HR: 0830h
AN: S31E-0807    [PDF]
TI: Teleseismic Tomographic Images of the Central Tien Shan
AU: * Yang, X
EM: xyang@geo.tamu.edu
AF: Xiujun Yang, Texas A & M Univ Dept Geology & Geophysics, College Station, TX 77843 United States
AU: Pavlis, G L
EM: pavlis@indiana.edu
AF: Gary L. Pavlis, Indiana Univ Dept Geological Sciences 1005 10th St, Bloomington, IN 47405 United States
AU: Roecker, S W
EM: roecks@rpi.edu
AF: Steven W. Roecker Steven W. Roecker Steven W. Roecker, Rensselaer Polytechnic Inst Dept Earth & Environmental Sciences, Troy, NY 12180 United States
AU: Vernon, F L
EM: flvernon@ucsd.edu
AF: Frank Vernon, Univ California San Diego Inst Gephy & Planetary Physics MS 0225, La Jolla, CA 92093 United States
AB: We analyzed teleseismic P arrival times recorded by three seismic networks in central Asia (KNET, KAZNET, and GHENGIS) to produce an image of the crust and upper mantle beneath the central Tien Shan. In the uppermost mantle, the wavespeeds beneath the Tien Shan are significantly lower than those beneath the Kazakh shield, consistent with previous tomographic studies of this region. Between about 200 and 400 km depth, however, there is clear evidence of a tabular, steeply dipping region of high wavespeeds about 100 km in width situated beneath the southern part of the range. There is no evidence to suggest that this feature extends below 400 km depth. Its origin is indeterminate but the primary candidates are a delaminated lithosphere from the central Tien Shan or a detached piece of subducting Tarim Basin. In either case the body is located several tens of kilometers south of where one might expect its location to be with respect to contemporary geologic features at the surface. This suggests that the Tien Shan has migrated northwards over the mantle as the crust shortened.
DE: 0935 Seismic methods (3025)
DE: 3260 Inverse theory
DE: 6982 Tomography and imaging
DE: 7218 Lithosphere and upper mantle
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Seismology [S]
MN: 2003 Fall Meeting