Vertical GPS ground motion rates in the Euro‐Mediterranean region: New evidence of velocity gradients at different spatial scales along the Nubia‐Eurasia plate boundary

Abstract

[1] We use 2.5 to 14 years long position time series from >800 continuous Global Positioning System (GPS) stations to study vertical deformation rates in the Euro-Mediterranean region. We estimate and remove common mode errors in position time series using a principal component analysis, obtaining a significant gain in the signal-to-noise ratio of the displacements data. Following the results of a maximum likelihood estimation analysis, which gives a mean spectral index~À0.7, we adopt a power law + white noise stochastic model in estimating the final vertical rates and find 95% of the velocities within ±2 mm/yr, with uncertainties from filtered time series~40% smaller than from the unfiltered ones. We highlight the presence of statistically significant velocity gradients where the stations density is higher. We find undulations of the vertical velocity field at different spatial scales both in tectonically active regions, like eastern Alps, Apennines, and eastern Mediterranean, and in regions characterized by a low or negligible tectonic activity, like central Iberia and western Alps. A correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area. Glacial isostatic adjustment and weathering processes do not completely explain the measured rates, and a combination of active tectonics and deep-seated geodynamic processes must be invoked. Excluding areas where localized processes are likely, or where subduction processes may be active, mantle dynamics is the most likely process, but regional mantle modeling is required for a better understanding.

3-D GPS velocity field and its implications on the present-day post-orogenic deformation of the Western Alps and Pyrenees

“…This pattern of uplift is clearly limited to the region north of about 44.5 • N, whereas the southern French Alps and the foreland regions of the Rhone Valley and the French Jura show no vertical motion within ± 0.5 mm yr −1 . Our results are consistent with the uplift pattern identified by Serpelloni et al (2013) in the Western Alps (average difference at common sites of 0.05 ± 0.79 mm yr −1 ), although the higher station density in our solution allows a sharper definition of region affected by significant uplift. In contrast, no significant vertical pattern can be observed in the Pyrenees, where most stations show vertical velocities about ± 0.5 mm yr −1 .…”

“…To first order, horizontal deformation across the Alps and the Pyrenees is unresolvable at the level of GPS uncertainty, ∼ 0.5 mm yr −1 (Nocquet, 2012;Rigo et al, 2015;Vigny et al, 2002), although recent studies suggest small possible extension in the French Alps (Walpersdorf et al, 2015) and the western Pyrenees (Asensio et al, 2012;Rigo et al, 2015). In contrast, studies of vertical velocities from GPS data indicate significant uplift rates in the Western and Central Alps (up to ∼ 2 mm yr −1 ), decreasing toward the Eastern Alps (Serpelloni et al, 2013).…”

Slow strain waves in blocky geological media from GPS and seismological observations on the Amurian plate

“…At the two observation sites, the horizontal displacement components in the north-south direction are represented by in-phase curves that can be approximated by a sinusoid (Fig. 3a), which is consistent with the approximation suggested in Serpelloni et al (2013). The vertical and horizontal displacement components in the eastwest direction vary in an anti-phase manner during separate periods of measurements (Fig.…”

Spatiotemporal analysis of GPS time series in vertical direction using independent component analysis

“…Its corresponding spatial response values to each point have the same sign (positive or negative) and similar size. However, for a large network, the PCs with smoothed transition pattern of the spatial responses are also likely CME (Serpelloni et al 2013), as the PC2 shows in Fig. 4.…”