According to the JMA, the probability of a strong earthquake in the Nankai Trench is relatively higher than usual, but this does not mean that an earthquake will necessarily occur within a certain period of time. The warning is expected to be in effect for a week, but officials warned that the public should not lose vigilance even after it is lifted, the Japan Times reports.
According to the Cabinet of Ministers of Japan, the JMA issues such warnings when abnormal phenomena are observed along the Nankai Trench or when it is assumed that the probability of an earthquake has increased dramatically.
The agency's information about mega-earthquakes in the Nankai trench is provided at two levels - "alert", which does not require evacuation of the population, and a higher level of warning (it means that people should be more vigilant, and officials at the same time urge those who cannot evacuate quickly to do so before it happens a strong earthquake).
From a seismological point of view, the probability of a strong earthquake in the Nankai Trench has increased several times, the agency said. Such earthquakes occur about once every 100 years, but it is impossible to predict them accurately. The last one occurred on December 21, 1946 and reached a magnitude of 8.1 - 8.4.
In a statement, the JMA said that in the event of a strong earthquake in the Nankai Trench, strong tremors are expected over a wide area from the Kanto region to Kyushu, as well as high tsunami waves along the Pacific coast from the Kanto region to Okinawa.
According to the Cabinet of Ministers, strong earthquakes in the Nankai Fault have historically caused serious damage. According to government damage estimates released in 2012, a tsunami caused by a mega-earthquake could kill up to 224,000 people. The death toll can be reduced by about 80 percent if sufficient evacuation measures are taken immediately after the earthquake, the Japanese authorities assure.
A warning about a possible mega-earthquake was issued after the 7.1 magnitude earthquake that occurred on August 8 off the coast of Kyushu Island. As previously reported, Japanese Prime Minister Fumio Kishida decided to cancel his trip to Central Asian countries due to the warning.
