Alerts Near and Far
Public earthquake warning systems have existed in one form or another for decades. In the 1960s Japanese engineers built seismometers into the tracks of the new Shinkansen bullet trains. Excessive shaking would sound an alarm, giving the conductor a chance to slow the train. Later, scientists designed systems that would use far-flung seismometers to relay warnings in advance of the heaviest shaking. Mexico’s network is designed to detect earthquakes near the coastline and broadcast warnings in Mexico City, an aging metropolis of more than 20 million people built on a silty lakebed that amplifies seismic waves. The distance between the coast and the city can provide more than 60 seconds of warning.
Mexico’s system came online back in 1993. Two years later it would experience its first serious test. On October 9, 1995, a magnitude 8.0 earthquake struck just off the coast of Manzanillo. The warning system picked up the tremor and broadcast alerts on television and radio stations in Mexico City and via a dedicated radio alert system similar to weather radio in the U.S. As a result of the warning, officials were able to stop the metro system 50 seconds before the shaking arrived, and schools were evacuated as planned.
Japan’s system, which went live in 2007, makes heavy use of personal technology. Alerts go out not only on television and radio but through special receivers in homes, offices and schools. Pop-up windows on computers show a real-time map with the epicenter’s location and the radiating seismic waves. A timer counts down to the shaking at your location and highlights predicted intensity. Cell phone providers broadcast a text message–like warning to all phones with a characteristic audible alarm. Critical industries such as nuclear power stations, rail systems, airports and hazardous manufacturing facilities use dedicated communications systems tailored to their needs.
Japan’s experience shows that earthquake warning systems do not just help protect lives, they also help the bottom line. In 2003 two earthquakes near Sendai, Japan, caused more than $15 million in losses to the OKI semiconductor manufacturing plant because of fire, equipment damage and loss of productivity. The plant had to be shut down for periods of 17 and 13 days, respectively, following the quakes. The company then spent $600,000 to retrofit the factory and to install a warning system. In two similar earthquakes since, the factory suffered only $200,000 in losses and 4.5 and 3.5 days of downtime.
The California Curse
California is earthquake country. In 2006 a consortium of universities and state and federal agencies joined forces to develop ShakeAlert, a warning system for the state. Right now a prototype system links together approximately 400 seismic stations and will soon send alerts to a small group of test users. The finished system will provide not only immediate single-station alerts to those near the epicenter but also widespread network-based alerts to those farther away. If all goes well, alerts will be available within five seconds after the first P-wave hits.
Yet California still has a long way to go before it can be blanketed with a comprehensive network such as Japan’s. The 400 existing seismic stations are concentrated around the San Francisco Bay and Los Angeles metropolitan areas, leaving gaps elsewhere. Even though most Californians live near these two areas, the gaps both slow the system and reduce its accuracy, because it takes longer to detect the P-waves at multiple locations. In Japan instruments are spaced every 15 miles across the entire country. That level of spacing in California would deliver the best system performance, with fewer false and missed alarms and more warning time.
Those alerts, like Japan’s, would leverage the networked gadgets that most people carry every day. Individuals would get an alert on their mobile phone indicating predicted shaking intensity, a countdown until the shaking starts, and perhaps a simple instruction such as “get under a table” or “move to your safe zone.” Larger organizations with infrastructure spread over a region will likely want more detailed information such as a real-time map showing the wave progression and the distribution of ground shaking across the affected area.