The Risk of Successive Disasters: A Blow-by-Blow Network Vulnerability Analysis

It is often assumed that a network will not be struck by multiple disasters in a relatively short period of time; that is, a subsequent disaster will not strike within the recovery phase of a previous disaster. However, recent events have shown that combinations of disasters are not implausible. This realization calls for a new perspective on how we assess the vulnerability of our networks and shows a need for a framework to assess the vulnerability of networks to successive independent disasters. We propose a network and disaster model capable of modeling a sequence of disasters in time, while taking into account recovery operations. Based on that model, we develop both an exact and a Monte Carlo method to compute the vulnerability of a network to successive disasters. By applying our approach to real empirical disaster data, we show that the probability of a second disaster striking the network during recovery can be significant even for short repair times. Our framework is a first step towards determining the vulnerability of networks to such successive disasters.