Development of stress field for the African tectonic plate from gravitational potential energy

Abstract

The World Stress Map is a global compilation of data on crustal stress designed to assess worldwide stress patterns and identify stress sources. However, its effectiveness is limited due to inadequate coverage in Africa. This research project aimed to model crustal stress patterns and understand the correlations with contemporary seismicity. To this end, these stresses were modelled from gravitational potential resulting from contrasts in the density structure and the topographic elevations of the African tectonic plate (TAP). Accordingly, the data set of crustal parameters from Crust1.0 and elevations of GEBCO-2022 (general bathymetric chart of the oceans) were used as inputs to determine the lateral forces on elements from gravitational potential. An elastic finite element analysis in plane stress was then employed to determine the present-day stress field of TAP. Subsequently, the simulation results were compared to the recent studies of stress indicators. The stress distributions obtained from the finite element model (FEM) are correlated and found to be in good agreement with the contemporary seismicity of Africa from empirical relations. High stresses were observed in eastern, northern, and southern Africa. At the same time, central Africa and western Africa exhibited low-stress levels. Maximum horizontal stress (SHmax) direction in the East Africa Rift System is roughly parallel to the rift. Generally, the observed stress orientations are in harmony with World Stress Map, with the errors in azimuths ranging from 5.4° to 21.5°.