Intraplate deformation in western Europe deduced from an analysis of the International Terrestrial Reference Frame 1997 (ITRF97) velocity field

Abstract

Abstract. Although tectonic deformation in western Europe is essentially concentrated in the Appenines and Alpine (Alps, Pyrenees) mountain ranges, several large historical and instrumentally recorded earthquakes (M>6) are known in the supposedly "stable" part of Europe. Because of its accuracy and internal consistency at a global scale, the International Terrestrial Reference Frame 1997 (ITRF97) velocity field allows testing of intraplate rigidity in western Europe at a millimeter per year level. Using the full statistical information available on the ITRF97 velocities, we identify a subset of sites located in central Europe that satisfies a rigid cap rotation with residual velocities <1 mm/yr and therefore provide a stable europe reference fYame (SERF). In this reference frame we find residual velocities at European ITRF sites that are consistent with known active tectonic features. We identify a northward motion at sites located in Italy, with internal deformation of the Adriatic block rather than rigid plate motion and a westward motion of the westernmost part of Europe of the order of 1-2 mm/yr relative to central Europe. The relative motion of the Adriatic block and western Europe agrees with the current extension known in the Tyrrhenian sea and the Apennines. In central Europe, we find active deformation < 1 mm/yr in the eastern Alps and western Carpathians. In the Alpine range our results indicate E-W extension across the western Alps and N-S compression across the central and eastern Alps, in agreement with the strain regime deduced from seismotectonic observations. In Belgium and the Netherlands we find residual velocities of 1-1.5 mm/yr to the northwest at all the sites, most likely accommodated along the Upper and Lower Rhine Graben structures. An important outcome of this study is the identification of internal deformation of the order of 1-2 mm/yr in an area usually interpreted as "stable" Europe. This result should be further checked as new, denser, and more accurate space geodetic data sets with longer observation time spans, become available for Europe.

Evidence for a post-3.16-Ma change in Nubia–Eurasia–North America plate motions?

“…This seems less likely for the Eurasian and North American plates, for which the de¢nition of the stable plate interiors is now relatively well understood thanks to the numerous, long-operating continuous geodetic stations on both plates (e.g., [16,17,26]). We also note that our results and those of the REVEL geodetic model [10] agree well, even though the underlying data, processing strategies, data time spans, and sites used to de¢ne the Eurasian and North American plates all di¡er.…”

“…1, top). In order to ¢nd the sites that best satisfy the condition of plate rigidity for each of the Nubian, Eurasian, and North American plates, we repeatedly inverted horizontal GPS velocities for each of these plates while searching for the combination of site velocities that are best ¢t by a single angular velocity vector, using M 2 tests and minimal variance criteria [16,17]. By doing so, we obtain angular velocity vectors for all three Fig.…”

Tectonics, climate, and mountain topography

“…[92] Pyrenees (France, PYR): No resolvable movement of continuously recording GPS sites in Western Europe [Nocquet and Calais, 2003;Nocquet et al, 2001] puts a maximum rate of movement across the Pyrenees of 0.6 mm/yr. We assume that no shortening across the range: 0 AE 0.6 mm/yr.…”

Regularized estimation of Euler pole parameters

“…The multicollinearity in the estimation of Euler vectors is often coupled with errors which come from the non-rigid behavior of the sites. Up to 3-4 mm/yr residuals are common after removing the Euler rotation from the site velocities (Qiang et al, 1999;Nocquet et al, 2001;Aktug et al, 2009b). The multicollinearity in the estimation problems is often handled with TykhonovPhillips regularization (Tykhonov, 1963;Phillips, 1962).…”

“…The Euler parameterization of tectonic plate motions provides an indispensible tool for modeling the rigid plates where the deformation along the plate boundaries are neglected or assumed comparatively small (McClusky et al, 2000;Nocquet et al, 2001;Aktug et al, 2009a, b). Even in those models which take the deformation along plate boundaries into consideration, the Euler parameterization is still employed with the compensation of the deformation Copyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.…”