Slow earthquakes in ocean subduction zones shed light on tsunami risk

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Understanding "slow-slip" earthquakes on the seafloor -- seismic events that occur over a period of days or weeks -- is giving researchers new insights into undersea earthquakes and the subsequent creation of tsunamis. Through an ocean discovery program supported by the National Science Foundation (NSF), scientists are studying the seafloor off the coast of Japan. The region could provide vital clues.

Two tectonic plates, the Pacific Plate and the Eurasian Plate, meet there. In this ocean trench zone, the Pacific plate slides beneath the Eurasian plate. Such subduction zones are often associated with large earthquakes.

"This area is the shallowest part of the plate boundary system," said Demian Saffer, a geoscientist at Penn State University. "If this region near the ocean trench slips in an earthquake, it has the potential to generate a large tsunami."

Saffer and Eiichiro Araki, senior research scientist at the Japan Agency for Marine-Earth Science and Technology, published the results of their investigations of the plate boundary in this week's issue of the journal Science.

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Photo: Instrumentation is readied for a borehole observatory installation during an expedition. Credit: Dick Peterse, ScienceMedia.nl