Drilling through the Japan Earthquake faultJuly 13, 2012
Drilling began out here on the JFAST2 expedition after successfully reentering the wellhead on the seafloor 6926 meters below the ship on the edge of the Japan Trench. The goal: to drill ~850 m below the seafloor across the plate boundary and through the fault that slipped more than 50 m at this location during the March 2011 Tohoku earthquake causing the enormous tsunami. We will then try installing a temperature observatory down into the hole to measure the remaining frictional heat across the fault.
Instead of using the standard top-drive drilling system on the ship to rotate the entire drill stem and create the torque on the drill bit 7 - 8 km below, as in the previous drilling at the site, this time we used a mud-motor located just above the bit to create the torque at the bit. The mud-motor causes rotation of the bit from pumping drilling mud (in our case the mud is actually sea-water) through the motor and out of the jets at the bit (see video above). Drilling with the mud motor has been incredibly effective and we quickly reached our target depth. We could see from the drilling parameters measured on board that when we started to drill through a hard chert we had previously encountered, confirming that we had successfully crossed the plate boundary fault and well into the down-going Pacific Plate.
The great water depth here is much deeper than conventional wells, and the total depth drilled for the observatory joins our other holes as part of JFAST project in being the deepest below the sea ever drilled for scientific ocean drilling. Our TD (total depth), as shown by the driller’s console in the picture below: 7780.81 meters below the ship’s rig floor!
Lastly, here I am in the picture below, happy for the great depth we were able to obtain. The depth of this deep borehole will provide space for us to install the observatory that will include temperature sensors that straddle the fault zone.
Next, the hole will be cleaned out and the all the drill pipe returned to the surface. We can then start assembling the observatory and lowering it down to the seafloor for the final, most difficult task of carefully installing it all the way down into the hole.
Wellhead reentry deep within the Japan Trench ? like threading a needle 7 km awayJuly 12, 2012
The goal we are working towards on the JFAST2 expedition is to install an observatory of temperature sensors across the fault zone that slipped more than 50 m during the March 2011 Tohoku Earthquake. The temperature sensors will allow us to measure the frictional heat and determine the strength of the fault. To accomplish a critical step of the installation, we must first find the wellhead we installed last May on the seafloor 7 km below the ship, reenter it with the drill bit, and then drill down ~850 m through the plate boundary fault.
The only way we are able to reenter the wellhead on the seafloor, which will allow us to install the observatory into hole after drilling across the fault, is by finding it with an underwater television camera system (UWTV), slowly moving the 8.5 inch drill bit above the 20 inch opening, and then lowering to pipe down into it. An added challenge is that only way to move the drill bit towards and above and well head opening is slowly moving the ship a few meters at a time and then waiting for the 7 km long string of drill pipe to swing beneath us.
Once we were positioned above the GPS location of the wellhead, we slowly lowered pipe down the nearly 7 km below our drilling ship, Chikyu, one 40 m stand at a time. We then attached the UWTV around the drill pipe and lowered it down (see photograph) to just above the drill bit. Last May, the stress of raising and lowering the fiberoptic cable connecting the UWTV to the ship in such deep water created some damage to the cable, and prevented us from seeing anything or installing the observatory. Now, at the start of this expedition, the cable was repaired and we attempted using it at depth again for the first time.
It was a long, tense night in the Doghouse (the small enclosure on the rig floor shown in the photograph) trying to find and position ourselves above the wellhead and wondering whether the UWTV would work okay. Luckily things went well, we found the wellhead with the help of the cameras and a small sonar device on the UWTV, and successfully reentered the hole.
The next critical step is to recover the UWTV, and then drill about 850 m through the fault zone and into the subducting plate below...
Return to the Japan Trench ? JFAST 2July 9, 2012
Greetings from the scientific deep sea drilling vessel Chikyu and the second part of the Japan Trench Fast Drilling Project: JFAST2 - IODP Expedition 343T. The focus of the JFAST project has been to quickly drill into and study the fault that slipped more than 50 m at shallow depths during the March 2011 M9.0 Tohoku Earthquake and caused the devastating tsunami.
In April and May, we (an international team of ~30 shipboard scientists along with a number of engineers, ship/drilling crew, and onshore support) successfully drilled across the plate boundary fault at ~820 m (0.5 miles) below the seafloor in water depth nearly 7 km (4.3 miles) deep. This ended up being the deepest below sea level any scientific ocean drilling project has ever gone. We actually did it twice! - the first time we used logging tools to map the geology as we drilled allowing us to pinpoint the fault, we then drilled another hole and collected spectacular core samples through the fault zone. The analysis of the rocks and data are already providing important insight into the mechanics of large earthquakes and tsunamis and will undoubtedly continue to be fruitful for many years to come.
Now I have returned to Chikyu to help undertake the other main goal of the JFAST project, to install a subsurface observatory that will measure the frictional heat signal remaining from the Tohoku earthquake. By measuring the extra heat across the fault at depth we can back out how much frictional resistance the fault had during the earthquake and possibly gain insight into why it slipped more than 50 m at our study location.
Together with the other JFAST analyses this unique and important data will not only help us understand the fault and earthquake here, but may also help us understand the potential hazards at other large faults like the Cascadia subduction zone fault off the Pacific Northwest of the United States and British Columbia, Canada.
During the first JFAST expedition, we had many technical problems associated with trying to drill in such deep water for the first time and many delays from weather that prevented us from installing an observatory in the time window we had. We now have been fortunate enough to be given the opportunity to return for one last try.
After flying on board Chikyu by helicopter and transiting North for a couple days, we are now on site and starting to lower pipe down to the seafloor. We plan to then drill across the plate boundary fault once again and then install our observatory of subsurface temperature sensors in the remaining hole. There are many unique challenges with installing such an observatory and with drilling in such deep water depths, but we are all ready and excited to try our best on this difficult mission so we can continue to learn as much as we can from the devastating Tohoku earthquake.
Stay tuned . . . more to come shortly.
Anniversary of 1st Deep Ocean DrillingApril 2, 2012
Today marked our first full day at sea on this historic ultra-deep ocean drilling and observatory installation expedition. We are all quite excited and prepared to take on the many challenges that will be involved.
Interestingly, today also marked another historic event in the history of scientific ocean drilling and our understanding of the Earth. It was on this day, 51 years ago on April 2nd 1961 that the very first deep ocean drilling expedition collected core samples confirming that the oceanic crust was composed of basalt (a volcanic rock). This was just one of many discoveries at the time that contributed to the development of the theory of plate tectonics.
I was surprised to learn that the shipboard historian on the expedition was none other than the very famous author, John Steinbeck, who later wrote an article about the adventure for LIFE Magazine.
An overhead view of the CUSS 1, the first scientific deep ocean drilling vessel. It was converted from an old Navy barge. While it is small and simple compared to the Chikyu, some the technology developed for it use, including dynamic positioning (using steerable thrusters or propellers to stay in one spot), is still used on the Chikyu today. (US-NSF Photo)
There was even a short documentary made at the time (The First Deep Ocean Drilling Part I, Part II ) about the engineering challenges they faced drilling in water depths of 3500 m that were roughly 30 times deeper than the depths the industry was drilling at the time. They also sought to take core samples that were considerably longer and deeper than commonly collected and to collect subsurface temperature measurements.
The challenges that were overcome with their expedition are in many ways similar to those associated with the JFAST project. We too will be drilling in water depths (7000 m) that are considerably deeper than even deep water commercial drilling. In addition, while two boreholes have previously been drilled at similar water depths, they were only drilled and cored to ~15 m below the seafloor; we plan to go to ~ 1000 m below the seafloor like IODP expeditions in shallower water, collect long sections of core from the fault zone, and also install underground observatories to monitor temperature and pressure.
Patrick (perhaps) contemplating the journey ahead
The JFAST project is going to be difficult, but I, for one, am humbled by the achievements and scientific legacy of this first scientific ocean drilling expedition and those that followed. While we too will be using state-of-the-art technology and even some new technology specifically designed for this expedition, in many ways we will be using many of the same techniques that were used and developed by these early ocean drilling scientists and engineers.