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What Is Japan’s Nankai Trough Megaquake Advisory?

Japan's earthquake experts panel chief Naoshi Hirata talks about probability of megaquake on the Nankai Trough; in Tokyo, Japan, 08 August 2024 (issued 09 August 2024) after a magnitude 7.1 earthquake hit southwestern Japan on the day. (EPA/JIJI Press)
Japan's earthquake experts panel chief Naoshi Hirata talks about probability of megaquake on the Nankai Trough; in Tokyo, Japan, 08 August 2024 (issued 09 August 2024) after a magnitude 7.1 earthquake hit southwestern Japan on the day. (EPA/JIJI Press)
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What Is Japan’s Nankai Trough Megaquake Advisory?

Japan's earthquake experts panel chief Naoshi Hirata talks about probability of megaquake on the Nankai Trough; in Tokyo, Japan, 08 August 2024 (issued 09 August 2024) after a magnitude 7.1 earthquake hit southwestern Japan on the day. (EPA/JIJI Press)
Japan's earthquake experts panel chief Naoshi Hirata talks about probability of megaquake on the Nankai Trough; in Tokyo, Japan, 08 August 2024 (issued 09 August 2024) after a magnitude 7.1 earthquake hit southwestern Japan on the day. (EPA/JIJI Press)

Japan issued its first-ever advisory on higher-than-usual risks of a megaquake, after a strong magnitude 7.1 quake occurred on Thursday at the edge of a tremulous seabed zone along the Pacific coast known as the Nankai Trough.

A possible Nankai Trough megaquake and tsunami disaster could kill hundreds of thousands of people and cause a trillion-dollar damage to Japan.

Here's a look at the risks of what could be the biggest natural disaster in Japan's modern history.

WHAT IS THE NEW RISK OF A MEGAQUAKE?

Japan's Nankai Trough quake advisory panel said the chance of a bigger earthquake striking after a magnitude 7 tremor was once in a few hundred cases, relatively higher than regular times. Earthquakes with a magnitude larger than 8 are considered megaquakes.

Japan estimates the next Nankai Trough megaquake could be as powerful as magnitude 9.1.

University of Tokyo professor Naoshi Hirata, who chairs the panel, said in a press conference that residents in areas that would be hit by such a disaster should review evacuation procedures and stay vigilant for a week.

Japan is one of the world's most earthquake-prone nations sitting on the Pacific "Ring of Fire" arc of volcanoes and oceanic trenches. In 2011, more than 15,000 people were killed in a magnitude 9.0 quake in northeast Japan that triggered a tsunami and triple reactor meltdowns at a nuclear power plant.

WHAT IS NANKAI TROUGH AND WHY IS IT SIGNIFICANT FOR QUAKES?

The Nankai Trough is off its southwest Pacific coast and runs for approximately 900 km (600 miles), where the Philippine Sea Plate is subducting under the Eurasian Plate and the accumulating tectonic strains could result in a megaquake roughly once in 100 to 150 years.

The Japanese government had previously predicted a 70-80% chance of a magnitude 8 to 9 earthquake happening along the Trough in the next 30 years.

The magnitude of an earthquake is related to the length of the fault on which it occurs, according to the United States Geological Survey. The largest earthquake ever recorded was a magnitude 9.5 on May 22, 1960 in Chile on a fault that is almost 1,000 miles long.

THE POTENTIAL DAMAGE FROM NANKAI TROUGH QUAKE AND TSUNAMI

A megaquake could result in maximum measurable tremors to areas from central Shizuoka - about 150 km (93 miles) south of capital Tokyo - to southwestern Miyazaki.

Tsunami of up to 30 meters (98 feet) may reach Japan's Pacific coasts within minutes after the quake, depending on the epicenter and tidal situation.

Coupled with landslides and fire, the disaster would be expected to claim the lives of as many as 323,000 people and destroy 2.38 million buildings, forcing nearly 10 million survivors to evacuate.

Economic damage could total up to 220 trillion yen ($1.50 trillion), or more than a third of Japan's annual gross domestic product, with long-lasting impacts on infrastructure and supply chains for coastal industrial powerhouses producing cars and other key Japanese products.

PREVIOUS NANKAI TROUGH RELATED QUAKES

Nankai Trough earthquakes have been marked on Japan's historic records multiple times since 684, often with accounts of tsunamis striking coastal villages.

The most recent Nankai Trough quake happened in 1946 with magnitude 8.0 tremor and 6.9 meter tsunami, killing 1,330 people.

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Varieties

Huge Rotating Structure of Galaxies and Dark Matter Is Detected

A figure depicting the rotation of neutral hydrogen in galaxies residing in an extended filament, where the galaxies exhibit a coherent bulk rotational motion tracing the large-scale cosmic web, is seen in this undated illustration obtained by Reuters on December 4, 2025. (Lyla Jung/Handout via Reuters)
A figure depicting the rotation of neutral hydrogen in galaxies residing in an extended filament, where the galaxies exhibit a coherent bulk rotational motion tracing the large-scale cosmic web, is seen in this undated illustration obtained by Reuters on December 4, 2025. (Lyla Jung/Handout via Reuters)
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Huge Rotating Structure of Galaxies and Dark Matter Is Detected

A figure depicting the rotation of neutral hydrogen in galaxies residing in an extended filament, where the galaxies exhibit a coherent bulk rotational motion tracing the large-scale cosmic web, is seen in this undated illustration obtained by Reuters on December 4, 2025. (Lyla Jung/Handout via Reuters)
A figure depicting the rotation of neutral hydrogen in galaxies residing in an extended filament, where the galaxies exhibit a coherent bulk rotational motion tracing the large-scale cosmic web, is seen in this undated illustration obtained by Reuters on December 4, 2025. (Lyla Jung/Handout via Reuters)

Scientists have observed the largest-known rotating structure in the cosmos - a gargantuan thread-like assemblage of hundreds of galaxies, gas and dark matter that makes up a filament in the macrostructure of the universe called the cosmic web.

The filament, located about 140 million light-years from Earth, was observed by scientists primarily using the MeerKAT radio telescope located in South Africa, an array of 64 interlinked satellite dishes.

The rotating filament is astonishingly large, measuring about 50 million light-years long and 117,000 light-years wide. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). By way of comparison, our Milky Way galaxy, which itself is part of a filament in the cosmic web, measures roughly 100,000 light-years in diameter.

"We believe that the universe on very large scales is made of a network-like distribution of galaxies, gas and dark matter," said University of Cambridge astrophysicist Madalina Tudorache, co-lead author of the study published this month in the journal Monthly Notices of the Royal Astronomical Society.

"This network is called the cosmic web, and it is formed of clusters, which are very dense clumps of matter, often formed of many groups of galaxies; voids - which are empty or almost empty regions of space; and filaments, which are strand-like structures which connect the very dense regions and border the voids," Tudorache said.

The rotating filament described in the new study is populated by nearly 300 galaxies of various sizes as well as gas and dark matter, the mysterious invisible stuff estimated to make up 27% of the cosmos.

Everything visible in the universe is made of ordinary matter - stars, planets, moons and all the stuff on Earth. It can be seen in wavelengths from infrared to visible light and gamma rays, but comprises only about 5% of the universe. Dark matter, on the other hand, does not absorb or reflect or emit light, but its presence is known through its gravitational effects on large scales.

The researchers determined that the filament is spinning by observing that the galaxies on either side of its central axis are moving through space in opposite directions, with the whole thing having a rotational velocity of about 246,000 miles (396,000 km) per hour.

"This is the largest individual spinning structure so far detected. Statistically, we believe there are other spinning structures, some of which could be larger. However, we have not been able to detect them directly with our current data and telescopes," said University of Oxford astrophysicist and study co-lead author Lyla Jung.

The researchers likened what they see in this filament to the amusement park attraction called a teacup ride.

"The teacup ride analogy explains the two levels of spinning motion that make this object unique," Jung said.

"First, each galaxy in the filament spins on its own. The gas and stars in each galaxy orbit around the galaxy center, like each teacup on the ride spins individually. Second, the entire cosmic filament also rotates. The filament is made of many galaxies, and this study demonstrates that the entire structure is rotating, like the teacup platform spins as a whole," Jung added.

In studying the cosmos, astrophysicists examine it at the smallest and largest scales. They look at tiny fundamental particles such as neutrinos. They look at objects such as comets, asteroids, moons, planets and stars that make up solar systems. They look at galaxies comprised of billions of stars and at clusters of galaxies. And then on the largest scales they look at filaments and other components of the cosmic web.

This study looks at the large end of things.

"This is a very exciting time to work in this field, as our capacity of discovering such structures is increasing with the advent of better radio and optical surveys. It will deepen our understanding of the universe," Tudorache said.

Varieties

NCW Releases 37 Wildlife Species in Hegra Reserve in AlUla

The release included six mountain ibex, 20 sand gazelles (reem), six idmi gazelles, and five ostriches - SPA
The release included six mountain ibex, 20 sand gazelles (reem), six idmi gazelles, and five ostriches - SPA
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NCW Releases 37 Wildlife Species in Hegra Reserve in AlUla

The release included six mountain ibex, 20 sand gazelles (reem), six idmi gazelles, and five ostriches - SPA
The release included six mountain ibex, 20 sand gazelles (reem), six idmi gazelles, and five ostriches - SPA

The National Center for Wildlife (NCW), in cooperation with the Royal Commission for AlUla, has released 37 wildlife species into Hegra Reserve as part of ongoing breeding and reintroduction programs aimed at restoring natural habitats, enriching biodiversity, supporting ecological balance, and promoting environmental tourism.

The release included six mountain ibex, 20 sand gazelles (reem), six idmi gazelles, and five ostriches, SPA reported.

This effort is part of NCW's continuing work to increase the numbers of threatened native species and expand their presence across suitable natural environments.

NCW CEO Dr. Mohammed Qurban stated that releasing these species into the reserve helps protect wildlife, safeguard ecosystems, and enrich biodiversity, strengthening the sustainability of the reserve and its role as a natural and cultural destination of national significance.

Qurban noted that this release is an extension of the center’s reintroduction efforts across reserves in the Kingdom, aimed at rehabilitating ecosystems, increasing biodiversity, and ensuring long-term sustainability. It aligns with the goals of Saudi Vision 2030, the Saudi Green Initiative, and the National Environment Strategy, while also adhering to global approaches to wildlife conservation.

Varieties

Australian Bushfires Raze Homes in Two States; Firefighter Dies 

Ruins of buildings and a car smolder after a wildfire destroyed houses in Koolewong, Australia, Saturday, Dec. 6, 2025. (Dan Himbrechts/AAP Image via AP)
Ruins of buildings and a car smolder after a wildfire destroyed houses in Koolewong, Australia, Saturday, Dec. 6, 2025. (Dan Himbrechts/AAP Image via AP)
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Australian Bushfires Raze Homes in Two States; Firefighter Dies 

Ruins of buildings and a car smolder after a wildfire destroyed houses in Koolewong, Australia, Saturday, Dec. 6, 2025. (Dan Himbrechts/AAP Image via AP)
Ruins of buildings and a car smolder after a wildfire destroyed houses in Koolewong, Australia, Saturday, Dec. 6, 2025. (Dan Himbrechts/AAP Image via AP)

An Australian firefighter was killed overnight after he was struck by a tree while trying to control a bushfire that had destroyed homes and burnt large swathes of bushland north of Sydney, authorities said on Monday.

Emergency crews rushed to bushland near the rural town of Bulahdelah, 200 km (124 miles) north of Sydney, after reports that a tree had fallen on a man. The 59-year-old suffered a cardiac arrest and died at the scene, officials said.

Prime Minister Anthony Albanese said the "terrible news is a somber reminder" of the dangers faced by emergency services personnel as they work to protect homes and families.

"We honor that bravery, every day," Albanese said in a statement.

A fast-moving fire over the weekend destroyed 16 homes in New South Wales state's Central Coast region, home to about 350,000 people and a commuter region just north of Sydney.

Resident Rouchelle Doust, from the hard-hit town of Koolewong, said she and her husband tried to save their home as flames advanced.

"He's up there in his bare feet trying to put it out, and he's trying and trying, and I'm screaming at him to come down," Doust told the Australian Broadcasting Corp.

"Everything's in it: his grandmother's stuff, his mother's stuff, all my stuff - everything, it's all gone, the whole lot."

Conditions eased overnight, allowing officials to downgrade fire danger alerts, though the weather bureau warned some inland towns in the state could hit more than 40 degrees Celsius (104 Fahrenheit) on Tuesday, raising fire dangers.

More than 50 bushfires were burning across New South Wales as of Monday.

On the island state of Tasmania, a 700-hectare (1,729 acres) blaze at Dolphin Sands, about 150 km (93 miles) northeast of the state capital of Hobart, destroyed 19 homes and damaged 40. The fire has been contained, but residents have been warned not to return as conditions remain dangerous, officials said.

Authorities have warned of a high-risk bushfire season during Australia's summer months from December to February, with increased chances of extreme heat across large parts of the country following several relatively quiet years.

In neighboring New Zealand, five helicopters and multiple crews were working to put out a fire near the country's oldest national park, a month after a wildfire burnt through 2,589 hectares (6,400 acres) of alpine bush there.

Police said they had closed a road near the state highway and advised motorists to avoid the area and expect delays after the blaze near Tongariro National Park, a popular hiking spot, spread to 110 hectares (272 acres) by Monday afternoon.