Japan, a nation frequently experiencing earthquakes, issued its inaugural “megaquake advisory” last week in response to a powerful earthquake that struck off the southeastern coast of Kyushu.

The magnitude 7.1 quake resulted in no fatalities or severe damage, but the advisory has sparked widespread confusion and anxiety among the population, accustomed to regular seismic activity, concerning the timing of the next major quake.

The Associated Press explains the implications of the advisory, the recommended actions for the public, and the potential consequences of a massive earthquake in Japan.

Following the August 8th magnitude 7.1 earthquake that occurred on the western edge of the Nankai Trough, the Japan Meteorological Agency issued the advisory, concluding that it heightened the probability of another significant earthquake.

There exists a 70-80% chance of a major earthquake associated with the Nankai Trough within the next three decades, and the JMA asserts that the probability is now “elevated” subsequent to the recent quake.

However, Naoshi Hirata, a seismologist at the University of Tokyo and head of the JMA’s expert panel, emphasizes that this advisory does not predict a megaquake at any specific time or location. He encourages vigilance and preparedness among the populace.

The Nankai Trough, an undersea trench extending from Hyuganada off the southeastern coast of Kyushu to Suruga Bay in central Japan, spans approximately 500 miles along the Pacific coast.

The JMA explains that the Philippine Sea Plate’s gradual downward movement on the Eurasian Plate occasionally causes a rebound effect, which could trigger a megaquake and tsunami.

The last Nankai Trough earthquake, which occurred off Shikoku in 1946, registered an initial magnitude of 8.0, causing the loss of over 1,300 lives.

In 2013, a government disaster prevention team projected that a magnitude 9.1 Nankai Trough quake could generate a tsunami exceeding 33 feet within minutes, resulting in the deaths of as many as 323,000 individuals, the destruction of over 2 million buildings, and economic damage exceeding $1.5 trillion to vast stretches of Japan’s Pacific coast.

In response to the “megaquake advisory,” Prime Minister Fumio Kishida cancelled his planned August 9-12 trip to Central Asia and declared his commitment to leading the government’s response, ensuring preventive measures, and facilitating public communication.

The Fire and Disaster Management Agency directed 707 municipalities identified as being at risk from a Nankai Trough quake to reassess their response measures and evacuation plans.

Experts and officials have urged the public to maintain composure and continue their daily social and economic activities while concurrently securing emergency food and water supplies and discussing evacuation plans with family members.

In a reassuring statement on Monday, JMA experts affirmed that they have not detected any abnormal seismic or tectonic activity indicative of an impending megaquake.

The “megaquake advisory,” filled with scientific terminology, has instilled anxiety and confusion among the populace nationwide. Some towns have closed beaches and cancelled annual events, creating challenges for travelers during Japan’s Obon holiday week, traditionally a time for festivals and fireworks across 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 goods, emptying shelves at numerous supermarkets in Tokyo, even though the capital is outside the at-risk area.

The Summit supermarket chain reported a shortage of microwavable rice and has imposed a limit of one pack per customer.

Yoshiko Kudo and her husband Shinya expressed difficulty in comprehending the exact implications 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,” Yoshiko Kudo remarked.

“We are unsure how to prepare while maintaining a normal lifestyle as advised by the experts,” said Shinya Kudo, a caregiver in his 60s.

Yoneko Oshima, walking near a major train station in Tokyo, expressed her apprehension: “It’s frightening… They say there’s a (70-80%) chance in 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 seize this opportunity to create a list and ensure we have everything readily available,” Oshima stated. While she has not altered her holiday plans for this week, her daughter cancelled a planned trip to Mount Fuji.

In Matsuyama city on the island of Shikoku, renowned for its hot springs, hotels, and resorts, have reviewed their evacuation procedures and emergency equipment, and have implemented a radio communication system for emergency use. They have received numerous cancellations since the advisory was issued, according to Hideki Ochi, director of the Dogo Onsen Ryokan Association.

Rail companies serving the region have reduced train speeds slightly as a precautionary measure.

A crisis management task force in the coastal town of Kuroshio in Kochi prefecture, where a major earthquake was predicted in the government risk analysis, initially established 30 shelters across the town. However, only two remain open following Monday’s JMA statement that there has been no indication of an imminent megaquake.

Higashi Osaka urged residents on the town’s website to refrain from “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. Saturday’s annual fireworks festival was also cancelled.