Numerical modeling of the distribution of horizontal stresses in a moving continental plate |
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Authors: | A M Bobrov |
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Institution: | 1.Schmidt Institute of Physics of the Earth,Russian Academy of Sciences,Moscow,Russia |
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Abstract: | The distribution and time evolution of overlithostatic horizontal stresses in the vertical cross-sections of the model of
a solid continent are studied in terms of a 2D numerical model. The continent is moving self-consistently with time-varying
mantle flows. Over a period of 50 Ma, the continent, which had been initially located at a distance of about 1500 km from
the downward mantle flow (subduction zone), first overlays the region of the marginal sea, then thrusts over the zone of subduction,
thus making it inclined and deforming it. It is found that the horizontal tensile stresses observed at the initial stages
are succeeded by compressive stresses, especially at the leading edge (up to 40 MPa). This is caused by the change of the
dragging action of the subduction zone into the retarding action during the continent crossing over this zone. The dependence
of the calculated stresses on the Rayleigh number and on the thickness of the model of the continent is estimated. It is obtained
also that the distribution of horizontal stresses along the strike of the continent is rather distinctly indicative of the
locations of upward and downward flows in the subcontinental mantle. With the considered values of the model parameters, the
tensile stresses in the near-to central regions of the continent may be twice to thrice the tensile stresses at its margins.
Hence, in the simplest case of a homogeneous continent, its division will occur in the zone directly above the upward subcontinental
flow. Detachment from the continent of the fragments of its edge adjacent to the marginal sea implies that the thickness of
the continental plate in that part and/or its strength is considerably lower than in the center of the continent. |
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