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

To understand fluid induced seismicity, we have designed a large-scale laboratory experiment consisting of a one-cubic-meter sandstone with an artificial fault cut and fluid-injection boreholes. The sandstone block is assembled in a true triaxial loading frame and equipped with 38 piezoelectric sensors to locate and characterise acoustic emission events. The differential stress on the artificial fault is increased in stages to bring it towards a critically stressed state. After each stage of differential stress increase, fluids are injected at low pressures through boreholes to test the potential of fault re-activation. In addition, a high-pressure injection was conducted that created a hydraulic fracture from the injection borehole towards the artificial fault. The newly generated fluid pathway resulted in an activation of the complete block through a stick–slip movement. We compare acoustic emission measurements from the laboratory experiment with seismicity observations from the field-scale CO₂ injection at Decatur, Illinois, U.S., and conclude that the existence of fluid pathways plays a decisive role for the potential of induced seismicity.