Tectonic stress in the plates
The state of stress in the lithosphere provides strong constraints on the forces acting on the plates. The directions of principal stresses in the plates as indicated by midplate earthquake mechanisms, in situ stress measurements, and stress-sensitive geological features are used to test plate tectonic driving force models. Force models include buoyancy forces at ridges, subduction zones, and continental convergence zones and variously parameterized viscous shear between the lithosphere and the asthenosphere. A linear finite element method, is used to predict the intraplate stress for each force model. Maximum compressive stresses trend E-W to NE-SW for much of stable North America and E-W to NW-SE for continental South America. In western Europe the maximum compressive stresses trend NW-SE, while in Asia the trend is more nearly N-S, especially near the Himalayan front. In the Indian plate the trend varies from nearly N-S in continental India to more nearly E-W in Australia. Horizontal stresses are variable in Africa, but tend to indicate a NW-SE trend for the maximum compressive stress in west Africa and an E-W trend for the minimum compressive stress in east Africa. Oceanic lithosphere away from plate boundaries is generally in a state of deviatoric compression. Ridge pushing forces are required in all models that match the stress orientation field. The net pulling force of subducted lithosphere, if such a force acts approximately symmetrically about the plate boundary, is at most a few times larger than other forces acting on the plates. Resistive forces associated with trench thrust faults and motion of the slab with respect to the mantle must therefore nearly balance the large gravitational potential of the slab. Forces acting to resist further continental convergence along the Alpine-Himalayan belt are important for models of the intraplate stress field in Europe, Asia, and the Indian plate.a, and the Indian plate.
- Research Organization:
- Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- OSTI ID:
- 6250868
- Journal Information:
- Rev. Geophys. Space Phys.; (United States), Journal Name: Rev. Geophys. Space Phys.; (United States) Journal Issue: 5 Vol. 17:5; ISSN RGPSB
- Country of Publication:
- United States
- Language:
- English
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