A new network of 250 Global Positioning System stations in California could provide rapid early warnings of major earthquakes. The alerts could provide enough warning to automatically shut down gas lines, slow or stop trains, warn doctors performing surgery or even prevent a nuclear reactor melt down.
At on date, there is no seismic early warning system in the United States.
Geophysicist Ken Hudnut, at the US Geological Survey in Pasadena, California, is the team that has just finished installing the GPS network in the Los Angeles area. And they have presented a research paper on it at the annual meeting of the American Geophysical Union in San Francisco.
It is designed to sense movement on the San Andreas Fault and the team is now waiting for an earthquake to test the system.
The network will work by detecting movement between GPS stations on opposite sides of the fault. The stations are capable of relaying their position once a second and can detect the first 5 cm of movement within 10 seconds, says Hudnut. Seismic waves travel at about 5 km/second, so cities more than 50km from the epicentre could receive a warning before any shaking starts.
Taiwan already has an alert system based on the seismographs that detect shaking.