Recent Geodynamics Upper Rhine Graben

Background

The Upper Rhine Graben (URG) is Germany's most prominent part of the European Rift System, which crosses the entire continent from the North Sea to the Mediterranean Sea.  The main formation phase of the ORG is in the Eocene to the Miocene, i.e. about 50 to 20 million years ago.

While in the Eocene a dominant northwest-southeast extension of the URG can be observed, today there is a sinistral strike-slip fault. Evaluations of GNSS time series (Global Navigation Satellite Systems), levelling and interferometric radar images (InSAR) performed at GIK show that tectonically induced subsidence of the inner trench of 0.5 to 0.8 mm/a still exists today.  Also the vertical surface velocities are in the range of sub-mm/a.

State of research

The individual geodetic methods - InSAR, levelling and GNSS - have certain advantages and disadvantages, some of them complementary. The GIK is working on the development and improvement of a methodology for the fusion of these procedures in order to make the best possible use of the advantages of each individual procedure. The spatial components, which can be well resolved by the individual methods, and the spatial coverage play a major role:

The current results of the 3D velocity field in the ORG are based on levelling data dating back to the 19th century; the GNSS time series originate from 85 permanent stations of the GURN project from the years 2002 to 2011; data from the ERS-1 & ERS-2 satellite missions and the Envisat satellite mission are included in the SAR interferometric analysis.

Current work

Currently, GIK is working on verifying the calculations of the velocity field using radar images of the Sentinel-1 satellite mission, which has been operational since 2014, longer time series of the GURN stations as well as time series of additional GNSS stations and on extending the investigation area to the north and south.

In view of the results so far, two questions are currently of central importance:

• Is it possible to separate anthropogenic from tectonic surface signals?

• Which statements can be made about tectonic processes in deeper layers of the earth using the 3D velocity field of the surface?

To answer these questions, the deformation processes are reconstructed using the finite element method.

Literature

• Fuhrmann, T. (2016): Surface Displacements from Fusion of Geodetic Measurement Techniques Applied to the Upper Rhine Graben Area. Dissertation, doi: 10.5445/IR/1000056073 2016.
• Fuhrmann, T., Caro Cuenca, M., Knöpfler, A., van Leijen, F.J., Mayer, M., Westerhaus, M., Hanssen, R.F., Heck, B. (2015): Estimation of small surface displacements in the Upper Rhine Graben area from a combined analysis of PS-InSAR, levelling and GNSS data. Geophysical Journal International, 203 (1): 614-631, doi: 10.1093/gji/ggv328.
• Fuhrmann, T., Zippelt, K., Heck, B. (2014): Historische Nivellements aus Preußen und Baden und ihre Bedeutung für die Bestimmung von Vertikalbewegungen im Oberrheingrabengebiet. Zeitschrift für Vermessungswesen (zfv), 139 (6), 389-397.
• Fuhrmann, T., Westerhaus, M., Zippelt, K, Heck, B. (2014): Vertical displacement rates in the Upper Rhine graben Area derived from precise leveling. Journal of Geodesy, Volume 88, Issue 8, pp 773-787, doi: 10.1007/s00190-014-0721-0.
• Fuhrmann, T., Heck, B., Knöpfler, A., Masson, F., Mayer, M., Ulrich, P., Westerhaus, M., Zippelt, K. (2013): Recent surface displacements in the Upper Rhine Graben - Preliminary results from geodetic networks. Tectonophysics, Special Issue "TOPO-EUROPE III", 602(0):300 – 315, doi: 10.1016/j.tecto.2012.10.012.