Liliana Minelli

Reply to comment by Andrea Argnani et al. on ''On the cause of the 1908 Messina tsunami, southern Italy''

Within minutes after the passage of the seismic waves, atsunami with maximum observed runup of almost 12 m hitthe coasts of Calabria and Sicily [Platania, 1909; Baratta,1910]. Soon after the catastrophic events, Omori [1909]concluded that: ‘‘One remarkable fact is that the tsunamiwasstrongestatthoseplaceswheretheearthquakeshockwasnot most violent, indicating the probable non-coincidencein position of the origin of the earthquake with that ofthe tsunami’’. By using computer simulations, Tinti andArmigliato [2003] reached a similar conclusion: ‘‘The firstconclusion we arrive at is that it is difficult to find a singlesource matching simultaneously both tsunami and levelingdata’’. Recently, we presented new results supporting thehypothesis that the tsunami was generated by a submarinelandslide triggered by the earthquake at c. 40 km from theepicentral area [Billi et al., 2008]. Argnani et al. [2009] nowproduce new marine data and numerical models to questionsome of our inferences. Here we reply to their criticisms.

Seismic hazard in southern Calabria (Italy) based on the analysis of a synthetic earthquake catalog

The application of a newly developed physics-based earthquake simulator to the active faults inferred by aeromagnetism in southern Calabria has produced a synthetic catalog lasting 100 ky including more than 18,000 earthquakes of magnitude ≥ 4.0. This catalog exhibits temporal, spatial and magnitude features, which resemble those of the observed seismicity. As an example of the potential use of synthetic catalogs, a map of the peak ground acceleration (PGA) for a given exceedance probability on the territory under investigation has been produced by means of a simple attenuation law applied to all the events reported in the synthetic catalog. This map was compared with the existing hazard map that is presently used in the national seismic building regulations. The comparison supports a strong similarity of our results with the values given in the present Italian seismic building code, despite the latter being based on a different methodology. The same similarity cannot be recognized for the comparison of our present study with the results obtained from a previous study based on our same methodology but with a different geological model.