Between ethics and territorial planning: the value of the ESI-2007 scale

A modern approach to the assessment of seismic hazard cannot disregard the study of effects induced by earthquakes in the natural environment. The knowledge and mapping of seismic-induced effects represent the basis for providing a more reliable and realistic scenario in territorial planning. In recent years this has been dramatically demonstrated by large subduction events (Indonesia 2004, Japan 2011, Ecuador 2016, Mexico 2017, etc.), but also, and remarkably, by moderate to small earthquakes which affected Italy (Emilia Romagna 2012, Casamicciola (Ischia) 2017, Fleri-Pennisi (Sicily) 2019). The introduction of the new ESI 2007 macroseismic scale (Michetti et al., 2007), has been fundamental in pursuing this ethically and scientifically comprehensive approach for evaluation of seismic hazard. The assessment of intensity based only on environmental effects is applicable everywhere in the world, regardless of the quality of the built environment, and therefore ethically more correct, being not influenced by the socio-economic conditions that affect the urban development of the various countries. The ESI scale integrates the traditional macroseismic scales, of which it represents the evolution, allowing to assess the intensity parameter also where buildings are absent or damage-based diagnostics saturate. For this purpose, we revisit three representative case histories from very different tectonic environments: the reverse faulting of the 2012 Emilia sequence (May 20, Mw = 5.8; and May 29, Mw = 5.6; Di Manna et al., 2012) in the Po Plain foredeep environment of N Italy; the normal faulting of August 21, 2017 Casamicciola earthquake (Md = 4.0; Nappi et al., 2018) in the Ischia volcanic island, S Italy; and the devastating February 4, 1976, Guatemala earthquake (M = 7.5; Porfido et al., 2015), along the leftlateral Motagua Fault at the boundary between the N America and Caribbean plates. The macroseismic study of these earthquakes with ESI 2007 scale has contributed to define more realistic seismic scenarios in terms of intensity. We show that this methodology is essential for seismic hazard evaluation, and a fundamental step towards appropriate post-seismic reconstruction. Di Manna P., Guerrieri L., Piccardi L., Vittori E., Castaldini D., Berlusconi A., Bondaleo L., Comerci V., Ferrario F., Gambillara R., Livio F., Lucarini M. & Michetti A.M. (2012) - Ground effects induced by the 2012 seismic sequence in Emilia: implications for seismic hazard assessment in the Po Plain. Ann. Geoph., 55(4), https://doi.org/10.4401/ ag-6143 Michetti A.M., Esposito E., Guerrieri L., Porfido S., Serva L., Tatevossian R., Vittori E., Audemard F., Azuma T., Clague J., Comerci V., Gurpinar A., Mc Calpin J., Mohammadioun B., Morner N.A. Ota Y. & Roghozin E. (2007) - Intensity Scale ESI 2007, Mem. Descr. Carta Geologica d'Italia, Roma, 74, 53 pp. Nappi R., Alessio G., Gaudiosi G., Nave R., Marotta R.E., Siniscalchi V., Civico R., Pizzimenti L., Peluso R., Belviso P. & Porfido S. (2018) - The 21 August 2017 Md 4.0 Casamicciola earthquake: First evidence of coseismic normal surface faulting at the Ischia volcanic island. Seism. Res. Lett., 89(4), 1323-1334. Https://doi.org/10.1785/0220180063. Porfido S., Esposito E., Spiga E., Sacchi M., Molisso F. & Mazzola S. (2015) - Impact of Ground Effects for an Appropriate Mitigation Strategy in Seismic Area: The Example of Guatemala 1976 Earthquake. In Lollino G., Giordan D., Crosta G.B., Corominas J., Azzam R., Wasowski J. & Sciarra N. (eds.): Engineering Geology for Society and Territory - Vol. 2. Springer, Cham.