Abstract
The 2016–2017 Central Apennines seismic sequence, comprising three mainshocks (24 August Mw 6.0, 26 October Mw 5.9, and 30 October Mw 6.5), provides a unique opportunity to reassess the role of static Coulomb stress transfer in driving earthquake cascades. We integrate a high-resolution template-matching catalog with fault geometry constraints from field surveys and seismic reflection data to compute stress changes on receiver faults. Our results show that 72% of aftershocks occurred in areas of positive Coulomb stress change (ΔCFS > 0.01 MPa) following the first mainshock, with a clear spatial correlation between stress enhancement and aftershock density. Stress changes from the second and third mainshocks further promoted seismicity along the Mt. Vettore–Mt. Bove fault system and adjacent normal faults. Statistical tests reveal a significant correlation (p < 0.01) between ΔCFS values and the logarithm of aftershock numbers in 2-km bins. However, we also identify regions of seismic quiescence in stress shadows, suggesting that static stress transfer is a first-order but incomplete explanation. Comparison with the 1997 Colfiorito and 2009 L’Aquila sequences indicates that the 2016–2017 sequence exhibits stronger stress triggering efficiency, likely due to the immature fault segmentation and higher regional stress accumulation. Our findings underscore the importance of incorporating detailed fault geometry and off-fault deformation in Coulomb models for aftershock forecasting. The study provides a reassessed framework for seismic hazard assessment in the Central Apennines, emphasizing the need for multi-mechanism approaches that combine static, dynamic, and viscoelastic stress transfer.
Keywords
Coulomb stress transfer, Central Apennines, seismic sequence, aftershock triggering, stress shadows, normal faulting, seismicity patterns, 2016 Amatrice earthquake