Many ways to slip: aseismic fault creep and its transition to dynamic rupture
Sohom Ray,  IIT Roorkee

The nucleation of an earthquake relies on an interfacial instability that facilitates the transition of a slow fault slip to a faster dynamic rupture. Previous studies focus on analyzing slip instabilities emerging from perturbations to steady-state sliding. The length scales obtained from stability analyses of steady sliding (nucleation lengths) are interpreted as the minimum fault size required to initiate an earthquake generating dynamic rupture. Here, we discuss how slow aseismic creep on (nearly) locked asperities can also contribute toward interpretations of the minimum fault size required to cause an earthquake. We explore how aseismic creep on rate-weakening interfaces (asperities) transition to instability or fail to do so. The transition to early-stage instability happens through an intermediate breathing type evolution of slip rate. We further assess how heterogeneities in fault’s physical (frictional) properties affect the development of late-stage slip instabilities and find self-similar solutions for diverging slip rate on heterogeneous faults. Analyses of their stability in similarity coordinates help knowing when heterogeneities strongly affect slip evolution (e.g., disordered slip) or weakly affect the slip evolution and hence can be homogenized. I further highlight some recent development towards (synthetic) data-driven discovery of PDEs governing earthquake and landslide nucleation. 

Theoretical insights on the arrest of earthquake rupture
Pablo Ampuero, University of Géoazur

What determines the size of an earthquake? How can we quantify the control of geometric and material heterogeneities on rupture segmentation? I will present recent progress in our theoretical understanding of earthquake rupture arrest, especially for the largest earthquakes. Recent advances in our group are based on extension of fracture mechanics theory to rupture with large aspect ratio, validated through large-scale 3D simulations as well as reduced 2.5D modeling.