My research is part of the ITN project Tread, which aims to improve the knowledge on seismic hazard risk assessment in the Mediterranean area. Because earthquakes in tectonically active regions in Europe are frequent in carbonate bearing rocks, I aim to investigate the rheology of carbonates during the seismic cycle. To study the processes that happen during the flow to friction transition, I plan to conduct experiments in fluid saturated carbonate rocks and fault gouge with the rotary shear apparatus and the gas apparatus at the High Pressure and Temperature Laboratory (HPT Lab). Further, I want to do microstructural analysis to investigate the prevailing microphysical processes and improve existing paleo-piezometers to estimate stress conditions at earthquake nucleation depths. By combining microstructural analysis, friction and flow experiments and comparing the results to natural fault rocks I aim to link laboratory experiments and natural occurring processes. The outcome of this study will help to better understand the viscous-plastic to elasto-frictional transition and, consequently, aseismic to seismic behaviour.