Three-Dimensional Numerical Modeling of Deformation and Stress in the Himalaya and Tibetan Plateau with a Simple Geometry
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The Himalaya-Tibetan region is the most active continent-continent collision zone in the world. To understand the tectonics of the region, we have numerically modeled the deformation and stress fields in the region by using a three-dimensional finite element technique. For the sake of simplicity, our model space has a simple geometry. It covers a fan-shaped region including the Himalayan Arc of about 2, 000 km in length in the south and the Tibetan Plateau in the north, and extends to a depth of 250 km. We consider several combinations of boundary conditions. In a typical case, the boundary conditions are as follows: on the southern boundary of the model space, we impose a uniform velocity of 50 mm/year northward in the direction normal to the Himalayan Arc; the northern and basal boundaries of the model space are constrained by "roller" conditions; and other boundaries of the model space are left free. We do not consider the gravitational forces. In this case, the deformation field shows that the region far inside the Tibetan Plateau is experiencing an east-west extension at a rate of 6 mm/year and that the maximum uplift at a rate of -4 mm/year occurs mostly along the Indus-Tsangpo suture zone. The stress field has interesting features; the magnitudes of the near-surface stresses beneath the Lesser and Greater Himalaya varies considerably along the arc. It is large in the western and eastern Himalaya (the maximum rate of stress build-up is - 0.003 MPa/year) and small in the central Himalaya. In the Tibetan Plateau, the stresses are quite large in the central portion. The modeled stresses far inside the Tibetan Plateau agree with strike-slip faulting predominantly observed there, while those in southern Tibet are not consistent with normal faulting revealed by focal mechanism solutions.
- Earth, Planets and Space
Earth, Planets and Space 44(3), 227-254, 1996-06
The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan