Ocean floor boring ship may aid quake prediction


By Will Knight and AFP A colossal vessel that will drill 7000 metres below the surface of the Earth – in an attempt to collect the first ever samples of the Earth’s mantle – has completed its first training mission at sea. The 57,500-tonne deep-sea drilling ship Chikyu made a port call in Yokohama on Thursday after collecting sub-surface samples, from relatively shallow depths, during its maiden voyage. The ship will try to take samples from unprecedented depths beneath the seabed and will bore through a “subduction zone” – the point where one tectonic plate descends underneath another. This should provide new data on the seismic activity that produces earthquakes on the surface. But the researchers also hope to detect primitive subsurface organisms known as extremophiles and to find clues to prehistoric climate change. Chikyu – which means “Earth” in Japanese – is equipped with a 121-metre drill tower capable of boring 7000 metres below the seabed. But it could take more than a year to drill so far down, so the ship will maintain its position above the drill hole using satellite and ocean bed navigation systems and six propellers located beneath its hull. The deepest hole drilled through the seabed so far reaches 2111 metres. Chikyu will set off in September 2007 to collect the first samples from 7000 metres, at a point some 600 kilometres southwest of Tokyo, Japan. The project, called the Integrated Ocean Drilling Program (IODP), is led by Japan and the United States with the participation of China and the European Union. The mantle lies around 30 kilometres below the continental crust, but is much closer to the surface beneath the oceans. Chikyu will insert a “conductor pipe” and a “casing pipe” hundreds of metres into the Earth’s crust, to support a thinner drill that will bore thousands of metres down. “This is like an Apollo project under the Earth,” says staff scientist Kan Aoike. “This is a serious attempt to complete another key exploration for mankind.” Asahiko Taira, director-general of the project, said he hoped the project would help scientists predict deadly earthquakes. “For Japan the most important thing is to drill through areas where plates are overlapping so that we can monitor an earthquake directly,” he said. Taira said the seabed off Sumatra in Indonesia, which produced the massive earthquake that triggered the Indian Ocean tsunami in December 2004, could be another potential drilling spot in the future. More on these topics:
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