The Marcus G. Langseth — denied access to some Chinese waters. Credit: Earth Institute, Columbia Univ.

The research vessel Marcus G. Langseth will have to steer clear of the waters that separate Taiwan from mainland China, after the Chinese government denied the US seismic research vessel permission to sail in the area.

The vessel, which is investigating earthquakes and mountain-building processes in the Pacific Ocean, set sail from the port of Kaohsiung in southwest Taiwan this morning. But it will now not be able to carry out experiments within the 200 nautical mile exclusive economic zone in the South China Sea and Taiwan Strait that is under Chinese jurisdiction.

"This will reduce the effectiveness of our experiment and limit our ability to understand the tectonic structure and activity of the region," says Kirk McIntosh, a geophysicist at the University of Texas in Austin and project investigator.

The vessel is part of the multi-million-dollar Taiwan Integrated Geodynamic Research (TAIGER) project, which is jointly funded by the US National Science Foundation (NSF) and several agencies in Taiwan such as its National Science Council, Ministry of the Interior and Central Geological Survey of the Ministry of Economic Affairs.

Scientific importance

Scientists aboard the research vessel — owned by the NSF and operated by Columbia University's Lamont-Doherty Earth Observatory in New York — are aiming to produce a comprehensive three-dimensional map of the structure of the region's tectonic plates. They will use data from shock waves induced by natural earthquakes or by artificial sources on-board such as compressed air. They will also collect data from seismic probes deployed on land and the ocean floor.

The region around Taiwan is important for studying how collisions between tectonic plates give birth to mountain belts, says Francis Wu, a seismologist at Binghamton University in New York, who leads the US arm of the TAIGER project.

Taiwan rose from the Pacific Ocean as a result of the collision between the Eurasian plate and the Philippine Sea plate 4-5 million years ago. Growing at 2-3 centimetres a year, the mountains on the island are among the youngest and fastest-rising in the world, he says.

The region is frequently hit by earthquakes of magnitude 6–7 because of tectonic-plate movement. Both the mainland and Taiwan have been affected. For example, in 1999, a 7.6-magnitude tremor in Taiwan killed more than 2,400 people. And in 1604, a quake of around magnitude 8 destroyed the Quanzhou seaport on the Chinese mainland.

In the wake of the 2004 Indian Ocean tsunami, the US Geological Survey investigated the potential risk of large tsunami hazard zones in the Pacific Ocean and found that the region between Taiwan and North Luzon in the Philippines ranked among those most at risk.

Missing piece

Extensive research has been conducted in the waters east of Taiwan and data have been collected from north–south transects along the strait. But little is known about the structure and activity of Earth's crust beneath the strait to the west of the island. "This is a missing piece of the puzzle," says Char-Shine Liu, a marine geophysicist at the National Taiwan University in Taipei, who heads the part of the TAIGER project funded by Taiwan. "Our knowledge of the geology of the region will be compromised without proper understanding of the strait," he says.

The narrow water passage, roughly 160–200 kilometres wide, has been seen as a political barometer of the relations between mainland China and Taiwan. Before 2000, when Taiwan's Democratic Progressive Party (DPP) took power, there had been active collaboration between Taiwanese and mainland geologists, including joint ship surveys in the South China Sea. This, however, gradually came to a halt during the DPP's eight-year term in office.

With last year's election putting the Kuomintang of China party, or KMT, which is friendlier towards mainland China, back in power, geologists are hoping that cross-strait collaboration will soon resume. Even though the Marcus G. Langseth will not be entering the exclusive economic zone, researchers at the China Geological Survey and China Earthquake Administration will record seismic signals sent from the vessel and conduct joint studies in the strait region, says Wu.

"Major earthquakes in Taiwan are likely to affect mainland China," says Liu. "A better understanding of the geology of the region will benefit people from both sides of the strait."