Forecasting Time-Variable Earthquake Risk for Reinforced Concrete Buildings During Aftershock Sequences Based on Operational Earthquake Forecasting and Resonance Period Elongation

Abstract

The probability of a reinforced concrete building to sustain cumulative damage during afterschock sequences is a key issue for crisis management. Assessments of time-variant probabilities of damage states are made herein for reinforced concrete building models the city of Thessaloniki, Greece, in the case of a mainshock scenario. The elongation of the first eigenperiod of the building is used as the engineering demand parameter in the computation of the fragility curves for the building models. Period elongation is selected, as it is readily available in the case of buildings with permanent monitoring systems, which are part of a critical infrastructure, and it may be used complementary to post-earthquake building inspection in order to assess earthquake damage. The increase of the vulnerability of the buildings with time due to potential earthquake damage accumulation is modeled with a probabilistic approach, which is based on the Markov chain. During the aftershock sequences the probability to exceed period elongation thresholds accumulates. Additional risk due to aftershocks as a function of time is estimated and the developed framework is based on the traffic-light concept (red-orange-green) for building-tagging with respect to seismic risk to support earthquake risk management in the course of aftershock sequences.