Geological cores explain how quakes occur

TOKYO, Feb. 7 (UPI) -- A Japanese and U.S.-led international research team has obtained sub-sea core samples that provide data on how earthquakes are generated.

The third expedition of the Integrated Ocean Drilling Program's Nankai Trough Seismogenic Zone Experiment completed its mission Tuesday off Japan's Kii Peninsula. The expedition, consisting of 26 scientists representing 10 nations, started Dec. 19 to evaluate the deformation, structural partitioning and physical characteristics of the Nankai Trough fault zone.

The scientists were led by Gaku Kimura of the University of Tokyo and Elizabeth Screaton of the University of Florida.

The investigators drilled and cored 13 boreholes in the fault zone.

"We collected more than 5,000 samples from the cores for further examination," said Screaton. "The resulting data will provide important new constraints on models of the evolution of the subduction zone and its relationship to earthquake and tsunami generation."

The Nankai Trough, a geological trench approximately 500 miles long, stretches from the Suruga Bay to where the Philippine Sea Plate slips under southwest Japan.

Screaton said scientists hoped to gain information about why some earthquakes cause disturbances at the seafloor that produce tsunamis.