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The government’s special advisory that urged residents to be cautious against a possible Nankai Trough earthquake has been lifted. However, this does not mean that the threat of a huge earthquake has disappeared. It is essential to continue to inspect the way information is disseminated.
The advisory, officially called Nankai Trough Earthquake Extra Information with the keyword Megathrust Earthquake Attention, was issued for the first time in response to a magnitude 7.1 earthquake that occurred in the Hyuganada Sea off Miyazaki Prefecture, with its epicenter within the presumed focal region of an anticipated Nankai Trough earthquake. The advisory noted that “the possibility of a huge earthquake has increased compared to normal times.”
In the 29 prefectures, 707 targeted municipalities were asked to reconfirm their earthquake preparedness for one week, among other measures.
During the summer vacation period, some people changed or canceled their travel and homecoming visit plans. In some areas, stores ran low on water and emergency supplies.
Nevertheless, the situation did not cause major disruption in general. This has been attributed to the fact that residents accepted the government’s information with composure and acted calmly.
On the other hand, local governments were divided in their judgments over whether to close beaches or cancel events such as fireworks displays. This may have reflected differences in local circumstances, such as how long it might take tsunami to arrive and whether or not evacuation guidance plans already existed.
There is no clear standard for the degree to which social activities should be restricted by government calls for action. It is a difficult issue to judge, as individual perceptions differ.
The government’s calls for action this time may have provided an important opportunity for people to confirm what they should do at home or at work in case of an emergency. It is hoped that the central and local governments will review their responses this time and determine whether there were any issues that have been overlooked so far.
Current science cannot completely predict when and where the next huge earthquake will strike. Even though the period of the government’s calls for action has ended, the probability of a Nankai Trough earthquake, which was originally estimated at “70% to 80% within 30 years,” has not changed.
In addition to the Megathrust Earthquake Attention issued this time, the extra information can also include the keyword Megathrust Earthquake Alert, which would indicate a higher degree of urgency. Not a few residents and people involved in local governments were puzzled over what level of caution was necessary when they experienced this information provision mechanism for the first time.
The central government should endeavor to make the extra information system well known to the public on a regular basis and try to provide explanations that are easy for the general public to understand when the information is announced.
When an earthquake measuring lower 5 on the Japanese seismic intensity scale of 7 occurred in Kanagawa Prefecture the day after the announcement of the extra information, a statement was issued saying that the earthquake was structurally different from and not related to a Nankai Trough earthquake. The dissemination of such information based on scientific findings may help prevent confusion and the spread of false rumors.
