A seismological and engineering perspective on the 2016 Central Italy earthquakes

Abstract

Abstract:The strong earthquake (M 6.0-6.2) that hit the central Apennines on August 24, 2016, occurred in one of the most seismically active areas in Italy. Field surveys indicated severe damage in the epicentral area where, in addition to the loss of human life, widespread destruction of cultural heritage and of critical buildings occurred. Using the neo-deterministic seismic hazard assessment (NDSHA), we apply the maximum deterministic seismic input (MDSI) procedure at two of the most relevant sites in the epicentral area, comparing the results with the current Italian building code. After performing an expeditious engineering analysis, we interpret as a possible cause of the reported damages the high seismic vulnerability of the built environment, combined with the source and site effects characterising the seismic input. Therefore, it is important to design and retrofit with appropriate spectral acceleration levels compatible with the possible future scenarios, like the ones provided by MDSI.

NDSHA - The New Paradigm for RSHA - An Updated Review

“…5). DGA estimation has been validated in many instances: both regionally and at regional and local scale (See Fasan et al, 2016;Panza, 2017;Parvez et al, 2017;De Natale et al, 2019;Panza, 2020).…”

“…The lower bound for magnitude inside the seismogenic zones is M = 5, that also is conventionally (D"Amico et al, 1999) taken as the lower bound magnitude of damaging earthquakes; (b) the lower bound of earthquake magnitude within the seismogenic nodes is the magnitude threshold identified for that node by the morphostructural analysis (Gelfand et al, 1972); (c) the orientation of the double-couple point source is the one representative of the parent seismogenic zone or seismogenic node; (d) hypocentral depth, in fairly good agreement with existing literature, is taken as a discrete function of magnitude f (M) = (10 km for M < 7) (15 km for 7 ≤ M < 8) and (25 km for M ≥ 8). A quite complete description of the NDSHA methodology, including the joint use of earthquake sources within seismogenic zones and seismogenic nodes, can be found in , and its updates and validations in Panza et al (2012), Fasan et al (2016, Magrin et al (2016), Parvez et al (2017 and Hassan et al (2017). Specific 3D NDSHA applications can be found in La Mura et al (2011) and Panza et al (2013).…”

NDSHA: A new paradigm for reliable seismic hazard assessment

“…Caputo et al, 1973;Molchan et al, 1997;Doglioni et al, 2015). A complete description of the NDSHA methodology can be found in Panza et al (2001) and its updates and validations in Panza et al (2012), Fasan et al (2016), Magrin et al (2016), Fasan (2017) and Hassan et al (2017). In addition, NDSHA permits, if really necessary, to account for earthquake occurrence rate (Peresan et al, 2013 and references therein;Peresan et al, 2014;Magrin et al, 2017).…”

“…Nonetheless this apparent "saving" has been unrealized and ultimately frustrated by the October 2016 earthquake -and now it is necessary to consider in the reconstruction and retrofitting the NDSHA values, which were unwisely ignored after the 1997 earthquakes. Lastly to consider (but not least), before the occurrence of 30 October 2016 the M=6.5 event, when Norcia was almost completely destroyed: (a) Fasan et al (2016) did show that the spectral accelerations for the 30 October 2016 M=6.5 event, with magnitude close to the maximum ever historically observed in the area, are in very good agreement with what had earlier been predicted, based on NDSHA ground motion simulations; (b) Panza and Peresan (2016) issued the warning that the 24 August 2016 M=6.0 earthquake did not Proceedings, International Conference on Disaster Risk Mitigation, Dhaka, Bangladesh, September 23 -24, 2017 necessarily generate the largest possible ground motion in the area: since the area had been previously hit by the 14 January 1703 M=6.9, Valnerina earthquake. They further warned that, in the ensuing reconstruction and retrofitting activity, engineers should take into account as well that, in the future, seismic source and local soil effects may lead to ground motion values exceeding the NDSHA value of 0.6g (predicted at the bedrock).…”

“…NDSHA, over now some two decades, provides both reliable and effective earthquake hazard assessment tools for understanding and mitigating earthquake risk. Unlike PSHA, NDSHA is falsifiable -however it has been, to the contrary, very effectively validated by all earthquake events which have occurred in regions where NDSHA hazard maps were already available at the time of the quake: (i) Emilia-Romagna ; (ii) Central Italy (Fasan et al, 2016); and (iii) Nepal (Parvez et al, 2017). It should be widely taken to heart, I believe, that the continued practice of PSHA for determining earthquake resistant design standards for civil protection, mitigation of heritage and existing buildings, and community economic well-being and resilience .…”