PEER Workshop on Earthquake Risks to Transportation Systems

Recent major earthquakes such as the 1989 Loma Prieta, 1994 Northridge, California, and the 1995 Kobe, Japan, earthquakes have provided compelling reminders of how critical transportation systems are to urban life and to ensure recovery.

A PEER workshop on the earthquake risks to transportation systems launched a demonstration project that will apply innovations and developments in risk analysis to a selected region with high earthquake vulnerability. The workshop was held July 10–11, at Stanford University, Palo Alto, California. Approximately 40 invited representatives attended from the academic, government, public, and private sectors with strong interests in seismic safety, transportation, and emergency planning and management issues. The workshop was hosted by Anne Kiremidjian, Director of the John A. Blume Earthquake Engineering Center at Stanford. Chairs of the different focus areas were James Moore of USC, Sam Chiu and Stephanie King of Stanford, and Frieder Seible of UCSD.

The objectives of the workshop were to identify issues critical (1) to modeling the earthquake risks to transportation systems for preparedness planning, emergency response, and economic recovery and (2) to developing technologies to enable emergency response and postdisaster recovery.

After an earthquake, changes in how people approach transportation occur as inevitably as other changes in behavior. Simulation-based methodologies were discussed that can account for the day-to-day dynamics that occur in route and departure-time choices.

Although the Loma Prieta and Northridge earthquakes resulted in the loss of major freeway and bridge arteries, little damage to local streets provided easy alternate routes for motorists and emergency vehicles. In the Bay Area, alternative means of transportation were readily embraced; in Los Angeles, even carpooling did not increase substantially. However, the rapid repair of roadways in Los Angeles, where "the car is king," brought overwhelming public support for rebuilding.

The Loma Prieta and Northridge earthquakes also provided strong regional contrasts in postearthquake decisions about moving traffic. The lack of a working transportation center in the Bay Area greatly hampered this process. The Metropolitan Transportation Commission (MTC) now unifies the Bay Area's institutionally complex 9 counties and 100 cities. MTC and the State Office of Emergency Services recently participated in a vulnerability assessment of transportation facilities based on forecast and mapping of road closures for each of 11 earthquake scenarios. MTC developed consensus among 32 agencies that resulted in the Trans Response Plan (TRP). When the next earthquake occurs, MTC will serve as a regional transportation information clearinghouse, providing interagency coordination and transportation information to the public.

A number of approaches to seismic risk analysis (SRA) of transportation systems rank transportation bridges by vulnerability and importance. One such methodology presented was based on data obtained on damage in the Northridge and Loma Prieta events, and applied to several case studies for Northridge. Fragility curves have been developed as an important part of this methodology. Following Northridge, Caltrans used a prioritizing system to inspect an astounding 1800 bridges in just two days.

Another SRA, based on a Memphis study, involves improving the prioritizing of the road and bridge components for seismic retrofit, and defining seismic performance requirements for new components. An important element of the SRA process is a GIS database to accommodate new developments in modeling.

The postearthquake process for gathering and transmitting reconnaissance data on roads and bridges is difficult and prone to errors. Future solutions may be mobile based, such as handheld PCs that would connect to a notebook or to a server.

Pacific Gas and Electric's (PG&E) William Savage pointed out that utility companies are also transportation providers. Because life-safety is paramount, PG&E's postearthquake goal is performance, not the physical reconstruction of its facilities. The numerous lines that cross the Hayward fault and all substations are being analyzed for a damage model so that PG&E can predict the outages after a major earthquake. PG&E has also been working with other agencies to create redundancies-alternative systems that can provide the same functions-for example, generators in Silicon Valley companies. Savage conceded that postearthquake redundancies could still be improved.

In discussing regional transportation vulnerabilities, Richard Eisner of the California Governor's Office of Emergency Services (OES) stressed that however much professionals have learned, this knowledge should be considered limited in the context of a major earthquake. The Bay Area's narrow transportation corridors, defined by geography, suggest a logical but uneasy comparison to Kobe, Japan, especially if the ground motion forces from an earthquake on the Hayward fault have been underestimated. According to Eisner, "Kobe is our worst nightmare...all systems going bad...." The unknowns of a major earthquake combined with little redundancy in the transportation systems—airports, bridges, port facilities, and interchanges—make the Bay Area very vulnerable. On an optimistic note, Eisner said that the OES provides "near failsafe communication": radio for MTC and a network-based response system using satellite and the Internet will facilitate communication.

Professors Anne Kiremidjian and Sam Chiu of Stanford, and Professor James Moore of USC