A first-order study of the tectonic stress field within the Indo-Australian plate in response to various plate boundary forces and intraplate stress sources was carried out using an elastic finite element analysis. The finite element mesh comprised of 1374 nodes and 2537 elements provided a spatial resolution of about 2 degrees. The study builds on the previous modeling studies through consideration of a wide range of plausible forces acting along the collisional and subduction zone boundaries and, importantly, through the inclusion of forces due to other lateral density variations within the lithosphere, such as those associated with the continental margins and high topography. The modeling was constrained by 251 stress indicators extracted from the World Stress Map Project (Zoback, 1992) which provide information about the orientation of the observed maximum horizontal compressive stress, SHmax. The indicators provide a five-fold increase in the the number of stress indicators than were used in previous modeling studies. The torques associated with the ridge push force is well constrained and the principal source of uncertainty relates to the boundary conditions used to represent the collisional resistance and subduction zones forces acting along the northern boundary. We demonstrate that if substantial focusing of the ridge push torque occurs along the collisional boundaries (i.e., Himalayan and Papua New Guinea), many of the broad scale features of the observed stress field can be reproduced without appealing to either subduction or basal drag forces. Lateral density variations within the continental areas of Australia and India were found to have a significant effect on the regional stress field in these areas. Predicted stresses for several areas of the plates were found to be robust for a large range in the magnitude of applied boundary forces, including the central India Ocean and northwest Australia. In contrast, stresses in southeast Australia were found to be sensitive to the forces acting along the eastern plate boundary about which little is understood. In as much as a wide range of boundary conditions can be configured to match the large portion of the observed intraplate stress field, the problem is poorly constrained. However, a very important aspect of our calculation is that the observed S$_{Hmax}$ orientation in the IAP can be modeled with applied boundary forces which do not produce large intraplate stresses magnitudes (on the order of hundreds of MPa (kbars), averaged over the thickness of the lithosphere).
Predicted stresses for Model 4 incorporating ridge push, collisional boundary and subduction zone forces. Solid bars indicate deviatoric compression, open arrows indicate deviatoric tension.