Massive Pluton Directing Quakes

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The Kumano Pluton (shown as red bulge) in southern Japan is a mountain size rock large and dense enough to interfere with earthquakes, according to a new 3D visualization by The University of Texas at Austin. Credit: Adrien Arnulf

Thanks to 20 years of seismic data processed through one of the world’s most powerful supercomputers, scientists have created the first complete, 3D visualization of a mountain-size rock called the Kumano Pluton buried miles beneath the coast of southern Japan. They can now see the rock could be acting like a lightning rod for the region’s megaquakes, diverting tectonic energy into points along its sides where several of the region’s largest earthquakes have happened.

Scientists have known about the pluton for years but were aware of only small portions of it. Thanks to new research by an international team of scientists led by the University of Texas Institute for Geophysics (UTIG), researchers now have a view of the entire subterranean formation and its effect on the region’s tectonics.

Japan Study
The Kumano Pluton is in southern Japan near the Nankai subduction zone. A research team led by UT Austin compiled seismic data to create a 3D model of the Earth beneath the study area. Credit: UT Jackson School of Geosciences

The findings will provide critical information for a major new Japanese government-funded project to find out whether another major earthquake is building in the Nankai subduction zone, where the pluton is located, said Shuichi Kodaira, director of the Japan Agency for Marine-Earth Science and Technology and a co-author of the study published in the journal Nature Geoscience.

“We cannot predict exactly when, where, or how large future earthquakes will be, but by combining our model with monitoring data, we can begin estimating near-future processes,” said Kodaira, who was among the scientists who first spotted signs of the Kumano Pluton in 2006. “That will provide very important data for the Japanese public to prepare for the next big earthquake.

”The full extent of the Kumano Pluton was revealed using the LoneStar5 supercomputer at UT’s Texas Advanced Computing Center to piece together 20 years of seismic data into a single high-definition 3D model. The study was led by Adrien Arnulf, a research assistant professor at UTIG.

The model shows the region around the Nankai subduction zone, with the Earth’s crust bending under the pluton’s weight. The researchers think the pluton’s interference with the wider subduction zone is influencing the tectonic forces that cause earthquakes.

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