4.24.2010

Speaking of News Pegs...

Lee Billings attempts to connect a top-of-the-ladder(of abstraction) concept -- the failure of interconnected networks of complex systems -- to a bottom-of-ladder, real life, TIMELY!, much-discussed example: the big volcano in Iceland. I think he succeeds. Here are a couple of the nerdiest grafs:

For me, the past week’s events resonated most strongly with a study from Sergey Buldyrev and colleagues that was published in Nature the day before Eyjafjallaj√∂kull’s eruption. The researchers investigated catastrophic failures in complex networked systems—systems like the closely coupled infrastructures underlying modern transportation, electricity distribution, telecommunications, and financial transactions. These systems are constructed from many interdependent nodes, which gives them greater stability and resilience: If one node fails, material, money, energy, or people are routed through other nodes, and functionality is maintained. But past a certain critical threshold of node failures, the system fragments and cannot function.

Buldyrev’s team modeled how disruptions percolate through a tightly linked pair of idealized interdependent networks, and found a counter-intuitive result: The failure of even a small number of nodes in one network can cause additional failures in the second. These failures can then feed back into the first network and cause yet more node failures. In other words, the greatest strength of an interdependent network in isolation is also the greatest weakness of interdependent networks as a whole. Two closely linked, highly resilient systems can suffer catastrophic failure through initially small disruptions that would have been essentially harmless to either network individually. What’s true for two linked networks presumably holds for larger assemblages.

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