Investigating the Last Millennium Coulomb Stress Transfer in the Central Apennine Fault System (CAFS)

The Central Apennine Fault System (CAFS) characterizes an active tectonic region of significant importance, witnessing numerous destructive seismic events over the last millennia. Although numerous studies have underscored the role of Coulomb stress transfer (CST) in initiating some of the most catastrophic earthquakes, investigations focusing on its specific influence within the CAFS are limited. This research delves into a thorough examination of the effects of CST on both historical and instrumental seismic events of significant magnitude associated with the CAFS. We selected nine seismic events for the CST investigation, dating from 1279 CE to present. Beyond analyzing the static stress transfer for each individual seismic event, the cumulative CST of recent instrumental earthquakes was also examined to provide a comprehensive overview of the current stress scenario. Leveraging an innovative approach, faults were modeled adopting a variable strike three-dimensional elliptical shape, ensuring enhanced calculation accuracy. Significant findings emerge from the analysis: CST has played a pivotal role in either activating or inhibiting the faults of the CAFS over the centuries. Several examined instances showcase fault reactivation following increased transferred stress within relatively short time frames, while others highlight the inhibitory effect of stress shadows. Examining the differences in seismic moment release across three seismicity windows (the first one between 1300 and 1400, the second around 1700, and the last one from 1979 to 2016) reveals distinct periods of higher seismicity in the past millennium. The latter shows the lowest cumulative seismic moment, suggesting a potential seismic gap equivalent to a Mw 6.67 earthquake. Deepening our understanding of CST illuminates the role of fault interactions in past earthquake occurrences, offering valuable insights into forecasting potential future seismic sequences. This awareness is vital in crafting targeted seismic risk mitigation strategies, thereby safeguarding local communities from the profound consequences of earthquakes.