A method for earthquake risk assessment of transportation network systems is presented that considers loss from damage to bridges and from opportunity costs from trips forgone due to increased traffic congestion. Earthquake hazards include ground shaking, landslides, and liquefaction. Transportation network analysis models are developed with fixed and variable travel demand assumptions. The method is applied to five counties in the San Francisco Bay Area. Four scenario earthquakes are defined: moment magnitude 7.0 and 7.5 events on the Hayward fault, and 7.5 and 8.0 events on the San Andreas fault.
For the four scenario earthquakes, losses from bridge damage due to ground shaking are estimated in millions as $77, $283, $285, and $634 million, respectively. These values increase to $475 million, $1.09 billion, $970 million, and $1.5 billion, respectively, when all hazards are considered with liquefaction as the main contributor to the increase. A retrofit analysis shows that a 20% increase in ground-shaking capacity uniformly for all bridges results in approximately 25% decrease in the loss. The opportunity costs for a two-hour peak A.M. traffic are estimated as $6M for commuter and $280M for freight traffic. Comparisons to the Loma Prieta 1989 earthquake were inconclusive.
An emergency traffic-routing algorithm, T-RoutER, is deve loped to demonstrate post- event travel paths. A key feature of T-RoutER is that it identifies available multiple origin- destination (O-D) pairs that are critical for emergency response.
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