Present day kinematics of Asia derived from geologic fault rates

G. Peltzer, F. Saucier
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

Abstract:

Active fault geometry, available Quaternary rates on major faults, and the far-field plate motion are used to determine crustal kinematics in the collision zone between India and Asia. Using a finite element formalism to construct a spherical shell model of the Asian continent with embedded faults, we seek a velocity solution approaching the motion of rigid blocks by minimizing the elastic strain energy in the fault-bounded blocks. By doing so, we test the assumption that long-term deformation within continents is mostly localized into major faults. In the solution, fault motion accounts for more than 80% of the deformation allowing us to describe our velocity model in terms of quasi-rigid block rotations on the sphere. South China is rotating clockwise about a pole located south-west of Borneo, implying an E-ESE velocity vector of  11 mm/yr for a point at Shanghai, in agreement with the velocity vector determined by Very Long Baseline Interferometry [Heki et al., 1995]. The eastward movement of South China is accommodated by oblique extension along the Red River fault at a rate of 10±5 mm/yr in the south, and by the combination of left-lateral strike-slip motion on the Qinling-Dabie Shan fault and the counterclockwise rotation of the Ordos and adjacent blocks in the north. The Tarim rotates clockwise with respect to Dzungaria about a pole located at , , consistent with increasing crustal shortening toward the west throughout the Tien Shan. Assuming incompressibility, a crustal volume budget over a domain encompassing the Tertiary mountain ranges in Asia shows that, over the last 10,000 years, 73±4% of the north south shortening between India and Asia has been absorbed by thickening of the lithosphere, and 27% accommodated by lateral extrusion of continental blocks. The present day predominance of thickening in Asia results from the relatively slow eastward motion of South China, controlled by strike-slip faulting in the Qinling Shan and oblique extension in north-eastern China.

AGU Index Terms: 8110 Continental tectonics-general; 8120Dyn8120 Dynamics of lithosphere and mantle-general; 8158 Plate motions-present and recent; 8107 Continental neotectonics
Keywords/Free Terms: Asia, India, continental collision, neotectonics.

JGR-Solid Earth 96JB02698
Vol. 101 , No. B12 , p. 27,943