Useful Geology Hiroki Kamata: Nankai Trough Earthquake Temporary Information 4 points to check to protect your life / 197 Economist Online Weekly

On August 8, a magnitude (M) 7.1 earthquake occurred off the coast of Miyazaki Prefecture, which is included in a high-level area known as the mega-earthquake Nankai Trough, and the Japan Meteorological Agency issued “ Nankai Trough Earthquake Temporary Information (Giant Earthquake Warning)” from Okinawa to Ibaraki. It was published in 707 cities in all prefectures (see Part 195 of this series). This is the first time which has been announced provisional information since the launch of the system in 2019, and calls for disaster prevention measures such as daily reconfirmation of preparedness in target areas.

The purpose of the temporary information is to quickly inform people of the relative increase in the potential of the Nankai Trough mega earthquake, and minimize the damage as much as possible. On the other hand, it is difficult to say that there is sufficient understanding of its meaning and the steps that should be taken. The temporary release of information has also caused unexpected financial losses, such as cancellation of accommodation, and discussions are still ongoing among experts and government departments as to how information should be provided.

There are two types of temporary information: the “Major Earthquake Warning” issued this time indicates the occurrence of an earthquake of magnitude 7 or higher in the area known as accept the center, and the “slow slide” in which the plate. the boundary surface moves slowly without vibration )” can be seen (see Part 45 of this series). Residents in the affected areas will be asked to reconfirm their daily preparations for about a week, and will also be asked to voluntarily evacuate if necessary.

Another type of “major earthquake warning” is when a major earthquake of magnitude 8.0 or greater occurs at a plate boundary within the assumed epicenter area, and areas where tsunami evacuation is not possible in time are urged to evacuate for a week in advance. . The basis of this “one week” is not based on seismology, but an administrative decision, and it was fully determined based on the results of a study carried out in the past regarding the period the country could sustain a life of evacuation.

Results are not very high

As the government has announced so far, there is still a 70-80% probability of a Nankai Trough mega earthquake occurring within the next 30 years, and a mega earthquake is likely to occur when surprising information will be revealed 0.1-0.5. %s is going up a bit. However, the price will not increase quickly, so this is provisional information…