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By New Scientist staff and Press Association

A major earthquake off Mexico's southern coast has killed at least five people, sparking tsunami warnings. Further dangerous aftershocks are also expected.

The US Geological Survey reported the earthquake's magnitude as 8.1, making it the biggest earthquake in Mexico since 1932.

The USGS said the quake struck at 11.49pm local time on Thursday and its epicentre was 165 kilometres west of Tapachula in Chiapas, not far from Guatemala. It had a depth of 69.7 kilometres.

Aftershock warning

The quake was so strong that it caused buildings to sway violently in Mexico's capital, more than 1,000 kilometres away. Houses toppled and the quake produced tsunami waves and sent people running into the streets in panic. President Enrique Pena Nieto said 62 aftershocks followed the quake and it was possible one as strong as 7.2 could hit in the next 24 hours.

"The house moved like chewing gum and the light and internet went out momentarily," said resident Rodrigo Soberanes, who lives near San Cristobal de las Casas in Chiapas.

Continue reading by clicking the name of the source below.

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Mexico on tsunami alert after biggest earthquake in 85 years

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By New Scientist staff and Press Association A major earthquake off Mexico's southern coast has killed at least five people, sparking tsunami warnings. Further dangerous aftershocks are also expected. The US Geological Survey reported the earthquake's magnitude as 8.1, making it the biggest earthquake in Mexico since 1932.

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A ROAD closure was in place after a sinkhole opened in Sutton Leach this morning.

The sinkhole appeared under a minibus, which was on Leach Lane, close to the junctions of Ilfracombe Road and Taunton Avenue, at 8.30am.

The fire service and police have attended the scene.

A spokesman from Merseyside Fire and Rescue Service said that there were three women on the vehicle, a white Ford Transit minibus, and that no injuries had been sustained.

He said: "We sent two fire engines and the search and rescue team.

"A sinkhole has opened up on the road and a minibus has gone into it."

United Utilities were also on the scene.

Leach Lane was closed following the incident.

St Helens Council confirmed the road has now been reopened, with four-way temporary lanes as repairs take place.

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Road reopens after sinkhole opens underneath minibus

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A ROAD closure was in place after a sinkhole opened in Sutton Leach this morning. The sinkhole appeared under a minibus, which was on Leach Lane, close to the junctions of Ilfracombe Road and Taunton Avenue, at 8.30am. The fire service and police have attended the scene.

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At least 32 people have died in the strongest earthquake to hit Mexico in 100 years - including a baby whose ventilator stopped working when a hospital suffered a power cut.

Tsunami waves have been confirmed off the southern coast of Mexico after a magnitude-8.1 earthquake struck shortly before midnight local time.

The Pacific Tsunami Warning Centre said waves of 3.3ft (1m) had been measured off the port of Salina Cruz. Multiple aftershocks ranged between 4.5 and 5.7 in magnitude, the US Geological Survey said.

Mexican President Enrique Pena Nieto said the quake was the biggest his country had seen in a century.

The governor of the southern Oaxaca state said at least 23 people died there.

Two children were killed in the state of Tabasco. Its governor, Arturo Nunez, said one was a baby who died at a children's hospital which lost power, causing the infant's ventilator to stop working.

Seven people were killed in neighbouring Chiapas state - among them two women who died in San Cristobal when a house and a wall collapsed.

Related: Mexico quake captured on office camera (Provided by: Sky News)

"Homes, schools and hospitals have been damaged," state governor Manuel Velasco said. In Juchitan in Oaxaca state, parts of the town hall, plus other buildings including a hotel and a bar were reduced to rubble.

People in the capital, Mexico City, ran out into the street in their pyjamas after the tremor shook buildings. Mr Pena Nieto said a million people had initially been left without power, but 800,000 now had it back.

The quake struck at a depth of 43 miles (69 km), 76 miles (123 km) southwest of the town of Pijijiapan.

It posed a potential tsunami threat to the Pacific coastlines of countries including Guatemala, El Salvador, Costa Rica, Nicaragua, Panama and Honduras, the US Tsunami Warning System said. Buildings in Guatemala were shaken by the tremor.

"I had never been anywhere where the earth moved so much," said 31-year-old architect Luis Carlos Briceno, who is visiting Mexico City. "At first I laughed, but when the lights went out I didn't know what to do. I nearly fell over."

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Baby on hospital ventilator among 32 dead in Mexico earthquake

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At least 32 people have died in the strongest earthquake to hit Mexico in 100 years - including a baby whose ventilator stopped working when a hospital suffered a power cut. Tsunami waves have been confirmed off the southern coast of Mexico after a magnitude-8.1 earthquake struck shortly before midnight local time.

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It is well known that humans are causing the Earth to warm. We also know that a warmer atmosphere has more water vapor. Just like the air is more humid when it is warm, and less humid when cold. The more humid air leads to more intense precipitation and potentially more flooding. But how much change we will see is an open scientific question.

This question is made complex by the fact that flooding isn't just about rain. It reflects a dependence on evaporation, rain, the ability of land and water management to handle water surges, and other factors. Fortunately, a very recent study out of Science Advances has helped advance our understanding of the confluence of global warming, intense rain and flooding.

The authors, Conrad Wasko and Ashish Sharma, from the University of New South Wales investigated various non-urban catchments. These are regions where precipitation drains to a common site. We know that in many places the rainfall is increasing. What these authors wanted to know was whether there was a coincident increase in floods found in these various catchments.

This study isn't as simple as it might sound. The authors had to make choices about which rainfall event and which temperature peak corresponded to each other and to a potential water flow peak. According to the paper, "precipitation events were identified where the precipitation was separated by five days of zero rainfall." That is, it had to be dry ahead of time. Streamflow and flooding events were selected as peaks separated by more than seven days. The authors then picked the largest peak from the precipitation and the streamflow observations and matched them to a coincident temperature measurement.

The tough part is that there can be a delay in temperatures and precipitation. Furthermore, there can be a physical distance between the source of the storm and the location of precipitation. Finally, many times we see flooding without the required five-day dry period. So admittedly this study has real limitations. On the other hand, the authors had to make some choices of selection and these are as good as any others. And, they compensated for these limitations by using extensive rainfall, temperature and streamflow data, data that represented the entire world and allows confident conclusions to be drawn.

What they found was that in most cases there is no direct link. That is, higher temperatures does not generally cause an increase in water flow or flood risk.

So this begs the question, why not? Why isn't there a clear direct relationship between the temperature peaks and flooding? Well the authors explain that there is an important role of hydrologic loss (water loss due to evaporation for instance). When the authors separated the results by size of catchment, they found that the importance of these water losses was reduced for smaller catchment areas. They write:

if the catchment or region capturing the precipitation is smaller, but the precipitation event intensity remains the same, the potential for losses is less. In large catchments, the peak streamflow is more likely to be influenced by the catchment wetness conditions preceding the storm event.

When they broke the analysis into different catchment sizes, the authors found that for extreme rainfalls, the flooding and temperature move together. The authors also broke analysis into different geographical zones and found that their conclusions held true, regardless of the zone location.

As I stated earlier, there are limitations to this study; the authors did a great job discussing those limitations. For instance, they point out it's possible that human changes to the catchment itself can affect flooding. Urbanization in recent years may have "increased streamflow due to a larger proportion of impermeable surfaces while the development of dams for storage may have had the opposite effect." They also report that the temperature at which the high water flows are recorded do not necessarily correspond to the temperature of the storm. Evaporation can happen for instance over an ocean, the moisture can be carried hundreds of miles inland, where it falls as rain. But, the fact that their results exclude urban catchments and use data from over 5,000 streamflow and 50,000 rainfall gauges lends credibility to their assertions.

So is this good news or bad news? Well, on the one hand it confirms that global warming leads to competing effects of more heavy rains and more drying of land - forces in opposition to each other. Higher temperatures dry out soils faster and they increase precipitation. If the soils are dryer when the rains fall, it means that the floods may be less severe. That is a good thing.

On the other hand, this study helps confirm that the Earth can move from dry to wet conditions more rapidly in a warmer environment. That is not a good thing. It also has implications for refilling groundwater supplies. Much of the recovery from drought and refilling of groundwater is through smaller flooding/high-flow events. Since those are not necessarily increasing, it means droughts are likely to linger.

As author Ashish Sharma told me:

What this study does is to show, using just data and no model projections, that flood risk is indeed increasing but at the rare to very-rare flood end. The milder floods that are more of a nuisance than a threat to property and lives, are actually decreasing. This is worse news than before though, as it is these milder floods that make up the bulk of the refill to our water supply reservoirs.

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Study: mild floods are declining, but intense floods are on the rise | John Abraham

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It is well known that humans are causing the Earth to warm. We also know that a warmer atmosphere has more water vapor. Just like the air is more humid when it is warm, and less humid when cold. The more humid air leads to more intense precipitation and potentially more flooding.

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Large parts of England and Wales have been hit by an earthquake measuring 4.8 on the Richter scale.

Buildings shook for up to 30 seconds in parts of the West Midlands, Wales, North Yorkshire, London, and Wiltshire.

The tremor began at 0053 BST and its epicentre was in Dudley in the West Midlands.

There was minor structural damage as homes were shaken, but no reports of any injuries.

Aftershocks were felt later on Monday morning from what is thought to be the UK's largest earthquake for 10 years.

Glenn Ford, a senior seismologist at the British Geological Survey (BGS), said: "It's an extremely large earthquake in UK terms but not large in world terms; we'd only classify it as a light earthquake."

BBC weather forecaster Pete Gibbs said: "It's not that unusual to have an earth tremor, but it is unusual to be that widespread and that widely reported.

"However, earth tremors are certainly not that uncommon in the UK."

West Midlands Police said they had 5,000 calls to their switchboard within an hour of the tremor happening and 600 calls to the 999 number.

Dudley police said 12 people in nightclothes walked into their local police station.

Sudden shocks

Julian Bukits, of the BGS, said an earthquake of magnitude four is equivalent to 1,000 tonnes of TNT - that in turn is equivalent to the power of a small nuclear weapon.

The BGS said the earthquake's epicentre could only be located to within about a kilometre, and not pinpointed to an exact street or address.

Dr David Kerridge, senior seismologist, said: "Aftershocks are a possibility but we wouldn't expect anything of the same magnitude."

Although Monday's earthquake was large by British standards, tremors in places like California, Japan and India can reach seven or more on the Richter scale.

The whole length of Wales was shaken and people over 120 miles (190 km) apart felt two sudden shocks.

'Frightening' experience

In south Wales, people in Cardiff, Newport, Caerphilly, the Vale of Glamorgan and as far west as Swansea, felt the powerful shocks.

Callers to the BBC reported doors slamming and windows rattling.

Many miles further north, in Wrexham, officers from North Wales Police said their control room in a tower block shook violently.

Richard Flynn, from Oldbury in the West Midlands, said: "The house started shaking quite violently at about 1am. All the power was cut off and seemed to be so for about a five-mile (8-km) radius.

"The shaking and trembling was really quite severe. Quite a few people came out of their houses wondering what was going on. The streets were in darkness."

Power was restored after about 20 minutes.

Ground swayed

One Birmingham resident, Alex Potter, told BBC Radio Five Live: "My first thought was it's a bomb and then an earthquake.

"There was an earthquake in Birmingham back in the fifties when I was a boy but back then the ground swayed. It was quite different this time."

He added: "It was really quite frightening. I'm convinced there were two booms - lasting five or six seconds each."

Bill Wilson, who was duty inspector for Merseyside Police at the time of the tremor, said he took up to 30 calls from people who initially thought there was an intruder in their home or there had been an explosion.

"I've never had to take calls like this and some people I rang up myself thought I was winding them up but I had to assure them that I was serious."

Between 200 and 300 quakes occur in Britain each year, but only about 10% are strong enough to be felt.

Buildings are deemed to be at risk from a quake over 5 on the Richter scale, according to the Environment Agency.

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Large parts of England and Wales have been hit by an earthquake measuring 4.8 on the Richter scale. Buildings shook for up to 30 seconds in parts of the West Midlands, Wales, North Yorkshire, London, and Wiltshire. The tremor began at 0053 BST and its epicentre was in Dudley in the West Midlands.

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Donald Trump visited a hurricane-stricken Houston and promised the "best ever" government response before pumping his fist from the steps of Air Force One as he departed.

Greg Abbott, the Texas governor, marveled that the state's "resilient spirit is alive and well". The phrase "Houston Strong" has been daubed as graffiti on city underpasses and held aloft as placards at home baseball games.

There has been plenty of defiance, heart-rending loss, and uplifting generosity, in the wake of Hurricane Harvey but one pressing topic has so far been largely overlooked: how will Houston rebuild in a better way should a storm like this ever again visit?

"When you talk about rebuilding a place like Houston, people's first thoughts are "I want it back the way it was", said Sandra Knight, a senior research engineer at the University of Maryland. "And unfortunately that's not the best thing to do. As a nation we aren't planning forward enough. We are developing in places that aren't sustainable. We need to start doing things differently."

Abbott has said a "Texas-sized storm needs a Texas-sized response", predicting that reconstruction after the heaviest rainfall event in recorded US history - around 25tn gallons of water were dumped upon a band of southeast Texas in just a few days - will top the $120bn required by New Orleans after Hurricane Katrina in 2005.

It may well cost taxpayers in excess of $180bn. And it's not yet clear what lessons will be learned ahead of the rebuild.

The US places huge emphasis on flood recovery, rather than avoidance, using the heft of Fema to help those in need as well as administer a national insurance scheme that ostensibly places restrictions on what is built where but in practice has repeatedly bailed out houses in flood-prone that are frequently inundated.

This emergency response is entirely appropriate in the immediate aftermath of a disaster, according to Jeff Herbert, chief resiliency officer for New Orleans. But, Herbert added, at some point a difficult conversation about whether a city needs to be refashioned as it recovers also needs to happen.

"Houston had 51in of rain and that would be disastrous for any city in the world, Mexico City, Bangkok, anywhere," Herbert said. "It was unprecedented. The priority now is rescuing people and helping them.

We have a completely different landscape and climate now. They are complete game changers

Sandra Knight, research engineer

"The next phase of recovery is the appropriate time to talk about how to rebuild the city. Houston will have to think about retrofitting to accept more water and think about its development patterns. The city will have to think about how it manages stormwater and its regulations."

Houston has taken a rather laissez-faire approach to city planning, with a lack of zoning allowing housing to spill out over a large expanse, often in areas next to bayous vulnerable to flooding. The city is lacking in sponge-like parklands and is rich in concrete, which helps push water into unplanned streetscape swimming pools. The flat terrain of Houston, along with its proximity to the hurricane-spawning Gulf of Mexico, are further vulnerabilities.

Climate change is playing a role - the warming atmosphere holds more moisture that falls in the sort of rain that swamped Houston. The seas are rising faster on the eastern seaboard of the US than almost anywhere else in the world, heightening the impact of storm surges from hurricanes. Studies have shown hurricanes are likely to get stronger, if not more frequent, threatening coastal areas that are growing in population size.

This challenge, plus the pummeling experienced during storms such as Katrina and Sandy, which hit New York and New Jersey in 2012, has forced several cities to think about more natural defenses to water, rather than simply rely upon levees and pumps.

"In Houston and elsewhere we've encroached upon our floodplains and we aren't leaving any natural environment to slow the flood waters," said Knight. "We build dams and levees and people assume they are safe behind them, or downstream from them. But look at New Orleans - the levees failed."

Knight said her initial training as a hydrological engineer focused on getting flood water off your land as quickly as possible. "But we've learned that's not the best way to deal with floods," she said. "We have a completely different landscape and climate now. They are complete game changers."

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The Lower Ninth Ward in New Orleans, one of the areas worst hit by Hurricane Katrina, in 2015. New Orleans now has the largest flood barrier in the world. Photograph: Carlos Barria/Reuters

In the 1950s, Dutch policymakers headed to New Orleans to learn how the city pumped excess water out into Lake Pontchartrain. A year after Katrina hit, the Netherlands returned the favour by briefing officials from the Louisiana metropolis about the Dutch mantra of "living with the water".

This principle involves huge fortifications in key areas against flood waters - New Orleans now has the largest flood barrier in the world - but also emphasizes the need for green, or natural, infrastructure such as grass, woodland and wetlands to soak up water. Innovations such as green rooftops, where plants absorb some rainwater before it's funneled to barrels rather than onto the street, and permeable pavements are also being embraced.

There are now seven "rain gardens" in New Orleans - essentially parks where water pools and is absorbed - and the city is spending a further $220m on new green areas that will draw away water that would otherwise end up in the streets or in people's homes. Building codes have been tightened up to focus more heavily on flooding.

Many cities have dams, levees and flood walls which are a fairly narrow and inflexible response to flooding

Jeff Opperman, freshwater scientist

New Orleans is a different sort of city to Houston - it's older and has less available land to be eyed by developers - but Herbert said its approach can be replicated.

"After Katrina we realized we had to live with water within the city," he said. "We have hard infrastructure such as pumps but also nature-based solutions because pumping can't handle it all. We had to go back to what existed in the city in the 1930s and 1940s, before mass development took place."

The idea that water must be given space to flow in times of flood isn't new; the Yolo Bypass was constructed in the 1930s to relieve Sacramento from the severe floods that plagued it. But many US cities are still developing close to low-lying coastal and riverine areas with barely a nod to what floodplains actually do.

Some have leaned heavily on technology - Miami Beach, which could soon be hit by the onrushing Hurricane Irma, has spent hundreds of millions of dollars on raising its streets and developing a network of pumping stations. The low-lying city sits on a barrier island that already regularly floods on sunny days due to hide tides.

"Many cities have dams, levees and flood walls which are a fairly narrow and inflexible response to flooding," said Jeff Opperman, global freshwater lead scientist at WWF. "There is growing appreciation in the US that we need to diversify, to set the levees back, use natural vegetation and allow the river room. But then there's political decisions around development and that's a less rational process."

'Cars flew over our heads': Hurricane Irma survivors recount the havoc - video

A 2015 study of six US cities found huge variations in response to extreme weather events fueled by climate change. While New York City and Los Angeles were deemed as making progress, Tampa in Florida, which may also suffer a brush with Irma, was found to be one of the least prepared cities in the nation, with its main hospital - situated on an isolated low-lying peninsula - demonstrative of the lack of preparedness.

"There's a big variation in how cities are preparing, some are doing almost nothing," said Sabrina McCormick, an academic at George Washington University and lead author of the research. "Houston's approach to similar to other cities in that it hasn't looked into the future and taken the risks seriously. Unfortunately we are seeing the ramifications of that."

McCormick said a lack of federal leadership is also a problem. The Trump administration has struck down several Barack Obama-era regulations designed to reduce climate-driven risks. Ten days before Harvey struck Houston, Trump tore up a rule that demands federally-funded projects consider climate change and sea level rise before they are built.

"Ideally we'd have a national plan to help guide cities toward some basic level of planning to address these risks," McCormick said. "If we don't see that leadership, cities will have to look to other cities to figure out where to go next. We also need to mitigate our greenhouse gases to reduce the impact in the first place."

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After the storm: how should cities rebuild post hurricanes like Harvey and Irma?

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Donald Trump visited a hurricane-stricken Houston and promised the "best ever" government response before pumping his fist from the steps of Air Force One as he departed. Greg Abbott, the Texas governor, marveled that the state's "resilient spirit is alive and well".

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7.4 magnitude earthquake strikes northern Japan

Tsunami of up to 90 centimeters recorded

1.4 metre tsunami hits Sendai

1 metre tsunami at Fukushima nuclear plant

Residents ordered to evacuate from coastal areas

Depth of the quake recorded at 10 km

A powerful earthquake off the northeast Japanese coast on Tuesday sent residents fleeing to higher ground and prompted worries about the Fukushima nuclear power plant destroyed by a tsunami five year ago.

Lines of cars were seen snaking away from the coast in the pre-dawn hours after authorities issued a tsunami warning and urged residents to seek higher ground immediately. The warning was lifted nearly four hours later.

Credit: AP

The magnitude 7.4 earthquake struck in the same region that was devastated by a tsunami in 2011, killing some 18,000 people.

There were reports of minor injuries and damage, Japanese broadcaster NHK said. The earthquake shook buildings in Tokyo, 150 miles southwest of the epicentre.

NHK also showed one person's video of water rushing up a river or canal, but well within the height of the embankment. It was eerily reminiscent of the 2011 disaster, when much larger tsunamis rushed up rivers and overflowed, wiping away entire neighbourhoods.

On Tuesday, tsunami waves were recorded along the coast. The highest one was 1.4 metres in Sendai Bay. A tsunami advisory was eventually lifted at 12.50pm local time.

Credit: AP

The operator of the Fukushima Dai-ichi plant said there were no abnormalities observed at the plant, though a swelling of the tide of up to 1 metre was detected offshore.

The plant was swamped by the 2011 tsunami, sending three reactors into meltdown and leaking radiation into the surrounding area. The plant is being decommissioned but the situation remains serious as the utility figures out how to remove still-radioactive fuel rods and debris and what to do with the melted reactor cores.

Plant operator Tepco said a pump that supplies cooling water to a spent fuel pool at the nearby Fukushima Dai-ni plant stopped working, but that a backup pump had been launched to restore cooling water to the pool.

Credit: AP

Naohiro Masuda, head of TEPCO's decommissioning unit, said he believed the pump was shut off automatically by a safety system as the water in the pool shook.

He said decommissioning work at the destroyed Dai-ichi plant had been temporarily suspended because of the earthquake.

The US Geological Survey measured the magnitude at 6.9.

1.4 metre wave spotted in Sendai

Flashbacks to the Great East Japan earthquake on 2011

Today's earthquake has prompted flashbacks to March 2011, when a 9.1 magnitude quake hit just off the Eastern coast, David Lawler writes.

That was the most powerful quake in Japan's history, and one of the largest recorded in modern history.

It triggered to a massive tsunami, with waves of up to 40 meters (133 feet) in height.

Explained: Fukushima nuclear plant clean-up 03:02

Fukushima nuclear plant being checked for earthquake damage

There were no immediate reports of damage or injury, which struck at 5:59 a.m. (2059 GMT).

Tokyo Electric Power Co was checking its nuclear plants in Fukushima for damage, public broadcaster NHK said.

Tohoku Electric Power Co said there was no damage to its Onagawa nuclear plant.

Television footage showed ships moving out to sea from Fukushima harbours, as the meteorological agency warned of a tsunami of 3 metres (10 feet) for Fukushima, where Tepco's Daiichi nuclear plant was devastated in a March 2011 quake and tsunami.

BREAKING: Tsunami warning issued after preliminary Magnitude 7.3 earthquake strikes off coast of Fukushima, Japan. More details to come pic.twitter.com/0NCIPOiaSz
- The Weather Network (@weathernetwork) November 21, 2016

Earthquakes are common in Japan, one of the world's most seismically active areas. Japan accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.

The March 11, 2011, quake was magnitude 9, the strongest quake in Japan on record. The massive tsunami it triggered caused world's worst nuclear crisis since Chernobyl a quarter of a century earlier.

The U.S. Geological Survey initially put Tuesday's quake at a magnitude of 7.3 but down graded it to 6.9.

All nuclear plants on the coast threatened by the tsunami are shutdown in the wake of the Fukushima disaster. Only two reactors are operating in Japan, both in the southwest of the country. Even when in shutdown nuclear plants need cooling systems operating to keep spent fuel cool.

1.4 metre wave spotted in Sendai

Flashbacks to the Great East Japan earthquake on 2011

Today's earthquake has prompted flashbacks to March 2011, when a 9.1 magnitude quake hit just off the Eastern coast, David Lawler writes.

That was the most powerful quake in Japan's history, and one of the largest recorded in modern history.

It triggered to a massive tsunami, with waves of up to 40 meters (133 feet) in height.

Explained: Fukushima nuclear plant clean-up 03:02

Fukushima nuclear plant being checked for earthquake damage

There were no immediate reports of damage or injury, which struck at 5:59 a.m. (2059 GMT).

Tokyo Electric Power Co was checking its nuclear plants in Fukushima for damage, public broadcaster NHK said.

Tohoku Electric Power Co said there was no damage to its Onagawa nuclear plant.

Television footage showed ships moving out to sea from Fukushima harbours, as the meteorological agency warned of a tsunami of 3 metres (10 feet) for Fukushima, where Tepco's Daiichi nuclear plant was devastated in a March 2011 quake and tsunami.

BREAKING: Tsunami warning issued after preliminary Magnitude 7.3 earthquake strikes off coast of Fukushima, Japan. More details to come pic.twitter.com/0NCIPOiaSz
- The Weather Network (@weathernetwork) November 21, 2016

Earthquakes are common in Japan, one of the world's most seismically active areas. Japan accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.

The March 11, 2011, quake was magnitude 9, the strongest quake in Japan on record. The massive tsunami it triggered caused world's worst nuclear crisis since Chernobyl a quarter of a century earlier.

The U.S. Geological Survey initially put Tuesday's quake at a magnitude of 7.3 but down graded it to 6.9.

All nuclear plants on the coast threatened by the tsunami are shutdown in the wake of the Fukushima disaster. Only two reactors are operating in Japan, both in the southwest of the country. Even when in shutdown nuclear plants need cooling systems operating to keep spent fuel cool.

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Japan earthquake: small tsunami strikes Fukushima coastline after 7.4 magnitude quake

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7.4 magnitude earthquake strikes northern Japan Tsunami of up to 90 centimeters recorded 1.4 metre tsunami hits Sendai 1 metre tsunami at Fukushima nuclear plant Residents ordered to evacuate from coastal areas Depth of the quake recorded at 10 km A powerful earthquake off the northeast Japanese coast on Tuesday sent residents fleeing to higher ground and prompted worries about the Fukushima nuclear power plant destroyed by a tsunami five year ago.