Stress State of the Stable Part of the Pacific Plate Predicted by a Numerical Model of Global Mantle Flow Coupled with Plate Motion

The Pacific plate, which is the largest oceanic plate on Earth, has implications for the general understanding of plate dynamics, including the origin of intraplate stress and the driving force for plate motion. However, this is currently limited by the scarcity of geophysical and geological observational data. In this study, an instantaneous global mantle flow calculation was performed to predict the intraplate stress field and stress regimes on the Pacific plate using a geodynamic model based on the density anomaly structure of the mantle converted from a seismic tomography model incorporating subducting plates. The numerical results demonstrate that the southern part of the Pacific plate is dominated by a normal faulting regime. In contrast, the northern part is dominated by a thrust faulting regime, in which the tensional stress axes in the older and stable part of the Pacific plate tend to be oblique to the direction of plate motion. This suggests that the stress state of the Pacific plate is almost neutral (i.e., neither compressional nor tensional) along the direction of plate motion. Furthermore, shallow positive buoyancy-induced asthenospheric flow is essential for reproducing the observed plate motion of the Pacific plate.