Large tsunami that swept the northeast coast of Japan after the devastating shock 9.0 on the Richter scale has power beyond estimates by experts. Research after the earthquake March 11, 2011 shows the strength was due to an unusual movement on the fault.
"Earthquakes of this magnitude was never predicted to arise from the plate boundary," said Greg Beroza, a geophysicist at Stanford University in San Francisco, USA.
The epicenter is located at subduction zones, namely the location of the meeting of two plates with one plate crashing another plate and reach the Earth's interior. In the Japanese earthquake, the plates are crashing on the sea floor and move to the west.When an earthquake occurs for the first time, fracture splitting to the west of the epicenter, moved toward the Japanese archipelago. As a result, the island of Honshu swayed for 40 seconds.
Surprisingly, the second quake came a few moments later. Fracture split to the east of the epicenter to the ocean. The process of ripping at the earth's plates is the case for 30 to 35 seconds, making the ocean floor to shift dramatically.
Tear that leads to the open sea has dangerous implications. In the open sea, the amount of water that is above the ocean floor more than in areas near the coast. "Changes in small-scale seafloor can cause major tsunamis," Beroza said.
He was surprised by the tear plates on two opposite directions that accompany the earthquake. According to him, something like this had never previously tereatat at subduction zones.
Previously, research experts geodesy Japan Coast Guard, Mariko Sato, showed a horizontal shift in the seabed up to 24 meters in the southeast. In the vertical direction, the seabed to rise up to 3 meters, causing a shift large amounts of water toward the coast of Japan.*** [NATURE | ANTON WILLIAM | KORAN TEMPO 3542]
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