Detecting seasonal and long-term vertical displacement in the North China Plain using GRACE and GPS
Linsong Wang1,2, Chao Chen1,2, Jinsong Du1, and Tongqing Wang31Hubei Subsurface Multi-scale Imaging Lab (SMIL), Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan, Hubei, China 2Three Gorges Research Center for Geo-hazard, Ministry of Education, China University of Geosciences, Wuhan, Hubei, China 3First Crust Deformation Monitoring and Administration Center, China Earthquake Administration, Tianjin, China
Received: 20 Oct 2016 – Accepted for review: 25 Oct 2016 – Discussion started: 25 Oct 2016
Abstract. We employ twenty-nine continuous Global Positioning System (GPS) time series data together with data from Gravity Recovery and Climate Experiment (GRACE) are analyzed to determine the seasonal displacements of surface loadings in the NCP. Results show significant seasonal variations and a strong correlation between GPS and GRACE results in the vertical displacement component; the average correlation and WRMS reduction between GPS and GRACE are 75.6 % and 28.9 %, respectively, when atmospheric and non-tidal ocean effects were removed, but the peak to peak annual amplitude of GPS (1.2 ~ 6.3 mm) is greater than GRACE-derived (1.0 ~ 2.2 mm). We also calculate the trend rate as well as the seasonal signal caused by the mass load change from GRACE data, the rate of GRACE-derived Terrestrial Water Storage (TWS) loss (after multiplying by the scaling factor) in the NCP was 3.39 cm/yr (equivalent to 12.42 km3/yr) from 2003 to 2009. For a 10-year time span (2003 to 2012), the rate was 2.57 cm/yr (equivalent to 9.41 km3/yr). Basing on spherical harmonic coefficients for the gravity field and load Love numbers, we use GRACE model to remove the vertical rates of elastic displacements due to the surface mass change from GPS data. An overall uplift for the whole region at the 0.04–1.47 mm/yr level from 2004 to 2009, but the rate of change direction is inconsistent in different GPS stations at −0.94–2.55 mm/yr level from 2010 to 2013.
Wang, L., Chen, C., Du, J., and Wang, T.: Detecting seasonal and long-term vertical displacement in the North China Plain using GRACE and GPS, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-552, in review, 2016.