Recent deformation in the Turan and South Kazakh platforms, western central Asia, and its relation to Arabia-Asia and India-Asia collisions

In this study, we investigate the recent and active tectonics of the Turan and South Kazakh platforms in western central Asia. This area, which has be en considered stable during the Tertiary, was struck in its eastern part (G azli and Kyzyl-Kum) by three earthquakes of magnitude Ms similar to 7.0 bet ween 1976 and 1984. From structural observations we show that in the Kyzyl- Kum, Cenozoic deformation on structures oriented NW-SE is dominated by dext ral strike-slip motion on a flower structure involving reactivated Late Pal eozoic faults. This deformation is compatible with the stress pattern induc ed by the Pamir/Tien Shan collision zone. At the scale of the Turan-South K azakh platform, comparison of repeated leveling measurements gives mean upl ift rates of 5 mm yr(-1) for most of the area south of the 44 degrees latit ude including the Kyzyl-Kum. These observations indicate that the Turan-Sou th Kazakh platform has been actively deforming since recent times (Pleistoc ene) in response to the collision of both India and Arabia with Asia. Earth quake data also reveal that propagation of deformation from the Kopet Dagh and the Pamir/Tien Shan collision zones into the Turan-South Kazakh platfor m is accommodated aseismically except in the Kyzyl-Kum. This might reflect differences in the deformation style and nature of the upper crust in the K yzyl-Kum and north of the Kopet Dagh respectively. We propose that the Gazl i earthquakes highlight the northwestward continuation, within the Turan-So uth Kazakh platform and along reactivated older structures, of the deformat ion related to the Pamir indentation and to a lesser degree to the Arabia-A sia convergence.