利用GRACE、GPS和水准数据研究西秦岭地区现今地壳垂直运动特征

利用GRACE卫星数据改正GPS连续站垂向位移时间序列中的周期变化,用主成分分析方法消除区域共模噪声误差,计算获取西秦岭地区GPS连续站的垂直运动速率,并将其作为速率参考基准,联合水准观测资料基于线性动态平差模型,处理得到西秦岭地区现今地壳垂直运动速度场。结果显示,西秦岭整体处于差异性的快速隆升,主要是由青藏高原东北缘的地壳缩短作用所致。六盘山和天水南侧均以3mm/a速率抬升,是本区上升最快的地方;其次是陇西地块和鄂尔多斯地块南部,分别以2mm/a和1mm/a的速率上升;秦岭造山带和渭河盆地的西部表现为下沉,但渭河盆地下沉最快。西秦岭现今地壳垂直运动可能暗示青藏高原东北缘的现今横向逃逸运动通道已从早期的西秦岭-秦岭地块向北转移到六盘山构造带、鄂尔多斯地块南部。

Crustal Vertical Movement of the West Qinling,Derived from GRACE,GPS and Leveling Data

We use GRACE-derived seasonal variations to correct GPS vertical annual and semi-annual displacements and principal component analysis(PCA) method to filter out the common mode errors. Vertical velocities of GPS sites in the west Qinling are estimated. The precise leveling data observed since 1970 are collected, and the GPS vertical rates are employed as a priori constraints to define the reference frame. Based on linear dynamic adjustment, the present crustal vertical velocity field of the west Qinling is acquired. The results suggest that most regions of the west Qinling uplift rapidly with different rates, which is caused by the crustal shortening of the northeastern Tibetan plateau. The Liupanshan and south of Tianshui uplift at rates of 3 mm/a, the Longxi block and southern Ordos block uplift at rates of 2 mm/a and 1 mm/a, respectively. The west sections of Qinling mountains and Weihe graben show subsidence, but the Weihe graben subsides faster. The present crustal vertical movement of west Qinling implies that the current eastward extrusion of the northeastern Tibetan plateau transfers from west Qingling-Qinling mountains to Liupanshan and southern Ordos block.