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 But the panic soon subsided after all warnings were eventually withdrawn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While alerts were originally issued across the entire west coast of America and Canada, they have since been withdrawn for all states.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 10:05 · Andrew Griffin]

The earthquake which has struck off Alaska overnight has brought a tsunami watch for the entire US West Coast, said the US Tsunami Warning System.

[23 January 2018 10:08 · Andrew Griffin]

The US Geological Survey's map of the area struck by the earthquake can be found here. As you can see, it was fairly close to the bottom of Alaska:

[23 January 2018 10:09 · Andrew Griffin]

The US Tsunami Warning Centre's website, usually found at http://www.tsunami.gov/, appears to be down. It's not clear whether that's related to the government shutdown that ended yesterday, or if it is a consequence of the major interest.

[23 January 2018 10:13 · Andrew Griffin]

Though the US government shutdown has now ended, it's not clear that everyone will be back at work. The US Geological Survey would usually be working on this, for instance, but it's last tweet makes clear that "During the federal government shutdown, we will not monitor or update social media". It's not posted since.

Services like the tsunami centre that are required to protect life are allowed to keep going even when the rest of the government is shut down. But the problems of the last few days might delay the response.

[23 January 2018 10:13 · Andrew Griffin]

"If you are located in this coastal area, move inland to higher ground. Tsunami warnings mean that a tsunami with significant inundation is possible or is already occurring," Anchorage Office of Emergency Management said in a warning for Alaska and British Columbia.

Tsunami warnings for parts of Alaska and Canada and a tsunami watch for the entire U.S. west coast and Hawaii were issued.

"Based on all available data a tsunami may have been generated by this earthquake that could be destructive on coastal areas even far from the epicenter," the Pacific Tsunami Warning Center said.

Japan's meteorological agency said it was monitoring the situation but did not issue a tsunami alert.

[23 January 2018 10:17 · Andrew Griffin]

Here's the tsunami centre's guidance for the US. Red indicates a "warning", while a yellow line indicates "watch"; all areas covered by those lines are potentially under threat.

[23 January 2018 10:18 · Andrew Griffin]

If a tsunami does reach the west coast, it will take some time. The earthquake hit just under an hour ago, and it will take around three hours in total before it arrives in the US.

[23 January 2018 10:24 · Andrew Griffin]

The Alaskan earthquake centre says in a tweet that it is aware of the potential tsunami and will monitor it. But a power outage on the campus where it is based is hindering its work.

"Most are aware already of the ~M8 event off Kodiak," it wrote. "Follow @NWS_NTWC for tsunami watch and warning info. Unfortunately a power outage at the UAF campus is hindering our operations, but we will keep you updated."

[23 January 2018 10:25 · Andrew Griffin]

The latest report from the tsunami centre suggests big waves might be on their way:

"Based on all available data... hazardous tsunami waves are forecast for some coasts," it reads.

[23 January 2018 10:27 · Andrew Griffin]

The centre advises people to stay alert and wait word from their authorities. Some are already advising people to head to high ground.