The Study Day Crustal Movement Characteristics Of Gps-based In Shaanxi Province

A Ms8.0 earthquake happened in Wenchuan County, Sichuan Province on May 12,2008. The high magnitude and large seismic intensity caused serious life and property loss. Shaanxi, located in the southern margin of ordos block, is one of the main regions of strong earthquake and tectonically deformed areas. It is therefore critical to analyse the influences of earthquake on crustal movement in Shaanxi. Based on the previous research and experience, utilizing the existing GPS observation data on crustal movement in Shaanxi from the 2^nd monitoring center of China Seismological Bureau, the author has studied the horizontal crustal movement, vertical deformation in Shaanxi and effects of Wenchuan earthquake. The results showed that:(1) Charactoristics of the horizontal crustal movement in Shaanxi: From 2001～2008, Shaanxi GPS network sites mainly moved to the south by east, which has no obvious differential movement. But it moved a little stronger at the west and east ends of Guanzhong basin. From 2006～2007, compared with the eurasian plate, Shaanxi region mainly moved to the south by east. The middle region of Guanzhong sites didn't show a unifed movement, but the direction of its two sides were consistent with Shaanxi area with a hith velocity. Compared with Yulin, the GPS sites showed parts divided movement with an obvious difference in the two sides. The west moved quickly to the south by west while the east to the south by east. From 2007～2008, compared with the eurasian plate, the western region of Guanzhong basin mainly moved to the east by north, the middle and eastern region to the east by south. Compared with Yulin, the GPS sites showed parts divided movement.(2) Charactoristics of the vertical crustal movement in Shaanxi: From 2006～2007, the settlement from south to north decreased gradually with a quantity from 10mm～15mm. From 2007～2008, the settlement from east to west increased gradually with a quantity from 5mm～10mm. But it declined after Tongchuan-Weinan.(3) Effects of Wenchuan earthquake on the crustal movement in Shaanxi: The velocity field from 2007～2008 showed the coseismic influence of Wenchuan quake that made the Shaanxi crust rotate to the north and that made the velocity of Guanzhongbasin and its two sides movements apparently higher than before. At the same time, theeffects on western Guanzhong were stronger than the eastern region. From 2007～2008,the vertical crustal movement of the overall and local areas didn't show inheritedmotion, which reflected the effects of Wenchuan earthquake.