Gamma modelling of aftershock reliability of elastic- perfectly-plastic systems

Major earthquakes (i.e., mainshocks) typically trigger a sequence of lower-magnitude events clustered both in time and space. Recent advances of seismic hazard analysis stochastically model aftershock occurrence (given the main event) as a non-homogeneous Poisson process with rate that decays in time as a negative power law . Risk management in the post-event emergency phase has to deal with this short-term seismicity. In fact, because the structural systems of interest might have suffered some damage in the mainshock, possibly worsen by damaging aftershocks, the failure risk may be large until the intensity of the sequence reduces or the structure is repaired . At the state-of-the-art, to quantitatively assess the aftershock risk serves to as building tagging , that is to regulate occupancy. The study, on the basis of age-dependent stochastic processes, derived closed-form approximations for the aftershock reliability of simple elastic-perfectly-plastic damage-cumulating systems, conditional on different information about the structure. Results show that, in the case hypotheses apply, the developed models may represent a handy tool for risk-informed tagging by stakeholders and decision makers.