depth, extends over 1300 km along strike and has a lateral extent of ~ 200 km. Two-dimensional (2D) profiles based on generalized inversion of free-air gravity anomaly data across different segments of the Andaman–Nicobar sector of the margin were analyzed by reconstructing the geometry of the converging India–Eurasia lithospheric plates. Detailed 2D structures of the Ninetyeast Ridge (NER), fore-arc basin, volcanic arc, back-arc basin, spreading ridge, Sewell Rise, Mergui Ridge and Mergui Basin, and depths of Moho and the lithosphere–asthenosphere boundary were delineated. The volcanic arc is located at a distance of ~ 150–200 km from the trench and is marked by a zone of positive gravity anomaly separated from the trench by the fore-arc basin with a zone of gravity low. The topographic and gravity anomaly patterns show complex geometrical patterns over the volcanic arc due to the presence of a number of regional faults striking parallel to the trench axis developing a series of pull-apart (transtensional) basins as well as the interaction of the spreading ridges on the overriding plate. A narrow zone of negative gravity anomaly (~ − 185 to − 110 mGal) observed in the gravity model of the margin is interpreted to be associated with fore-arc shear fault above a zone of fractured oceanic crust with a thick sedimentary layer, located above a zone of sharp bending of the eastward converging Indian lithosphere in the fore-arc basin. A high concentration of seismicity and a trench-parallel band of moderate moment energy release along this fault might have been caused by concentrated deformation within the zone of flexing of the descending plate. A wide fore-arc (> 200 km) and the enhanced deformation of the subducting Indian oceanic plate in central sectors possibly resulted from increased interaction between the NER and the Andaman trench and extension in the Andaman back-arc. Appearance of a second moderate energy band and shifting of seismicity toward the trench axis following the 2004 M_W 9.2 mega-event are apparently caused by the migration of the stress field from deeper to shallower part of the Indian lithosphere. A similar type of seismicity migration toward shallower part of the descending plate has been recorded along other subduction margins around the globe.

安达曼–尼科巴–苏门答腊俯冲带边缘，发育良好的贝尼奥夫带低至约200 km深度，沿走向延伸超过1300 km，横向范围为〜200 km。通过重构印度-欧亚大陆岩石圈汇聚板块的几何形状，分析了跨边界安达曼-尼科巴扇形不同段的自由空气重力异常数据的广义反演的二维（2D）剖面。描绘了九十里脊（NER），前弧盆地，火山弧，后弧盆地，扩张脊，塞维尔上升，梅尔吉里奇和梅尔吉盆地的详细二维结构，以及莫霍面和岩石圈-软流圈边界的深度。火山弧位于距海沟约150-200 km处，其特征是正重力异常区与前海盆地相距较远，海弧区的重力区较低。地形和重力异常模式显示出火山弧上的复杂几何模式，这是由于存在许多平行于沟槽轴线的区域性断裂，形成了一系列拉张（张性）盆地以及扩张脊的相互作用在最上面的盘子上。在边缘重力模型中观察到的负重力异常的狭窄区域（〜-185至-110 mGal）被解释为与具有厚沉积层的破碎洋壳区域上方的前弧剪切断层有关，位于弧前盆地向东汇聚的印度岩石圈急剧弯曲的区域上方。高度地震活动性和沿断层释放适度矩能量的沟槽平行带可能是由于下降板弯曲区域内的集中变形引起的。宽的前弧（> 200 km）和俯冲的印度洋板块在中央区域的变形增强，可能是由于NER与安达曼海沟之间的相互作用增加以及安达曼后弧的延伸所致。2004年之后出现第二个中等能带，地震活动向沟槽轴移动 高度地震活动性和沿断层释放适度矩能量的沟槽平行带可能是由于下降板弯曲区域内的集中变形引起的。宽的前弧（> 200 km）和俯冲的印度洋板块在中央区域的变形增强，可能是由于NER与安达曼海沟之间的相互作用增加以及安达曼后弧的延伸所致。2004年之后出现第二个中等能带，地震活动向沟槽轴移动 高度地震活动性和沿断层释放适度矩能量的沟槽平行带可能是由于下降板弯曲区域内的集中变形引起的。宽的前弧（> 200 km）和俯冲的印度洋板块在中央区域的变形增强，可能是由于NER与安达曼海沟之间的相互作用增加以及安达曼后弧的延伸所致。2004年之后出现第二个中等能带，地震活动向沟槽轴移动 中号_W¯¯ 9.2大型活动，显然是从更深层的应力场的迁移造成的印度岩石圈浅一部分。沿地球上其他俯冲带边缘也记录了类似类型的地震活动向下降板较浅部分的迁移。