A government panel has recommended giving up on short-term earthquake predictions, a cornerstone of current disaster policy, and focusing instead on preparedness.
A government panel has recommended giving up on short-term earthquake predictions, a cornerstone of current disaster policy, and focusing instead on preparedness.
The panel's final report, released May 28, was the first attempt for the central government to undertake a thorough review of the scientific ability to predict earthquakes shortly before they strike.
The panel concluded that it will be difficult to predict a quake along the Nankai Trough off Japan's Pacific coast by monitoring tectonic plate movement, which occurs between a few hours to a few days before it strikes.
There has not been a single case of accurately observing precursor plate movement to provide a hint for predictions, and the unexpected nature of the magnitude-9.0 Great East Japan Earthquake two years ago only provided further evidence that quake prediction would be extremely difficult.
The report instead recommended focusing on additional measures to prepare for a major quake that could strike at any time. Specifically, it encouraged households to stock up on enough food and supplies for at least a week, and called on local governments to implement measures against a possible large tsunami triggered by a quake along the trough.
Keiji Furuya, the state minister in charge of disaster management, said the central government would compile guidelines for dealing with natural disasters by the end of the current fiscal year.
That will likely involve a major overhaul of policy measures, which until now have focused on predicting a quake striking the densely populated Tokai region. Those measures are based on a 1978 special measures law to deal with major disasters that was passed after experts said a major quake could strike there at any time. The disaster management structure that was put in place was based on the supposition that such a quake could be predicted.
The Japan Meteorological Agency operates an around-the-clock monitoring system based on its observation network set up in the Tokai region using instruments costing 200 million yen ($2 million) each that are installed at 27 locations in the area.
Under the current plan for dealing with a Tokai quake, if any unusual crustal movement is observed, a panel of seismologists will be convened to predict that a quake would strike. Once that decision is made, the prime minister will issue a warning statement, and areas where major damage was forecast would prepare by limiting social and economic activities by, for example, suspending bullet train operations or canceling classes at schools.
According to a Cabinet Office estimate, the economic effect from the stoppage of railways and factories once a warning statement is issued would be about 170 billion yen a day.
When that structure to deal with a possible Tokai quake was established, there was some optimism that quake prediction might be possible, especially after a report that China had succeeded in making such a prediction.
However, further research showed the difficulties of making an accurate prediction and that became the majority opinion among academics after the 1990s. Many scientists also pointed to the fact that any Tokai quake would not occur independently, but would likely strike in conjunction with a Tonankai or Nankai quake.
For that reason, in 2003, the central government put together guidelines for dealing with a Tokai quake that called for strengthening anti-quake measures for buildings as one way to prepare for a sudden quake that could not be predicted.
Another law was passed that included measures to deal with a possible Tonankai or Nankai quake. That law led to the establishment of areas that were urged to promote measures for disaster management.
However, those laws and guidelines still did not cover every possibility.
Although there was agreement that a Tonankai or Nankai quake would likely occur at the same time as the Tokai quake, there were no legal provisions that called for special measures to be taken by municipalities in the Shikoku and Kinki regions even if a warning statement was issued for a possible Tokai quake.
Reflecting on that inadequacy, Furuya said on May 28, "We want to establish a forum for discussions on the desired measures under the current structure as well as on a future system for quake observation and information."
The review of the disaster management structure will involve comprehensive measures to deal with a possible quake along the Nankai Trough rather than deal separately with a possible Tokai quake and a possible Tonankai or Nankai quake.
A government panel earlier released
Quakes with magnitudes of about 8 have occurred along the Nankai Trough at intervals of roughly 100 to 150 years, but following the Great East Japan Earthquake, the central government decided to compile a scenario for a catastrophic earthquake that might be a once-a-millennium event.