The role of dehydration reaction in seismogenic processes at subduction plate boundaries

2009 Fiscal Year Final Research Report

• Project/Area Number: 19340147
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geology
• Research Institution: The University of Tokyo
• Principal Investigator: SHIMIZU Ichiko The University of Tokyo, 大学院・理学系研究科, 助教 (40211966)
• Co-Investigator(Kenkyū-buntansha): HIRAGA Takehiko 東京大学, 地震研究所, 助教 (10444077) ; MICHIBAYASHI Katsuyoshi 静岡大学, 理学部, 準教授 (20270978)
• Project Period (FY): 2007 – 2009
• Keywords: レオロジー

Research Abstract

A popular hypothesis for the occurrence of double seismic zones, observed at the intermediate depth of about 50-200km, is dehydration embrittlement of the serpentinized slab mantle. The weakening of serpentinite was attributed to excess pore fluid pressure caused by dehydration reaction of serpentine. However, the confining pressure of these experiments using gas-medium apparatus was limited up to 500MPa (corresponding to 15km depth). It is questionable if the same mechanism could be effective in subducting slabs at higher pressures. We conducted constant strain-rate experiments of serpentinite using a solid-medium deformation apparatus and found that the yield strength of serpentinites drastically decreased when dehydration reaction proceeded. This phenomena, named "dehydration weakening", would be a key to understand seismogenic processes in the serpentinized mantle slabs.

Research Products

• [Journal Article] 沈み込みスラブの二重震発面と蛇紋岩の脱水不安定性 (2010)
  • Author(s): 清水以知子
  • Journal Title: 月刊地球 32 Pages: 162-166
• [Journal Article] Synthesis of highly dense and fine-grained aggregates of mantle composites by vacuum sintering of mineral nano-powders (2010)
  • Author(s): Koizumi, S., Hiraga, T., Tachibana, C., Tasaka, M., Miyazaki, T., Kobayashi, T., Takamasa, A., Ohashi, N., Sane, S
  • Journal Title: Physics and Chemistry of Minerals
• [Journal Article] Grain growth systematics for forsterite±enstatite aggregates : Effect of lithology on grain size in the upper mantle (2010)
  • Author(s): Hiraga, T., Tachibana, C., Ohashi, N., Sano, S.
  • Journal Title: Earth and Planetary Science Letters 291 Pages: 10-20
• [Journal Article] Trench-parallel anisotropy produced by serpentine deformation in the hydrated mantle wedge (2009)
  • Author(s): Katayama, I., Hirauchi, K. Michibayashi, K., Ando, J.
  • Journal Title: Nature 461 Pages: 1114-1117
• [Journal Article] Hydration due to high-T brittle failure within in situ oceanic crust, 30°NMid-Atlantic Ridge (2008)
  • Author(s): Michibayashi, K., Hirose, T., Nozaka, T., Harigane, Y., Escartin, J., Delius, H., Linek, M., Ohara, Y.
  • Journal Title: Earth and Planetary Science Letters 275 Pages: 348-354
• [Journal Article] Theories and applicability of grain size piezometers : The role of dynamic recrystallization mechanisms (2008)
  • Author(s): Shimizu, I.
  • Journal Title: J.Struct.Geol. 30 Pages: 899-917
• [Journal Article] B-type olivine fabrics developed in the fore-arc side of the mantle wedge along a subducting slab (2008)
  • Author(s): Tasaka, M., Michibayashi, K., Mainprice, D.
  • Journal Title: Earth and Planetary Science Letters 272 Pages: 747-757
• [Presentation] 改良熊沢型固体圧試験機による高圧実験 (2010)
  • Author(s): 清水以知子
  • Organizer: 地球惑星科学連合大会
  • Place of Presentation: 千葉県幕張メッセ
  • Year and Date: 2010-05-19
• [Presentation] 蛇紋岩の脆性-延性転移 (2009)
  • Author(s): 清水以知子
  • Organizer: 地球惑星科学連合大会
  • Place of Presentation: 千葉県幕張メッセ
  • Year and Date: 2009-05-26
• [Presentation] 蛇紋岩の脱水軟化と沈み込みスラブにおける地震発生過程 (2009)
  • Author(s): 清水以知子・渡邉悠太, 道林克禎, 高橋美紀
  • Organizer: 地球惑星科学連合大会
  • Place of Presentation: 千葉県幕張メッセ
  • Year and Date: 2009-05-16