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The withering tsunami that struck Japan last March killed more than 15,000 people , disrupted power and service across the country and cripple the Fukushima Dai - ichi atomic magnate plant . The massive waves were triggered by a 9.0 - magnitude seism that gave the sea floor a immense shove toward Honshu , Japan ’s largest island .
But exactly how much the earth moved in the quake has been unclear — until now .
A map of estimated tsunami travel times. CREDIT: NOAA.
A new feel at the ocean floor before and after the2011 Tohoku earthquakereveals massive slip in the ocean crust . Energy from the uplifted sea floor — which was thrust 164 foot ( 50 metre ) horizontally and 33 feet ( 10 meters ) vertically — spark off theimmense tsunami wavesthat struck the coast of Japan .
An ' abnormally huge ' seism
Themagnitude of the Tohoku quakemade it possible for scientists to detect the fault with vulgar sea - story - survey techniques , something that " has never been done before , " tell Toshiya Fujiwara , a geophysicist at the Japan Agency for Marine - Earth Science and Technology .
A map of estimated tsunami travel times. CREDIT: NOAA.
" This seism was extraordinarily , abnormally huge , " Fujiwara order OurAmazingPlanet .
Fujiwara ’s team used multibeam bathymetric survey — which use echolocation to assess water depth and the material body of the underlying sea base — to map out orbit around the Japan Trench after the quake . The team compared it with interchangeable data taken in 1999 and 2004 from the same belt of sea level . The difference between the information Seth give away large translation in the ocean freshness — more than 100 times great than shifts measured after other seism .
" We did n’t ask the displacement to be detected by using such an ordinary sea - floor - resume instrument , " Fujiwara say . " Crustal move usually happens on a millimeter- or centimeter - scale , not over 10s of meters . "
The 2005 7.2 - order of magnitude Miyagi seism , for example , registered a shift of 4 inches ( 10 centimeters ) at a geodetic place near the Japan Trench . The 2011 Tohoku earthquake measured 49 feet ( 15 meters ) at the same station , said Fujiwara — larger by more than two orders of magnitude . In other words , most quakes give the ocean floor a gentle nudge , but the Tohoku earthquake gave it a huge shove .
Massive consequences
In improver to the 33 - foot ( 10 - meter ) vertical shift , a large slab of ocean crust between the Japan Trench and the Honshu seashore was hike up upwards another 12 - 18 animal foot ( 4 - 6 measure ) or more , Fujiwara ’s team find .
This uplift helped bring forth the " monumental pulsating pattern of tsunami waves " that make Japan , the team explicate in their paper , which will appear in the Dec. 2 issue of the journal Science . [ History ’s Biggest Tsunamis ]
The fault that shift the sea impudence so dramatically likely extends all the way to the axis of the Japan Trench , Fujiwara said , further foreground the magnitude of the Tohoku quake .
" Previously , we thought the displacement stopped somewhere underground , " Fujiwara said , " but this seism destroy the entire home base bound . "
This storey was provide byOurAmazingPlanet , a sister site to LiveScience .
