National Geographic News: NATIONALGEOGRAPHIC.COM/NEWS
 

 

Shaky Start for New Quake Alert System in Japan

Julian Ryall in Tokyo
for National Geographic News
May 30, 2008
 
After late or missed warnings, operators are struggling to figure out why a recently launched earthquake early-alert system in Japan isn't working as planned.

The system, run by the Japan Meteorological Agency (JMA), is designed to give people in the quake-prone country up to two minutes' warning of approaching shock waves.

"If the system works properly, then it will contribute significantly to reducing the impact of disasters," said Masahiko Murata, deputy director of the projects department at the Disaster Reduction and Human Renovation Institution in Kobe.

"Even a few seconds' warning will enable construction sites to stop heavy machinery, let people get out of elevators in tall buildings, or give time for trains to come to a stop."

But an earthquake in January failed to trigger an alert, and another in April saw the warning arrive too late.

Critics are now concerned that further failures may cause the public to distrust the system and ultimately ignore warnings.

"The alert is issued after a seismic wave is observed from an earthquake, but there is very little time for us to analyze the data and estimate the scale of the event," said Keiji Doi, JMA's senior coordinator for seismic information.

"There may be errors in determining the exact location of the quake, its magnitude, the energy that has been released, and the intensity," he added.

"We are constantly working on the system and making improvements that we hope will make it more accurate in the future."

Approaching Waves

The Real-Time Earthquake Information Consortium, a Tokyo-based nonprofit organization, has estimated that the death toll from a major tremor can be reduced by 25 percent if an area receives just a two-second warning.

That figure jumps to 80 percent if a five-second warning is given, enabling people to take cover under tables, stand in doorways, or cover their heads with cushions or bedding.

JMA's early-warning system gathers data from a series of a thousand seismographs across Japan—200 operated by the agency and another 800 used by the National Institute for Earth Science and Disaster Prevention.

The seismic stations measure the intensity of a quake's primary wave, or P-wave, which travels through rock at about 4.3 miles (7 kilometers) a second. This data gets sent automatically to the agency.

Scientists can then use the P-wave to determine the scale of the quake's secondary wave, or S-wave. This wave moves slower—about 2.5 miles (4 kilometers) a second—but is what causes damage at the surface.

Prerecorded alerts are automatically broadcast on television and radio and are electronically transmitted to municipal governments, hospitals, construction sites, and railway operators.

The agency issues a warning only if the quake is predicted to be at level 5 or higher on the Omori Seismic Intensity Scale, the seven-point scale used widely in Japan.

Tetsuzo Fuyushiba, Japan's minister of land, infrastructure, and transport, launched the warning system in October 2007 amid high hopes for its effectiveness.

But on January 27, 2008, a level 5 quake struck in the early morning in Ishikawa Prefecture on Japan's northern coast.

No alert was issued, because the early-warning system predicted the tremor would be a level 4. No injuries were reported.

And on April 29 the agency issued a warning to residents of Okinawa Prefecture of a level 5.2 earthquake near the island of Miyako Jima—some four seconds after a level 4 tremor had shaken the area.

Once again no one was injured, but school buildings and airport facilities were damaged.

The agency believes the warning went out late because the quake's epicenter was very close to the island, so data on the seismic waves didn't arrive at the agency in time.

(Related: "Earthquake Fault Under Tokyo Closer Than Expected, Study Finds" [July 14, 2005].)

Nature's Power

These glitches in the warning system highlight the difficulty scientists face trying to anticipate an earthquake's destructive power.

(Related: Read about technologies for predicting the next "big one" in National Geographic magazine.)

And even with advance notice, some temblors are likely to be too strong to avoid significant damages.

In 1995 a level 7.3 quake hit the city of Kobe just before dawn, killing more than 6,400 people.

"Even if we had received a warning a few seconds in advance, there would have been nothing we could have done," said Nobuo Nakai, 69, who helped pull his neighbors from their wrecked homes in the quake's aftermath.

"Nature is so powerful, and we cannot accurately predict events such as this," he said.

"Some people say that animals like frogs and catfish can sense when an earthquake is coming and that they act oddly," Nakai added.

(Related: "Pandas Sensed China Quake Coming?" [May 15, 2008].)

But for the Kobe quake "no one was watching them at the time."
 

© 1996-2008 National Geographic Society. All rights reserved.