13:45 〜 14:00
[G01-3-02] Three Dimensional Strain-Rate Field from Geodetic Measurements on the Surface
Geodetic measurements for strain determination are in many cases carried out at the Earth's surface, thus topologically remaining in a 2D manifold. Even though changes in the third component are determined e.g. by levelling it will hardly be possible to determine the real 3D strain. Our method circumvents this problem by introducing a crustal model. Even simple models help and deliver quite realistic results as shown in this paper. In the case of Switzerland, however, this remains very demanding because of the very small yearly movements generating equivalently small yearly crustal distortions at a maximum of 25 nstrain per year.
The available time series of GNSS and levelling measurements acquired and treated by the Swiss office of topography, are sufficiently long to reveal deformations in Switzerland. They make it possible to determine a coherent kinematic deformation field of Switzerland by geodetic means.
Further development of the ‚Adaptive Least-Square Collocation (ALSC)‘, which was devised at ETH, and the implementation of a physical crustal model made it possible to directly calculate a three dimensional strain tensor field out of the available measurements e.g. GPS and levelling. The geodetically determined strain-tensors are verified versus focal mechanisms obtained from seismological data. The mechanism of a recently induced earthquake mechanism in the region of St. Gallen close to a geothermal test site is in agreement with the strain tensors determined by GPS-data. The described method can also be applied to more local events, e.g. the analysis of subsidence or landslides. It will allow to gain more insight into subsurface processes from geodetic measurements.
The paper presents the method and shows results of geodetic determination of strain field in the complex tectonic setting of the Swiss Alps.
Project partly funded by the Swiss Nat. Sci. Foundation and the Competence Center Environment and Sustainability of ETH Domain (CCES), and swisstopo.
The available time series of GNSS and levelling measurements acquired and treated by the Swiss office of topography, are sufficiently long to reveal deformations in Switzerland. They make it possible to determine a coherent kinematic deformation field of Switzerland by geodetic means.
Further development of the ‚Adaptive Least-Square Collocation (ALSC)‘, which was devised at ETH, and the implementation of a physical crustal model made it possible to directly calculate a three dimensional strain tensor field out of the available measurements e.g. GPS and levelling. The geodetically determined strain-tensors are verified versus focal mechanisms obtained from seismological data. The mechanism of a recently induced earthquake mechanism in the region of St. Gallen close to a geothermal test site is in agreement with the strain tensors determined by GPS-data. The described method can also be applied to more local events, e.g. the analysis of subsidence or landslides. It will allow to gain more insight into subsurface processes from geodetic measurements.
The paper presents the method and shows results of geodetic determination of strain field in the complex tectonic setting of the Swiss Alps.
Project partly funded by the Swiss Nat. Sci. Foundation and the Competence Center Environment and Sustainability of ETH Domain (CCES), and swisstopo.