Editorials

Don't rely on quake predictions

There exists a law that empowers the prime minister to issue an emergency alert of an imminent Tokai earthquake — a major temblor long forecast to hit Shizuoka Prefecture and its adjacent areas — on the basis of a short-term forecast. The Abe administration now plans to widen the application of the law to cover a Nankai Trough earthquake — which is predicted to wreak massive damage over wide areas stretching from Kanto to Shikoku and Kyushu. However, the validity of the law itself is in question since there is no scientific grounds for the presumption that it is possible to predict an earthquake just before it strikes.

The Law on Special Measures Concerning Countermeasures for Large-Scale Earthquakes went into force in 1978. At that time, even the National Land Agency (one of the predecessors of today’s Land, Infrastructure, Transport and Tourism Ministry), which was in charge of disaster prevention, was said to be reluctant about enacting the law due to the lack of scientific evidence supporting short-term earthquake predictions. It is believed that then-Prime Minister Takeo Fukuda strongly pushed for the legislation.

The law empowers the prime minister to issue an official alert when a large-scale quake is forecast as imminent. Under the law, a six-member panel was set up in 1979 to evaluate precursors of a large-scale temblor whose hypocenter would be in a zone covering the central and western parts of Shizuoka Prefecture, Suruga Bay and the Sea of Enshu. The panel receives data from strain meters installed by the Meteorological Agency several hundred meters underground in 27 locations in Shizuoka Prefecture and the eastern part of Aichi Prefecture. If the expansion or contraction of bedrock is detected in at least three locations, the panel will examine the data to determine if a large temblor is imminent. If the panel predicts that the quake will hit shortly, the prime minister will issue an alert and take such steps as evacuating local residents, stopping train services, restricting road traffic and stopping bank operations to prevent confusion and reduce damage — measures bordering on martial law.

The problem, however, is that the core of the scenario envisaged in the law — that an imminent earthquake is predictable — had no scientific basis. Nevertheless, the law has for decades been spared abolition — likely because of the don’t-rock-the-boat mentality among bureaucrats, lawmakers and government leaders. This in itself is a serious problem, but the Abe administration is seeking to expand the law’s application to cover a Nankai Trough quake.

As justification for the move, the government uses the following explanation: Although it was thought in the past that a Tokai earthquake would occur independently, it is now thought that a Nankai Trough quake can originate in vast areas extending from Shizuoka — where a Tokai quake is forecast to strike — to the sea off Kyushu. Therefore under the government’s logic the law’s application should be widened.

A study group including seismologists under the Central Disaster Management Council, headed by the prime minister, said in its 2013 report that it is technologically possible to detect precursors of a major quake if the signs are large enough, and that if they are detected, it can be stated that the probability of a major temblor is high, even if uncertain. But the conclusion is problematic because it omits the fact that precursors that can serve as grounds for the predication of imminent quakes have yet to be discovered.

The Meteorological Agency’s website says that a Tokai earthquake is deemed the only one in Japan for which there is the possibility of a short-term forecast. But there is little scientific support for such a statement. The 2013 panel report itself admits that generally speaking it is difficult to make a short-term prediction of an earthquake with the method used for the observation of a Tokai quake.

In 2012, an Italian court sentenced six seismologists and one government official to six years in prison on a charge of manslaughter for giving an assuring message that there was no danger of a major quake coming just six days prior to a 2009 magnitude-6.3 quake that hit the city of L’Aquila, killing 309 people. The International Association of Seismology and Physics of the Earth’s Interior declared after the court ruling that “reliable short-term prediction of earthquakes is not possible at present” and that “claims to the contrary may induce false expectations and incorrect behavior in the population and authorities.” In the appellate trial in 2014, the six seismologists were acquitted while the government official had his jail term reduced to two years. The ruling was finalized by the Italian Supreme Court the next year.

Two months after the March 2011 Great East Japan Earthquake and tsunami devastated the Pacific coastal areas of the Tohoku region, the International Commission on Earthquake Forecasting for Civil Protection, which comprised seismologists from various countries including Japan, said in a report titled “Operational Earthquake Forecasting — State of Knowledge and Guidelines for Utilization” that “in spite of continuous research efforts in Japan, little evidence has been found for precursors that are diagnostic of impending large earthquakes, including the Tokai event (which has not yet happened).” The report also said, “The Commission has identified no method for the short-term prediction of large earthquakes that has been demonstrated to be both reliable and skillful,” adding that “in particular, the search for precursors that are diagnostic of an impending earthquake has not yet produced a successful short-term prediction scheme.”

These statements show that methods for short-term prediction of earthquakes have not been established. While it is worthwhile for scientists to continue to search for such methods, it will be wrong to keep in force a law that assumes without scientific basis that an imminent earthquake is predictable. Instead of expanding the law’s scope and investing time and effort into an endeavor that has no scientific basis, the government should abolish the law, and concentrate its efforts on minimizing the damage caused by quakes.