Host institution: GFZ (GeoForschungszentrum) Helmholtz Centre Potsdam
|main supervisor:||Christoph Sens-Schönfelder (GFZ, D)|
|co-supervisors:||Georg Dresen (GFZ, D)|
This position is filled
Time-dependent monitoring of seismic velocity changes in the past decade has shown that the velocity of seismic waves is not constant but varies in response to a number of external drives like precipitation, temperature and deformation from passing seismic waves. Especially the systematic decrease of elastic wave velocities during dynamic deformation and the subsequent recovery that may last for months to years are of interest potentially providing a window into physical processes affecting hazard relevant material properties.
Within SPIN we investigate the different expressions of the complex mechanical behavior of heterogeneous materials in laboratory experiments to develop an empirical and physical description of time variable material properties. A calibrated setup allows to jointly observe changes in wave velocity, attenuation, waveform distortion together with changes in static modulus - both in the fast damage phase when the material is loaded and during the slow recovery phase. Using static loading as well as dynamic loading with oscillatory strain are expected to lead to a strain and strain-rate dependent model for the damage and recovery processes.
The developed concepts are tested against centimeter scale rock-laboratory observations, measurements on meter scale concrete specimens and seismological observations on the decameter to kilometer scale. The results will aid the interpretation of seismological field observations of nonlinear effects in terms of mechanical property changes and may improve time dependent assessment of natural hazards related to material failure.