Odd waves in fjords traced to their source thousands of miles away
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| The Aurland-Flåm fjord in Norway, where the 2011 Japan earthquake triggered seiche waves. (Leif Haug) |
On a calm winter's day in Norway two years ago, the sea suddenly started to boil and rise, sending freak waves rolling onto nearby shores and mystifying residents. Turns out, the massive magnitude-9.0 earthquake that shook Japan in 2011 also triggered these surprise seiche waves, a new study shows.
Seiche (pronounced "saysh") waves are standing waves that form in closed or semi-enclosed water basins, such as Norway's narrow, steep-walled fjords. Smaller examples of standing waves include water sloshing in a bathtub from a wriggly child, or in a swimming pool after an earthquake.
The roiling seas surprised and shocked Norwegians when the waves rolled in after 7 a.m. local time on March 11, said lead study author Stein Bondevik, a geologist at Sogn og Fjordane University College in Sogndal, Norway. The waves measured nearly 5 feet from trough to crest (their lowest to highest point). No damage was reported, however. "Luckily, they happened at low tide," Bondevik said.
A tsunami expert, Bondevik was called on by local media to explain the source of the surge. Bondevik said he first thought an underwater landslide generated the waves. "They looked like tsunamis," he said. But as the day wore on, more reports of coastal flooding came in from faraway fjords, blowing a hole in his landslide theory.
"Later in the evening I realized there must be a connection with the big earthquake in Japan," Bondevik told LiveScience. "I was so excited I couldn't sleep that night thinking about it."
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