Changing Disaster Measures in Great Earthquake

Central Disaster Management Council decided to review its system of measures for huge earthquake in offshore Japan on Tuesday. While it had been based on the prediction of earthquake in Tokai area, new measures would be informing likeliness of great earthquake with a hint of abnormal seismic phenomenon for the greater area called South Sea Trough. The experts realized that science would not be able to predict a great earthquake.

According to Great Earthquake Management Special Measures Act in 1978, Prime Minister issues declaration of warning for evacuation of the people or stopping public transportation. The declaration would be announced with predictive information about diastrophism or quakes from Japan Meteorological Agency. While that information has been supposed to be provided with two or three days before the great earthquake, the experts of the council concluded that the prediction would actually be difficult to contribute to the declaration.

JMA is going to stop updating Tokai Earthquake Prediction Information or Caution Information to the residents of Tokai region on November 1^st. Instead, the agency will issue information on earthquake in South Sea Trough, which extends to a broad coastal area from Shizuoka to Kochi. That will be made with phenomenon such as a major earthquake in the east of the trough or an earthquake with Magnitude 7 within the trough. The government will then issue information for evacuation.

Forty years ago, the experts thought that the possibility of a great earthquake was high in Tokai area. With advanced study on seismic science after East Japan Great Earthquake in 2011, they realized that they could not determine where a great earthquake would occur not only in Tokai area but broader South Sea Trough.

The final report of the council requires the government to make evacuation plan in a great earthquake. The evacuation will be started not with auspice but with actual earthquake in South Sea Trough. The experts found that former great earthquakes in the trough were consecutive quakes from Shizuoka to Kochi. As series of earthquakes may occur within three days after one major earthquake, the report recommended that the people in western area of the trough should evacuate as soon as a major earthquake occur in the east area.

The experts have been highly reluctant to review the measures based on scientific study about earthquake prediction. However, huge impact of great earthquake on the society could not afford them to stay on expecting ambiguous information. It is obvious that disaster cannot be exactly predicted.