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Center for Nonlinear Studies |
The ability to study the nonlinear response of elastic materials to a cyclic deformation is strongly improved when changes of the material properties can be observed on a time scale that is shorter than the time scale of the deformation. This is achieved in Dynamic Acoustoelastic Testing and has provided new insight into the evolution of the material during dynamic softening. I will discuss a simple conceptual model to explain typical observations of DAET on the basis of inter-grain sliding. In the second part I will a present results of a fully natural field-scale DAET experiment performed with a single seismometer. In this experiment with use the ambient seismic noise as probe wave and the periodic deformation caused by of the solid Earth tides as pump. We observe velocity changes caused by different tidal constituents of sun and moon and changes related to the thermal radiation of the sun. Moreover we observe a nonlinear coupling between the perturbations due to tidal forces and solar radiation that excites velocity changes at the sum and difference frequencies.
Host: Esteban Rougier