Response to: Comment on “New simulations and understanding of the 1908 Messina tsunami for a dual seismic and deep submarine mass failure source” by L. Schambach, S.T. Grilli, D.R. Tappin, M.D. Gangemi, G. Barbaro [Marine Geology 421 (2020) 106093]

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In this response, we address and refute the comments made by Argnani (2021) on our 1908 Messina tsunami paper (Schambach et al., 2020), regarding the poor geological constraints underpinning the numerical tsunami modeling. Earthquake mechanisms can be constructed from ‘geology’, but because ruptures are usually blind, seabed evidence may be absent. Alternatively, with small magnitude earthquakes, such as Messina 1908, the small vertical displacements may not be resolved on seismic or multibeam echosounder bathymetric records, because of the relatively low frequencies of the recording equipment. Hence, for earthquake tsunami, seismological data may be more appropriate as the basis for numerical modeling. With regard to submarine mass failure, when interpreting seismic and bathymetry data, the frequency content should again be carefully considered, because smaller features may not be resolved. Regarding the 1908 tsunami, the Mw 7.1 earthquake magnitude would not be expected to generate the recorded tsunami runups for the 5 sources we modeled, as is proved from our modeling; this would also be the case for the Barreca et al. (2021) source proposed in the discussion. Combined with any of these earthquake sources, the submarine mass failure we identified and mapped, however, in large part does. The evidence most critical to the age dating of our identified SMF, presented as too old in the discussion, is that: (i) it is at the location predicted by the inverse wave ray tracing based on tsunami arrival observations; and (ii) upon forward modeling, this tsunami mechanism generates the onland tsunami record.

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Marine Geology