Insights into plate tearing and subduction dynamics in the Andaman Nicobar region through 3D geodynamic and gravity modeling

Abstract

The Andaman and Nicobar region is a geologically complex area characterized by active subduction and tectonic activities, including the collision of the Indian Plate with the Burma Plate. Seismological studies suggest that differential subduction and rollback velocities in this region may lead to tearing of the subducting plate, potentially dividing it into three distinct segments. Slab tearing plays a critical role in influencing various geodynamic processes such as earthquakes, volcanism, uplift rates in mountain ranges. While lithospheric tears are typically identified through seismic tomography and seismicity trends, gravity anomalies provide a valuable complementary approach. In this study, we employ a 3D thermo-mechanical visco-plastic model, I3ELVIS, to simulate the subduction and tearing processes. We will explore the interaction between subduction, rollback, and tearing of the plate and its influence on the gravitational field of the region. Forward simulation of Gravity anomaly is conducted on different modeled geodynamic scenarios, and resulting 2D profiles of gravity anomalies are compared with observed gravity data from the region to assess the validity of the plate tearing hypothesis. Our findings indicate that slab tearing indeed plays a crucial role in subduction dynamics in the Andaman-Sumatra subduction zone.