A crew in Japan has set the record for the deepest sea drilling and the deepest sub-sea level sample after recovering a 37-meter-long (121 feet) sediment core from a site on the seabed just over 8 kilometers (5 miles) below sea level.
The research vessel KAIMEI set the record on the morning of May 14, 2021, at a site in the Japan Trench in the Western Pacific, according to an announcement on the project’s blog. The previous record was set in 1978 when the drilling vessel Glomar Challenger recovered a sediment core from the seabed at 7-kilometers (4.3 miles) water depth in the Mariana Trench.
For the new feat, drilling equipment was sent into the water a 9:20 am local time and it took 2 hours and 40 minutes to reach the seafloor. It wasn’t until 3:00 pm local time it was successfully recovered and brought back to the ship deck.
The project, known as Expedition 386, is a collaboration between the European Consortium for Ocean Research Drilling (ECORD) and the Japan Agency of Marine-Earth Science and Technology (JAMSTEC). As of May 10, the researchers had collected a total of 342 meters of core samples from a total of eight sites along the entire Japan Trench.
They aim to use the deep-sea sediment cores to understand the history of earthquakes in Japan and the Western Pacific. The Japan Trench, the area being studied, is an oceanic trench part of the Pacific Ring of Fire, a horseshoe-shaped belt around the rim of the Pacific Ocean that's rife with volcanic activity and earthquakes. While ancient earthquakes were not measured scientifically, it’s clear this part of the world has been wracked by earthquakes for millions of years, but scientists aren't sure how often they occurred nor how powerful they were.
Earthquakes have left their mark on Japan in many ways. In Japanese mythology, earthquakes were caused by a giant catfish that lives beneath the ground named Namazu or Ōnamazu. The team isn't expecting to find any giant catfish, but the cores will be closely studied to understand the earthquakes that shook the world some 50,000 to 100,000 years ago, long before the invention of instruments and historical records.
"These ultra-deep water basins are among the deepest and least-explored environments on Earth, but they comprise the terminal sink of earthquake-triggered sediment remobilization, thus providing excellent and continuous archives of past earthquake occurrences," Professor Michael Strasser, co-chief scientist and geologist at the University of Innsbruck in Austria, said in a statement.
"It's as if the sedimentary archive were an ultra-deep-water seismograph that has been recording major earthquake events over time periods extending several tens of thousands of years into the past. The most recent giant 2011 Tohoku-oki Earthquake and older megathrust earthquakes documented in Japanese written history allow us to calibrate this 'natural seismograph' to unravel this sedimentary deep-time archive of past earthquakes."