Expedition 343/343T summary

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doi: 10.2204/iodp.proc.343343T.101.2013
Author(s): Mori, James J.; Chester, Frederick M.; Eguchi, Nobuhisa; Toczko, Sean; Kido, Yukari; Saito, Saneatsu; Sanada, Yoshinori; Anderson, Louise; Behrmann, Jan H.; Bose, Santanu; Conin, Marianne; Cook, Becky; Fulton, Patrick; Hirose, Takehiro; Ikari, Matt; Ishikmawa, Tsuyoshi; Jeppson, Tamara; Kameda, Jun; Kirkpatrick, James; Lin, Weiren; Mishima, Toshiaki; Moore, J. Casey; Nakamura, Yasuyuki; Regalla, Christine; Remitti, Francesca; Rowe, Christie; Sample, James; Sun, Tianhaozhe; Takai, Ken; Toy, Virginia; Ujiie, Kohtaro; Wolfson, Monica; Yang Tao
Integrated Ocean Drilling Program, Expedition 343/343T Scientists, College Station, TX
Author Affiliation(s): Primary:
Kyoto University, Disaster Prevention Research Institute, Kyoto, Japan
Other:
Texas A&M University, United States
Japan Agency for Marine-Earth Science and Technology, Japan
University of Leicester, United Kingdom
Helmholtz Centre for Ocean Research Kiel, Germany
University of Calcutta, India
Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, France
University of Southampton, United Kingdom
University of Texas at Austin, United States
University of Bremen, Germany
University of Wisconsin at Madison, United States
University of Tokyo, Japan
University of California at Santa Cruz, United States
Osaka City University, Japan
Pennsylvania State University, United States
Universita di Modena e Reggio Emilia, Italy
McGill University, Canada
Northern Arizona University, United States
University of Victoria, Canada
University of Otago, New Zealand
University of Tsukuba, Japan
University of New Hampshire, United States
China Earthquake Administration, China
Volume Title: Proceedings of the Integrated Ocean Drilling Program; Japan Trench Fast Drilling Project (JFAST); Expedition 343/343T of the riser drilling platform, Shimizu, Japan, to Sendai, Japan; Site C0019; 1 April-24 May 2012; and Minami-Ise, Japan, to Hachinohe, Japan, Site C0019, 5-19 July 2012
Volume Author(s): Mori, James J.; Chester, Frederick M.; Eguchi, Nobuhisa; Toczko, Sean; Kido, Yukari; Saito, Saneatsu; Sanada, Yoshinori; Anderson, Louise; Behrmann, Jan H.; Bose, Santanu; Conin, Marianne; Cook, Becky; Fulton, Patrick; Hirose, Takehiro; Ikari, Matt; Ishikmawa, Tsuyoshi; Jeppson, Tamara; Kameda, Jun; Kirkpatrick, James; Lin, Weiren; Mishima, Toshiaki; Moore, J. Casey; Nakamura, Yosuyuki; Regalla, Christine; Remitti, Francesca; Rowe, Christie; Sample, James; Sun, Tianhaozhe; Takai, Ken; Toy, Virginia; Ujiie, Kohtaro; Wolfson, Monica; Yang Tao
Source: Proceedings of the Integrated Ocean Drilling Program; Japan Trench Fast Drilling Project (JFAST); Expedition 343/343T of the riser drilling platform, Shimizu, Japan, to Sendai, Japan; Site C0019; 1 April-24 May 2012; and Minami-Ise, Japan, to Hachinohe, Japan, Site C0019, 5-19 July 2012, James J. Mori, Frederick M. Chester, Nobuhisa Eguchi, Sean Toczko, Yukari Kido, Saneatsu Saito, Yoshinori Sanada, Louise Anderson, Jan H. Behrmann, Santanu Bose, Marianne Conin, Becky Cook, Patrick Fulton, Takehiro Hirose, Matt Ikari, Tsuyoshi Ishikmawa, Tamara Jeppson, Jun Kameda, James Kirkpatrick, Weiren Lin, Toshiaki Mishima, J. Casey Moore, Yosuyuki Nakamura, Christine Regalla, Francesca Remitti, Christie Rowe, James Sample, Tianhaozhe Sun, Ken Takai, Virginia Toy, Kohtaro Ujiie, Monica Wolfson and Yang Tao; Integrated Ocean Drilling Program, Expedition 343/343T Scientists, College Station, TX. Proceedings of the Integrated Ocean Drilling Program (Online), Vol.343/343T, 28p. Publisher: IODP Management International, Washington, DC, United States. ISSN: 1930-1014
Note: In English. 37 refs.; illus., incl. sects., 1 table, sketch map
Summary: The main science goal of the Japan Trench Fast Drilling Project (JFAST) is to understand the physical mechanisms and dynamics of large slip earthquakes, which is fundamental to understanding the huge tsunami that caused extensive damage during the 2011 Tohoku-oki earthquake. Specifically, the level of frictional stress during the earthquake rupture and the physical characteristics of the fault zone are investigated through drilling. The objectives of JFAST include locating the fault that ruptured during the Tohoku-oki event using logging while drilling (LWD); characterizing the composition, architecture, and fundamental mechanisms of dynamic frictional slip and healing processes along the fault by taking core samples; and estimating the frictional heat and stress within and around the fault zone by placing a temperature measurement observatory across the fault. During the main JFAST expedition (Integrated Ocean Drilling Program [IODP] Expedition 343 in April and May 2012), LWD was completed in a borehole drilled to 850.5 meters below seafloor (mbsf) (total depth [TD] = 7740 meters below sea level [mbsl]), and a coring hole was drilled to 844.5 mbsf (TD = 7734 mbsl) to acquire 21 cores that spanned the two main fault targets. Because of delays associated with severe weather and technical challenges of operating in great water depths, installation of the observatory for temperature and pressure measurements was not completed during the main expedition. However, temperature sensors were successfully deployed during a short technical extension of JFAST, IODP Expedition 343T, in July 2012. Principal results of Expedition 343/343T include the following: 1. The overall structure at the drill site consists of a prism of faulted and folded clayey to silty mudstones above and in fault contact (at ∼820 mbsf) with a largely undeformed, relatively thin sequence of hemipelagic and pelagic sediments that were deposited on top of the incoming Pacific plate. The primary constituents of the mudstones that make up the prism are terrigenous silt and clay, vitric ash, and biogenic silica. The fault contact, interpreted as the plate boundary decollement, is defined by a subhorizontal, <5 m thick zone of highly sheared clay that displays penetrative scaly fabric and localized slip surfaces 2. Faults and bedding are variable in dip magnitude, but faults and bedding at all depths in the prism show a preferred northeast strike direction reflecting horizontal contraction and local extension (at shallower depths) approximately parallel to the plate convergence direction. 3. Borehole breakouts are evident in image logs from the LWD hole and indicate several different in situ stress domains along the borehole. At shallow depths (from <200 to ∼500 mbsf), the maximum horizontal compressive stress ( SHmax ) is variable and shows a complicated pattern. At deeper levels in the prism (537-820 mbsf), SHmax displays a single preferred orientation ∼20° clockwise from the plate convergence direction. 4. Fault slip during the 2011 event and other past earthquakes likely occurred on the plate boundary decollement. However, slip on other faults cutting the prism could have also occurred during the Tohoku-oki event. One possible location of recent fault slip is identified at ∼700 mbsf on the basis of a local H2, methane, and chlorinity anomaly. Several core samples from a fractured and brecciated zone at ∼720 0mbsf contain faults, the largest of which is a high-angle reverse fault that occurs at the same depth as a low-resistivity feature identified in image logs. The fault at ∼720 mbsf and the decollement at ∼820 mbsf are the two primary targets for the temperature measurement observatory. 5. Successful recovery of ∼1 m of highly sheared clay from the plate boundary decollement and of the neighboring sediments provide material for mechanical and physical properties testing, as well as for geochemical, mineralogical, and microstructural analyses. Four special interest structural whole-round samples taken from the sheared clay of the decollement, as well as three other structural whole rounds capturing secondary faults, will provide material for coordinated nondestructive and destructive investigations of structure, chemistry, and mineralogy of the faulted sediments. 6. An observatory consisting of 55 temperature sensors and autonomous data loggers was successfully installed across the two fault targets. These instruments are monitoring temperature distribution across the lower portion of the borehole to estimate the amount of frictional heat dissipated along the slip zone of the Tohoku-oki earthquake in order to estimate the level of dynamic frictional strength during the earthquake. The temperature data loggers are scheduled to be retrieved in February 2013.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 13 Areal Geology, General; =; Biostratigraphy; Boreholes; Cenozoic; Clastic rocks; Cores; Cretaceous; Decollement; Earthquakes; Expedition 343/343T; Fault zones; Faults; Geochemistry; Geophysical methods; Geophysical profiles; Geophysical surveys; Great earthquakes; Hydrochemistry; IODP Site C0019; Integrated Ocean Drilling Program; JFAST; Japan Trench; Japan Trench Fast Drilling Project; Lithostratigraphy; Marine sediments; Mesozoic; Mudstone; North Pacific; Northwest Pacific; Pacific Ocean; Physical properties; Pore water; Sedimentary rocks; Sediments; Seismic methods; Seismic profiles; Shear; Stress; Surveys; Tohoku-Oki earthquake 2011; Vertical seismic profiles; West Pacific
Coordinates: N375600 N375600 E1435500 E1435500
Record ID: 2013063608
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