The magnitude of driving forces of plate motion

Shoji SEKIGUCHI
1985 Journal of Physics of the Earth  
The absolute magnitudes of a variety of driving forces that could contribute to the plate motion are evaluated, on the condition that all lithospheric plates are in dynamic equilibrium. The method adopted here is to solve the equations of torque balance of these forces for all plates, after having estimated the magnitudes of the ridge push and slab pull forces from known quantities. The former has been estimated from the age of ocean floors, the depth and thickness of oceanic plates and hence
more » ... teral density variations, and the latter from the density contrast between the downgoing slab and the surrounding mantle, and the thickness and length of the slab. The results from the present calculations show that the magnitude of the slab pull forces is about five times larger than that of the ridge push forces, while the North American and South American plates, which have short and shallow slabs but long oceanic ridges, appear to be driven by the ridge push force. The magnitude of the slab pull force exerted on the Pacific plate exceeds to 40 % of the total slab pull forces, and that of the ridge push force working on the Pacific plate is the largest among the ridge push forces exerted on the plates. The high correlation that exists between the mantle drag force and the sum of the slab pull and ridge push forces makes it difficult to evaluate the absolute net driving forces. However, the slab resistances appear to contribute more to cancelling the driving forces than the mantle drag force. From stress estimation, it was found that high stresses are concentrated around the leading edge of the downgoing slab.
doi:10.4294/jpe1952.33.369 fatcat:23trrdw5ofeqhilahek4c2htny