GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 73 Following the analysis of the damage distribution and EEEs triggered by the Pedernales earthquake, we observe a systematic distance-dependent difference of macroseismic fields as derived from EMS-98 and ESI-07 scales. Near field values and epicentral intensity are ca. one degree lower in EMS-98, while ESI-07 values are more consistent with epicentral intensities recorded by previous similar subduction events. This observation, even if not necessarily systematic, has been done in other case studies (Mosquera - Machado et al. , 2009; Papanikolaou et al., 2009; Di Manna et al. , 2012) and it can be ascribed to an underestimation of traditional macroseismic scales in the near field, at least for strong earthquakes occurred in the last decades. Underestimation of traditional intensity scales in the near field, can possibly be ascribed to a considerable improvement of building parameters with time, including recent economic development and the introduction of building codes, resulting in an overall less vulnerable built environment. Conversely, since ESI-07 scale is, by definition, less sensitive to moderate shaking effects, as experienced in the far-field areas (e.g., Papanikolaou et al., 2009), here traditional scales work better in depicting the overall macroseismic field. Nevertheless, to our knowledge, a quantitative comparison with traditional intensity scales, in terms of attenuation regressions, has never been tried before, neither for large subduction earthquakes. These results strongly suggest that, in the future, EEEs should be considered to evaluate the earthquakemacroseismic field, as initially suggested by the pioneers ofmacroseismic investigation (e.g., Sieberg, 1930; Wood and Neumann, 1931; Richter, 1958; Medvedev et al. , 1964). References Bakun, W. U., and C. M. Wentworth (1997). Estimating earthquake location and magnitude from seismic intensity data , Bull. Seism. Soc. Am . 87 (6) 1502-1521. Di Manna, P., L. Guerrieri, L. Piccardi, E. Vittori, D.Castaldini, A. Berlusconi, L. Bonadeo, V. Comerci, F. Ferrario, R. Gambillara, F. Livio, M. Lucarini, and A. M. Michetti (2012). Ground effects induced by the 2012 seismic sequence in Emilia: implications for seismic hazard assessment in the Po Plain , Ann. Geophys . 55 (4) 697–703. Gasperini, P., F. Bernardini, G. Valensise, and E. Boschi (1999). Defining seismogenic sources from historical earthquake felt reports, Bull. Seismol. Soc. Am. 89 94–110. Gasperini, P., Vannucci, G., Tripone, D., and Boschi, E. (2010). The location and sizing of historical earthquakes using the attenuation of macroseismic intensity with distance. Bull. Seismol. Soc. Am. 100 (5A) 2035-2066. Hough, S. E., J. G. Armbruster, L. Seeber, and J. F. Hough (2000). On the modified Mercalli intensities and magnitudes of the 1811–1812 New Madrid, central United States earthquakes, J. Geophys. Res. 105 , 23,839–23,864. Medvedev, S., W. Sponheuer and V. Karník (1964). Neue seismische Skala Intensity scale of earthquakes, 7. Tagung der Europäischen Seismologischen Kommission vom 24.9. bis 30.9.1962. In: Jena, Veröff. Institut für Bodendynamik und Erdbebenforschung in Jena, vol 77. Deutsche Akademie der Wissenschaften zu Berlin, pp 69–76. Michetti A.M., E. Esposito, L. Guerrieri, S. Porfido, L. Serva, R. Tatevossian, E. Vittori, F. Audemard, T. Azuma, J. Clague, V. Comerci, A. Gürpinar, J. McCalpin, B. Mohammadioun, N.A. Mörner, Y. Ota, and E. Roghozin (2007). Environmental Seismic Intensity Scale 2007 - ESI 2007. Memorie Descrittive della Carta Geologica d’Italia, 74, 7-54, Servizio Geologico d’Italia – Dipartimento Difesa del Suolo, APAT, Roma, Italy. Available online at http:// www.isprambiente.gov.it/en/publications/technical-periodicals/descriptive-memories-of-the-geological-map-of/ intensity-scale-esi-2007?set_language=en Fig. 3 - Intensity versus epicentral distance. For each earthquake, median epicentral distances for each intensity-source pair are plotted and fitted with least-squares straight lines.