Present-day surface deformation of the Alpine region inferred from geodetic techniques
Authors: Sánchez Laura , Völksen Christof , Sokolov Alexandr , Arenz Herbert , Seitz Florian 
Published: August 2018

Abstract. We provide a present-day surface-kinematics model for the Alpine
region and surroundings based on a high-level data analysis of about 300
geodetic stations continuously operating over more than 12 years. This model
includes a deformation model, a continuous surface-kinematic (velocity)
field, and a strain field consistently assessed for the entire Alpine
mountain belt. Special care is given to the use of the newest Global Navigation Satellite Systems
(GNSS) processing standards to determine high-precision 3-D station coordinates. The
coordinate solution refers to the reference frame IGb08, epoch 2010.0. The
mean precision of the station positions at the reference epoch is ±1.1 mm in N and E and ±2.3 mm in height. The mean precision of the
station velocities is ±0.2 mm a−1 in N and E and ±0.4 mm a−1 in height. The deformation model is derived from the point-wise station
velocities using a geodetic least-squares collocation (LSC) approach with
empirically determined covariance functions. According to our results, no
significant horizontal deformation is detected in the Western Alps, while
across the Southern and Eastern Alps the deformation vectors describe a
progressive eastward rotation towards Pannonia. This kinematic pattern also
makes evident an increasing magnitude of the deformation from 0.1 mm a−1 in
the western part of Switzerland up to about 1.3 mm a−1 in the Austrian Alps.
The largest shortening is observed along the southern front of the Eastern
Alps (in the northern area of the Venetian-Friuli Basin) and in the northern
part of the Apennine Peninsula, where rates reach 2 and 3 mm a−1,
respectively. The average accuracy of the horizontal deformation model is
±0.2 mm a−1. Regarding the vertical kinematics, our results clearly
show an ongoing average uplift rate of 1.8 mm a−1 of the entire mountain
chain, with the exception of the southern part of the Western Alps, where no
significant uplift (less than 0.5 mm a−1) is detected. The fastest uplift
rates (more than 2 mm a−1) occur in the central area of the Western Alps, in
the Swiss Alps, and in the Southern Alps in the boundary region between
Switzerland, Austria, and Italy. The general uplift observed across the
Alpine mountain chain decreases towards the outer regions to stable values
between 0.0 and 0.5 mm a−1 and, in some cases, to subsidence like in the
Liguro-Provençal and Vienna basins, where vertical rates of −0.8
and −0.3 mm a−1 are observed, respectively. In the surrounding region, three
regional subsidence regimes are identified: the Rhône-Bresse Graben with
−0.8 mm a−1, the Rhine Graben with −1.3 mm a−1, and the Venetian-Friuli Basin
with −1.5 mm a−1. The estimated uncertainty of our vertical motion model
across the Alpine mountain belt is about ±0.3 mm a−1. The strain field
inferred from the deformation model shows two main contrasting strain
regimes: (i) shortening across the south-eastern front of the Alps and the
northern part of the Dinarides and (ii) extension in the Apennines. The pattern
of the principal strain axes indicates that the compression directions are
more or less perpendicular to the thrust belt fronts, reaching maximum
values of 20×10-9 a−1 in the Venetian-Friuli and Po basins.
Across the Alpine mountain belt, we observe a slight dilatation regime in
the Western Alps, which smoothly changes to a contraction regime in western
Austria and southern Germany, reaching maximum shortening values of 6×10-9 a−1 in north-eastern Austria. The numerical results of
this study are available at https://doi.pangaea.de/10.1594/PANGAEA.886889.