Aboard Scientific Drill Ship Near Japan, UMass Hydrogeologist Will Study a Major Pacific Earthquake-Birthing Zone

June 3, 2009

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Janet Lathrop 413/545-0444

AMHERST, Mass. – When the world’s first ocean research vessel equipped with super-deep core-drilling equipment begins its next scientific cruise this month, hydrogeologist David Boutt of the University of Massachusetts Amherst will be aboard, preparing to study subsurface fluids from 1.25 miles below the sea floor, the deepest ever sampled, at a premier earthquake-spawning ground off the coast of Japan.

Goals of the two-stage summer project led by the Japanese government and known as Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) include installing sensors in deep boreholes to monitor the Earth’s crust for earthquake and tsunami activity off the coast of Japan, in an area where two massive tectonic plates, the Eurasian and the Philippine, meet to create one of the most seismically active areas on the planet. UMass Amherst’s Boutt is one of about a dozen scientists from seven nations who will staff the research vessel for its first six-week cruise that begins June 11.

He says that once in place, the long-term monitoring packages should allow scientists “to collect the data to help us better understand the mechanics of the often massive earthquakes in this area. It’s a very active zone.” Chikyu’s special drill will be positioned over an area called the Nankai accretionary prism that’s adjacent to an extremely deep ocean trench off the Japanese coast at the mid-ocean ridge where the Philippine plate is being pulled under or subducted beneath the Eurasian plate. An accretionary prism is a wedge-shaped bunched-up divot of Earth’s crust that’s been scraped off by subduction and deposited at the edge of the trench.

Boutt is an expert in the mechanics of and flow paths of subsurface aqueous fluids, a name for the superheated, pressurized water that’s been so altered by sediment load, dissolved chemicals, or both, that it can’t be called simple water anymore. It’s clear that these fluids get forced along and out of ocean floor cracks near accretionary prisms, but their role in earthquake- and tsunami-genesis is not well understood. For example, it’s been suggested that because of water’s ability to bear tremendous weight, subsurface fluid behavior near places where tectonic plates collide could be a key to “slip” events that release the tremendous amounts of energy that we know as earthquakes.

Boutt will attempt to determine where the subsurface fluids come from, whether the volume is sufficient to bear tremendous plate weights, their flow path, and whether they are they chemically interacting with rock and crust. “These fluids are an integral part of the earthquake cycle and their role can’t be ignored when studying these tectonic events,” he points out.

Aside from the expedition’s compelling scientific mission, the research vessel itself has become something of an engineering celebrity. During its construction, the huge Chikyu, whose name means “Earth” in Japanese, was nicknamed the “Godzilla maru” because of its monster size and ungainly look. Chikyu’s deck carries the world’s tallest ship-borne drill rig, a 327-foot derrick specially made to allow scientists to drill deeper than ever before, up to 4.34 miles below the sea floor. An essential part of its equipment is a stable platform, called a riser, that is lowered to sit on the ocean floor below the ship to stabilize the drill site and borehole against enormous internal and external pressures.

The special drill and rig have the ability to insert a stable casing into the borehole that won’t collapse on itself, thus allowing placement of deep, long-term sensors and monitors. The NanTroSEIZE Deep Sea Drilling Vessel (D/V) Chikyu is the first riser-equipped scientific drilling vessel designed and built for science from the earliest planning stage. It is capable of drilling up to 4.3 miles below the sea floor into Earth’s mantle and seismogenic zone. Chikyu is the main platform of the Integrated Ocean Drilling Program (IODP). Overall, NanTroSEIZE project organizers say, “This deep sea drilling research opens the new frontier of earth and life science for future of mankind by revealing the system of major earthquakes, global changes and origin of life.”

Contact: David Boutt, dboutt@geo.umass.edu

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