INFLUENCE OF SOME RHEOLOGICAL PARAMETERS ON FLEXURE OF THE OCEANIC LITHOSPHERE

Rheological parameters describe properties of the lithosphere, but it is generally impossible to measure them in situ. Thus a model has to b e developed to relate parameters to observables. We consider flexure o f the oceanic lithosphere. A quantitative representation of a brittle- elastic-ductile rheology is based on a semi-empirical model. The non-l inear problem of plate flexure is solved by the multiple-shooting algo rithm using a Runge-Kutta procedure from analytical solutions for an e lastic model. The bending moment and its derivatives have been deduced analytically to improve the accuracy and speed of computations. A fam ily of numerical solutions was built that describes flexure of the oce anic lithosphere at subduction zones for various ages, strain rates, a nd activation energies. Relative contributions of rheological paramete rs are discussed. The model is then used to evaluate rheological param eters of the Kuril trench from gravity data. The strain rate estimates are found to be about 3 . 10-(16+/-1) s-1 assuming creep activation e nergies between 520 kJ/mole and 550 kJ/mole for lithospheric age rangi ng from 90 Ma to 110 Ma.