International Ocean Discovery Program; Expedition 372 preliminary report; creeping gas hydrate slides and Hikurangi LWD; 26 November 2017-4 January 2018

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doi: 10.14379/
Author(s): Pecher, Ingo A.; Barnes, Philip M.; LeVay, Leah J.; Bourlange, Sylvain M.; Brunet, Morgane M. Y.; Cardona, Sebastian; Clennell, Michael B.; Cook, Ann E.; Dugan, Brandon; Elger, Judith; Gamboa, Davide; Georgiopoulou, Aggeliki; Han, Shuoshuo; Heeschen, Katja U.; Hu Gaowei; Kim, Gil Young; Koge, Hiroaki; Machado, Karina S.; McNamara, David D.; Moore, Gregory F.; Mountjoy, Joshu J.; Nole, Michael A.; Owari, Satoko; Paganoni, Matteo; Rose, Paula S.; Screaton, Elizabeth J.; Shankar, Uma; Torres, Marta E.; Wang Xiujuan; Wu, Hung-Yu
International Ocean Discovery Program, Expedition 372 Scientists, College Station, TX
Author Affiliation(s): Primary:
University of Auckland, School of Environmental and Marine Sciences, Auckland, New Zealand
National Institute of Water and Atmospheric Research, New Zealand
Texas A&M University, United States
Université de Lorraine, France
University of Bremen, Germany
Colorado School of Mines, United States
CSIRO Energy, Australia
Ohio State University, United States
Christian-Albrechts-Universität zu Kiel, Germany
British Geological Survey, United Kingdom
University College Dublin, Ireland
University of Texas at Austin, United States
German Research Centre for Geosciences, Germany
Qingdao Institute of Marine Geology, China
Korea Institute of Geosciences and Mineral Resources, South Korea
University of Tokyo, Japan
Federal University of Parana, Brazil
National University of Ireland-Galway, Ireland
University of Hawaii at Manoa, United States
Chiba University, Japan
University of Oxford, United Kingdom
Texas A&M University-Corpus Christi, United States
University of Florida, United States
Banaras Hindu University, India
Oregon State University, United States
Chinese Academy of Sciences, Institute of Oceanology, China
Japan Agency for Marine-Earth Science and Technology, Japan
Source: Preliminary Report - International Ocean Discovery Program, Vol.372, 35p. Publisher: International Ocean Discovery Program, College Station, TX, United States. ISSN: 2372-9562
Note: In English. 64 refs.
Summary: International Ocean Discovery Program (IODP) Expedition 372 combined two research topics, slow slip events (SSEs) on subduction faults (IODP Proposal 781A-Full) and actively deforming gas hydrate-bearing landslides (IODP Proposal 841-APL). Our study area on the Hikurangi margin, east of the coast of New Zealand, provided unique locations for addressing both research topics. SSEs at subduction zones are an enigmatic form of creeping fault behavior. They typically occur on subduction zones at depths beyond the capabilities of ocean floor drilling. However, at the northern Hikurangi subduction margin they are among the best-documented and shallowest on Earth. Here, SSEs may extend close to the trench, where clastic and pelagic sediments about 1.0-1.5 km thick overlie the subducting, seamount-studded Hikurangi Plateau. Geodetic data show that these SSEs recur about every 2 years and are associated with measurable seafloor displacement. The northern Hikurangi subduction margin thus provides an excellent setting to use IODP capabilities to discern the mechanisms behind slow slip fault behavior. Expedition 372 acquired logging-while-drilling (LWD) data at three subduction-focused sites to depths of 600, 650, and 750 meters below seafloor (mbsf), respectively. These include two sites (U1518 and U1519) above the plate interface fault that experiences SSEs and one site (U1520) in the subducting "inputs" sequence in the Hikurangi Trough, 15 km east of the plate boundary. Overall, we acquired excellent logging data and reached our target depths at two of these sites. Drilling and logging at Site U1520 did not reach the planned depth due to operational time constraints. These logging data will be augmented by coring and borehole observatories planned for IODP Expedition 375. Gas hydrates have long been suspected of being involved in seafloor failure; not much evidence, however, has been found to date for gas hydrate-related submarine landslides. Solid, ice-like gas hydrate in sediment pores is generally thought to increase seafloor strength, as confirmed by a number of laboratory measurements. Dissociation of gas hydrate to water and overpressured gas, on the other hand, may weaken and destabilize sediments, potentially causing submarine landslides. The Tuaheni Landslide Complex (TLC) on the Hikurangi margin shows evidence for active, creeping deformation. Intriguingly, the landward edge of creeping coincides with the pinch-out of the base of gas hydrate stability on the seafloor. We therefore hypothesized that gas hydrate may be linked to creep-like deformation and presented several hypotheses that may link gas hydrates to slow deformation. Alternatively, creeping may not be related to gas hydrates but instead be caused by repeated pressure pulses or linked to earthquake-related liquefaction. Expedition 372 comprised a coring and LWD program to test our landslide hypotheses. Due to weather-related downtime, the gas hydrate-related program was reduced, and we focused on a set of experiments at Site U1517 in the creeping part of the TLC. We conducted a successful LWD and coring program to 205 mbsf, the latter with almost complete recovery, through the TLC and gas hydrate stability zone, followed by temperature and pressure tool deployments.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Australasia; Boreholes; Cores; Creep; Dissociation; Downhole methods; Faults; Gas hydrates; Geophysical methods; Geophysical profiles; Geophysical surveys; Hikurangi Margin; IODP Site U1517; IODP Site U1518; IODP Site U1519; IODP Site U1520; International Ocean Discovery Program; Marine sediments; Mass movements; Measurement-while-drilling; New Zealand; North Island; Overpressure; Pacific Ocean; Physical properties; Sediments; Seismic methods; Seismic profiles; Slumping; South Pacific; Southwest Pacific; Subduction zones; Surveys; Well logs; West Pacific
Coordinates: S385000 S385000 E1782900 E1782900
S385200 S385200 E1785400 E1785400
S384400 S384400 E1783700 E1783700
S385800 S385800 E1790800 E1790800
Record ID: 2018028000
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