日本地球惑星科学連合2015年大会

講演情報

口頭発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG59] 地球惑星科学におけるレオロジーと破壊・摩擦の物理

2015年5月27日(水) 16:15 〜 18:00 106 (1F)

コンビーナ:*桑野 修(独立行政法人海洋研究開発機構)、大内 智博(愛媛大学地球深部ダイナミクス研究センター)、清水 以知子(東京大学大学院理学系研究科地球惑星科学専攻)、石橋 秀巳(静岡大学大学院理学研究科地球科学専攻)、座長:清水 以知子(東京大学大学院理学系研究科地球惑星科学専攻)

17:51 〜 17:54

[SCG59-P08] 高圧条件下におけるアコースティックエミッション測定の技術開発

ポスター講演3分口頭発表枠

*大内 智博1雷 興林2肥後 祐司3丹下 慶範3入舩 徹男1 (1.愛媛大学地球深部ダイナミクス研究センター、2.産業技術総合研究所、3.高輝度光科学研究センター)

The subduction zone produces a major fraction of the Earth’s seismic activity. Intermediate-depth earthquakes within the subducting slab form a double seismic zone. The cause of intraslab seismicity have been attributed to dehydration of hydrous minerals (e.g., Peacock, 2001). Brittle fracture associating dilatancy is difficult at high pressures (i.e., depths at which intermediate-depth and deep-focus earthquakes occur), although dilatancy prior to failure usually occurs in the case of shallow-depth earthquakes.
At deeper depths, dehydration embrittlement (i.e., hydrofracturing) is expected to play an important role in failure of rocks because the overall volume change of the dehydration reaction is positive and thus pore pressure can be increased (e.g., Raleigh and Paterson, 1965). However, experimental results on dehydration embrittlement of antigorite are controversial. Dobson et al. (2002) conducted a series of experiments on dehydration of antigorite, and they reported that dehydration of antigorite associates acoustic emission (AE) when the dehydration reaction is positive. Even though the volume change becomes strongly negative above 2 GPa, Jung et al. (2004) reported that brittle failure of antigorite occurs at pressures up to 6 GPa. Recently, Gasc et al. (2011) reported that no detectable AEs through dehydration of antigorite-rich serpentinite. Therefore, the cause of intermediate-depth earthquakes is still unclear.
In some of subduction zones, a significant activity of deep-focus earthquakes has been reported (e.g., Kirby et al., 1996). It has been proposed that deep-focus earthquakes are triggered by an instability faulting caused by olivine phase transformations (Kirby et al., 1991; Green et al., 1992). Schubnel et al. (2013) conducted deformation experiments on germanium olivine (Mg2GeO4) at 2-5 GPa and 1000-1250 K, and they observed many AEs generated in the sample. Schubnel et al. (2013) discussed that fractures nucleated at the onset of the olivine-to-spinel transition.
To investigate the brittle properties of rocks, determination of AE source is critical. In the community of high-pressure rock physics, Green et al. (1992) conducted AE monitoring by using a Griggs apparatus combined with an AE sensor. Dobson et al. (2002, 2004) and Jung et al. (2006) adopted 2 or 4 AE sensors to a multianvil apparatus. However, the position of AE source has not been determined in the experiments because of not enough number of sensors used in the experiments. De Ronde et al. (2007) adopted 8 AE sensors to a multianvil apparatus and they succeeded to determine the position of AE sources. Recently, Gasc et al. (2011) succeeded to develop an experimental setup that allows determining the position of AE source by using DIA-type multianvil apparatus combined with 6 AE sensors. Schubnel et al. (2013) adopted the experimental setup reported by Gasc et al. (2011) to a D-DIA apparatus installed at a synchrotron facility, and they succeeded to measure strain and stress of the sample and AE signals. We have developed an experimental setup that is optimized for the determination of the position of AE source in a synchrotron D-DIA apparatus. We will report some preliminary experimental results on AE monitoring under the upper mantle conditions.