TOKYO — Japan, a nation highly susceptible to earthquakes, issued its first-ever “megaquake advisory” last week after a significant earthquake struck off the southeastern coast of Kyushu, the southern main island.
The magnitude 7.1 earthquake did not result in any fatalities or major damage. However, the advisory has caused widespread confusion and lingering anxiety among a population accustomed to regular seismic activity, sparking concern about the timing of the next major earthquake.
The Associated Press clarifies the meaning of the advisory, explains the recommended actions, and outlines the potential consequences if a massive earthquake were to strike Japan.
What is a megaquake advisory?
The Japan Meteorological Agency (JMA) issued the advisory after concluding that the magnitude 7.1 earthquake that occurred on August 8 on the western edge of the Nankai Trough increased the likelihood of another powerful earthquake.
There is a 70-80% probability of a magnitude 8 or 9 earthquake associated with the Nankai Trough within the next 30 years, and the probability is now “higher than normal” following the recent earthquake, according to the JMA.
However, this does not constitute a prediction of a megaquake at a specific time or location, emphasizes Naoshi Hirata, a seismologist at the University of Tokyo who leads the JMA’s expert panel. He urged the public to exercise caution and preparedness.
What is the Nankai Trough?
The Nankai Trough is an undersea trench that extends from Hyuganada, located in the waters off the southeastern coast of Kyushu, to Suruga Bay in central Japan. It stretches approximately 800 kilometers (500 miles) along the Pacific coast.
The Philippine Sea Plate in this region slowly pulls down on the Eurasian Plate, causing it to occasionally snap back. This action could potentially trigger a megaquake and tsunami, as stated by the JMA.
The last Nankai Trough earthquake off Shikoku in 1946, preliminarily estimated at magnitude 8.0, resulted in over 1,300 fatalities.
How damaging can a megaquake be?
In 2013, a government disaster prevention team projected that a magnitude 9.1 Nankai Trough earthquake could generate a tsunami exceeding 10 meters (33 feet) within minutes, potentially causing the deaths of up to 323,000 people, the destruction of over 2 million buildings, and economic damage exceeding 220 trillion yen ($1.5 trillion) to vast areas of Japan’s Pacific coast.
What is the government doing to prepare?
In response to the “megaquake advisory,” Japanese Prime Minister Fumio Kishida canceled his planned August 9-12 trip to Central Asia and announced that he would lead the government’s response, ensuring preventative measures and effective communication with the public.
The Fire and Disaster Management Agency directed 707 municipalities considered at risk from a Nankai Trough earthquake to review their response measures and evacuation plans.
Experts and officials have urged the public to remain calm and continue their daily social and economic activities while also securing emergency food and water and discussing evacuation plans with family members.
In a reassuring statement on Monday, JMA experts reported that they have not detected any abnormal seismic or tectonic activity that would indicate an imminent megaquake.
How are people reacting?
The “megaquake advisory,” filled with scientific terminology, has caused worry and confusion among the population. Some towns have closed beaches and canceled annual events, leading to challenges for travelers during Japan’s Obon holiday week, a time traditionally marked by festivals and fireworks throughout the nation.
Many individuals have postponed planned trips and rushed to stock up on rice, dried noodles, canned food, bottled water, portable toilets, and other emergency supplies. This surge in demand has resulted in empty shelves at numerous supermarkets in western Japan and Tokyo, even though the capital city is outside the at-risk area.
The Summit supermarket chain reported a shortage of microwavable rice and implemented purchase limits of one pack per customer.
Yoshiko Kudo and her husband Shinya expressed their difficulty in understanding the precise meaning of the advisory, the level of concern warranted, and the appropriate actions to take.
“We are trying not to go overboard. Excessive worry is not beneficial,” said Yoshiko Kudo.
“We are uncertain about how to prepare while still living normally as the experts advise,” remarked Shinya Kudo, a caregiver in his 60s.
Yoneko Oshima, while walking near a major train station in Tokyo, stated: “It’s frightening… They mention a (70-80%) chance within the next 30 years, but it could happen tomorrow.” Her recent purchase was a portable toilet. She emphasizes the importance of water for her diabetic husband, who requires medication after every meal.
“I intend to use this opportunity to create a list and ensure we have everything readily available,” Oshima said. She has not altered her holiday plans for this week, but her daughter canceled a planned trip to Mount Fuji.
In Matsuyama city, situated on the island of Shikoku, which is known for its hot springs, hotels, and resorts, establishments have reviewed their evacuation procedures and emergency equipment. They have also implemented a radio communication system for emergency use. Since the advisory was issued, they have received hundreds of cancellations, according to Hideki Ochi, director of the Dogo Onsen Ryokan Association.
Rail companies operating in the region have announced that their trains are operating at slightly reduced speeds as a precautionary measure.
A crisis management task force in the coastal town of Kuroshio in Kochi prefecture, where a tsunami as high as 34 meters (111 feet) was predicted in the government’s risk analysis, initially established 30 shelters across the town. However, only two remain open following Monday’s JMA statement that there is no indication of an impending megaquake.
Higashi Osaka urged residents on its town website to avoid “unnecessary and non-urgent” travel in the event of a major earthquake.
The popular seaside town of Shirahama in Wakayama prefecture announced that its four outdoor hot springs, parks, and other facilities would be closed for a week. The town’s annual fireworks festival, scheduled for Saturday, was also canceled.