Earthquake induced rotational ground motions
Final Report Abstract
This project focused on progress on all aspects of measuring, analysing, and interpreting rotational ground motions. The most spectacular result is the emergence of ocean generated Love waves in the ring-laser records at the Fundamentalstation in Wettzell, Kötzting. After a considerable improvement of the data acquisition system the sensitivity improved substantially which led to the first observation of the Earth’s free oscillations on a rotation sensor (previous project phase) followed by the recognition of Love waves in the microseismic frequency band. This opens interesting opportunities in connection with the understanding of the ocean generated noise field that is now used widely for seismic tomography and the detection of time-dependent structural changes (e.g. after earthquakes or before and after volcanic eruptions). The generation of Love waves in the oceans is currently not understood at all. There is currently no standard instrument for measuring broadband observations (like the STS2 for translations). By comparing different sensor technologies we could identify that the fibre-optic principle is the most promising technology to pursue. In addition, we addressed a fundamental theoretical question for the first time: the coupling of strain and rotations in heterogeneous media. We could forecast under what conditions this coupling may be relevant.
Publications
- Examining ambient noise using colocated measurements of rotational and translational motion, J Seismol (2012) 16:787–796
Hadziioannou, C., P. Gaebler, U. Schreiber, J. Wassermann , H. Igel
(See online at https://doi.org/10.1007/s10950-012-9288-5) - Rotational sensors - a comparison of different sensor types, J Seismol (2012) 16:595–602
Bernauer, F., Wassermann, J., Igel, H.
(See online at https://doi.org/10.1007/s10950-012-9286-7) - Strain rotation coupling and its implications on the measurement of rotational ground motions, J. Seismol (2012), 16, no. 4, 657–668
van Driel, M., J. Wassermann, M. F. Nader, B. S. A. Schuberth, and H. Igel
(See online at https://doi.org/10.1007/s10950-012-9296-5)
