Seismic wave monitoring provides breathing space

In 1868, the year a magnitude 7 earthquake hit the San Francisco Bay Area, J.D. Copper, a physician, gave the first description of an early warning system in an editorial for a local newspaper. Copper believed the public could be given advanced warning by the use of seismic waves.

"A very simple mechanical contrivance can be arranged at various points from 10 to 100 miles from San Francisco, by which a wave of the Earth high enough to do damage will start an electric current over wires now radiating from this city and almost instantaneously ring an alarm bell, which should be hung in a high tower near the center of the city," he wrote.

Almost a century later, in 1965, engineers for Japan Railways Group decided to install seismometers on the routes used by their newly designed bullet trains to warn drivers to brake and slow their trains to avoid being derailed. It was the first time an early warning system had been used anywhere in the world.

The application of early warning systems on trains has improved constantly, and in the early 1990s, Japan introduced the Urgent Earthquake Detection and Alarm System, aka UrEDAS, a seismic network for railways.

In 2007, the idea of exploiting the time between the nondestructive primary wave and the damaging secondary wave was put into large-scale use by UrEDAS for the first time. Taking that as its model, the Japan Meteorological Agency designed an earthquake early warning system for general use.

By deploying seismic stations nationwide, the agency uses a number of methods to notify the public of imminent earthquakes, including television and radio bulletins and alerts sent to mobile phones. Japan's major mobile phone carriers support this service free of charge, which is crucial in a country with millions of phone users.

In 1991, Mexico, another earthquake-prone country, introduced an early warning system for its capital, Mexico City. Using the same approach as UrEDAS, the country installed seismometers along the coastline to detect temblors. Warnings are broadcast in the capital via television or loudspeakers, usually about one minute in advance of the quake.

In 2009, Canada deployed an on-site earthquake early warning system called ShakeAlarm in a highway traffic tunnel. To protect the transportation infrastructure, when a quake occurs, the system is triggered and closes the gates at the tunnel's entrances.

In 2011, the United States introduced ShakeAlert, an experimental early warning system for the West Coast and the Pacific Northwest. Automated alerts are issued to give people time to take action, and the system halts traffic and transportation in addition to automatically shutting down sensitive public facilities.

According to the Los Angeles Times, to expand funding for the development of the early warning system, the US Congress approved the allocation of $5 million as part of the Consolidated Appropriation Act. It was a milestone in the country's early warning system.