Comment on "The 28 December 1908 Messina Straits Earthquake (Mw 7.1): A Great Earthquake throughout a Century of Seismology" by N. A. Pino, A. Piatanesi, G. Valensise, and E. Boschi

Abstract

The recent paper “The 28 December 1908 Messina Straits Earthquake ( Mw 7.1): A Great Earthquake throughout a Century of Seismology” by Pino et al. (2009) provides a review of the observations, early studies, and main accomplishments in the investigation of the source of the 1908 Messina Straits earthquake. Figure 9 in Pino et al. (2009) is the main reason for this comment. The authors assert that the figure shows the slip distribution along-strike of the fault resulting from various studies, including Amoruso et al. (2002). In fact, they compare the seismic moment per unit fault length (shown as an equivalent along-strike slip distribution under the assumption of uniform along-dip slip distribution on a 20-km wide fault) obtained by Pino et al. (2000) from seismic data with the maximum slip along each section of the distributed-slip fault resulting from different geodetic models. Here we show that Figure 9 in Pino et al. (2009) is inconsistent and misleading, because incomparable quantities are compared. Before we address this point, we will discuss the reference in Table 2 of Pino et al. (2009) to the size (100 × 30 km2) of the variable-slip fault of Amoruso et al. (2002), clarifying its real meaning through a short summary of our computation procedure. We also report the main results in Amoruso et al. (2006), omitted in Pino et al. (2009). In Amoruso et al. (2002) we performed a joint inversion of P -wave first-motion polarities and geodetic data (leveling lines along the Calabrian and Sicilian sides of the Straits) under the assumption that uplifts are uncorrelated experimental data. The static baseline corrections for leveling lines were additional free parameters of the model. Fault slip was at first assumed uniform, then independent in a small set of coplanar subfaults sharing the same rake angle (see Figure …