A shallow earthquake of magnitude 8.2 struck the Alaska Peninsula late last night, prompting tsunami warnings for the region. The earthquake was the largest in Alaska since 1965.
The US Geological Survey (USGS) said the quake, which struck at 10:15 pm local time, was at a depth of 20 miles. Earthquakes at a depth up to ~45 miles are considered shallow. The main quake was followed by two strong aftershocks, including a preliminary 6.2 and 5.6.
“This event was felt throughout the Alaska Peninsula and Kodiak.”
– Alaska Earthquake Center
In Alaska, the National Tsunami Warning Center (NTWC) issued warnings for South Alaska and the Alaska Peninsula, from Hinchinbrook Entrance to Unimak Pass, and for the Aleutian Islands, from Unimak Pass to Samalga Pass, Alaska. The Pacific Tsunami Warning Center (PTWC) issued a warning for Hawaii and the U.S. Pacific territory of Guam. The NTWC was also evaluating the level of tsunami danger for other US and Canadian Pacific coastal areas.
“A tsunami has been confirmed and some impacts are expected.”
– US National Tsunami Warning Center
Citizens of Kodiak, the largest town on the island of Kodiak, were advised by police to move to high ground.
Less than two hours after the initial warning, it was downgraded to an advisory. The first waves triggered by the quake had already landed, about seven inches above normal with at least one later wave one foot above normal.
Tsunami warnings mean that a tsunami with significant inundation is expected or occurring. Warnings indicate that widespread dangerous coastal flooding accompanied by powerful currents are possible and may continue for several hours after the initial wave arrival.
Tsunami advisories mean that a tsunami capable of producing strong currents or waves dangerous to people in or very near the water is expected. Significant widespread inundation is not expected for areas under an advisory. Currents may be hazardous to swimmers, boats, and coastal structures and may continue for several hours after the initial wave arrival.
Just after 1:30 a.m. this morning, the advisory was canceled completely.
Wednesday’s earthquake was Alaska’s largest since an 8.7 quake hit off the Aleutians in 1965. The Good Friday earthquake in 1964, which caused massive damage and loss of life across Southcentral Alaska, was 9.2, reports Anchorage Daily News.