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Environmental loading, in particular from continental water storage changes, induces geodetic station displacements up to several centimeters for the vertical components. We investigate surface deformation due to loading processes in South America using a set of 247 permanent GPS (Global Positioning System) stations for the 2003–2016 period and compare them to loading estimates from global circulation models. Unfortunately, some of the hydrological components, and in particular surface waters, may be missing in hydrological models. This is especially an issue in South America where almost half of the seasonal water storage variations are due to surface water changes, e.g., rivers and floodplains. We derive river storage variations by rerouting runoffs of global hydrology models, allowing a better agreement with the mass variations observed from GRACE (Gravity Recovery and Climate Experiment) mission. We extract coherent seasonal GPS displacements using Multichannel Singular Spectrum Analysis (M-SSA) and show that modeling the river storage induced loading effects significantly improve the agreement between observed vertical and horizontal displacements and loading models. Such an agreement has been markedly achieved in the Amazon basin. Whilst the initial models only explained half of the amplitude of GPS, the new ones compensate for these gaps and remain consistent with GRACE. [ABSTRACT FROM AUTHOR]

Abstract: We have organised afield study of ocean tide loading in the northwestern part of France, where tidal amplitudes are known to be among the highest in the world. GPS and gravimetric techniques have already proved their capability to measure such weak and high-frequency signals. In this study, these classical observations are complemented with less usual techniques, such as tiltmeter and Satellite Laser Ranging (SLR) measurements. We present here the preliminary results for a common period of observations spanning from 12–19 May 2004. Additional measurements from the French Transportable Laser Ranging Station (FTLRS) were available during September and October 2004. Observation residuals are computed as the difference between the observed and the predicted time signals. We obtain small RMS residuals for GPS measurements (2.5/3.1/4.5mm for the eastward, northward and upward components), for absolute and relative gravimetry (9nm/s2 and 13nm/s2) and for tiltmeters (0.05μrad for EW component). We also fit the amplitude of the main M2 tidal constituent to FTLRS observations and we find a value of 3.731cm, which is comparable to the theoretical value. [Copyright &y& Elsevier]

Abstract The rate of seismic activity around lake Nasser rapidly increased after the creation of the High Dam. The largest earthquake was of magnitude M L 5.6 ; it occurred on November 14th 1981, 60 km southwest of the Aswan High Dam. We use 16 years of GPS measurements collected around the northern part of lake Nasser, represented by 27 GPS sites, plus eight years of Envisat SAR scenes, 35 descending scenes, to estimate the recent ground movement of this area. GPS and InSAR showed a land subsidence localized around lake Nasser. The subsidence has a magnitude of 1–2 mm/yr. Therefore, we model the Earth's response to water level changes, using full daily water level variations starting from 1982 to 2016. Our loading model captures a similar deformation pattern, like ones estimated from GPS and InSAR, around the lake with comparable amplitudes. With respect to stable Nubia, most of GPS sites around the lake show a negligible North to Northeast motion of <1 mm/yr. Along Kalabsha fault, we estimate a strike-slip motion with an extension component of 0.6 mm/yr. GPS sites around Sayal fault do not show any differential motion along the fault in both fault-parallel and fault-normal components. The InSAR result would not be able to capture the deformation at Kalabsha and Sayal region, since the deformation in this area is <1 mm/yr. Highlights • We used 16 years of GPS data with 8 years of Envisat SAR scenes to estimate the ground motion around lake Nasser, Egypt. • Based on InSAR and GPS velocities, we estimated a land subsidence of 1–2 mm/yr around the lake. • We regarded the deformation in the vicinity of the lake to the viscoelastic respond to the lake level variations. • In Nubia fixed frame, GPS sites show a negligible motion of less than 1 mm/yr toward North to Northeast direction. [ABSTRACT FROM AUTHOR]