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.