We present a full 3-D velocity field of the Earth's surface in the Euro

We apply a blind source separation algorithm to the ground displacement time series recorded at continuous Global Positioning System (GPS) stations in the European Eastern Alps and Northern Dinarides. As a result, we characterize the temporal and spatial features of several deformation signals. Seasonal displacements are well described by loading effects caused by Earth surface mass redistributions. More interestingly, we highlight a horizontal, nonseasonal, transient deformation signal, with spatially variable amplitudes and directions. The stations affected by this signal reverse the sense of movement with time, implying a sequence of dilatational and compressional deformation that is oriented normal to rock fractures in karst areas. The temporal evolution of this deformation signal is correlated with the history of cumulated precipitations at monthly time scales. This transient horizontal deformation can be explained by pressure changes associated with variable water levels within vertical fractures in the vadose zones of karst systems. The water level changes required to open or close these fractures are consistent with the fluctuations of precipitation and with the dynamics of karst systems.

[1] We present crustal deformation results from a geodetic experiment (Retreating-Trench, Extension, and Accretion Tectonics (RETREAT)) focused on the northern Apennines orogen in Italy. The experiment centers on 33 benchmarks measured with GPS annually or more frequently between 2003 and 2007, supplemented by data from an additional older set of 6 campaign observations from stations in northern Croatia, and 187 continuous GPS stations within and around northern Italy. In an attempt to achieve the best possible estimates for rates and their uncertainties, we estimate and filter common mode signals and noise components using the continuous stations and apply these corrections to the entire data set, including the more temporally limited campaign time series. The filtered coordinate time series data are used to estimate site velocity. We also estimate spatially variable seasonal site motions for stations with sufficient data. The RMS scatter of residual time series are generally near 1 mm and 4 mm, horizontal and vertical, respectively, for continuous and most of the new campaign stations, but scatter is slightly higher for some of the older campaign data. Velocity uncertainties are below 1 mm/yr for all but one of the stations. Maximum rates of site motion within the orogen exceed 3 mm/yr (directed NE) relative to stable Eurasia. This motion is accommodated by extension within the southwestern and central portions of the orogen, and shortening across the foreland thrust belt to the northeast of the range. The data set is consistent with contemporaneous extension and shortening at nearly equal rates. The northern Apennines block moves northeast faster than the Northern Adria microplate. Convergence between the Northern Apennines block and the Northern Adria microplate is accommodated across a narrow zone that coincides with the northeastern Apennines range front. Extension occurs directly above an intact vertically dipping slab inferred by previous authors from seismic tomography. The observed crustal deformation is consistent with a buried dislocation model for crustal faulting, but associations between crustal motion and seismically imaged mantle structure may also provide new insights on mantle dynamics.

In this work we present and discuss new geodetic velocity and strain-rate fields for the Euro-Mediterranean region obtained from the analysis of continuous GNSS stations. We describe the procedures and methods adopted to analyze raw GPS observations from >4000 stations operating in the Euro-Mediterranean, Eurasian and African regions. The goal of this massive analysis is the monitoring of Earth’s crust deformation in response to tectonic processes, including plate- and micro-plate kinematics, geodynamics, active tectonics, earthquake-cycle, but also the study of a wide range of geophysical processes, natural and anthropogenic subsidence, sea-level changes, and hydrology. We describe the computational infrastructure, the methods and procedures adopted to obtain a three-dimensional GPS velocity field, which is used to obtain spatial velocity gradients and horizontal strain-rates. We then focus on the Euro-Mediterranean region, where we discuss the horizontal and vertical velocities, and spatial velocity gradients, obtained from stations that have time-series lengths longer than 6 and 7 years, which are found to be the minimum spans to provide stable and reliable velocity estimates in the horizontal and vertical components, respectively. We compute the horizontal strain-rate field and discuss deformation patterns and kinematics along the major seismogenic belts of the Nubia-Eurasia plate boundary zone in the Mediterranean region. The distribution and density of continuous GNSS stations in our geodetic solution allow us to estimate the strain-rate field at a spatial scale of ∼27 km over a large part of southern Europe, with the exclusion of the Dinaric mountains and Balkans.

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