Consider the following scenario: a nuclear missile is launched from North Korea on a direct path for Honolulu.

For at least five minutes, Hawaiians are blissfully unaware of the danger.

Suddenly, the US Pacific Command detects the missile in mid-air and sends an alert to Hawaii's State Warning Point, which instantly activates its public warning system.

Sirens begin blaring across the state and an alert is sent to mobile phones, radio and television.

Panicked residents and visitors have no more than 15 minutes to find somewhere to find cover — but there are no public fallout shelters.

Twenty minutes after launch, a nuclear bomb detonates 1,000 feet above the Hawaiian capital, and thousands are killed and many more are left with burns and radiation poison.

That exact scenario is being seriously considered

It's the very real scenario Hawaiian authorities are preparing for, laid out in a document about the US state's preparedness for a nuclear attack.

Although Saturday's missile warning was a false alarm, US authorities believe there's a very high likelihood that Hawaii — particularly Honolulu and the island of Oahu — would be the primary target of a North Korean nuclear attack.

The "Emergency Preparedness" document, published in November by Hawaii's Emergency Management Authority, warns that Hawaiian residents and visitors would have "less than 12 to 15 minutes" to seek shelter in the event of a real nuclear missile threat.

Such an attack would "likely occur without prior warning", it warns.

What would the toll be?

Sorry, this video has expired Honolulu residents speak of panic following false missile alarm

It says that a single-kiloton range nuclear weapon detonated at 1,000 feet could kill almost 18,000 people and cause 50,000 to 120,000 trauma and burn casualties.

As well as widespread building collapses and structural fires, up to 30 per cent of survivors would suffer acute radiation syndrome.

The document, while offering advice to residents on how to survive a nuclear attack, also confirms that Hawaii has no public fallout shelters or shelter supply caches.

Instead, it advises people to seek shelter in a building away from windows, or lie flat on the ground.

Hawaiians are unprepared

The actions of many panicked residents after Saturday's false alarm were a far cry from what authorities recommend, and show just how unprepared Hawaii is for a North Korean nuclear missile attack.

Many people ran around on the streets "crying and screaming" after the warning was wrongly sent to mobile phones and other devices: "Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill."

ABC's David Spicer received a ballistic missile threat alert, January 14, 2018. ( ABC News: David Spicer )

"We were so scared, we had no clue what to do or think," one woman told one US radio station.

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Some sought protection under mattresses.

Others reportedly lifted manhole covers to climb into the sewers for protection.

One man was filmed helping a girl climb into a concrete drain.

Sorry, this video has expired A child was lowered into manhole following false missile warning

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"How stupid are some people," another man tweeted.

"I see them putting their children into a Sewer for safety. SEWERS contain Methane GAS which kills. Also in a missile blast would occur sewers would fill up with water, drowning anyone in there."

The safest place to seek shelter is in a concrete building or structure

Despite the high death toll the Emergency Management Agency predicts, more than 90 per cent of the population would likely survive a nuclear strike, with expectations that such an explosion would measure less than 10 kilometres in diameter.

However, residual radiation and nuclear fallout could last as long as 14 days, making it unsafe to venture outside until the threat has subsided.

"Debris including soil, fragments of destroyed buildings and other material will be drawn into the cloud of a nuclear detonation and propelled into the sky. This debris will begin to settle back to earth within hours," the document says.

Sorry, this video has expired 'Wrong button' caused false missile alert in Hawaii

In the event of a genuine alarm, the US Pacific Command would issue a warning about five minutes after a missile is launched from North Korea.

About two minutes later, Hawaii's State Warning Point would activate an "Attack-Warning" signal on all outdoor sirens and transmit a warning advisory on radio, television and mobile phones.

That would give Hawaiian residents and visitors "less than 12 to 15 minutes before missile impact".

Many Hawaiians say they knew immediately that Saturday's alert was fake, because none of the official sirens were going off. Many say they kept drinking on the beach.

The emergency document shows the safest place to seek shelter from a nuclear strike is in a concrete building or structure, preferably underground or in the basement.

In a high-rise building, the safest place above ground is in the centre of the building.

The worst building to stay in is a single standing house, particularly made of wood.

Hawaii's Emergency Preparedness document ( Hawaii Emergency Management Agency )

Hawaiian authorities have begun an investigation into Saturday's blunder and have suspended regular testing of the Attack-Warning system introduced in November.

The system is similar to the air raid sirens used during the Cold War.

History shows the survival rate from a nuclear attack is still high

The atomic bombs dropped on Hiroshima and Nagasaki during World War II killed hundreds of thousands of people, many of them from burns or radiation sickness in the days or weeks after the initial blast and shock.

But tens of thousands survived, even though they had little or no warning of the attacks.

Many were buried under houses or buildings.

Some made it to homemade bomb shelters, moments after seeing or hearing the warplane above.

Others were just far enough away from the bomb's pressure wave that incinerated tens of thousands of their compatriots in an instant.

Many survivors lived with cancer, burns and appalling injuries.

Indeed at least 165 people known as "Niju Hibakusha" are reported to have survived both the atomic bombings on Hiroshima and Nagasaki.

One of them, Tsutomu Yamaguchi, from Nagasaki, was on a work trip to Hiroshima when the first bomb detonated as he stepped off a tram.

He was temporarily blinded and left with serious burns.

When he came to he crawled to a bomb shelter where he found several colleagues who had also survived.

They returned to Nagasaki the following day, and three days later survived the second atomic bomb at Nagasaki.

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