A gravimetric method to determine horizontal stress field due to flow in the mantle in East Africa Great Rift Valley

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Addis Ababa University


The gravimetric approach has been widely used to determine the stress field of subsurface geology of the earth crust. Mainly this study aimed to determine lithospheric shear stress in the Earth’s mantle and its temporal changes caused by geodynamical movements. The gravimetric approach is applied, to evaluate the stress at the base of lithosphere and to detect changes in stress using static gravity field model EGM08 and GRACE monthly solutions respectively. In addition to the static gravity field data some physical information about topographic height, crustal thickness, and lithospheric thickness are incorporated in this method. As a result, more geophysical information and data are applied for computation of horizontal lithospheric stress in this approach. To do so, depth of the base of lithosphere determined by subtracting topographic height from lithospheric thickness is needed, thus the lithospheric shear stress component computed at the base of lithosphere. Moreover, the comparison of lithospheric shear stress using different static gravity field models are performed. The estimated horizontal shear stress at the base of the lithosphere throughout the study area revealed 55.68% of the stress is oriented in a northward direction and the remaining 44.32% is oriented in the southward direction; 44.41% of the stress is oriented in an eastward direction and the remaining 55.59% is oriented in the westward direction: and the result of the estimated horizontal shear stress magnitude ranges from ≈ 0.04 MPa to ≈ 15.32 MPa. Furthermore, the estimated horizontal shear stress components show good agreement with the tectonic boundaries and the location of stress regimes in the WSM2016 database, as well as the seismic events in the study area.