Drilling and coring the Northern Hikurangi subduction margin to unlock the secrets of slow slip; International Ocean Discovery Program Expeditions 372 and 375

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http://abstractsearch.agu.org/meetings/2018/FM/T54C-03.html
Author(s): Barnes, Philip; Saffer, Demian M.; Wallace, Laura M.; Pecher, Ingo Andreas; Petronotis, Katerina E.; LeVay, Leah J.
International Ocean Discovery Program (IODP), Expedition 372 Scientists
Author Affiliation(s): Primary:
National Institute of Water & Atmospheric Research, Wellington, New Zealand
Other:
Pennsylvania State University, United States
GNS Science, New Zealand
University of Auckland, New Zealand
International Ocean Discovery Program, United States
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Slow slip events (SSEs) at the northern Hikurangi subduction margin, New Zealand, are well documented, and recur every 1-2 years. Because they occur at shallow depths (2-15 km), and potentially reach the seafloor at the deformation front, they offer a unique opportunity to use scientific ocean drilling to investigate the processes and in situ conditions associated with SSEs. International Ocean Discovery Program (IODP) Expedition 375 (March-May 2018) together with part of Expedition 372 (November 2017-January 2018) were designed to address three broad scientific objectives: (1) characterize the incoming plate and shallow plate boundary fault near the trench, which represent the protolith and initial conditions for fault zone rocks hosting SSEs at greater depths; (2) characterize material and physical properties in the upper plate above the primary SSE source further landward; and (3) install borehole observatories at two upper plate sites to measure temporal variations in deformation, temperature, and fluid flow over multiple SSE cycles. We will present preliminary results of logging-while-drilling (LWD; Exp. 372) and coring (Exp. 375) at four sites, tied to regional seismic reflection profiles. The two upper plate sites were located within an active thrust fault near the deformation front (site U1518, drilled to 600 m below seafloor (mbsf)) and in a sedimentary basin above the high-slip SSE source region (U1519; drilled to 650 mbsf). Pleistocene mudstone samples and geophysical logs from the thrust fault zone provide insights into the composition, physical properties, and structure of a shallow splay fault that potentially hosts slow slip behavior, as well as providing constraints on the growth of the frontal accretionary wedge. At two sites on the incoming Pacific Plate we sampled and logged the Early Cretaceous to Holocene terrigenous, pelagic, and volcaniclastic sedimentary succession in the Hikurangi Trough (U1520, 1054 mbsf), and atop the Turanganui Knoll seamount (U1526, 84 mbsf). These drilling data tied to seismic reflection profiles provide insights into the lithological and structural assemblages that may exist in the plate boundary fault zone undergoing slow slip and other seismic phenomena.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 18 Geophysics, Solid-Earth; Crust; Expedition 375; Hikurangi Margin; IODP Site U1518; IODP Site U1519; IODP Site U1526; International Ocean Discovery Program; Lithosphere; Oceanic crust; Oceanic lithosphere; Pacific Ocean; Plate tectonics; Slip rates; South Pacific; Southwest Pacific; Subduction; Subduction zones; West Pacific
Coordinates: S385133 S385133 E1785346 E1785346
S384338 S384338 E1783654 E1783651
S390119 S390119 E1791445 E1791445
Record ID: 2019050446
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