STRAIN · fault STRength breAkdown and Implications for earthquake Nucleation

fault STRength breAkdown and Implications for earthquake Nucleation

Most earthquakes are generated along pre-existing faults that suddenly fail after prolonged periods of tectonic stressing. Indeed, an earthquake is generated by the imbalance between the elastic energy provided by the rocks surrounding the fault and the strength drop of the fault itself, which is degraded by progressive slip. A large number of experimental and geophysical data well characterize the first-order resistance of the rocks either before (“static” strength) or after the initiation of seismic slip (“dynamic” strength). However, there is a fundamental lack of understanding about how exactly the fault strength decrease slip (STRAIN weakening) and about the real elasticity of the rock masses around the fault, i.e. the “spring” that triggers the earthquakes. Our ability to limit the societal and economic impact of the earthquakes is strongly tied to our understanding of the physics lying behind the earthquake phenomenology. The objective of this project is the systematic study of the changes in rock strength with progressive strain using two world-class deformation apparatuses hosted at Durham University, integrating a wide range of microstructural observations and potentially lab seismology to have insights into the microphysics of deformation. This multidisciplinary study will provide laboratory datasets to formulate new strain-dependent rheological laws applicable to the upscaling of brittle rock deformation from the laboratory to the field and, for the first time, will provide a dataset on real fault rocks elasticity at earthquake nucleation conditions. In the process, we will improve the present conceptual framework to understand the dynamics of earthquake nucleation, including the potential study of seismic precursors.

Data: CORDIS, © European Union