A BOUND ON THE RHEOLOGY OF CONTINENTAL LITHOSPHERE USING VERY LONG-BASE-LINE INTERFEROMETRY - THE VELOCITY OF SOUTH CHINA WITH RESPECT TO EURASIA

Very long baseline interferometric (VLBI) measurements using the anten na near Shanghai, China, between 1987 and 1994 show that this site mov es at 8 +/- 0.5 mm/yr (1 sigma) in the direction N116.5 degrees E (+/- 4.1 degrees) with respect to VLBI sites in Europe on the Eurasia plat e. Independent measurements of the site at Shanghai with respect to si tes on nearly all major plates (Eurasist, North America, Pacific, Aust ralia, and Africa) determine this velocity. South China translates eas t-southeast relative to Eurasia more slowly than 20% of India's roughl y 50 mm/yr convergence rate with Eurasia and hence accommodates only a small fraction of India's penetration into Eurasia. Apparently, crust al thickening absorbs most of India's convergence. The relatively low speed of south China supports treatments of continental lithosphere as a thin viscous sheet whose strength is governed primarily by power la w creep in the upper mantle, and not by friction in the crust.