非构造形变对GPS连续站位置时间序列的影响和修正

GPS观测得到的地壳形变场通常包含有构造形变与非构造形变二类信息, 去除其中的非构造形变信息对于有效运用GPS数据研究构造形变场至关重要. 本文运用国际卫星对地观测资料及各类地球物理模型, 定量计算海潮、大气、积雪和土壤水、海洋非潮汐4项负荷效应造成的地壳非构造形变, 并以此研究和修正这些非构造形变对中国地壳运动观测网络GPS基准站位置时间序列的影响. 研究发现此4项负荷效应, 特别是大气、积雪和土壤水, 对于测站垂向位置的影响显著. 通过模型改正可以使测站垂向位置的RMS降低～1 mm, 占其总量的～11％. 对于垂向时间序列的周年项部分, 这一改正可降低其振幅的37％. 研究还表明经过地球物理模型改正和周年、半周年谐波拟合改正的时间序列比起仅经过周年、半周年谐波拟合改正的时间序列更为平滑, 表明地球物理模型改正对于消除非构造形变场的作用不是周年、半周年谐波拟合改正所能替代的.

Effects of non-tectonic crustal deformation on continuous GPS position time series and correction to them

A crustal deformation field observed by GPS usually includes both tectonic and non-tectonic deformation signals, and it is vitally important to remove the non-tectonic deformation signals from the data in order to effectively use GPS observations to study tectonic deformation. Using the Earth satellite data and geophysical models, we calculate non-tectonic crustal deformation caused by ocean tide loading, atmospheric mass loading, snow and soil moisture mass loading, and non-tidal ocean mass loading. Based on the quantitative analyses, the effects of non-tectonic crustal deformation on the position time series of GPS fiducial stations from the Crustal Movement Observation Network of China are studied and corrected. Our study shows that these effects on the vertical components of station positions are remarkable, especially those resulted from the atmospheric mass loading and snow and soil moisture mass loading. Using these models to correct for the non-tectonic deformation, we have reduced the RMS of the station vertical position by about 1 mm, which is about 11% of the total RMS. The amplitudes of annual vertical position variations are also reduced by about 37%. Moreover, we find that the position time series corrected using geophysical models followed by an empirical fitting of annual and semi_annual variations are smoother than that corrected using the empirical fitting of annual and semi_annual variations only, indicating that geophysical model corrections can not be substituted by pure empirical fitting in removing the non_tectonic deformation effects.