JAMSTEC: Japan deep sea drilling boat Chikyu casts off to find Earthquakes

Japan's deep-sea drilling vessel Chikyu is anchored at Shimizu port, Shizuoka prefecture on September 11, 2013. 

A Japan-led team of seismologists set off Friday on a mission to drill deep beneath the seabed in a search for the origin of earthquakes.

A Japan-led team of seismologists set off Friday on a mission to drill deep beneath the seabed in a search for the origin of earthquakes.

The scientists weighed anchor on Japan's deep-sea drilling vessel Chikyu, heading for a spot in the ocean off the Kii peninsula, southwestern Japan, and a fracture in the Earth's crust known as the Nankai Trough.

Experts have warned the trough, which marks the place where the Philippine Sea plate slides under the Eurasian plate, is the likely source of a monster earthquake sometime in the near future.

Tamano Omata

Japan's government last year unveiled a worst-case scenario, warning a big quake in the area could kill over 320,000 people, dwarfing the March 11, 2011, quake-tsunami disaster.

In its four-month mission, the latest stage of a multi-year project that began in 2007, the team plans to drill 3,600 metres (2.2 miles) down and take samples from the crust.

They will also be readying for another trip next year in which they hope to get 5,200 metres down, to the spot where the action actually happens.

"It would be unprecedented to drill directly into a seismogenic zone, the area believed to release great energy and cause crusts to slide along fault lines and trigger tsunami," said Tamano Omata, a researcher for the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).

Scientists want to plant sensors—such as seismometers, deformation-measuring devices and thermometers—in the zone, that will form part of a system called Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET), which is linked directly to onshore monitors.

"We expect to become able to monitor how the crusts move immediately before a quake hits," Omata said.

Shinichi Kuramoto

Shinichi Kuramoto, deputy director of JAMSTEC's Center for Deep Earth Exploration, said recent research has shown mild earthquakes, in which the two crusts slip gently past each other, have occurred frequently over stretches of the Nankai Trough in the past five years.

He said it was possible these were precursors to a mega-quake.

"Directly drilling into and observing the place that may release a big quake would be a big step towards understanding the seismological mechanism," he said.

The 56,752-ton Chikyu—"Earth" in Japanese—has been anchored in central Shimizu port, and was open to foreign press this week ahead of the mission.

The vessel, built in 2005 at a cost of $500 million, is equipped with a 121-metre (400-foot) drill tower that can descend 7,000 metres below the seabed, nearly three times as deep as its predecessors.

It depends on satellite location systems with pinpoint accuracy that allow its captain to know exactly where the ship is in relation to the Earth's crust.

Seismically-active Japan experiences 20 percent of the world's major earthquakes every year.

Building standards are high and its people are well-practised at taking cover when quakes strike, meaning damage and death tolls are often much lower than in other parts of the world.

But its proximity to major tectonic faults means the risk is ever-present.

DONET is a submarine cabled real-time seafloor observation infrastructure which was designed to realize precise earthquakes and tsunamis monitoring on seafloor in the long period of time. 

It consists of an approximately 300km length of backbone cable system, 5 science nodes, and 20 observatories. 

Its installation on 20 stations at Kumanonada started in 2006 and has been completed in July 2011.