US authorities lifted a string of tsnuami warnings after an earthquake of magnitude 8.2 struck the Alaska Peninsula on Thursday.

The US Geological Survey (USGS) had initially reported that the magnitude was 7.2.

It measured the quake as having a depth of 35 kilometers (21.7 miles).

The earthquake hit 56 miles (91 kilometers) southeast of the town of Perryville, some 500 miles from Anchorage, Alaska's biggest city.

Why were the tsunami warnings canceled?

Tsunami warnings were issued for Alaska, Hawaii, and the Pacific territories of Guam and the Northern Mariana Islands. But authorities later canceled those warnings.

In Alaska, there were no immediate reports of injuries or damage. Several coastal communities had been evacuated as a precaution.

In Seward on the Kenai Peninsula, south of Anchorage, sirens blared as residents were ordered to move to higher ground.

Officials at the Pacific Tsunami Warning Center scrapped the alerts when it emerged that the threat was not as great as first feared.

Japanese public broadcaster NHK reported that there is no risk of tsunami damaging Japan's coast after it said there might be small changes to tide levels.

Earthquakes are the result of sudden movement along faults within the Earth caused by the release of built-up pressure at plate boundaries.

When plates snap back into position, the energy from this movement can cause huge waves to form.

Has Alaska been hit by earthquakes before?

Alaska was was hit by a 9.2-magnitude earthquake in March 1964, the strongest ever recorded in North America.

The US state is part of the seismically active Pacific Ring of Fire where earthquakes are very common.

The 1964 quake claimed the lives of more than 250 people, destroying Anchorage and unleashing a tsunami that wreaked havoc across the Gulf of Alaska.

Alaska was struck by two weaker earthquakes last year.

One in October had a magnitude of 7.4, while another quake in July 2020 measured 7.6.

jf/nm (AFP, Reuters)