川藏地区质量负荷地表形变特性分析

Surface deformation characteristics of mass loading in the Sichuan-Xizang region

针对大气、水文等地表负荷的重新分配会引起地壳发生弹性形变,分析其形变规律并在GNSS坐标时间序列中予以精确剔除的问题,该文基于德国地球科学研究中心(GFZ)发布的地表质量负荷形变格网模型,获取我国川藏地区60个测站10年内的非潮汐大气负荷位移和水文负荷位移,对地表负荷形变的量级和周期性规律进行分析。结果表明:研究区域非潮汐大气负荷和水文负荷的形变量级总体相当,水文负荷形变略大于非潮汐大气负荷;两类负荷垂向形变均显著大于水平方向,最大垂向位移均可达到厘米级;对于各类质量负荷形变的地理分布,非潮汐大气负荷形变受海拔影响显著,呈“东大西小”分布,水文负荷形变则随着纬度的降低有逐渐增大的趋势。两类负荷形变均具有显著的年周期和半年周期特性,年周期信号强度大于半年周期信号;西藏和四川两地区在水平南北向和垂向年内形变极值对应的时间分布总体一致,而在水平东西向不一致甚至相反,形变季节性规律与各地气温、降水等自然因素相关。质量负荷形变对川藏地区影响显著,在GNSS坐标时间序列数据处理中应重点关注。

The redistribution of surface mass loadings, such as atmospheric loading and hydrological loading, will cause elastic crustal deformation and it is an important source of non-tectonic deformation of the earth's surface. Analyzing mass loading deformation and eliminating it accurately from the GNSS coordinate time series are of great significance for providing accurate datum maintenance, location services and geophysical interpretations. Based on the surface mass loading deformation grid model provided by GFZ German Research Centre for Geosciences, we obtain the non-tidal atmospheric loading displacement and hydrological loading displacement of 60 stations in the Sichuan-Xizang region for 10 years and analyze their magnitude and periodicity. The results show: The non-tidal atmospheric loading deformation and the hydrological loading deformation are generally at the same level and the hydrological loading deformation is slightly larger than the non-tidal atmospheric loading deformation. The vertical deformation of both types of loading is significantly larger than that in the horizontal directions, and the maximum vertical displacement can both reach the centimeter level. For the geographical distribution, the non-tidal atmospheric loading deformation is significantly affected by the altitude with a distribution of “large in the east and small in the west”,while the deformation of the hydrological load tends to increase with the decrease of latitude. Both types of loading deformation have significant annual and semiannual periodic characteristics, and the intensity of the annual signals is greater than that of the semiannual signals. The time spans corresponding to the extreme values of deformation within a year in Xizang and Sichuan are generally consistent in the horizontal north-south direction and vertical direction, while they are inconsistent or even opposite in the horizontal east-west direction. The seasonal variations of deformation are related to natural factors such as temperature and precipitation in different regions. The mass loading deformation has a significant impact on the Sichuan-Xizang region, which deserves attention during the GNSS coordinate time series processing.