渭河盆地现今三维地壳运动及断裂活动性研究

Present Crustal Motion in Three-Dimensional Orientations and Fault Activities in Weihe Basin

渭河盆地GPS(1990～2015年)水平运动速率为4.3～11.6mm/a,方向在107.8°E和110.5°E依次由西部的SEE转为中部的SE及东部的近E向。1980～2014年水准资料揭示,该地区垂向以继承性运动为主,速率-4.6～6.2mm/a。鄂尔多斯地块以3mm/a抬升,内部差异运动小于1mm/a;盆地相对其以5mm/a下沉,相对秦岭以4mm/a下沉。垂向运动在凹陷和凸起区表现为四象限特征,断块/断裂交接处差异运动大、地震多发,西、南部断裂活动大于东、北部。岐山-马召等断裂以差异运动为主,渭河断裂中段达5mm/a,其他断裂在3mm/a以内。

We analyze the 3-D deformation observed by GPS(1990~2015)and precise leveling(1980~2014)in Weihe basin.The results show the horizontal movement rates are 4.3~11.6 mm/a and the directions change in the vicinity of 107.8°and 110.5°E from SEE in western,to SE in central,and E in eastern basin.The vertical movement in more than 30 years shows priority to inherited movement at the rates-4.6~6.2 mm/a relative to ITRF2008.There are obvious differential movements between the basin and mountain,the different block in the basin.The Ordos block moves upward at a rate of 3 mm/a as a stable block within a differential rate of 1 mm/a.With respect to central Ordos,Weihe basin is undergoing subsidence at a rate of 5 mm/a,while at Qinling the subsidence rate is about 4 mm/a.The upward and downward movements present four quadrants:Xi’an and Gushi sag,while Lishan and Xianyang uplift.The big differential movement and quake-hit area appear in the intersection of faults or blocks.The activities of the faults in the western and southern basin are stronger than those in the eastern and northern regions,based on the observations in the cross-faults.Based on the data of leveling profiles on a long timescale,the major activities of the Qishan-Mazhao,Qinling,Huashan and Weihe faults are normal slip.The rates are up to 5 mm/a in the central Weihe fault which is divided into Xi’an sag and Xianyang uplift,while the slip rates of other faults are within 3 mm/a.