A strong 8.2 magnitude earthquake off the south coast of Alaska on Wednesday evening shook a tsunami warning for parts of the state and a tsunami watch as far as Hawaii. They were lifted within hours. According to seismologists, it was the largest earthquake in the United States in 50 years.
The earthquake was discovered about 75 miles southeast of Chignik, Alaska, around 10:15 p.m. local time, the United States Geological Survey said.
The earthquake was felt across the Alaska Peninsula and Kodiak Island, the Alaska Earthquake Center reported. Tsunami sirens wailed in Kodiak and people began moving to higher elevations as the warning spread.
There were no immediate reports of damage.
The alert issued by the National Tsunami Warning Center lasted about two hours in southern Alaska, the Alaska Peninsula, and the Aleutian Islands.
A tsunami clock was also briefly issued for Hawaii and canceled just over an hour later, Governor David Ige said on Twitter. The National Weather Service’s office in Beach, Hawaii, had warned, based on preliminary measurements of the quake, that “widespread dangerous tsunami waves are possible”.
Tsunamis form as a series of waves caused by a large or sudden shift in the ocean, the weather service said, citing severe earthquakes below or near the ocean floor as the most common cause. The waves radiate outward in all directions from the disturbance and can move across ocean basins.
The earthquake recorded on Wednesday was one of only 17 since 1990, with a magnitude of 8.2 or greater anywhere in the world, according to USGS data.
At least two dozen aftershocks have been recorded in Alaska, the USGS said. One of the largest, about 70 miles southeast of Perryville, on the Alaska Peninsula, measured 6.1.
Alaskan earthquakes are not uncommon. The Alaska Earthquake Center reported more than 49,000 seismic events in the state and surrounding areas in 2020. The center also said that last year Alaska recorded the strongest and third largest earthquakes in the world.
Last December, a 6.4 magnitude earthquake struck off the coast of a remote area in southern Alaska, but it didn’t trigger tsunami warnings that could threaten the region’s sparsely populated chain of islands. About six months earlier, a 7.8 magnitude quake struck an area off the coast south of the Alaska Peninsula, near the main quake activity on Wednesday. A 7-magnitude earthquake struck Anchorage in 2018, tearing buildings, damaged roads, and crumbled bridges.
In 1964, a 9.2 magnitude earthquake struck southern central Alaska, making it the strongest North America quake in recorded history. For four and a half minutes the ground shook violently on a huge area. More than 125 people died, Anchorage was badly damaged, and much of the young state’s infrastructure was destroyed.
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