MAL6a

Experimental rock deformation research plays an important role in understanding the mechanical behavior, deformation microstructures, and physical properties of rocks and minerals. In practice, most experiments are designed to isolate a given process, limiting access to the interplay between various processes that takes place in nature. This is in part because changes in microstructure are commonly documented after an experiment has ended. The loss of information during deformation makes quantifying feedback of different mechanisms extremely challenging. However, natural processes often involve concurrent inelastic deformation mechanisms and simultaneous metamorphic or diagenetic reactions. Quantitative accessment of these processes demands better constraints of the feedback between rock deformation and the evolving rock properties and microstructures.

Recent dynamic microtomography experiments have shown great potential in characterizing the evolution of microstructure and strain distribution during fault growth at in-situ pressure and temperature conditions. Using an X-ray transparent deformation apparatus that operates at crustal stress conditions, we have imaged the process of fault nucleation and propagation in natural rocks undergoing brittle faulting.  Applying the digital volume correlation technique to time-resolved 3-dimensional microtomographic datasets, we documented the evolution of strain distribution within a deforming rock. These results elucidate how fractures open, slide, coalesce, and propagate in rock samples responding to increasing shear stress.  

Using dynamic microtomography, it is now possible to address the effect of chemo-mechanical coupling on the emergent properties of rocks by conducting deformation experiments in which several mechanisms operate simultaneously. We studied the effect of chemo-mechanical coupling on fracturing induced by hydration reaction in serpentinite. Quantitative characterization of evolving mechanical behavior and microstructure enables us to understanding the feedback between thermal load, chemical reaction rate, and mechanical failure. Dynamic microtomography provides a promising approach to link evolving mechanical behavior with evolving microstructures. New experimental constraints on microstructural and internal stress-strain evolution can lead to more robust extrapolations of laboratory results to large scale geologic processes.

How to cite: Zhu, W.: New Constraints on Fault Nucleation and Propagation Using Dynamic Microtomography Experiments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8520, https://doi.org/10.5194/egusphere-egu21-8520, 2021.

Earthquakes are spectacular natural disasters, with for example the recent disastrous Sumatra and Tohoku-Oki earthquakes (2004 and 2011, respectively). Presently, predicting earthquakes remains one of the biggest societal challenges in natural science. While seismological observations have much improved in recent years, our understanding of earthquake source physics remains limited due to the scarcity of monitored seismic rupture along similar fault systems, making long- or short-time scale predictions impossible. Friction and fracture are the two keys to understanding earthquakes. Laboratory experiments could be a robust solution to study earthquakes under safe and controlled conditions, which is mandatory to understand and compare the details of earthquake source physics. Conversely to common friction experiments conducted at both slow and seismic slip rates, the stick-slip mechanism is associated to the propagation of a rupture front, i.e. the radiation of seismic waves. Using stick-slip as an earthquake analog coupled to a state-of-the-art high frequency acoustic monitoring system, we demonstrated in the past that accelerations recorded in the kilohertz range on centimeter-sized samples were self-similar to the ones one can expect at the kilometric scale for a large earthquake. Based on this laboratory earthquakes catalogue, we highlighted that acoustic and strain measurements can be used to (i) locate and follow seismicity, (ii) estimate the energy budget of laboratory earthquakes, (iii) discriminate the mode of slip and the rupture speed. Lately, using medium scale experiments, we studied the scale dependence of rupture processes. These new results, notably in term of weakening of faulting and energy balance allowed us to initiate a bridge between laboratory earthquakes, fracture mechanics and natural seismicity. We discuss here how these experimental results can be upscaled to natural earthquakes.

How to cite: Passelegue, F., Paglialunga, F., Schubnel, A., and Di Toro, G.: The dynamics of earthquakes rupture : A view from the laboratory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9725, https://doi.org/10.5194/egusphere-egu21-9725, 2021.