For the estimation of “local personal risk,” i.e., the annual probability of fatality for a hypothetical person continuously present in or near a building, an analytical methodology based on the probability of partial and complete collapse mechanisms (fragility models) and the probability of death given those collapse mechanisms (consequence models) for a building stock exposed to induced seismicity ground shaking is presented.

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This paper describes the ongoing experimental and analytical activities that are being carried out to develop fatality and consequence models for the estimation of 'Inside Local Personal Risk' (ILPR) of buildings within the Groningen field. ILPR is defined as the annual probability of fatality for a hypothetical person who is continuously present without protection inside a building. In order to be able to estimate this risk metric, a robust estimate of the probability of collapse of structural and non-structural elements within a building is needed, as these have been found to be the greatest drivers of fatality risk.To estimate the collapse potential of buildings in Groningen, structural numerical models of a number of representative case studies have been developed and calibrated through in situ and laboratory testing on materials, connections, structural components and even full-scale buildings. These numerical models are then subjected to increased levels of ground shaking to estimate the probability of collapse, and the associated consequences are estimated from the observed collapse mechanisms.

Recent literature about life-cycle models for earthquake resistant structures considers that damage accumulation and failure are possibly due to subsequent shocks occurring during the time period of interest. In fact, most of these models only consider the effect of mainshocks. On the other hand, it is well known that earthquakes occur in clusters in which the mainshock represents only the principal (e.g., prominent magnitude) event. Because there is a chance that aftershocks can also cause deterioration of structural conditions, it may be appropriate to include this effect in the life-cycle assessment. Recently, stochastic processes describing the occurrences of aftershocks and their effect on cumulative structural damage have been formalized. These can be employed to develop stochastic damage accumulation models for earthquake resistant structures, accounting for the cluster effect. In the paper, such a model is formulated with reference to simple elastic-perfectly-plastic single degree of freedom systems. Temporal distribution of mainshocks is modeled via a homogeneous Poisson process. Occurrence of aftershocks is modeled by means of non-homogeneous Poisson processes conditional to the characteristics of the triggering mainshock. Approximate closed-form solutions are derived for the reliability assessment under the two hypotheses that total damages produced by events pertaining to different clusters can be assumed to be independent and identically distributed gamma or inverse-Gaussian random variables. An application illustrates the implications of the model on the life-cycle assessment when compared to the case where the effect of damaging aftershocks is ignored