"It's one of the less understood processes that go on at subduction zones," said Demian Saffer, who builds computer simulations of subduction zones at Pennsylvania State University.
Seamounts are thought to do one of two things, Saffer explained. On one hand they could gunk up the smooth working of the "subduction factory" and therefore increase resistance and create a more jerky, quake-prone subduction zone.
On the other hand, seamounts help break rocks up and drag down wet material — as might be the case at Japan's Nankai Trench fault — which makes the subduction zone weaker, more lubricated and perhaps less able to produce large quakes.
Sorting out which is the case has implications far beyond Japan, said Bangs. The infamous Sumatra subduction zone that let loose the monstrous Dec. 2004 mega-quakes and Indian Ocean tsunami is also affected by seamounts, he said. "It is a similar situation and a similar problem."
It's that sort of danger that keeps people like Saffer and Bangs busy trying to figure out how these subduction zones really work.
Providing funding for a lot of this work is the 21-nation, 10-year, $1.5 billion Integrated Ocean Drilling Program (IODP), which is already underway with plans to drill right down into the Nankai Trench fault, Bangs said.
In fact it was the search for good drilling sites that led Bangs and his colleagues to stumble onto the seamounts, he said. The IODP plans include creating a Nankai Trench fault-observatory similar to the San Andreas Fault Observatory at Depth (SAFOD) in California.
