  This paper analyzes the survivability of a physical network against
earthquakes and proposes spatial network design rules to make a network robust
against earthquakes. The disaster area model used is fairly generic and
bounded. The proposed design rules for physical networks include: (i) a shorter
zigzag route can reduce the probability that a network intersects a disaster
area, (ii) an additive performance metric, such as repair cost, is independent
of the network shape if the route length is fixed, and (iii) additional routes
within a ring network does not decrease the probability that all the routes
between a given pair of nodes intersect the disaster area, but a wider detour
route decreases it. Formulas for evaluating the probability of disconnecting
two given nodes are also derived. An optimal server placement is shown as an
application of the theoretical results. These analysis results are validated
through empirical earthquake data.
