Shaking scenarios from multiple source models shed light on the 8 September 1905 Mw 7 Calabria earthquake (Southern Italy)

The earthquake (Mw 7) that struck western Calabria (southern Italy) on 8 September 1905 profoundly struck a broad region, causing 557 deaths, injuring more than 2000 people, and leaving about 300,000 people homeless. Historical documents also reported a tsunami, although not devastating, for which effects were observed both along the coast and offshore. For all the damage it caused, this event was much studied but not fully explained. Literature source models for the 1905 earthquake are numerous and diverse, in fault geometry, location, and even associated magnitude. They also differ in nature, because these solutions are either field-based or derived from tsunami modeling and macroseismic data inversion. Above all, few or none of the previously published source models appear to be fully compatible with the damage pattern caused by this earthquake. To contribute to the identification of the seismogenic source of this destructive event, we computed a series of ground-shaking scenarios based on the different fault-source models that various authors associated with this event. The only documented data available that are suitable for our comparative purposes are the macroseismic intensities associated with localities affected by the event. Our results show that shaking scenarios for two out of seven literature source models are compatible with the damage distribution caused by the 1905 earthquake. The different parameters and boundary conditions constraining these two solutions suggest that either seismogenic source should include further complexities. Alternatively, because these two sources are antithetic and partially form a graben, they might have kinematically interacted, if passively, on 8 September 1905. Also, our critical analysis attempts to take site effects into account, at least qualitatively, allowing a more robust evaluation of damage distribution against numerical models.