Frictional properties of incoming pelagic sediments at the Japan Trench; implications for large slip at a shallow plate boundary during the 2011 Tohoku earthquake

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doi: 10.1186/1880-5981-66-65
Author(s): Sawai, Michiyo; Hirose, Takehiro; Kameda, Jun
Author Affiliation(s): Primary:
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
Other:
Hokkaido University, Japan
Volume Title: Earth, Planets and Space
Source: Earth, Planets and Space, 66(1). Publisher: Terra Scientific Publishing Company (TERRAPUB), Tokyo, Japan. ISSN: 1343-8832
Note: In English. This article is part of the series "New perspective of subduction zone earthquake", edited by Gaku Kimura, Juichiro Ashi, Masataka Kinoshita, Christie Rowe, and David Shelly. 30 refs.; illus., incl. 1 table, sketch map
Summary: The 2011 Tohoku earthquake (Mw 9.0) produced a very large slip on the shallow part of a megathrust fault that resulted in destructive tsunamis. Although multiple causes of such large slip at shallow depths are to be expected, the frictional property of sediments around the fault, particularly at coseismic slip velocities, may significantly contribute to large slip along such faults. We have thus investigated the frictional properties of incoming pelagic sediments that will subduct along the plate boundary fault at the Tohoku subduction zone, in order to understand the rupture processes that can cause large slip in the shallow parts of subduction zones. Our experimental results on clayey sediment at the base of the sedimentary section on the Pacific Plate yield a low friction coefficient of <0.2 over a wide range of slip velocities (0.25 mm/s to 1.3 m/s), and extremely low fracture energy during slip weakening, as compared with previous experiments of disaggregated sediments under coseismic slip conditions. Integrated Ocean Drilling Program (IODP) Expedition 343 confirmed that the clay-rich sediment investigated here is identical to those in the plate boundary fault zone, which ruptured and generated the Tohoku earthquake. The present results suggest that smectite-rich pelagic sediment not only accommodates cumulative plate motion over interseismic periods but also energetically facilitates the propagation of earthquake rupture towards the shallow part of the Tohoku subduction zone. Copyright 2014 The Author(s) and Sawai et al.; licensee Springer.
Year of Publication: 2014
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IPOD International Phase of Ocean Drilling
Key Words: 16 Structural Geology; 19 Geophysics, Seismology; Clay minerals; Cores; Coseismic processes; DSDP Site 436; Deep Sea Drilling Project; Deformation; Displacements; Earthquakes; Expedition 343; Expeditions 343/343T; Experimental studies; Fault zones; Faults; Fractures; Friction; IPOD; Integrated Ocean Drilling Program; Japan Trench; Japan Trench Fast Drilling Project; Leg 56; Marine sediments; Mechanical properties; North Pacific; Northwest Pacific; Pacific Ocean; Pelagic environment; Rupture; Sediments; Shear; Sheet silicates; Silicates; Slip rates; Smectite; Subduction zones; Thrust faults; Tohoku-Oki earthquake 2011; Velocity; West Pacific; X-ray diffraction data
Coordinates: N395557 N395558 E1453329 E1453328
Record ID: 2015009316
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