Spatio-temporal change of seismic anisotropy in seismogenic zones

Since I recently started my post-doc I will present my thesis project that was about investigating the changes of seismic anisotropy in seismogenic zones. The work included the three different aspects of research: theoretical analysis, numerical investigation and application on real data. Seismic anisotropy can be induced by the alignment of crack distribution when subject to a stress field. Thus, it can be used as a stress meter in seismogenic zones. The first part of the project consisted of theoretical and numerical investigations in order to understand the effect of anisotropy on the propagation of surface waves, in particular on their polarization and to investigate its signature on the cross-correlation tensor. Results show that the polarization anomaly of surface waves in an anisotropic medium is very significant compared to travel time measurements. The second part of the project was devoted to the application to real seismic data. It consisted of developing the method for monitoring continuously seismic anisotropy using cross-correlation of ambient seismic noise and applying the method to different tectonic contexts, such as: the 2008 Iwate-Miyagi earthquake and the data of Mt. Fuji for the 2011 Tohoku earthquake.