基于GPS的陕西地区现今地壳运动特征研究

【作者】 李超；

【导师】 李天文；

【作者基本信息】 西北大学 ， 地图学与地理信息系统， 2009， 硕士

【摘要】 2008年5月12日四川省汶川县发生了8级地震,此次地震震级高、烈度大,使人们的生命财产遭受重大损失。陕西地区位于鄂尔多斯块体南缘,是我国重要的强震活动和构造变形区之一,分析此次地震对陕西地区地壳运动的影响十分必要。本文总结前人研究成果,利用陕西省地震局震后对陕西地区地壳形变的GPS观测资料和已有的数据,对陕西地区地壳水平运动和垂直形变以及汶川地震对其的影响进行了研究,结果表明:(1)陕西地区地壳水平运动特征:2001～2008年期间,陕西地区整体以南东向运动为主,关中盆地东西两端运动速率稍大,但总体上站点之间差异运动不明显;2006～2007年期间,相对欧亚板块,陕西地区整体以南东向运动为主,其中关中地区中部站点运动方向较为凌乱,两侧与陕西地区整体运动方向基本一致且速率较大;相对榆林站点,陕西地区地壳呈现分块式运动特征,两侧运动方向有明显差异,且速率较大,西部以南西向运动为主,东部以南东向运动为主。2007～2008年期间,相对欧亚板块,关中盆地西部以东北向运动为主,中、东部则以东南向运动为主,站点差异运动明显;相对榆林站点,陕西地区地壳水平运动整体连续性变化不明显,关中西部以东北向运动为主,渭河盆地内部GPS站点运动方向较散乱,但整体呈现出东北向运动趋势,关中地区东部运动速率较小,以南东向为主。(2)陕西地区地壳垂直运动特征:2006～2007年间,由南向北沉降量逐渐减少,沉降量主要集中在10mm～15mm之间;2007～2008年期间,由东向西沉降量逐渐增加,过了铜川-渭南一线后沉降量又逐渐减少,沉降量主要集中在5mm～10mm之间。(3)汶川地震对陕西地区地壳运动的影响:2007～2008年的速度场总体反映了汶川8.0级地震的同震影响,使得陕西地壳整体向北旋转。同时显示,对关中西部的影响明显大于东部,而且关中盆地及其两侧向东运动的速率与往年相比也有明显增大。2007～2008年陕西地区整体与局部地区地壳垂直运动均不再出现继承性运动趋势,基本反映了汶川地震的影响。更多还原

【Abstract】 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.更多还原