The Effect and Correction of Non-Tectonic Crustal Deformation on Continuous GPS Position Time Series

Abstract

GPS observed crustal deformation usually includes both tectonic and non-tectonic deformation signals, and it is vitally important to remove the non-tectonic deformation signals in the data in order to effectively use GPS observations for tectonic deformation studies. Using the Earth satellite data and geophysical models, we calculate non-tectonic crustal deformation caused by the 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 due to 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 the effects resulting 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 1mm, 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 alone, indicating that the geophysical model corrections can not be substituted by pure empirical fitting in removing the non-tectonic deformation effects.