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Challenges to Unravel the Mystery of Earthquakes

Part 1

Japan is one of the countries in the world where earthquakes happen frequently. Many precious lives were lost in the Great East Japan Earthquake on March 11, 2011. After the earthquake, Japan is trying even harder to find ways to make earthquake damage be as little as possible and is conducting more research to find out what it is that causes earthquakes to occur. Japan aims to detect a tremor or a tsunami before it arrives as soon as possible so that it can protect many lives and houses.

Shinkai 6500

Shinkai 6500, a manned research submersible, can make the deepest dive in the world. Three people can work inside the ship. The vessel is used not only for earthquake research but also for research on deep-sea life. ©JAMSTEC

Japanese Deep-sea Drilling Vessel Chikyu Explores Seabed


The illustration shows four tectonic plates. These plates move in the direction of arrows and cause earthquakes.
1. A drilling site in the Japan Trench which is believed to be a seismic source of the Great East Japan Earthquake.
2. A drilling site in the Nankai Trough where boring will start this fall.

Shinkai 6500 found a crack

Shinkai 6500 found a crack in the Japan Trench off the Pacific coast of the Tohoku Region, which may have been caused by the Great East Japan Earthquake. Photo: August 2011 at a depth of 5.3 km. ©JAMSTEC

Why do many earthquakes happen in Japan? Experts think that it is because some of the solid rock masses - known as tectonic plates - that cover the earth's surface crash against each other in and around Japan. A dozen or so of the Earth's plates, large and small, move over a soft layer beneath them - called the mantle - and cause friction against each other where they meet, thus bringing about an earthquake.

At the bottom of the sea about 200 km off the coast of Japan's Tohoku region in the northeast, there is a boundary of the plates called the Japan Trench, which is like a huge underwater valley. The Japan Trench is 8 km beneath the sea, at its greatest depth, and about 800 km long from north to south. The Great East Japan Earthquake occurred near this region. Shinkai 6500 is a Japanese manned research submersible and it has the world's deepest diving capability. Five months after the earthquake, Shinkai 6500 dived 5.3 km beneath the sea and found a huge crack at the bottom of the sea. The crack is believed to have been caused by the huge earthquake.


Chikyu, a deep-sea drilling vessel, explores an area where big earthquakes can occur. ©JAMSTEC

Chikyu (meaning “the earth” in Japanese), a Japanese deep-sea drilling vessel, is now boring into the seabed near the Japan Trench to try to learn how earthquakes happen. The ship has already sent a drill 7 km beneath the sea’s surface and bored a hole through the bedrock about 1 km deep. This research aims to measure the underground temperature of the seabed where the earthquake happened, calculate the heat caused by friction when the earthquake occurred and finally analyze what sort of earthquake activity it was.

Chikyu crew members on top of a tower from which a drill is suspended

Chikyu crew members on top of a tower from which a drill is suspended. A helicopter deck is seen below. The tower stands about 100 meters above sea level. ©JAMSTEC

Chikyu is a scientific drilling vessel capable of boring - for the first time in the history - up to the mantle layer as well as at plate boundaries where gigantic earthquakes are caused. Diverting technology originally developed for oil drilling to scientific purposes, the vessel can drill up to 7.5 km below the seabed that is 2.5 km underwater, keeping the drilled hole as it is without damage, which is the most advanced technology in the world.

Chikyu will begin drilling in the coming fall off the southeastern Pacific coast of Japan aiming to reach the plate boundary 7 km beneath the seabed. This place is called the Nankai Trough and is believed to be a nest for major earthquakes that happen at an interval of 100 to 150 years. No one has ever seen so deep beneath the earth's crust. What sorts of earthquakes happened in the past? Researchers from 25 countries will join the research to try to unravel the mystery of how earthquakes happen.