Scientists Obtain Rocks Moving into Seismogenic Zone
Filed under: Discovery,Scientific Ocean Drilling
(Click to enlarge image) Scientists document and sample cores. (Credit: JAMSTEC/IODP)
IODP Expedition 322 of the Nankai Trough Seismogenic Zone Experiment Stage 2 complete
Dr. Michael Underwood, professor at University of Missouri, USA, and co-Chief Scientists of the expedition said, “We identified an interface of Miocene sediment and basement rock around 540 meters beneath the seafloor and successfully sampled basaltic pillow lava rocks that make up the basement.” He added “These sedimentary and volcanic rocks in the lower part of Shikoku Basin are key intervals for generating large earthquake slip after they are transported to the seismogenic zone. Studying their petrological, geotechnical, frictional and hydrogeological properties prior to subduction is expected to contribute significantly to the understanding of rupture dynamics in the seismogenic zone.”
The science party included 26 onboard research specialists from international member countries. “Scientists observed, measured and analyzed geological samples by day and night working shifts in the onboard laboratories,” said Dr. Saneatsu Saito from JAMSTEC who led research activities as another co-Chief Scientist. He explained the importance of the variety of data obtained, “The sand-rich volcanic sediments were confirmed in large quantity and may have been transported from the easterly located Izu-Bonin Arc about 5 to 11 million years ago. Other sandstones contain abundant minerals derived from land, implying the extensive supply of sand to the Shikoku Basin from the Japanese islands.” Prof. Underwood added, “Analysis of pore water and hydrocarbon gases retrieved from the sedimentary layers above the basement indicates multiple sources and migration paths of fluids. These results have important implications for understanding the properties of fluids within the seismogenic zone.”
(Click to enlarge image) Researchers spent 40 days off the coast of Japan drilling key targets in this earthquake-generating area. (Credit: JAMSTEC/IODP)
The IODP Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is an ocean drilling project that drills in the plate boundary fault and the megasplay fault believed to have generated tsunami. It aims to gain insight into the transition from aseismic to seismic slip within the plate boundary fault zone, as well as the processes of earthquake or tsunami occurrences, by collecting geological samples and measuring geophysical conditions. The research project consists of four stages in all, planned to conduct drilling operations at several sites located along a line orthogonally crossing the Nankai Trough region from Shikoku Basin (seaward) to Kumano Basin (landward). The first stage was carried out between September 21st, 2007 and February 5th, 2008. To learn more about NanTroSEIZE, visit www.iodp.org/NanTroSEIZE/
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IODP is an international marine research drilling program dedicated to advancing scientific understanding of Earth by monitoring, sampling, and instrumenting subseafloor environments. Through multiple platforms, preeminent scientists explore IODP principal themes: the deep biosphere, environmental change, and solid Earth cycles. IODP has operated since October 2003, funded jointly by the Japan Ministry of Education, Culture, Sports, Science and Technology and the U.S. National Science Foundation. Additional support is provided by the 17-member European Consortium of Ocean Research Drilling, the People’s Republic of China, the Republic of Korea, Australia, India, and New Zealand. www.iodp.org.
