A national study group has published a report on disaster prevention measures for the huge earthquakes and tsunamis that are expected in the "Kuril Trench" and "Japan Trench" offshore from Hokkaido to Iwate Prefecture.
In the event of a magnitude 7 class earthquake that is one size smaller than the expected mega-earthquake, information should be issued to call attention to the occurrence of a mega-earthquake.
On the other hand, since the frequency of actual earthquakes is low, about 1 in 100, experts point out that it is necessary to carefully consider the content and method of communication.
Regarding the area along the "Kuril Trench" from the Kuril Islands to the offshore of Hokkaido and the area of the "Japan Trench" from the south of Hokkaido to the offshore of Iwate Prefecture, the national government has estimated damage from a magnitude 9 class giant earthquake and tsunami. It was announced in December last year, and the report of the study group on disaster prevention measures was released on the 22nd.
Among these, in addition to hardware measures such as securing evacuation towers and evacuation buildings in consideration of snow and cold, if a magnitude 7 class earthquake occurs in or around the assumed epicenter area, a larger magnitude will occur. It also included information that calls attention to large earthquakes of 8 classes or more and should lead to reconfirmation of preparations.
As a countermeasure, "reconfirm daily preparations"
The measures called for do not include evacuation of residents, and it is said that they will reconfirm their daily preparations while continuing their daily lives and economic activities.
Residents are asked to fix furniture, check evacuation routes, and prepare items to bring out, and the response period is one week.
On the other hand, there is a low probability behind the demand for "not excessive response".
A magnitude 7 class earthquake is followed by an 8 class megathrust earthquake because it is about 1 in 100 in global statistics, and even lower in 9 class.
Information may be released about once every two years
While the probability of a huge earthquake is low, seismic activity is active off the coast of Hokkaido and Tohoku and in the coastal areas, so this information may be issued as frequently as once every two years.
The specific content of the information and how to convey it will be examined in the future, but experts have pointed out that careful consideration is required.
Disaster information expert “How to raise the level of regular preparation is important”
Toshitaka Katada, a specially appointed professor at the University of Tokyo's graduate school, who is a member of the national study committee, said, "If you repeat the response to this information, it will become like a" wolf boy. " It's not about how to raise the level of preparation for a huge earthquake and a big tsunami. "
The target area and conditions are
Information that calls attention to a huge earthquake is issued when an earthquake with a magnitude of 7.0 or more occurs from off Tokachi in Hokkaido to Iwate Prefecture.
The huge earthquake 11 years ago that caused the Great East Japan Earthquake had a magnitude of 7.3 two days ago, and post-mortem analysis points out that it may have led to a magnitude 9 earthquake.
The national government is planning to consider the areas to be called attention in the future, but since the impact of the tsunami caused by the huge earthquake is expected to extend from Hokkaido to Chiba prefecture, it is possible that a wide range will be covered.
"The response period is one week"
On the other hand, the content of the call is "Be careful not to respond excessively", and it is said that daily life and economic activities will be continued.
This is because in the global case, the number of cases that actually lead to a huge earthquake is about once in 100 times, and it is even less likely in the magnitude 9 class.
For this reason, residents are not required to evacuate in advance, and we call on them to fix furniture, check evacuation routes, and prepare items to bring out.
It is also necessary to secure a large stockpile of water and food as needed.
In addition to the means of confirming the safety of employees, it is also envisioned that companies will check the availability of stockpiles and refrain from working in places where there is a risk of flooding due to landslides or tsunamis as necessary. ..
The response period is one week.
It is necessary to prevent confusion, but we will consider how to convey it in the future.
The national and local governments will hold meetings in response to the announcement of information to confirm disaster prevention measures and inform residents.
The government will consider what kind of information will be announced in what form in the future, but it is also necessary to take measures to prevent confusion, such as buying up food while preparing for earthquakes and tsunamis.
"Temporary information" in the Nankai Trough is a model
The "Nankai Trough Earthquake Temporary Information" is a model for disseminating information that calls attention to this "subsequent earthquake," which is a huge earthquake that occurs following a single earthquake.
"Nankai Trough Earthquake Temporary Information" is information that calls attention and caution when an earthquake with a magnitude of 6.8 or more occurs along the Nankai Trough.
Even if you ask for evacuation in the Nankai Trough
In the event of a huge earthquake with a magnitude of 8 or more, residents who cannot evacuate from the tsunami in time after the earthquake is called to evacuate in advance as a “giant earthquake warning”.
This is because in the Nankai Trough, cases of a huge earthquake actually occurring on the east side and then on the west side have been confirmed not only in the Edo period but also in the Showa period.
On the other hand, in the event of a magnitude 7 class earthquake, you will be asked to "reconfirm your daily preparations and evacuate voluntarily if necessary" as a "caution for a huge earthquake".
This framework was used as a reference when the national study group examined disaster prevention measures for the "Kuril Trench" and the "Japan Trench".
However, since there have been no confirmed cases of large earthquakes with a magnitude of 8 or more, such as the Nankai Trough, we have not provided information such as "giant earthquake warning" and are trying to introduce a mechanism close to "giant earthquake caution". is.
In the Nankai Trough, it is a well-known issue even after 3 years
However, there is also a problem with "Nankai Trough Earthquake Temporary Information".
Even though it has been three years since the system was introduced, it has not spread to the residents.
When NHK surveyed 139 municipalities from Kanto to Kyushu from January to February, nearly 80% of the local governments answered that the content was "almost not permeated" or "not so permeated" to the residents. Has been reached.
Many local governments were worried about the confusion of residents due to the lack of information.
Expert “Discuss the risk of“ missed swing ”, which is a big difference from the Nankai Trough”
On the other hand, seismologists have pointed out that it is necessary to be careful about applying the mechanism of the Nankai Trench to the Japan Trench and the Kuril Trench.
Professor Satoshi Ide of the University of Tokyo Graduate School, who served as a member of the committee established under the national review committee, emphasizes that there is a big difference between the Japan Trench and the Chishima Trench and the Nankai Trench.
Regarding past activities, in the case of the Nankai Trench, the details are left in historical materials, but the knowledge of the Japan Trench and the Kuril Trench is limited.
Also, looking at how earthquakes occur, it is quite different from the Nankai Trough, where large-scale earthquakes are usually unlikely to occur, such as active magnitude 7 class earthquakes off the coast of Tohoku and Hokkaido.
“Telling you to know something is a minus”
Based on this, Professor Ide said, "There is a possibility that the number of missed shots will increase and the residents will get tired of the countermeasures themselves." Isn't it more negative to "specially treat" only "Tohoku Japan" and tell them that something is known? Social science, such as how much risk society can tolerate. It is necessary to think about appropriate measures from a different point of view. "
Minister of Disaster Prevention "Considering to save lives at all costs"
At the press conference on the 22nd, the Minister of State for Disaster Management Ninoyu said, "The huge earthquake we are targeting is one of the largest based on the latest scientific knowledge, and based on the lessons learned from the Great East Japan Earthquake, we aim to save lives at all costs. In the report, we set the three goals of saving lives, minimizing damage, and speeding up recovery as much as possible. We are going to promote measures. "
He added, "There was an earthquake that had its epicenter off the coast of Fukushima Prefecture on the 16th of this month, but I don't know when a huge earthquake will occur. ..