The Northridge earthquake: progress made, lessons learned in seismic-resistant bridge design.

At 4:31 a.m. PST on Monday, Jan. 17, 1994, the ground shook for approximately 20 seconds in the Northridge section of the San Fernando Valley in Los Angeles, Calif. The earthquake had a Richter magnitude of 6.7. Its epicentral region was the same area that had been rocked during the 1971 San Fernando earthquake. Fifty-seven people lost their lives as a result of the Northridge quake.

Introduction: FHWA and the Challenge of Natural Hazard Mitigation

Our society--our way of life--depends on a complex network of infrastructure systems. These systems are lifelines that provide transportation and communication services, a supply of energy and fresh water, and the disposal of wastewater and waste products. Among the oldest of these lifelines are our transportation systems--highways, railroads, mass transit, ports, waterways, and airports.

The Federal Highway Administration (FHWA) has a vested interest in ensuring that the critical resource represented by the nation's roads and bridges is not undermined, threatened, or destroyed by natural hazards. To this end, it conducts, sponsors, or otherwise participates in extensive research to identify new technologies or new applications of existing technologies that will mitigate the effects of such natural hazards as flood, fire, windstorm, and earthquake. Specifically, this effort tries to determine how highway structures should be built or how they should be strengthened (retrofitted) to minimize the effects of natural hazards.

This research has paid off! Many valuable lessons have been--and continue to be--learned about how to build and retrofit better, stronger, more hazard-resistant roads and highways. Slowly and steadily, these lessons have been translated into practical technological applications. New highway structures replace the old; existing structures are strengthened through retrofitting. These new and strengthened structures are helping to avoid much of the worst damage and are precluding additional damage when new disasters strike. But it takes a long time to do research and apply technologies. Also--and unfortunately--this research is, of necessity, grounded in tragedy and destruction, since we learn from yesterday's failures.

Thus, when a disaster such as the Jan. 17, 1994, Northridge, Calif., earthquake occurs, the results are simultaneously: unfortunate--the lives lost, the destruction of property and infrastructure; positive--the enhanced performance of new and retrofitted infrastructure; and hopeful--the improvements the Northridge lessons will allow us to make as our knowledge base grows.