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Stress Change During the 2011 Tohoku-Oki Earthquake from Seafloor Boreholes

The 11 March 2011 Tohoku-Oki earthquake (Mw9.0) produced the largest slip ever recorded in an earthquake, over 50 meters. Such huge fault movement on the shallow portion of the megathrust boundary came as a surprise to seismologists because this portion of the subduction zone was not thought to be accumulating stress prior to the earthquake. In a recently published study, scientists from the Integrated Ocean Drilling Program (IODP) shed light on the stress state on the fault that controls the very large slip. The unexpectedly large fault displacements resulted in the devastating tsunamis that caused tremendous damage and loss of lives along the coast of Japan. The study, published in 8 February 2013 issue of the journal Science, presents compelling evidence that large slips are the results of a complete stress drop during the earthquake. These new findings from IODP Japan Trench Fast Drilling Project (JFAST) research are relevant to better understanding earthquakes and tsunamis in many areas of the world. (IODP Press Release, 7 Feb 2013)

Virginia Toy from the University of Otago participated in the expedition. Her participation was possible through New Zealand's membership of the Integrated Ocean Drilling Program as part of the Australian-NZ IODP Consortium.  

Hear Virginia Toy talk about the study on Radio New Zealand National Morning Report on Friday 8 February 2013.