Seismic damage accumulation in multiple mainshock–aftershock sequences

Abstract

Earthquakes are generally clustered, both in time and space. Conventionally, each cluster is made of: foreshocks, the mainshock, and aftershocks. Seismic damage can possibly accumulate because of the effects of multiple earthquakes in one cluster and/or because the structure is unrepaired between different clusters. Typically, the performance-based earthquake engineering (PBEE) framework neglects seismic damage accumulation. This is because: (a) probabilistic seismic hazard analysis (PSHA) only refers to mainshocks and (b) classical fragility curves represent the failure probability in one event, of given intensity, only. However, for life-cycle assessment, it can be necessary to account for the building-up of seismic losses because of damage in multiple events. It has been already demonstrated that a Markovian model (i.e., a Markov chain), accounting for damage accumulation in multiple mainshocks, can be calibrated maintaining PSHA from the classical PBEE framework, and replacing structural fragility with a set of statedependent fragility curves. In fact, the Markov chain also works when damage accumulates in multiple aftershocks from a single mainshock of known magnitude and location, if aftershock-PSHA replaces classical PSHA. Herein this model is extended further developing a Markovian model that accounts, at the same time, for damage accumulation: (i) within any mainshock-aftershock seismic sequence and (ii) among multiple sequences. The model is illustrated through applications to a series of six-story reinforced-concrete moment-resisting-frame buildings designed for three sites with different seismic hazard levels in Italy. The time-variant reliability assessment results are compared to the classical PBEE approach and the accumulation model that only considers mainshocks, so as to address the relevance of aftershocks for life-cycle assessment.

Simulation‐based methodology to identify damage indicators and safety thresholds for post‐earthquake evaluation of structures

“…The damage state of each component (𝑑 𝑖 for the 𝑖-th component) is used to compute a floor damage index (𝐹𝐷𝐼) from 0 to 1, where 1 means that all beam-column connections are fractured. Applying this idea to ductile RC-frames, the beam and column hinge damage indices on each floor are combined to compute 𝐹𝐷𝐼 using Equation (9). Note that the damage state of each component in Equation ( 9) is divided by 3, the total number of damage states in this case.…”

“…In parallel, Luco et al 7 used a similar approach to explore the effects of a damaging mainshock ground motion to evaluate the structural collapse safety to a subsequent aftershock. Maffei et al 8 extended the use of SDOF models to quantify post-earthquake safety to various structural systems, and Iervolino et al 9 developed a method to account for multiple aftershocks. While the SDOF model studies provide valuable understanding of the general response of structures under sequential ground motions, they do not provide the level of detail necessary to translate simulation results into practical recommendations that could be used in post-earthquake inspection and evaluation guidelines.…”

“…Maffei et al 8 . extended the use of SDOF models to quantify post‐earthquake safety to various structural systems, and Iervolino et al 9 . developed a method to account for multiple aftershocks.…”

Comparing Short-Term Seismic and COVID-19 Fatality Risks in Italy

“…Thus, as described in more details by Iervolino et al (2015), MANTIS-K provides risk assessment with a probabilistically-consistent approach and, in addition to the uncertainties in earthquake occurrence and magnitude considered by the OEF models it has as an input, it accounts for uncertainties in: (i) ground motion intensity produced by an earthquake of given magnitude and location; (ii) observed damage in a building of a given typology, given the ground motion intensity at the construction site; (iii) consequences due to a specific structural damage; (iv) residents exposed to structural failure at the time of the earthquake. On the other hand, MANTIS-K has some limitations related to the non-evolutionary characteristics of the vulnerability and exposure models (Chioccarelli and Iervolino, 2016); however, studies to over overcome such limitations are underway (Iervolino et al, 2020).…”

Seismic vulnerability assessment of ageing reinforced concrete structures under real mainshock-aftershock ground motions

“…While in a great number of studies the seismic vulnerability of structures is assessed considering the single MS(s) event, such assessments considering MS-AS sequences have received significant attention over the previous decade (Acito et al, 2014(Acito et al, , 2020Chase et al, 2019;Goda & Taylor, 2012;Hatzivassiliou & Hatzigeorgiou, 2015;Hatzigeorgiou & Liolios, 2010;Hosseinpour & Abdelnaby, 2017;Iervolino et al, 2020;Jalayer et al, 2011;Jeon et al, 2015;Naderpour & Vakili, 2019;Raghunandan et al, 2015). Using real and synthetic MS-AS sequences (generated based on Omori's law (Shcherbakov et al, 2005)), Goda and Taylor (2012) investigated the extent of additional damage caused by AS.…”