PRESENT-DAY CRUSTAL MOVEMENT OFNORTH-EASTERN QINGHAI-TIBET PLATEAU

GPS observations of CMONOC and other network reveal that, relative to Dingxin fiducial station in Alashan block, the crustal movements of north-eastern Qinghai-Tibet plateau and its adjacent regions have the following characteristics: (i)The western part of Qilian block is shortening and moving mainly northeastward, the 8 mm/a motion of southern margin of Qaidam basin is almost completely absorbed by compressed subsidence of Qaidam basin and uplift of Qilian mountain; (ii) Eastern part of Qilian block manifests itself mainly as block-like rotation or extrusion along Haiyuan left-lateral fault,with an angular velocity of 0.135 /Ma; (iii) Due to the clockwise rotation of the eastern Qilian sub-block in the NW Liupanshan range, Ordos block shows a slight anticlockwise rotation; (iv) Haiyuan left-lateral fault and northern edge thrust fault of Qilian mountain jointly constitute the major northeastern boundary of Qinghai-Tibet plateau judging from the present-day crustal movement.