Tsunami warning as it happened: Threat to US and Canada ebbs away after earthquake sparks panic

Tsunami warning issued on USA's east coast after earthquake off coast of Alaska

Much of the west coast of the US was woken by the threat of a huge tsunami overnight. But the panic soon subsided after all warnings were eventually withdrawn

Alaska and other parts of North America were bracing itself for disaster after a huge 7.9-magnitude earthquake struck at a shallow depth some 160 miles off the state's coast.

While alerts were originally issued across the entire west coast of America and Canada, they have since been withdrawn for all states. That was after people were told to head to high ground and get safe amid fears the tsunami could cause serious damage.

The US Geological Survey said the quake struck 256 km (157 miles) southeast of Chiniak, Alaska at a depth of 10 km at 0931 GMT on Tuesday morning.

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Key Points

• Emergency alerts sent to phones across the US, telling people to move to high ground
• Map shows how long potential tsunami would take to reach land
• Tsunami watch and warning cover much of the west coast of the US and Canada

[23 January 2018 11:02 · Andrew Griffin]

The tsunami centre has sent out this advice on how any potential activity might look:

Impacts will vary at different locations in the warning

areas.

If you are in a tsunami warning area;

 * A tsunami with damaging waves and powerful currents is

   possible.

 * Repeated coastal flooding is possible as waves arrive

   onshore, move inland, and drain back into the ocean.

 * Strong and unusual waves, currents and inland flooding

   can drown or injure people and weaken or destroy structures

   on land and in water.

 * Water filled with floating or submerged debris that can

   injure or kill people and weaken or destroy buildings and

   bridges is possible.

 * Strong and unusual currents and waves in harbors,

   marinas, bays, and inlets may be especially

   destructive.

 * Some impacts may continue for many hours to days after

   arrival of the first wave.

 * The first wave may not be the largest so later waves may

   be larger.

 * Each wave may last 5 to 45 minutes as a wave encroaches

   and recedes.

 * Coasts facing all directions are threatened because the

   waves can wrap around islands and headlands and into bays.

 * Strong shaking or rolling of the ground indicates an

   earthquake has occurred and a tsunami may be imminent.

 * A rapidly receding or receded shoreline, unusual waves and

   sounds, and strong currents are signs of a tsunami.

 * The tsunami may appear as water moving rapidly out to sea,

   a gentle rising tide like flood with no breaking wave,

   as a series of breaking waves, or a frothy wall of water.

[23 January 2018 11:03 · Andrew Griffin]

And it provides this advice on what to do:

Actions to protect human life and property will

vary within tsunami warning areas.

If you are in a tsunami warning area;

 * Evacuate inland or to higher ground above and beyond

   designated tsunami hazard zones or move to an upper floor of a multi-story building depending on your situation.

 * Move out of the water, off the beach, and away from

   harbors, marinas, breakwaters, bays and inlets.

 * Be alert to and follow instructions from your local

   emergency officials because they may have more detailed or specific information for your location.

 * If you feel a strong earthquake or extended ground rolling take immediate protective actions such as moving inland and/or uphill preferably by foot.

 * Boat operators,

     * Where time and conditions permit, move your boat out to sea to a depth of at least 180 feet.

     * If at sea avoid entering shallow water, harbors,

       marinas, bays, and inlets to avoid floating and

       submerged debris and strong currents.

 * Do not go to the shore to observe the tsunami.

 * Do not return to the coast until local emergency officials

   indicate it is safe to do so.

If you are in a tsunami watch area;

 * Prepare to take action and stay alert for further

   information.

[23 January 2018 11:06 · Andrew Griffin]

If there's a tsunami, it will hit land in the next few minutes. The first hit will be Kodiak, in Alaska. Local reports say the entire town has been evacuated.

[23 January 2018 11:10 · Andrew Griffin]

Authorities in Kodiak, Alaska, are telling residents to move to higher ground after a strong earthquake struck nearby, prompting tsunami warning for a large swath of coastal Alaska and Canada's British Columbia while the remainder of the U.S. West Coast was under a watch. 

A dispatcher at the Kodiak police department answered a call from The Associated Press by saying, "If this about the tsunami, you need to get to higher ground immediately."

[23 January 2018 11:13 · Andrew Griffin]

The Kodiak police department posted an update 15 minutes ago:

TSUNAMI UPDATE

0155 update.

So far no waves have hit. Still waiting for the updates.

Please remain on high grounds.

We will continue to update you as best as we can.

Thanks you.

[23 January 2018 11:23 · Andrew Griffin]

The tsunami watch has been cancelled for Hawaii, reports suggest. A watch is still in effect for the west coast of the mainland US, and the more dramatic warning is in place for the Canada and Alaska coast.

[23 January 2018 11:30 · Andrew Griffin]

The first tsunami observations are coming in. In Old Harbor, Alaska, waves of half a foot were detected, the tsunami centre says.

[23 January 2018 11:36 · Andrew Griffin]

Another update from the police in Kodiak, where any tsunami would be detected first:

TSUNAMI UPDATE: 0229 hours

Harbor officers report water reciding from our harbor. Citizens should remain in place and wait for further updates.

[23 January 2018 11:39 · Andrew Griffin]

The Kodiak PD update about water leaving the harbour is the first reliable report about the channel clearing in Alaska. But a number of other reports on social media suggest the same.

If true, that is a worrying sign: the waters move back as the wave gathers, and so a substantial amount of change in sea levels could suggest something large on its way.

[23 January 2018 11:51 · Andrew Griffin]

Here's the latest on the advice to follow if you're in an affected area: