MANOA (HawaiiNewsNow) – A visiting seismologist from Tohoku University in Sendai, Japan has first of its kind evidence showing the ocean floor off the coast of Japan's Northern Honshu Island near the Japan trench shifted as much as 80 meters (87 yards) in the earthquake March 11, 2011.
Yoshihiro Ito is a marine geophysicist at Tohoku University. He will make a presentation Friday to faculty and students at the University of Hawaii School of Ocean and Earth Science Technology.
The highlight of his presentation will be data on just how much the sea floor shifted in the violent March 11 quake.
"The maximum slip on the plate boundary is 80-meters," Ito told Hawaii News Now.
In October, 2010, six months before the earthquake and tsunami, Ito and colleagues from Tohoku University placed pressure gauges on the ocean floor 5,000 meters below the surface near the Japan Trench. Those gauges measured vertical uplifting of the sea floor as much as five meters. The gauges also moved as much as 80 meters horizontally along the sea bed.
"The work that our Japanese colleagues have been doing is really significant because they are the first ones to have actually put instruments down on the sea floor and recorded the movement along the big fault plane during a subduction zone earthquake," said Greg Moore, professor and chair of the U.H. Geology and Geophysics Department.
Moore told Hawaii News Now Ito's data not only helps explain the size tsunami but raises questions about the possibility of a similar event along the Aleutian Trench South of Alaska.
"This earthquake in the Tohoku area tells us that it may be possible that the Aleutians could break that way as well, and unfortunately for us the Aleutians are pointing directly at Hawaii," Moore explained.
The March 11 tsunami hit Japan less than half an hour after the quake. It would take a tsunami from the Aleutians at least four and a half hours to reach Hawaii. That extra time could save lives but it would not prevent widespread damage along the coast.