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Norwegian seiches from the giant 2011 Tohoku earthquake

Seismic waves of the giant 2011 Tohoku earthquake triggered seiches in western Norwegian fjords. The seiching began a half hour after the earthquake origin time. The oscillations were noted by eyewitnesses and recorded by surveillance and cell phone cameras. The observations show maximum trough‐to‐p...

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Bibliographic Details
Published in:Geophysical research letters 2013-07, Vol.40 (13), p.3374-3378
Main Authors: Bondevik, Stein, Gjevik, Bjørn, Sørensen, Mathilde B.
Format: Article
Language:English
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Summary:Seismic waves of the giant 2011 Tohoku earthquake triggered seiches in western Norwegian fjords. The seiching began a half hour after the earthquake origin time. The oscillations were noted by eyewitnesses and recorded by surveillance and cell phone cameras. The observations show maximum trough‐to‐peak amplitudes of 1.0–1.5 m and periods of 67–100 s. The water waves were not triggered from the arrival of the surface waves, the timing inferred for other seiches. Instead, the seiching began during the passage of horizontal S waves. We reproduced the S wave trigger by means of a shallow‐water wave model calibrated previously to Norwegian tides and storm surges. The simulations, which used the observed earthquake motion as forcing, show water waves with periods and amplitudes similar to those in the film clips. However, the strongest horizontal ground oscillations with shorter periods (20–30 s) did not contribute much to the formation of the seiches. Key Points Norwegian fjords seiched in response to the 2011 Tohoku earthquake The water waves in film clips resemble those simulated numerically The seiching was triggered from the arrival of S waves
ISSN:0094-8276
1944-8007
DOI:10.1002/grl.50639