Page last updated at 09:59 GMT, Saturday, 30 May 2009 10:59 UK

Q&A Nankai Trough expedition

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.

You sent us your questions. Here, they are answered by those working and staying on the vessel.

Q: Andrew Grantham, Eureka, California, US

What is the greatest magnitude earthquake that we could expect to see from the Nankai Trough? Would a tsunami generated by a "catastrophic" movement of the trough reach North America? How does the Nankai Trough differ from the Cascadia subduction zone along the west coast of North America?

A: Nobu Eguchi, expedition project manager, Jamstec

Chikyu (BBC)
The ship is drilling into an active seismogenic zone

Earthquakes generated here have typically exceeded magnitude eight - among the biggest on the planet. The 1944 Tonankai quake produced a tsunami here that made the coast of Alaska, so yes, they can go across the entire Pacific, in both directions.

A: Harold Tobin, co-chief project scientist

The Nankai Trough and Cascadia are very similar subduction zones in that they have large accretionary prisms and produce large earthquakes and tsunami.

Q: Yasir Javed, New Zealand

If we can get data on the patterns of small tremors before big devastating earthquake from the past, why can't we use such patterns to predict the future devastating earthquake by such tremor patterns currently?

Q: Gio Ramos, Manila, Philippines

Could we ever predict when earthquakes will happen..?

A: Harold Tobin

Despite a century of seismological observation we haven't found reliable common patterns in small tremors than happen before a major earthquake. So it's not proving as simple as that. That's not to say that we won't find some indications of an earthquake's imminence in future - we simply don't know.

Q: Steve Ward, Chelmsford, UK

I am fascinated by the changing face of the Earth, and trying to understand the mechanics of tectonic plates. Do scientists understand the overall picture of how the plates move about the planet and interact with each other, generating pressure points and future problems? Are volcanoes linked to earthquakes in respect of volcanoes acting like pressure relief valves?

A: Nobu Eguchi

The overall nature of plate tectonics is understood pretty well, although there are things left to discover. There are links between volcanoes and some types of earthquakes, but not really this type of subduction zone quake which is the biggest on the planet.

The hydra-rackers bring lengths of drillstring to the drill floor

Q: Hamza Ya'u Sade, Bauchi, Nigeria

Who funds the NanTroSEIZE Project (Jamstec or international)? And how was the Chikyu team selected? Is Steve Krukowski a manager or civil engineer?

A: Tadashi Yoshizawa, IODP project outreach co-ordinator, Jamstec

The operational costs of Chikyu are funded by Jamstec for Integrated Ocean Drilling Program (IODP) projects such as NanTroSEIZE. That's the major part of the cost. A portion of IODP's international budget goes for scientific services. Scientists aare supported by national funding agencies.

A: Steve Krukowski, offshore installation manager (OIM)

I'm a manager now, but I worked up through various jobs in the offshore industry, starting from roustabout. For the drilling team we're really looking for experience in deep-sea drilling. And you've got to have people you can trust.

Q: Greg Pouch, Normal IL, US

Are you entirely certain that "hydro-racker" is the term you wanted? I've worked as a petroleum geologist, and have never heard the term, and Google doesn't seem to get many hits.

A: Richard Black, BBC

Partly my bad, Greg, for mis-spelling the name - it's actually hydra-racker, the "hydra" being short for "hydraulic". It's the machine inside the derrick that brings lengths of drillstring on to the drill floor ready for use, or stores them away after use.

Q: Doc Dougherty, Playa del Rey, CA, USA

How cohesive does sediment have to be to collect a core sample?

A: Harold Tobin

We can collect core samples even from the very first few metres where the sediment is very soft.

Q: Liam, San Francisco, US

Can you take pictures of the area of the ship where the drill goes through the ship? I am very interested in knowing more about a ship that has a "hole" in the middle of it.

A: Richard Black

Liam, just for you, I went down to photograph where the drill passes through the ship. There are two places really: the small hole on the drill floor, which can be expanded by taking out annular bits of steel; and below it the "moon-pool" in the hull, which is vast by comparison.

Where the drill passes through the Chikyu ship (BBC)
The vast moon pool allows the drill to pass through the ship

Q: David Raynor, Slough, UK

Do the scientists think that drilling into an earthquake zone could ever be used to mitigate earthquakes? In other words, not just help to predict where, when and how big they might be, but actually release the stress, or move it to a less critical place?

A: Nobu Eguchi

Some scientists are actually proposing this. Getting approval for such a project might be an issue. But given that our understanding of the patterns of stress in the fault is so primitive, we're a long way from being able to pinpoint an effort like that.

Q: Lorna Banks, Bay Of Plenty, New Zealand

Is the gas content in the deep rocks higher than expected? Any novel compounds discovered?

A: Toshikatsu Kuramoto, laboratory chief

The gases coming out of the cores are generally methane and ethane, and sometimes hydrogen sulphide. We check the mixture of methane and ethane very carefully. Generally there are few surprises.

Q: Fred Mrozek, Freeport, Illinois, US

Plate tectonics seems to require subduction zones and processes as a matter of faith in order maintain a Geoid of constant surface area and volume. But what if this assumption of constancy is wrong? Are the researchers on this vessel free to interpret physical evidence outside of the dogma of plate tectonics?

A: Harold Tobin

Many different lines of evidence show that subduction is a fact. Most prominent among these is that we can now actually measure the motion of the plates with GPS technology, and the data are completely consistent with plate tectonic theory.

Q: Sylva Keshishian, US

What precautions have you taken to ensure that your drilling will not disturb the tectonic plate of the Nankai Trough and trigger a tremor?

Infographic (BBC)

Q: Paul, Coventry, UK

Could the drilling potentially upset the pressures on the bedrock and cause an earthquake? What can you learn from cores in the Nankai Trough that you couldn't from the same from land-based earthquake zones?

Q: Pam Harman, Chicago, USA

Do you have any concerns that drilling underwater at or near a fault will introduce water as a lubricant which will have an effect on tectonic plate movement? Or that water introduced into heated rock will form steam which will act with pressure like a piston? If you introduce instruments into a bore hole and there is an earthquake, won't the instruments be crushed thus defeating the purpose of putting them there?

A: Nobu Eguchi

If you look at the scale of a tectonic plate and the size of one of our boreholes, there's really no chance that what we're doing could trigger any kind of tremor. Water doesn't really go into the rock especially after we put steel casing down the walls of the holes.

As to an earthquake crushing instruments - certainly that would happen, but so long as the instruments sent back data up to the point of crushing, that would be ok with us - in fact those might be the most important bits of data we received! And if we want to get into subduction zones, where the biggest earthquakes are caused, we have to do it at sea because that's where the subduction zones are.

Q: Laura Parish, Wellington, New Zealand

How has this experiment been influenced my other international drilling projects like the one on the San Andreas Fault, and ANDRILL for instance? Will the scientists be looking at recurrence rates of earthquakes in the sediments or specific strain fabric within the rock sample themselves? Would the cores be able to date tsunamis that didn't radiate out from the trench?

Infographic (BBC)

A: Harold Tobin

The NanTroSEIZE project has been developed hand in hand with the San Andreas Fault drilling project, and results coming from each will inform the other. ANDRILL is also an exciting project but focuses on climate change rather than earthquakes. We will be looking at strain fabrics within the rock samples as clues to conditions during past earthquakes. The temporal resolution needed to date individual tsunami isn't really feasible with this kind of core sampling.

Q: Harold Brown, US

Does the European Champion's League Final have a large effect on earthquakes?

A: Richard Black

Manchester United's defeat certainly caused seismic shocks among some of the crew, balanced by eruptions of joy in Catalonia.

Q: Magne Hungnes, Alesund Norway

What if they by accident hit a "bulb" of molten lava, in their search? How do they contain the pressure without experience the drill to "Melt"?

A: Steve Krukowski

It's extremely unlikely that we'd hit a lava bulb because the scientists go through seismic data very carefully long before we begin drilling. If we did hit one, it would certainly disintegrate the drill bit; but the lava would soon cool and solidify on contact with sea water.

Q: Johnas, Canada via Chiba, Japan

What is the one ("possible dream") conclusion that you would like to prove or disprove by your research? If you were able to reach such a conclusion, what would that mean for future research and development on earthquake matters?

A: Harold Tobin

We'd like to discover whether processes that lead to a major earthquake provide any clues that it's coming - whether there are any precursory signals before a major quake occurs. If we did discover some signal like that, the next step would be to see if it applies in other places round the world beside this one, and use it to develop some sort of early warning system.

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