GPS监测的中国及其周边现时地壳形变

利用多个全国性的GPS监测网、中国地壳运动主要活动带的区域性GPS监测网以及亚太地区大地测量计划(APRGP)的GPS监测网自1991年以来近10年的GPS资料,通过旋转变换将不同方法得出的各个子网的速度解进行统一,给出一个自恰的、完整的ITR一7框架下的速度场综合解.为了研究中国现时地壳运动在欧亚板块内形变的特征,基于一个现时板块运动模型ITRF97VEL,给出了3类网共260多个站的形变速度场.结果表明中国地壳运动有明显的不均匀性,以南北地震带为界,西强东弱;中国西部受印度板块强烈的冲挤,地壳运动由南向北逐渐减慢,呈现南北向缩短,东西向伸展,有明显的块体特征;喜马拉雅和天山西部分别提供了约15mm/a和9-13mm/a的汇聚速率;拉萨块体有(20.2±1.2)mm/a的伸长;喀喇昆仑一嘉黎断裂的右旋走滑速率和阿尔金断裂的左旋走滑速率分别为2-3mm/a和4-6mm/a,穿过龙门山断裂带的缩短速率小于7mm/a,这些都支持地壳增厚学说;沿阿尔金断裂带到喜马拉雅存在一个NNE弥散带,它是形变速度有东和西分量的分界线,是一个有特殊意义的动力学带.中国东部以走滑为主,东北块体是中国最稳定的地区,华北块体具有较大走滑性,是东部较易变形区.

PRESENT-TIME CRUSTAL DEFORMATION IN CHINA AND ITS SURROUNDING REGIONS BY GPS

Applying recent 10 year GPS measurement data from several nationside GPS networks, serveral regional GPS monitoring networks and the Asia Pacific Regional Geodetic Project （APRGP）, we give out a combined and consistent velocity field solution in ITRF97 by rotation transformation of regional GPS network results. In order to study the characteristics of present time intra plate crustal deformation of China, we have constructed a new present time plate motion model named ITRF97VEL. The model can better describe present time features of global plate motion than the geological model NNR NUVEL1A. Based on ITRF97VEL, deformation velocities of more than 260 GPS sites are determined. The results show that the crustal motion is very inhomogenous. The crustal deformation in the west of China is far stronger and more complicated than that in the east of China, taking the N S seismic belt of China as a boundary. The deformation velocity gradually reduces from south to north in the west of China by energy release in several W E direction arc suture zones. The Qinghai Xizang plateau is shortening in north south direction and extending in west east direction due to the strong shove of Indian plate. The shortening of about 15mm/a and 9\₁3mm/a is accommodated across Himalayan block and the west Tianshan, respectively. Between the longitudes of 80°E to 91°E in southern Tibet, there is E W extension of 20.2±1.2mm/a. The slip rates of KJFZ in south Qinghai Xizang plateau and Altun Tahg fault are 2\₃ mm/a and 4\₆mm/a, respectively. Our GPS results indicate that there is a shortening of less than 7 mm/a within the Longmen shan. These results support the supposition of crustal thickening.