PRESENT-DAY CRUSTAL MOVEMENT OF NORTH-EASTERN QINGHAI-TIBET PLATEAU

1　IntroductionEnclosedbyBayankalablockatsouth ,Alashanblockatnorth ,Tarimblockatwest,OrdosatnortheastandSouthChinablocksateast,thenorth easternQinghai Tibetanplateau ,geologicallynamedasQilianblockanditsadjacentarea ,isanidealre gionforstudyingcontinentaldynamics,suchascrustalthickening ,extrusionandblockinteraction(Fig .1 ) .ThetectonicmovementsofnortheasternQinghai Tibetanplateau ,thestrongnappe (thrust ing)movementofnorthernQilianmountainandtheextensiveleft lateralslipalongQilian Hai…

PRESENT-DAY CRUSTAL MOVEMENT OF NORTH-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.