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@INPROCEEDINGS{Stipp:206278,
      author       = {Stipp, Michael and Schumann, Kai and Leiss, Bernd and
                      Ullemyer, Klaus},
      title        = {{C}auses and {C}onsequences of the great strength
                      variability among soft {N}ankai {A}ccretionary {P}rism
                      {S}ediments from offshore {SW}-{J}apan},
      reportid     = {PUBDB-2015-00783},
      year         = {2014},
      abstract     = {Geophysical Research AbstractsVol. 16, EGU2014-10666,
                      2014EGU General Assembly 2014© Author(s) 2014. CC
                      Attribution 3.0 License.Causes and consequences of the great
                      strength variability among softNankai accretionary prism
                      sediments from offshore SW-JapanMichael Stipp (1), Kai
                      Schumann (1), Bernd Leiss (2), and Klaus Ullemeyer (3)(1)
                      GEOMAR, Marine Geodynamics, Kiel, Germany (mstipp@geomar.de,
                      kaschumann@geomar.de), (2)Geowissenschaftliches Zentrum,
                      Universität Göttingen, Germany (bleiss1@gwdg.de), (3)
                      Institut für Geowissenschaften,Universität Kiel, Germany
                      (kullemeyer@geomar.de)The Nankai Trough Seismogenic Zone
                      Experiment of the International Ocean Discovery Program
                      (IODP) isthe very first attempt to drill into the
                      seismogenic part of a subduction zone. Offshore SW-Japan the
                      oceanicPhilippine sea plate is subducted beneath the
                      continental Eurasian plate causing earthquakes of magnitude
                      8.0 to8.5 and related tsunamis with a recurrence rate of
                      80-100 years. For the tsunamigenic potential of the forearc
                      slopeand accreted sediments their mechanical strength,
                      composition and fabrics have been investigated. 19 drill
                      coresamples of IODP Expeditions 315, 316 and 333 were
                      experimentally deformed in a triaxial cell under
                      consolidatedand undrained conditions at confining pressures
                      of 400-1000 kPa, room temperature, axial shortening rates
                      of0.01-9.0 mm/min, and up to an axial strain $of64\%$ (Stipp
                      et al., 2013). With respect to the mechanical behavior,two
                      distinct sample groups could be distinguished. Weak samples
                      from the upper and middle forearc slope ofthe accretionary
                      prism show a deviatoric peak stress after only a few percent
                      strain (< $10\%)$ and a continuousstress decrease after a
                      maximum combined with a continuous increase in pore
                      pressure. Strong samples fromthe accretionary prism toe
                      display a constant residual stress at maximum level or even
                      a continuous stressincrease together with a decrease in pore
                      pressure towards high strain (Stipp et al., 2013).
                      Synchrotron textureand composition analysis of the
                      experimentally deformed and undeformed samples using the
                      Rietveld refinementprogram MAUD indicates an increasing
                      strength of the illite and kaolinite textures with
                      increasing depth downto 523 m below sea floor corresponding
                      to a preferred mineral alignment due to compaction.
                      Experimentallydeformed samples have generally stronger
                      textures than related undeformed core samples and they show
                      alsoincreasing strength of the illite and kaolinite textures
                      with increasing axial strain. Mechanically weak samples
                      havea bulk clay plus calcite content of 31-65 $vol.-\%$ and
                      most of their illite, kaolinite, smectite and calcite
                      [001]-polefigures have maxima >1.5 mrd. Strong samples which
                      were deformed to approximately the same amount of strain(up
                      to $40\%)$ have no calcite and a bulk clay content of 24-36
                      $vol.-\%.$ Illite, kaolinite and smectite [001]-pole
                      figuremaxima are mostly <1.5 mrd, except for one sample
                      which was deformed to a considerably higher strain
                      $(64\%).The$ higher clay and calcite content and the
                      stronger textures of the mechanically weak samples can be
                      related toa collapsing pore space of the originally
                      flocculated clay aggregates. This process is insignificant
                      in the strongsamples from the prism toe, for which
                      deformation would tend to involve large rock volumes and
                      lead to straindissipation. The weak samples from the forearc
                      slope which become even weaker with increasing strain
                      mayprovoke mechanical runaway situations allowing for
                      earthquake rupture, surface breakage and tsunami
                      generation.Stipp, M., Rolfs, M., Kitamura, Y., Behrmann,
                      J.H., Schumann, K., Schulte-Kortnack, D. and Feeser, V.2013.
                      G-Cubed 14/11, doi: 10.1002/ggge.20290.},
      month         = {Apr},
      date          = {2014-04-27},
      organization  = {European Geosciences Union General
                       Assembly 2014, Vienna (Austria), 27 Apr
                       2014 - 2 May 2014},
      cin          = {DOOR},
      cid          = {I:(DE-H253)HAS-User-20120731},
      pnm          = {DORIS Beamline W2 (POF2-54G13)},
      pid          = {G:(DE-H253)POF2-W2-20130405},
      experiment   = {EXP:(DE-H253)D-W2-20150101},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://bib-pubdb1.desy.de/record/206278},
}