Japanese Govt Makes 1st Major Revisions to Nankai Trough Earthquake Guidelines for Enhanced Preparedness

The Yomiuri Shimbun

20:00 JST, August 8, 2025

In response to an increased likelihood of a Nankai Trough earthquake, the government has revised its guidelines for special preparations, such as ensuring cash and personal identification cards are readily available.

On Thursday, the Cabinet Office announced revised Nankai Trough Earthquake temporary information guidelines that outline the actions that residents, businesses and local governments should take.

The guidelines’ content has been expanded based on problems that were highlighted when the information was publicly issued for the first time in August last year.

The revised guidelines urge residents to prepare for immediate evacuation in the event of an earthquake and ask businesses and local governments to secure safety while continuing operations.

The guidelines were first established as a framework in May 2019, coinciding with the launch of the temporary information system. This is the first major revision since their creation.

The Nankai Trough earthquake envisioned is a massive earthquake of magnitude 8 or 9 that occurs along the Nankai Trough, extending from off the coast of Shizuoka Prefecture to off the coast of Miyazaki Prefecture.

According to the government’s Earthquake Research Committee, there is an “about 80% probability” of its occurrence within the next 30 years. In March, the government released a damage estimate projecting up to 298,000 direct deaths.

The temporary information system issues a megaquake advisory for earthquakes of magnitude 7 or higher and a megaquake alert for those of magnitude 8 or higher along the Nankai Trough.

The megaquake advisory was first issued on Aug. 8 last year following a magnitude 7.1 earthquake off the coast of Miyazaki Prefecture.

However, the lack of clear guidelines resulted in conflicting responses from different sectors, such as event cancellations and railway operations. Ultimately, this confused the public.

The revised guidelines primarily expand on the actions to be taken during a megaquake advisory.

In the event a temporary advisory is announced, residents are urged to undertake “special preparations” in addition to confirming emergency stockpiles and securing furniture.

These preparations include keeping an identification card and cash accessible in case of an immediate escape during an earthquake and taking disaster preparedness actions depending on the situation.

The guidelines state that companies and local governments should “judge their actions independently while considering the balance between ‘securing safety’ and ‘continuing socioeconomic activities,’” adding that it is desirable to “continue operations as much as possible” after confirming safety.

The revised guidelines included examples from last year, such as a case in which a bon dance was held after an evacuation plan was publicized and a case in which a fire department event was postponed, prioritizing immediate readiness.

For public transportation, the guidelines stipulate that, in principle, no restrictions will be placed on operations when a megaquake advisory is issued, to ensure both safety and economic activities.

The responses for a megaquake alert were also partially reviewed. The guidelines state that for areas of advanced evacuation — where residents are asked to evacuate a week in advance — it is also effective to designate below-sea-level areas as pre-evacuation zones. These areas are at risk of inundation from levee breaks during an earthquake.