Earthquake Scenario Reduction by Symmetry Reasoning
  A recently identified problem is that of finding an optimal investment plan
for a transportation network, given that a disaster such as an earthquake may
destroy links in the network. The aim is to strengthen key links to preserve
the expected network connectivity. A network based on the Istanbul highway
system has thirty links and therefore a billion scenarios, but it has been
estimated that sampling a million scenarios gives reasonable accuracy. In this
paper we use symmetry reasoning to reduce the number of scenarios to a much
smaller number, making sampling unnecessary. This result can be used to
facilitate metaheuristic and exact approaches to the problem.
