Tsunami Warning Issued After Twin Earthquakes Strike Cruise Port

Tsunami Warning Issued After Twin Earthquakes Strike Cruise Port (see video below) –  The first earthquake, a 7.0 magnitude, struck at 17:29:28 (UTC), 8:29 a.m. local time about seven miles north of Anchorage (61.340°N  149.937°W), the U.S. Geological Survey reported.

An aftershock, struck six minutes later with a 5.7 magnitude earthquake, 4 kilometres NNW of Anchorage, Alaska (61.259°N 149.921°W) at 17:35:37 (UTC)

Anchorage, Alaska is a cruise ship port, along with nearby Seward and Whittier. To the south, cruise ships call at Skagway, Juneau, Sitka, Icy Straight and Ketchikan during a typical voyage originating in Vancouver, British Columbia, Canada or from Seattle, Washington.

The National Tsunami Warning Center in Palmer, Alaska, issued a warning for coastal areas of Cook Inlet and the Southern Kenai Peninsula in Alaska. High Seas wave heights exceeding 21 feet are expected across the region from Alaska to California.

Anchorage, Alaska

Anchorage had an estimated 298,192 residents in 2016, it is Alaska’s most populous city and contains more than 40 percent of the state’s total population; among the 50 states, only New York has a higher percentage of residents who live in its most populous city. All together, the Anchorage metropolitan area, which combines Anchorage with the neighboring Matanuska-Susitna Borough, had a population of 401,635 in 2016, which accounts for more than half of the state’s population. At 1,706 square miles of land area, the city is larger than the smallest state, Rhode Island, at 1,212 square miles.

Aleutian Islands

The Aleutian Islands arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench.

The curvature of the arc results in a westward transition of relative plate motion from trench-normal (i.e., compressional) in the east to trench-parallel (i.e., translational) in the west, accompanied by westward variations in seismic activity, volcanism, and overriding plate composition. The Aleutian arc is generally divided into three regions: the western, central, and eastern Aleutians. Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from roughly 60 mm/yr at the arc’s eastern edge to 76 mm/yr near its western terminus.

The eastern Aleutian arc extends from the Alaskan Peninsula in the east to the Fox Islands in the west. Motion along this section of the arc is characterized by arc-perpendicular convergence and Pacific plate subduction beneath thick continental lithosphere. This region exhibits intense volcanic activity and has a history of megathrust earthquakes.

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