What Controls the Presence and Characteristics of Aftershocks in Rock Fracture in the Lab?

Aftershock cascades are a characteristic feature of natural seismicity, but underlying mechanisms remain debated. Here, we experimentally explore the presence or absence aftershocks during failure intact rock and slip on newly created laboratory faults. We show that overall activity increase spatial localization acoustic emission (AE) events fracture nucleation occurs without temporal (Omori-type) correlations. Our analysis shows this aftershock sequences even beyond peak stress also when macroscopic has formed post peak-stress propagates. Instead, triggering does occur post-fracture relaxation along lab-fault in large-scale heterogeneities, for example, imposed by saw-cut notch. The detected these cases can be described standard seismological relationships such as modified Omori-Utsu relation its associated inter-event time distribution productivity relation. Moreover, AE within all experiments follow Gutenberg-Richter relation, with smaller -values triggered compared to non-triggered events. Performing full-moment tensor inversions, find seismic significant isotropic, compaction components play an important role triggering. resulting tend have focal similar their trigger. Seismic predominant tensile components, other hand, little evidence This opens up new perspective aftershocks, going not only rate-and-state paradigm limited purely frictional sliding shear mainshock attribute where attributes control patterns.