A major earthquake in the Gulf of Alaska sent jolts through several cities and towns on the Alaskan coast Monday, but authorities reported no injuries and only minor damage to buildings.
The earthquake struck at 11:23 a.m. PST with an epicenter about 290 miles southeast of Anchorage. Throughout the day, varying magnitudes on the Richter scale of 7.4 to 7.7 were reported by seismology stations, making it the largest quake to strike the United States since an 8.3-magnitude earthquake devastated Anchorage in 1964.
For 90 minutes after the quake, a tsunami warning was issued for the entire southern coastline of the state and British Columbia. A lower-level tsunami watch was issued for Washington, Oregon and California. Tsunamis are very large ocean waves occasionally created by offshore earthquakes that can inundate low-lying areas, and the warning triggered evacuations in several Alaskan coastal towns.
Headed for Higher Ground
As emergency sirens blared and police loudspeakers announced the warning, residents fled their homes and headed for higher ground. Alaskan officials estimated that several thousand people evacuated as a result of the danger.
However, only minor tsunamis were observed. At Yakutat, a small village closest to the earthquake, the wave was measured at 3.3 feet. In other locations the size was smaller still. "The wave was just insignificant," said Tom Sokolowski, a geophysicist at the Alaska Tsunami Warning Center.
In Yakutat, about 100 miles from the epicenter, the earthquake shook buildings and briefly interrupted electrical power but did little damage.
"This one was a low rumbler," said City Manager Jim Filip. "Most people in Alaska are used to earthquakes. But in my experience, this was a good one."
In Seward, the city's emergency siren also was used to evacuate residents from low-lying areas. Mayor Harry Geiseler said an initial survey revealed no serious damage. "It rattled pictures and shook things around a great deal," he said.
Monday's quake was the second in two weeks to trigger the tsunami warning system. On Nov. 17, a 7-magnitude temblor struck in about the same area and caused evacuations along the coast. Both earthquakes were caused by slippage of two huge blocks of the Earth's crust along an undersea fault. The blocks, known as the Pacific plate and the North American plate, have caused major earthquakes from Alaska to Southern California.
At Caltech, seismologist Kate Hutton said the minor impact of the quake could be attributed to the distance of the epicenter from populated areas. Only when unusual geological circumstances exist do such quakes produce severe damage, she said.
Frank Baldwin, a seismologist at the National Earthquake Information Center in Golden, Colo., said earthquakes of magnitude 7.5 occur somewhere several times a year. He said a precise measurement of Monday's quake likely would be produced today after scientists had more time to study charts of seismographs.