HR: 14:15h
AN: T23A-02    [Abstracts]
TI: Structure and Dynamics of Tien Shan From Integrative Modeling of the new GPS, Gravity and Seismic Data
AU: * Kaban, M K
EM: kaban@gfz-potsdam.de
AF: GeoForschungsZentrum, Dept. 1, GeoForschungsZentrum, Potsdam, 14473, Germany
AB: The Tien Shan range is the longest and most active mountain belt in Central Asia. The lithosphere deformations result from a fast convergence rate between India and Eurasia, whilst Tien Shan absorbs almost half of the ongoing convergence. This situation is absolutely unique for intracontinental mountain belts. The mechanism, which controls crustal shortening in this area, remains up to now unclear. For example, a striking disagreement exists between the shortening rates of ~20 mm/yr (from GPS measurements) and ~10 mm/yr (from seismic moments of large crustal earthquakes). We analyse jointly the gravity data from the new satellite missions CHAMP and GRACE, regional GPS observations and new seismic data to model structure of the crust and upper mantle and to identify the style and intensity of the tectonic processes, which are responsible for strong crustal deformations in the region. As a basis for the geodynamic modelling we use the new 3D seismic model of the Tien Shan lithosphere (Vinnik et al., 2004,2006), which is based on a joint inversion of P and S receiver functions for almost 40 local broadband seismograph stations. The new gravity, GPS and seismic data have been jointly analysed to construct a dynamic model of Tien Shan. The obtained results can be summarized in the following points: (1) We detect a very strong deflection of the Tien Shan lithosphere from isostatic equilibrium. The model of pure crustal shortening does not work in the studied area. The best fit of the modelling results is found for the model according to which the Tarim plate partially underthrusts Tien Shan; (2) It is necessary to assume partial detachment of the lithosphere if the present convergence rate was kept during all history of Tien Shan; (3) Large density-velocity anomalies in the upper mantle are found in the central part of the studied area. These anomalies could be a result of magmatic underplating during the initial stage of tectonic evolution; (4) The weak lithosphere, which is a result of magmatic intrusion, could be the factor that provoked growth of mountains after collision of India and Eurasia.
DE: 0520 Data analysis: algorithms and implementation
DE: 0545 Modeling (4255)
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly