Applications and Benefits of Earthquake Early Warning: Implementation and Alert Times Across California

Richard M. Allen and Ajay Limaye
University of California Berkeley

1906 Earthquake Conference/SSA April 2006

Earthquake Early Warning (EEW) systems are intended to complement existing long-term mitigation and rapid response strategies by offering short-term seismic hazard mitigation. EEW has the potential to reduce fatalities, casualties, costs and the long-term disruption of future earthquakes while using existing seismic infrastructure. The probabilistic distribution of warning times provided by an EEW in the San Francisco Bay Area can be estimated using the set of likely future earthquakes identified by the Working Group on California Earthquake Probabilities. The warning times for the city of San Francisco vary from a few seconds to ~70 sec. For the most damaging events, similar to the 1906 rupture, it is likely that an EEW system would provide more than 15 sec of warning.

EEW is already operational in Japan, Taiwan, Mexico, Turkey, and Romania, and is under development in Italy, Greece, and the U.S. Warning messages are currently used by transportation systems such as rail and metro, as well as private industries, including construction, manufacturing, and chemical plants. They are also used by utility companies to shut down generation plants and dams, and emergency response personnel to initiate action before ground shaking. In addition, schools receive warnings, allowing children to take cover beneath desks, housing units automatically switch off gas and open doors and windows, and entire complexes evacuate. Many of these applications would also be appropriate in California.

EEW systems are no panacea for the mitigation of seismic hazard, but they represent a significant new effort to supplement the approaches currently used in California. No single approach to earthquake hazard mitigation is sufficient or able to prevent all losses. Building codes are intended to prevent collapse of most structures in most earthquakes. Similarly, while EEW cannot warn everyone prior to all ground shaking events, it can offer warning to many affected people most of the time. If the mitigation of natural hazards is our intent, it is important to ensure that we continually ask what more could be done and what new technologies can be applied.

© Richard M Allen