Image Courtesy of university of california, berkeley
Shock Waves Harmless shock waves known as primary waves (yellow circle) come seconds before slower, destructive secondary waves (red circle).

An early warning system that predicts an earthquake's approaching shock wave up to a minute before it strikes is ready to become operational throughout California. Further, a recently proposed bill would fund expansion of the system.

The bill, introduced by state Sen. Alex Padilla (D), would support the ShakeAlert system, developed by the U.S. Geological Survey and an international coalition of universities. It is based on Japan's primary-wave, or p-wave, detection system.

Japan has used the system to anticipate oncoming shock waves, says Padilla.

"The system is ready for use," says Richard M. Allen, director of the University of California, Berkeley Seismological Laboratory. The system will expand and improve upon the existing California Integrated Seismic Network (CISN), which currently has 400 instruments positioned to detect an earthquake's primary shock wave. While the primary wave is harmless, the secondary wave is slower and can be destructive, says Allen. The ShakeAlert system uses an algorithm to predict a quake's magnitude and when the secondary wave will reach certain regions. To make the system fully operational, some regions in the state need more sensors.

"The warning can be sent over the emergency broadcasting system," says Allen. The goal is to send an alert to personal cell phones, too, as Japan's system does, he says.

The bill would expand CISN's network, adding density to the system and upgrading sensors. Test phases of the current system proved successful enough to be adopted by Bay Area Rapid Transit. If the warning system were to send an alarm, the trains would stop automatically.

Allen says $80 million would cover the build-out costs and five years of operating costs. After this time, he predicts the annual operating costs at $16 million.