Effects of Energy Dissipation on Precursory Seismicity During Earthquake Preparation

The b-value of the magnitude distribution of natural earthquakes appears to be closely influenced by the faulting style. We investigate this in the laboratory for the first time by analyzing the moment tensor solutions of acoustic emissions detected during a triaxial compression test on Berea sandstone. We observe systematic patterns showing that faulting style influences the b-value and differential stress. Similar trends are observed in a complementary physics-based numerical model that captures mechanical energy dissipation. Both the differential stress and dissipation are found to be inversely correlated to the b-value. The results indicate that, at late stages of the test, the dissipation increases and is linked to a change in AE faulting style and drop in b-value. The patterns observed in the laboratory Frohlich diagrams could be explained by the integrated earthquake model: damaged rock regions form as microcracks coalesce, leading to strain localization and runaway deformation. The modeling results also align with the micromechanics responsible for dissipation at various stages of the experiment and agrees with moment tensor solutions and petrographic investigations. The integration of physics-based models that can capture dissipative processes of the earthquake cycle could assist researchers in constraining seismic hazard in both natural and anthropogenic settings.