Last year the 27- member team, representing 10 countries, spent weeks working 1 2-hour shifts round the clock to study the Japan Trench.
It's one of the deepest in the ocean, and the site where one day in March 201 1, one of the earth's plates dove under another and slid for 50 meters, triggering a magnitude-9 earthquake and devastating tsunami. These scientists were seeking an answer to what caused the plate to slip so far, the farthest distance ever recorded. To find out, they needed to reach the fault itself, dredge up rock samples, and bury instruments beneath the seafloor.And the best place to do that was underneath 7000 meters of ocean water. Drilling at Depth Drilling through water is complicated, but not as difficult as drilling through rock. To reach the fault zone underneath Japan itself would mean drilling through many miles of solid Earth.
Out at sea, the fault zone is much closer to the surface, about 800 meters (half a mile) below the sea floor. In April of 2012, the team took a boat named Chicks, designed and built by the Japan Agency for Marine-Earth Science and Technology (GAMETES), out about 1 55 miles due east of Sensed and parked it over the trench.The boat carried almost 5 miles of pipe in segments of about 10 meters long, which ere stacked in vertical racks and clanged like wind chimes when the boat rocked in a storm. In the bottom of Chicks is an opening called the Moon Pool, and it was through this opening that engineers, with the help of robots about twice as tall as a human, twisted one piece of pipe into another, lowering the pipe piece by piece down to the ocean floor as the full length of the pipe came together.They drilled three places overall: one to collect geophysical data, one to bring rock cores up to the surface, and one to install what the scientists call the observatory, essentially a rope with 55 sensors to measure the temperature f the fault zone in relation to the surrounding rock, which would reveal how much friction there had been between the two plates during the quake.
Installing the observatory meant not only drilling a hole but then finding it again to insert the temperature sensors-?and coming back to the same spot nine months later to pick them up. A Wet Spaghetti Noodle" The first step is to install a 20-inch wellhead, which keeps the hole open to a depth of 30 meters. But once that's done, the team needs to drag all the piping back up to the surface so it can install a drill bit, about 8 inches around, on the end. Then it lowers the whole assembly back into the water, where the engineers must find the wellhead again to continue drilling down past the fault. The bottom of the pipe carried two underwater television cameras, along with some lights and sonar equipment, which allowed the team on board the boat to search for the hole opening via video.
