Seismic risk assessment of transportation network systems

When evaluating the earthquake risk to transportation system it is important to take into account the integrated effect of ground motion, liquefaction, and landslides on the network components and System. In this article, the risk from earthquakes to a transportation system is evaluated in terms of direct loss from damage to bridges and travel delays in the transportation network. The contribution of site effects to the loss from damage to bridges is estimated using the San Francisco Bay area as a test bed. Damage and loss to bridges from ground shaking and ground displacements (vertical and horizontal) from liquefaction and landslides are computed for a magnitude 7.0 scenario earthquake on the Hayward fault in California. It is found that liquefaction damage is the largest contributor to the repair cost which is used as a measure of the loss from damage. The performance of the transportation network is evaluated in terms of travel delay times. Travel delays resulting from damage due to ground shaking and changes in travel times are evaluated for the scenario event under the assumptions of fixed and variable travel demands. It is found that with fixed travel demand, the postevent travel times increase significantly. Travel times remain relatively unchanged and decrease with the variable demand time assumption.