Early-warning Sensors in Focus After New Zealand Quake
Authorities from Asia to California are working on computerized systems to warn people of large earthquakes, which are in focus again after the deadly temblor in New Zealand. None of the warning systems have faced the real thing yet, though.
Researchers in the U.S. say networks of common laptop computers may be able to provide city-dwellers advance warning when big quakes are detected. Japan has already installed an automated system to send warnings several seconds before people feel the earth move. And on Tuesday a government-funded laboratory in Taiwan said it had developed equipment to sense earthquakes up to 27 seconds in advance, enough time to order evacuations and shut down mass transit.
The 6.3 magnitude quake in New Zealand on Tuesday killed at least 75 people and left hundreds missing, according to news reports.
In the U.S. state of California, where active fault lines periodically jolt Los Angeles and San Francisco, university researchers with federal government money have looked at algorithms that could take raw data from existing collection systems to determine a quake's magnitude, the degree of shaking and distance from a given location.
Scientists at one University of California campus have tapped networks of laptop PCs to detect earth movement by using data from their in-built accelerometers and software that works even when the machines are idle. Supercomputers may also be used to simulate the effects of a southern California quake.
On the other side of the Pacific Ocean, Taiwan's National Applied Research Laboratories said on Tuesday it had developed sensors 15 cm in diameter and 10 cm high to be placed on the ground to pick up nearby quakes up to 27 seconds before people feel them. It gives the early warning by detecting the faster-moving but harmless P waves to anticipate the slower but more dangerous S waves that arrive a few seconds later. The system cost NT$10 million (about US$338,000) and took three years to develop.
Of a 90-second quake, people are usually aware of just 40 seconds, and some of the unnoticed time comes ahead of the more obvious part, said laboratory researcher Lin Pei-yang. The system is also designed to tell how big a quake will be.
The sensors send data to small localized computers, which are programmed to guess an incoming quake's magnitude from the first vibrations and then broadcast messages to simple amplifiers and speakers. The computers would then send text messages to LED displays in the area, warning people of impending quakes and ordering evacuations or elevator shutdowns, for example.
Taiwan's system, to be tested in three schools and one building management firm, does not link the local sensors to a centralized computer or pick up more distant quakes. The group is pushing local systems for now, but many of the earthquake-prone island's quakes occur just a few dozen kilometers off its east coast.
One test school on Taiwan's northeast coast will program the equipment to order evacuations of the first floor and tell people upstairs to duck under their desks when a quake is detected. Taiwan's sensor setups, which are compatible with existing emergency broadcast systems, would eventually be installed in local schools, government offices and major company offices, Lin said. Local governments are expected to buy sets of them to distribute as they see fit.
"We hope to use these systems for whole districts of Taipei," he said.
In late 2007, Japan installed an automated system to send warnings several seconds before people feel any shaking. The Japanese meteorological agency's system can also calculate the location and strength of an earthquake within a few seconds before it hits. Cellular networks said that year they were planning to develop a way of routing government alerts automatically to phone users.
Japan's is the farthest along of the three systems.
Scientists have long warned that there is no reliable way to warn of an earthquake in time to be useful. What technology works best may come down to a sensor's distance from a quake's epicenter.
"To predict earthquakes is pretty hard," said Kuo Kai-wen, director of the Taiwan Central Weather Bureau's seismology center. "In the future, I think if the epicenter is close, like 10 kilometers away, you can't detect it (in time), as in New Zealand. But if they're further away, like 100 kilometers, the early detection system will have some use."
Taiwan's and Japan's positions on the Pacific Rim give both high odds of suffering a quake like the one in New Zealand. Taiwan's last major earthquake, in September 1999, killed about 2,400 people and injured 11,300. The island's Central Weather Bureau logs a minor quake almost every two days. In Japan, a 7.4 magnitude quake struck about two months ago in the outlying Bonin Islands.