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 nonhomogeneous 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 worsened 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, the quantitative assessment of aftershock risk is aimed at 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 nonevolutionary 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 basis for handy tools enabling risk-informed tagging by stakeholders and decision makers. Copyright © 2013 John Wiley & Sons, Ltd.