The Wide Angle: How to Master a Seismic Disaster

Twenty-two seconds may not sound like a lot, but for anything controlled by a microprocessor, it's usually more than enough time to react, Kamigaichi notes. Elevators, for instance, tend to jam between floors when strong shaking sends their cables swinging. After a magnitude 6.0 earthquake in Chiba prefecture in 2005, 78 elevators got stuck. But with, say, a 6-second lead time, a moving elevator could stop at the ­closest floor and open its doors. Since April, in fact, all 227,000 elevators in Japan must now be equipped with control systems that accept JMA's signals.

The alerts could also trigger automated responses at power and chemical plants, dams, computer and communications networks, trains, and hospitals. And that's not all. Fujinawa's REIC now has more than 120 member companies, all of which see a lucrative market in selling early-warning products and services.

These include home systems that could automatically shut off gas valves and unlock doors, portable earthquake beepers that would flash a light or sound a chime when an alert is received, and data-distribution services that take the JMA alerts and relay them to customers. Last October, Nikkei Weekly reported that some analysts predict a $2.5 billion market for such applications.

According to Caltech's Heaton, early-warning systems "hold the greatest promise in the largest earthquakes." In those massive upheavals, he explains, the fault rupture occurs over a large area and can take some time to develop -- maybe as long as five minutes. "So while it's still rupturing, you can predict how large the earthquake is likely to become, given its current size."

Linking the Network

To ensure that you can detect the first rumblings of any earthquake, you need a dense network of seismometers blanketing the entire country. Japan's arrangement of about 1,000 stations also includes high-speed communication links connecting each station to a central data-processing center in Tokyo, plus software to do the seismic calculations and distribute the alerts. The seismic stations cost several billion dollars; the five-year effort to create the early-warning network and its attendant applications began in 2002 and is expected to eventually cost about $160 million.

Japan didn't start entirely from scratch. The country already had a number of stations, used by government and academic scientists to study seismic phenomena and to prepare public bulletins immediately following an earthquake. (If you've been in Japan during a sizable earthquake, you may have noticed that TV stations there broadcast announcements within a few minutes of the actual event.) Separately, Japan Railways had developed its own automated early-warning sensors along its bullet-train routes; they offered strong proof that the concept of early-warning alerts could work.

In the current network, JMA runs about 200 of the stations; another 800 or so stations are maintained by the National Research Institute for Earth Science and Disaster Prevention (NIED). A few dozen others belong to universities. The stations come in various shapes and sizes. JMA's are located on the surface; inside each concrete container sit a coffee-can-size strong-motion seismometer (which detects the strong shaking most likely to damage structures) and a similarly proportioned seismic-intensity meter (designed to measure lower levels of shaking). NIED's stations are all buried in boreholes -- some as shallow as 100 meters, some as deep as 3 kilometers -- to help isolate the instruments from artificial noise.

The communications links also differ. JMA uses leased lines, which can transmit a signal from the station to the JMA data center in about 0.2 seconds. NIED's signals travel through the regular Internet -- which takes an average of 1.5 seconds but is much less expensive.

After testing the network for about two years, JMA began transmitting the first earthquake early-warning alerts last August to a limited set of 70 recipients, including REIC and Nippon Telegraph and Telephone Corp. (NTT). Since then, more than 300 organizations have signed up to receive the information. Some of the groups have a direct link to the JMA data center; others receive the information, repackaged to suit their needs, from groups such as REIC.

Having the data flow through an intermediary may seem like it would introduce an undesirable delay -- especially when the warning itself comes only a few seconds in advance of the quake -- but traveling through REIC servers adds only about a tenth of a second to the transmission time. Hiroshi Tsuda, general manager of C5, a Tokyo Internet service provider, says it can take about four seconds from when the P wave is detected until the alert reaches REIC; from there, it takes just one more second to pass through C5's own data center (where it's encoded to prevent tampering by malevolent hackers and routed through the regular Internet) and then on to C5's customers.

The Quake Warning System in Practice

Masanori Kanazawa is one of those customers. He and his orange tabby cat recently moved into a modern two-bedroom apartment in the Dynacity Tokyo River Gate complex at the northeastern corner of the city. One of the big draws of moving there, he says, is the built-in earthquake alarm.

During a demonstration in January, he was sitting on his living room couch reading the newspaper when suddenly the alarm emitted a piercing bleat, followed by a prerecorded female voice counting down the seconds to the earthquake's arrival. Kanazawa jumped to his feet, went to the kitchen to check that the gas stove wasn't on, and then headed for the front door."I feel safer," he said later. "Now all my friends want one, too."

Currently only a dozen or so apartment buildings in Tokyo have such early-warning systems, and like Kanazawa's they don't do much more than tell you an earthquake is approaching. One big improvement would be to have the alert automatically shut off gas lines. As yet, though, no gas company in Japan has agreed to do that, mainly because of the cost involved in retrofitting each gas meter but also because the companies are reluctant to relinquish control of their equipment, Fujinawa says.

Still, he projects that in five years more than half of Japanese residences will be equipped with earthquake alarms. He's particularly encouraged by NTT's entry into the field. The Japanese telecom giant plans to start offering earthquake alerts this year to subscribers of its high-speed communications service.

The company considered a number of ways to deliver the alerts, including leased lines, satellite, regular Internet, and Internet Protocol v6 multi-casting. According to Tsuyoshi Abe, manager of broadband business development at NTT, the last of those alternatives offers the best combination of cost and performance. In particular, IPv6 suffers fewer delays and is more secure than standard IPv4.

Abe says the company probably will charge around $2.50 per month for the earthquake alerts, on top of the regular roughly $50 monthly fee. Users could have their alerts arrive on their computers or on intercom-style phones. He expects the new feature to be popular. When the company ran a TV ad last fall touting the earthquake alerts, he says, "We got a very big response -- and we haven't even started it yet."

Broadcasting Controversies and False Alarms

In fact, broadcasting earthquake alerts to the general public has been a matter of some controversy. Originally, JMA planned to start such announcements in January. Concerned that the alerts would generate more panic and chaos than useful activity, however, it decided to delay the start until this September.

In the meantime, promotional campaigns in schools and the media have been educating people on how to behave in the face of an alert. Even then, Fujinawa concedes, "Some people can't control themselves. So we'll need others to act as disaster managers."

Another concern is false alarms. The initial early-warning alert is based on readings at just one seismic station, and there's some room for error. Alerts at present are issued whenever a station detects a tremor larger than 3.5 magnitude; there were about 430 such earthquakes in Japan from 2004 through 2006. About 20 others turned out to be false alarms and were subsequently canceled, usually within seconds.

"Of course we need to avoid false alarms, but it's impossible to make it zero," says JMA's Kamigaichi. "It's up to the public and the users to decide how they'll use the information."

If a train receives what turns out to be a false alarm and responds by slowing down, it's no big deal; the train simply accelerates again. But a semiconductor plant that shuts down its production line based on an erroneous warning could suffer big losses. In such cases, Kamigaichi says, the plant might wait a few seconds before shutting down, until a second alert confirms the initial report.

For the general public, too many false alarms might leave people frazzled or, more likely, jaded.

Ironing Out Technical Wrinkles

There are also a number of technical problems to be sorted out. Tests are being done on issuing alerts to cellphones, but in a real event, that would involve instantaneously reaching millions of users at once. "We don't yet have a good result there," Fujinawa says.

Heaton, the Caltech seismologist, thinks people will quickly learn to appreciate being notified about impending temblors. "One of the scariest things about an earthquake is that it starts without warning, and then once it starts you have no idea how large it will be," he says. "But if people got a message on their cellphones -- 'Light shaking will begin in 3-2-1' -- they might even enjoy it."

Since Japan began developing its seismic network, a number of other earthquake-prone countries have followed suit, including Mexico, Taiwan and Turkey. But no other nation "is even close in terms of investment in seismometers, communications and software development," Heaton says.

"It's easy to think of how these systems can work in theory, but to actually turn it into practice ... that's hard, and it's expensive." His own university operates about 150 seismic stations throughout Southern California that could in principle form the basis of an early-warning network. But the political will isn't there. "It's much easier to get money for counter­terrorism these days," he says. Other places in the developing world that might benefit from an early-warning system, such as Indonesia and Iran, can't afford the huge investment involved.

Just how well Japan's early-warning system will work is not yet known. There are some instances when it won't work at all: for those at or near an earthquake's epicenter, the S wave will arrive before an early-warning alert can even be issued, let alone be acted on. "It's not perfect information," cautions JMA's Kamigaichi. "It's not almighty."

"Still, even imperfect data are preferable to none at all. "The Japanese government has set a goal to reduce earthquake hazards by half in the next 10 years," notes REIC's Fujinawa. "Without the early-warning system, this goal will never be achieved."

Get the original story on IEEE Spectrum's Web site.

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