D/V Chikyu has contributed to the Integrated Ocean Drilling Program, and as of 2013, the International Ocean Discovery Program. A platform for investigating some of the most interesting and perplexing scientific questions, Chikyu has made some major scientific contributions to our understanding of Deep Life, Earthquake Mechanisms, and drilling in harsh and unforgiving environments. As a ‘tool’ for the international ocean drilling community, Chikyu provides facilities equal to shore-based institutes and equipment, some new to scientific drilling, in support of the geologic and biologic exploration of the sub-surface Earth.

Investigating Mega-Earthquakes and Tsunamis

Contributing to research on great earthquakes and tidal waves One of the challenges to investigate is the effect sudden changes in our environment can have on society and even civilization – even more so for such swift and sudden events as Mega-Earthquakes and Tsunami. This is especially important for regions, like subduction zones, where these events periodically re-occur throughout history.Understanding the underlying mechanisms that trigger these events can help with future natural hazard preparation and warning systems. However, these investigations are extremely complex, expensive, and take a long time to complete.

One example is the Nankai Trough, a region off the Kii Peninsula off Japan, where large-scale earthquakes and tsunamis have been recorded for the past 1300 years; the last earthquakes here were the 1944 Tonankai (Mw 8.2) and 1946 Nankai (Mw 8.3), both of which also created massive tsunamis. The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) was begun in 2007, designed for Chikyu’s unique scientific capabilities, to try and better understand the whys and hows of large-scale earthquakes and tsunamis. This project is the biggest single scientific investigation of a subduction zone and accretionary prism complex in history, and the final targets are now beginning to be in reach – direct sampling and monitoring of the plate interface where earthquakes are generated.Having reached a new scientific depth record of 3058.5 meters below seafloor, the next target lies at approximately 5200 meters below seafloor. Of course, earthquakes and tsunamis occur all over the world, and Chikyu is investigating these as well.

The Japan Trench Fast Drilling Project (JFAST) was successful in collecting geophysical data and core samples from the 2011 Tohoku earthquake in a very challenging environment. Record water depths of nearly 7000 meters, and drilling to over 850 meters below seafloor, recovered extremely scientifically important data related to the physical characteristics of the fault that slipped and the frictional energy released by the earthquake.

Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE)
Japan Trench Fast Drilling Project (JFAST)

Sub Seafloor Biosphere

The Origin of Life

Life on Earth began in a world totally unlike the one we live in today. An oxygen-free atmosphere, and seas provided an environment where the very first single-celled organisms could develop, while the land was still and barren. Deep-sea hydrothermal vents and superhot springs on land are thought to represent remnants of the early crucibles of life.

Accordingly, these are objects of great scientific interest, and scientists are increasingly interested in the communities of life found in these zones, as well as the presence of life in rocks deep below the seafloor. Recent expeditions on D/V Chikyu have found microorganisms living in coal seam beds deeply buried below the ocean floor.

Research into this extremely slow living and metabolizing kind of life is continuing, and may lead to important applications in science and society. An important part of studying such life is maintaining the temperatures and pressures these deep living organisms experience. New tools that allow us to collect samples at in situ pressures will go far in advancing this research. This research is also showing us that these microbial communities are phylogenetically distinct from species from other biospheres (e.g. on land or at sea), with genes new to science.

Our Challenge

CHIKYU +10 Workshop

CHIKYU +10 Workshop In September 2013, the Integrated Ocean Drilling Program ended, and the International Ocean Discovery Program began. CDEX/JAMSTEC held the CHIKYU+10 International Workshop in Tokyo in April 2013 to discuss the future direction of scientific drilling with Chikyu together with the international science community. Great interest was shown in Chikyu-led scientific drilling projects, with over 400 people in attendance at the 3-day workshop, producing a list of riser-drilling proposals and important scientific themes for future research.

These proposals and themes were classed into 5 groups:
(1) Dynamic Fault Behavior
(2) Ocean Crust and Earth's Mantle
(3) Deep Life and Hydrothermal Systems
(4) Continental Formation
(5) Sediment Secrets

Chikyu IODP Board (CIB)
Chikyu+10 International Workshop

Mission to the Mantle

Mantle drilling was a big theme of discussion at the CHIKYU+10 meeting, and is one of the motivations for building D/V Chikyu. The discovery of plate tectonics and the impact it has on the Earth has radically impacted many sciences and discussion of the past and the future. As part of the ‘machine’ of plate tectonics, a better understanding of the mantle could have a profound impact on science.

Since the first, tentative steps taken by Project Mohole in 1961, drilling down and accessing the mantle has remained a dream. However, technology and science have made great progress since the 1960’s, and more than ever have put this goal within reach. Learning more about the mechanisms surrounding the creation of the tectonic plates at the ocean ridges, the forces that destroy the plates as they subduct beneath the continents, and how these actions differ from plate to plate, and from ocean to ocean will go far to advance our understanding of the Earth.

The technical challenges to achieve these goals are immense; choosing a proper site will most likely require drilling in water >4000 meters deep, another 7 km (at least) will be needed to reach the crust/mantle interface, and temperatures at that depth will likely exceed 250ºC. This will also require a complex logistical support system to remain on site drilling at sea for the time needed to reach the target. However, these technological developments will undoubtedly benefit Japan, Earth, and Biological Science.