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

Abstract

The destructive earthquake (M 7) that struck western Calabria (southern Italy) on 8 September 1905 profoundly hit a broad region, also generating a feeble tsunami. For all the damage it caused, this event was as much studied as not fully explained. Literature source models are numerous and diverse, in fault geometry, location, and associated magnitude. They also differ in nature, since these solutions are either field- based, or deriving from tsunami modeling, and macroseismic data inversion. Most. Neither all of these literature source models are not consistent with the damage pattern caused by the 1905 earthquake. To contribute to the identification of the seismogenic source of this destructive event, we performed a series of ground shaking scenarios, based on different faults that various authors associated with this event. The only documented data available suitable for our comparative purposes are the macroseismic intensities associated with localities affected by the event. We transformed the values of ground motion we computed for the same datapoints into intensities. We then attributed a quantitative fit to each modeled seismogenic source, evaluated with the quadratic sum of residuals between observed and calculated intensities. Our results show that two out of 7 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, since these two sources are antithetic and partially form a graben, they might have kinematically interacted, if passively, on 8 September 1905.