An Alaska earthquake on Monday that measured 7.9 triggered only a small tsunami, and by evening a tsunami warning was downgraded to an advisory and then canceled entirely.
The earthquake struck Monday in the Aleutian Islands, prompting a tsunami warning for coastal areas. Waves were expected to reach the cities of Unalaska and Saint Paul, and in the city of Adak people were ordered to abandon the coast for higher ground.
"When there's a significant earthquake such as this, we have a tsunami siren similar to a tornado alarm," City Manager Layton Lockett told the Los Angeles Times. "It just blares," and people head to safety.
But the waves did not reach Adak, and later in the day the mayor, police chief, and city manager decided to call off the evacuation.
The Alaska earthquake struck in the Aleutian Islands, close to 20 miles from Little Sitkin Island. The U.S. Geological Survey initially listed the quake as a 7.1, then upgraded it to 8.0 before downgrading it to 7.9. It was a deep earthquake, striking at a depth of 250 kilometers, and not expected to cause any significant damage.
As the USGS noted, the region of Alaska is particularly active for earthquakes:
"The Aleutian arc is a seismically active region, evidenced by the many moderate to large earthquakes occurring each year. Since 1900, this region has hosted twelve large earthquakes (M>7.5) including the May 7, 1986 M8.0 Andreanof Islands, the June 10, 1996 M7.9 Andreanof Islands, and the November 17, 2003 M7.8 Rat Islands earthquakes. Six of these great earthquakes (M8.3 or larger) have occurred along the Aleutian arc that together have ruptured almost the entire shallow megathrust contact."
Other tsunami warnings were canceled after the Alaska earthquake, including one for the island of Shemya. The island is home to an Air Force command center, but a spokesperson said no one was hurt and no damage reported.