Elusive seismogenic sources of historical earthquakes: insights from the Mw 6.8, 1706 Maiella earthquake (central Italy)

The central Apennines are renowned for their active NW-SE striking and SW-dipping normal-fault systems responsible for significant seismic events. However, uncertainties persist in attributing some past destructive earthquakes to seismogenic sources, as in the case of the 1706 Maiella earthquake (Mw 6.8, Abruzzi region). This study comprehensively assesses competing source hypotheses derived from the literature and uses geological and geophysical data to constrain their possible fault geometry. Employing a 3D seismogenic source model approach, we rigorously analyze the earthquake-fault association, assessing the misfit between the simulated site intensities and the macroseismic values estimated from the historical accounts. Our findings highlight the complexities in determining a reliable source for the 1706 earthquake. Finally, the best-fit source model was adopted to produce ground motion predictions regarding Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and macroseismic intensity, including site effects, coupling the ground motion model (GMM-ITA18; Lanzano et al. 2019) and the ground motion intensity conversion equation (GMICE; Gomez Capera et al., 2020). The presented outcomes possibly unveil the shaking scenario that occurred in the past and perhaps in the future. These results, shedding light on one of the most relevant unknowns of the Apennine seismicity, offer valuable insights to better constrain the seismic hazard of this region, with implications for seismic risk mitigation strategies.