Reporting in the journal Science, researchers say they’ve discovered a surprising wrinkle in the geologic story behind one of the most devastating earthquakes in recent memory: the March 2011 Tohoku earthquake that spawned 130-foot tsunami waves, killed 15,800 people and led to a crisis at the Fukushima Daiichi nuclear power plant. The researchers determined that current shear stress on the fault that generated the earthquake is nearly zero. In other words, the violent spasm that released the earthquake also shook out all the pent up stress on the fault.
Alan McStravick, writing in a recent article for the website Red Orbit, explained why this was such a shocker: “The paper’s presentation of this fact flies in the face of the prevailing wisdom that earthquakes will typically only release a portion of the stress on the fault.”
The new results suggest the risk of large earthquakes may be much higher than previously thought, not only in Japan, but near similar megathrust faults around the world.
Working aboard the scientific drilling vessel Chikyu, scientists from the International Ocean Drilling Program (IODP) drilled through the plate boundary fault about 820 meters (0.5 miles) below the seafloor in water nearly 7 kilometers (4.3 miles) deep. They took measurements in the borehole as they drilled, collected core samples and left behind instruments to continue collecting more data over time. (Read the IODP press release about the latest announcement)
Patrick Fulton, a postdoctoral researcher at the University of Texas at Austin’s Institute for Geophysics now at the University of California, Santa Cruz, was a part of the JFAST team and a co-author on the latest study. Fulton blogged about his experiences during the research cruise (read his posts).
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