Tsunami watch cancelled for Calif. after 7.9 magnitude quake in Alaska

A 7.9 magnitude earthquake hit just before 2 a.m. Pacific time Tuesday in the Gulf of Alaska and triggered a tsunami warning for the region, along with a tsunami watch for California, including the San Francisco Bay Area, Washington and Oregon before the National Weather Service cancelled the watch.

A wave of only six inches was reported in Alaska according to the National Weather Service, but emergency workers were being cautious, and continuing to monitor the impact of the quake and its aftershocks.

At 4:15 a.m., the National Weather Service in Monterey officially announced the watch was cancelled, but the San Francisco Department of Emergency Management still recommends caution, tweeting, "Tsunami Watch CANCELLED in #SF, but shoreline areas, marinas, & harbors may have dangerous, strong, & unpredictable currents. Stay away from coastlines for at least 12 hours. Visit http://sf72.org/hazard/tsunamis to learn more about tsunami preparedness"

Debris litters Santa Cruz Harbor in Santa Cruz, Ca., on Friday March, 11, 2011, following the aftermath of the hugh Japan earthquake which triggered a tsunami that reached the West Coast of California today. Debris litters Santa Cruz Harbor in Santa Cruz, Ca., on Friday March, 11, 2011, following the aftermath of the hugh Japan earthquake which triggered a tsunami that reached the West Coast of California today. Photo: Michael Macor, The Chronicle Photo: Michael Macor, The Chronicle Image 1 of / 28 Caption Close Tsunami watch cancelled for Calif. after 7.9 magnitude quake in Alaska 1 / 28 Back to Gallery

Energy from an earthquake travels at roughly the speed of a jet across the ocean, meaning the energy from the quake and tsunami will arrive in California early Tuesday morning. While the waves will not be noticeable without scientific equipment, the tsunami energy at least will arrive in San Francisco at 6:15 a.m., and at Crescent City at 5:20 a.m.

The weather service uses information from coastal buoys that measure wave height hundreds of miles away to determine whether to upgrade the "watch" to a "warning," meaning a tsunami is going to occur.

Those buoys did indeed measure a tsunami working its way down the coast precisely on time this morning. The Point Arena tide gauge at Arena Cove showed the anomaly on the chart as the energy arrived from far off Alaska.

Photo: National Weather Service Bay Area National Weather Service Bay Area reports: "#PointArena tide gauge...

The earthquake initially registered as high as magnitude 8.2 before the U.S. Geological Survey finalized the measurement at 7.9. Several aftershocks, the largest a 5.6 magnitude, continue to rock the area.

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Previous earthquakes of similar magnitude have triggered nearly imperceptible wave action, while the exponentially stronger 1964 Alaska earthquake registered a monstrous 9.2 and triggered the deadly tsunami that caused widespread devastation in Crescent City and other ports along the coast.

NO TSUNAMI INFO FROM NOAA: Government website still shut down during emergency

Many tsunami resources were unavailable after the early morning earthquake because of the earlier government shutdown. While President Donald Trump signed an order ending the 69-hour shutdown late Monday night, NOAA had not updated websites overnight, leaving many mapping tools like this site that predicts tsunami arrival times, unavailable.

Photo: NOAA/Screenshot

NOAA did issue the following information about arrival times of what will now be an imperceptible wave.

Estimated tsunami start times for selected sites are;

Neah Bay Washington 450 AM. PST. January 23.

Moclips Washington 500 AM. PST. January 23.

Long Beach Washington 500 AM. PST. January 23.

Port Orford Oregon 505 AM. PST. January 23.

Seaside Oregon 505 AM. PST. January 23.

Westport Washington 510 AM. PST. January 23.

Charleston Oregon 510 AM. PST. January 23.

Newport Oregon 515 AM. PST. January 23.

Brookings Oregon 515 AM. PST. January 23.

Crescent City California 520 AM. PST. January 23.

Horse Mountain California 525 AM. PST. January 23.

Fort Bragg California 525 AM. PST. January 23.

Port Angeles Washington 530 AM. PST. January 23.

Monterey California 555 AM. PST. January 23.

Port Townsend Washington 555 AM. PST. January 23.

San Francisco California 615 AM. PST. January 23.

Port San Luis California 620 AM. PST. January 23.

Santa Barbara California 635 AM. PST. January 23.

Los Angeles Harbor California 650 AM. PST. January 23.

Oceanside California 700 AM. PST. January 23.

Newport Beach California 700 AM. PST. January 23.

La Jolla California 705 AM. PST. January 23.

While waves were not seen along the Canadian and Alaskan coasts, emergency managers were urging caution. 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."

People reported on social media that the quake was felt hundreds of miles away, in Anchorage.

Keith Perkins, who lives in the southeast Alaska community of Sitka, arrived at the high school early Tuesday morning, after an alarm on his cellphone alerted him of the tsunami warning. He says the city's sirens also went off later.

He said people on Facebook were chattering back and forth about whether this was real or not and what they should do.

Given the magnitude of the earthquake, Perkins said he thought it best to head to school, the tsunami evacuation point, even though in the past he felt his home was at a "high-enough spot."

"I figured I'd probably just better play it safe," he said.

He said police officers were directing traffic and the parking lot at the school was filling up. He said he saw some people carrying suitcases or backpacks. Perkins said he didn't bring anything along.

The Associated Press contributed to this report.