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Blobrana


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RE: CDEX
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For the first time, researchers have been able to drill deep (more than 1,600 meters) into an ocean fault zone.
The expedition team, onboard the Japanese research ship Chikyu, is searching for answers in the depths of the Nankai Trough about why the previously active fault has locked up in the past several decades - and
what type of activity might be likely in the near future.

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Blobrana


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Every hundred years or so, an unwelcome visitor arrives on the south-eastern coast of Honshu, Japan's largest island.
Heralded by a tremendous shaking of the ground, the sea sucks back before rushing onto the shore with devastating force, bringing destructive surges nine or 10 metres high.
The activity continues for maybe a year maybe two; then the Earth calms, apparently at ease, and the inhabitants of the Kii Peninsula and the surrounding lands - shorn of some of their fellows, now - can return to their fields and rebuild their houses.
Welcome to the Pacific "Ring of Fire"; welcome to the Nankai Trough.

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Blobrana


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Nankai Trough
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Quake zone diary: Out to sea
A pioneering project off the coast of Japan aims to go further into an earthquake zone than ever before.
BBC environment correspondent Richard Black is the first journalist to visit the research ship Chikyu while it is drilling for rock cores from the quake-generating Nankai Trough to explore what causes tremors.

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Blobrana


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Title: Three-Dimensional Splay Fault Geometry and Implications for Tsunami Generation
Authors: G. F. Moore, N. L. Bangs, A. Taira, S. Kuramoto, E. Pangborn, H. J. Tobin

Megasplay faults, very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism, are thought to play a role in tsunami genesis. We imaged a megasplay thrust system along the Nankai Trough in three dimensions, which allowed us to map the splay fault geometry and its lateral continuity. The megasplay is continuous from the main plate interface fault upwards to the sea floor, where it cuts older thrust slices of the frontal accretionary prism. The thrust geometry and evidence of large-scale slumping of surficial sediments show that the fault is active and that the activity has evolved toward the landward direction with time, contrary to the usual seaward progression of accretionary thrusts. The megasplay fault has progressively steepened, substantially increasing the potential for vertical uplift of the sea floor with slip. We conclude that slip on the megasplay fault most likely contributed to generating devastating historic tsunamis, such as the 1944 moment magnitude 8.1 Tonankai event, and it is this geometry that makes this margin and others like it particularly prone to tsunami genesis.

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Blobrana


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Nankai Trough Seismogenic Zone Experiment
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Harold Tobin is interested in deep scientific questions, whose answers lie thousands of meters underwater.
The UW-Madison geologist studies deep oceanic earthquake faults, which extend miles into the Earths crust below the seafloor, to learn what causes earthquakes and tsunamis.
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Blobrana


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One of the most ambitious earth science expeditions yet mounted to gain a better understanding of the earthquake process, has begun off the coast of Japan, involving geologists from the universities of Southampton and Leicester. Dr Lisa McNeill, of the University of Southamptons School of Ocean and Earth Science, based at the National Oceanography Centre, Southampton, and Joanne Tudge, of the Department of Geology, University of Leicester, are taking part in the multi-disciplinary study of a subduction zone off the Japanese coast, aboard the deep-sea drilling vessel Chikyu (which means Planet Earth in Japanese). This is the maiden scientific voyage of this vessel, which has unique capabilities enabling it to access new regions of the Earths crust.

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Blobrana


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Nankai Trough Seismogenic Zone Experiment
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Scientists have begun exploring the origins of earthquakes at their source with the launch of the Nankai Trough Seismogenic Zone Experiment.
On Sept. 21, the Japanese drilling vessel Chikyu departed from Shingu Port with scientists aboard, ready to log, drill, sample and install monitoring instrumentation in one of the most active earthquake zones on Earth. Situated off Japan's southwest coast, the Nankai Trough has generated large-scale earthquakes and tsunamis for millions of years.

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136.90422E_33.03527N
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Latitude: 32.73536, Longitude: 136.91712

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Blobrana


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CDEX
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Japanese scientists are preparing to dig deep inside the Earth.
The researchers hope to collect the first samples of the Earth's mantle for clues on the primitive organisms that were the forerunners of life -- and study tectonic plates.

"Deep underground -- under high pressure, high temperature, with little air -- is the environment similar to the time when the Earth was created? By collecting geological samples from there, we might find biological beings that might have existed when the Earth was born. Samples of the Earth's mantle and crust will also tell us how the Earth's climate has changed in the past. Analysis of these data should give us clues as to how the Earth's environment will change in the future " - Jun Fukutomi, an official with the Centre for Deep Earth Exploration (CDEX).

The government-backed CDEX will start training of the crew and scientists once the 57,500-ton, deep-sea drilling vessel Chikyu is delivered at the end of July.

Chikyu, which means the Earth in Japanese, will embark on experimental voyages later this year.
The 60-billion-yen ship will begin full-scale drilling around the end of September 2007 at waters off the Pacific coast of Japan with an initial project to dig some 3,500 metres into a seabed that is some 2,500 metres under the ocean surface.

The initial project will study the tectonic plate as it is an area where seismologists expect giant quakes within the next several decades. Japan accounts for a quarter of the world's major tremors.
Eventually, researchers hope to send Chikyu's drill pipes down to the sea bottom 4,000 metres underwater and dig 7,000 metres from there.

"Up until now, scientists have dug down for about 2,000 metres. That's like only scratching the surface. This time, we hope to go deeper. Layers of sediment should tell us climate changes that the Earth has experienced and the component of the atmosphere at the time" - Jun Fukutomi.

The deep sea drilling project is a part of the multi-national Integrated Ocean Drilling Program, which is led by Japan and the United States, with participation from China and 12 EU nations.

Oceanic drilling is preferred over land drilling because the crust at the sea bed is thinner and allows for deeper digs into the crust and mantle.
Chikyu uses technology that exists for oil drilling, but is specially equipped to prevent damage from sudden bursts if it accidentally strikes oil or gas reserves.
The drilling ship uses the satellite-based Global Positioning System to stay in one position.

Chikyu is also rigged with a system that keeps itself and its drill pipes stable by adjusting to the rolling motions from the drilling and waves.
The ship also carries a laboratory that can shut down the effects of the Earth's magnetic fields to allow better observations.

The completion of the drilling vessel is a big step forward for scientists.
The researchers will eagerly look at the microbes found under the ocean floor because they may be key in studying how life began.

"We may take a step to better understanding the origin of life. They (the organisms) may be somehow related to the evolution of the Earth. This is one of the most important life science projects.
We hope this project will be the start of a new era for life science"- Jun Fukutomi.

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