Credit: IODP/JAMSTEC

The first scientific ocean-floor drilling project to use a riser drill — equipment previously used in oil exploration — was completed last week.

The Japanese research vessel Chikyu (pictured) drilled 1,600 metres below the sea floor of the Nankai Trough, an earthquake-generating zone off the Pacific coast of Japan.

Riser drilling circulates mud in an extra casing around the drill to prevent the collapse of a borehole in deep, high-pressure zones. Chikyu had already tested its riser-drilling equipment while on loan to an Australian oil company (see Nature 442, 964; 2006).

The vessel is taking a leading role in the Integrated Ocean Drilling Program, a collaboration of Japanese, US and European scientists studying rock and sediment samples to learn about Earth's structure and history. It is due to drill two more sites in the Nankai Trough.