More than one ocean motion determines tsunami size | Science News

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More than one ocean motion determines tsunami size

Giant wave forecasts need to take into account horizontal motion on sloped seafloors

7:00am, April 14, 2017
2011 tsunami visualized

OCEAN MOTION  The 2011 tsunami that devastated Japan (forecast shown) was fueled by both the horizontal and vertical motion of the seafloor, new research suggests. Darker colors represent higher waves. Black triangles mark tsunami-measuring buoys.

Earthquake-powered shifts along the seafloor that push water forward, not just up, could help supersize tsunamis.

By combining laboratory experiments, computer simulations and real-world observations, researchers discovered that the horizontal movement of sloped seafloor during an underwater earthquake can give tsunamis a critical boost. Scientists previously assumed that vertical movement alone contributed most of a tsunami’s energy.

More than half of the energy for the unexpectedly large tsunami that devastated Japan in 2011 (SN Online: 6/16/11) originated from the horizontal movement of the seafloor, the researchers estimate. Accounting for this lateral motion could explain why some earthquakes generate large tsunamis while others don’t, the researchers report in a paper to be published in the Journal

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