After being tossed about and damaged by the tsunami that devastated northeastern Japan on March 11, Japan's drilling ship the Chikyu has been given an especially fitting assignment: to drill into the fault zone and take temperature measurements near the epicentre of the magnitude-9.0 Tohoku earthquake that caused the tsunami. It will be the first time that researchers have drilled into an underwater fault soon after a quake. The aim of the exercise is to solve a decades-old mystery about the part that friction plays in such an event. This should help scientists to understand why some faults are more likely than others to cause tsunamis — in this case, one that ultimately claimed more than 23,000 lives.

"It would be a great disservice to society if we did not learn as much as possible from the fault zone heated by this huge earthquake," says Kiyoshi Suyehiro, president and chief executive of the management group of the Integrated Ocean Drilling Program (IODP). Following its initial approval of the proposal in September, the IODP has now confirmed that funding is available for the Chikyu to set sail in April and drill at a site south of the quake's epicentre (see map).

The scientific rationale for the expedition, officially called the Japan Trench Fast Drilling Project, is detailed in a 2009 report promoting rapid-response drilling through fault lines as soon as possible after an earthquake in which the ground slips by more than one metre. The Tohoku event set a new record for the greatest amount of slippage ever observed — a whopping 50 meters — making it an ideal target.

"It's a fundamental issue in seismology right now: how do you get rock to slip tens of metres?" says James Mori, a seismologist at the Disaster Prevention Research Institute of Kyoto University in Japan, a co-author of the rapid-response report and joint chief of the upcoming drilling expedition. Researchers think that an important part of the answer is that resistance between the plates of rock, sand and water in a fault line drops significantly during a quake — because of rock melting or increased water pressure, for example — but no one has been able to measure this effect properly. Because friction is dissipated as heat, precise temperature data should fill a crucial knowledge gap.

"We did a lot of planning, not knowing what kind of quake we'd have to do it with," says Emily Brodsky of the University of California, Santa Cruz, who is also involved in the mission.

Researchers have attempted to monitor the underground temperature after an on-land earthquake on three previous occasions — after the 1995 Kobe earthquake in Japan, the 1999 Chi Chi quake in Taiwan and the 2008 Wenchuan quake in Sichuan Province, China. But these projects produced only a few temperature readings between them, and found only tiny temperature increases, or nothing at all — perhaps because the temperature rise was too small to see, or because of imperfect monitoring techniques. "The recurring theme is that the faults tend to be colder than they should be," says Brodsky. A larger slip event provides a better chance of tracking the expected temperature increase of up to 0.5 °C, she says. "We need to do this now, and do it fast, and do it correctly."

The Chikyu will drill down 1 kilometer through the fault, and drop a string of temperature sensors down the hole. By tracking temperatures for one to three years — much longer than has been attempted before — researchers should be able to calculate the total amount of heat that was generated by the quake. That will provide them with the resistance forces felt in the fault during the slip, filling in a blank in models of earthquake dynamics. "This is a key missing ingredient," says Jean-Philippe Avouac, a geologist at the California Institute of Technology in Pasadena, who is not involved in the project.

Completing the drilling won't be easy. At the proposed site, the Tohoku fault lies under 7 kilometers of water and some 700 meters of Earth's crust, so a huge drill string will be needed. Previously, only a tiny 15-meter core has ever been extracted from beneath water of that depth, says Brodsky; most cores are taken from beneath 6 kilometers of water or less.

In addition to temperature measurements, the project will also examine the sediments pulled up in the core. Certain sediment textures, such as ball-bearing-like particles of clay, might be associated with large-slip earthquakes. Identifying such features should help scientists to forecast the slip potential of other faults.

The chance to collect precious information from the Tohoku event represents "an opportunity, maybe even a responsibility", says Mori. Almost all of the damage caused by the quake was done by the tsunami, he points out. "What we really want to understand is what caused that."

This article is reproduced with permission from the magazine Nature. The article was first published on October 31, 2011.

8 Comments

1. 1. David Russell 08:26 PM 10/31/11

   I am glad someone is taking a lead on this issue. I just finished a book that studied the Cascadia fault zone that is closely related to the type of zone that this ship is studying. The book called Cascadia’s Fault. The following is an overview of the book and its relation to the Japanese fault that has a lot of the same symptoms.
   Geologically, the Japanese scenario is a mirror-image of our geological setting here: a sometimes-locked subduction zone, where the Pacific tectonic plate moves in fits and starts beneath the thicker continental plate. Socially, the Japanese scenario is analogous to our own as well — directly above those subducting plates are modern cities sprinkled with mammoth structures of concrete and metal: highrises, industrial facilities, and highway overpasses.
   
   The Cascadia subduction zone is an active fault that is 1,300 kilometres in length, extending from Northern California to northern Vancouver Island. When it finally slips — which could be in 200 years or it could be tonight — the destruction will be analogous to what happened in Japan, devastating a region 200 kilometres wide along the entire length of the fault, including the cities of Vancouver, Victoria, Seattle, Portland and Sacramento.
   
   We have several geological issues to keep an eye on and currently we see some of the dots but I think they may be more connected especially with the Cascadia Zone. Yellowstone is a super volcano waiting to happen and the clock is ticking, the San Andreas Fault is related to the Cascadia zone and recently the East Coast had a wake up jolt.
   
   The Madrid fault seems to be getting a pass right now with blame being pointed to the ground adjusting to the last ice age (8,000) years ago but we seem to think the events of the early 1800's may be its last gasps. Time will tell.
   
   I believe on republican governor (Bobby Jindal)says we are wasting money on studies on volcanoes and other geologic issues. I wish he lived in Seattle's Mt. Rainer which if it blows will make Vesuvius and Pompeii a drop in the water. We keep worrying about CO2 and do little to plan for things that do go boom in the night and some are way overdue.

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2. 2. sethdayal 11:17 AM 11/1/11

   This is well understood.
   
   It was Big Oil - lit won off hoping to shut down that nuclear renaissance in the bud.
   
   So far its working!!!

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3. 3. alan6302 02:00 PM 11/1/11

   Since the pressure wave hit the atmosphere first, it must have been an alien attack.

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4. 4. chimesickle 10:27 PM 11/1/11

   I thought someone would worry that drilling into the fault might trigger another quake? Nobody mentions maybe the oil lubricates the tectonic plates, and when we pump oil out, water in, it creates friction? Maybe oil is not fossilized plant matter, but a byproduct of the plates moving? Just idle speculation

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5. 5. David Russell in reply to Nagnostic 07:30 PM 11/2/11

   You need to be writing letters to Penthouse. I don't think having sex with mother earth is healthy for your body. But do take a cold shower while you can... :) I wonder how greasy your key board is?

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6. 6. pwjohnson 06:55 PM 11/4/11

   I know that this researcher has put a lot of effort into his work but I am really put off by the "Sky is Falling" tone of his contribution. This kind of paranoid presentation of scientific data is obviously designed to stampede Governments into wheel barrows of money to do more study. This is a necessary evil in academia these days but I find it distasteful and self serving

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7. 7. David Russell in reply to pwjohnson 08:21 PM 11/6/11

   I would think since over 60% of civilization lives on coastal zones and we have earth quakes in all parts of the earth that any studies that deal with earth jarring events would merit more money and research not less.
   
   We have experienced 2 9.+ earthquakes in the last 10 years,Oklahoma is having tens of quakes that are building currently and Cascadia is ripe for the same level event as Japan (a 9.0 or bigger). Yellowstone is on a 625,000 year cycle and it has been 625,000 years since the last event. Something went boom in the night about 13,000 years ago and wiped out the mega fauna in North America and flash froze the mega fauna in Siberia. In 1908 something big exploded over Siberia and leveled several thousand square (desolate thank God) miles and it did its damage without an impact.
   
   We are moving into a solar maximum and still do not know what effect the Suns magnetic field has over our magnetic field. But we have technology that can start to look into these mysteries. So your suggestion that this esoteric information or useful probably needs a chance to prove itself. The bottom line is that no matter what we humans can do to the earth, the earth and its association with the solar system, galactic system and intergalactic system is probably a lot worse than the sky is falling. If we have some insight to the possibilities we may have some options. Or we can bury our head in the sand and save a lot of money right now. Or do you have a plan B, because I haven't heard of one yet.

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8. 8. kebil in reply to pwjohnson 09:18 PM 11/6/11

   Um, I am not sure what article you read, or exactly what was between the lines that you read that I did not, but I did not find anything in the article that was paranoid, or that foretold of coming disasters. The message I took from the author's account was that a drilling ship was setting out to do some temperature measurements deep under the ocean, in a geological fault. The aim was to get some data that might be able to give us some information on the role of friction in keeping plates from sliding smoothly over each other, or something to that effect.
   
   I believe that you read some of the posted comments, some of which talked about other geological faults, some of which was nonesense (much of it amusing, some confusing, such as plate slippage creating oil deposits... ...come on, really?). You should not fault the author for inspiring people to daydream (dream is the perfect word to use when people's logic falls to the wayside and flights of fancy take hold, reason exchanged for ridiculousness, not that I find anything wrong with that) and extrapolate far beyond anything he has written.
   
   You may have a case of confirmation bias, wherein you find examples of your preformed prejudice in many various circumstances, possibly going to the extent of taking things out of context, attributing things to aberrant sources, and presenting your presuppositions to others as actual fact rather than what they are.

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