Three-dimensional magnetotelluric resistivity imaging of Andaman Islands, NE Indian Ocean

Abstract The Andaman Arc, located along the eastern boundary of the Indian Plate, represents a complex tectonic system defined by several key structural and geodynamic features. The ongoing subduction of the Indian Plate beneath the Burma Plate generates a dynamic regime of interacting compressional and extensional forces that govern the tectonic evolution of the region (as well as the formation of the Andaman Islands). The West Andaman Fault, a major transform fault system, delineates the western margin of the arc, while the Andaman Sea to the east is characterized by intricate tectonic processes associated with active deformation. To better understand the complex tectonic processes in the region, a Long-Period Magnetotelluric (LMT) survey was conducted in the Andaman Islands, focusing on the subduction dynamics of the Indian plate beneath the Andaman Sea. 3D modeling of the LMT data reveals the following: (a) obducted sediments are scraped off the subducting plate to form an accretionary wedge or prism extending to a depth of about 6–8 km along the eastern margin of the Andaman Islands, and (b) a high-resistivity mafic crust beneath the Middle Andaman Islands, likely formed under deformation associated with ongoing E–W compressional forces, appears to function as a mechanically rigid block. This feature significantly influences the spatial distribution of faulting, uplift, and strain partitioning across the arc. Graphical abstract