Quantification of Seismic Resilience

The concept of seismic resilience needs a unified terminology and a common reference frame for quantitative evaluation. The evaluation can be based on nondimensional analytical functions related to variations of losses within a specified “recovery period”. The resilience must refer to both direct and indirect losses. The path to recovery usually depends on available resources and may take different shapes which can be estimated by proper recovery functions. The loss functions have major uncertainties due to the uncertain nature of the earthquake and structural behavior as well as due to uncertain description of functionality limits. Therefore losses can be described as functions of fragility of systems’ components. These fragility functions can be determined through the use of multidimensional performance limit thresholds, which allow considering simultaneously different mechanical-physical variables such as forces, velocities, displacements and accelerations along with other functional limits. A procedure which defines resilience as function of losses and loss recovery based on multidimensional system fragility is formulated and an example is presented for a typical California hospital considering direct and indirect losses in its physical system and in the population served by the system.