日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

[S-IT24] Attenuation from crust to core: in situ experiments, observaions and implications

2019年5月26日(日) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:小西 健介(台湾中央研究院地球科学研究所)、片山 郁夫(広島大学大学院理学研究科地球惑星システム学専攻)、芳野 極(岡山大学惑星物質研究所)、Alexandre Schubnel(CNRS)

[SIT24-P01] 水に飽和した花崗岩の三軸試験中での地震波減衰の測定

*片山 郁夫1山田 恵也1財間 寛太1 (1.広島大学大学院理学研究科地球惑星システム学専攻)

Rock microfracturing significantly affects attenuation of seismic wave as well as seismic velocity. In this study, seismic wave attenuation in fluid-saturated granite was estimated during triaxial deformation experiments, with particular attention focused on how microfracturing affects the attenuation. Fine-grained Aji granite was used for experiments, with 40 mm long and 20 mm in diameter. Triaxial experiments were carried at a constant strain-rate of ~10-6 s-1 under confining pressure of 20 MPa and pore pressure of 10 MPa. During deformation, elastic wave was monitored by a pulse transmission method using both P and S wave transducers with a resonant frequency of 2 MHz. In the early stage of deformation, amplitudes of both P and S waves increase slightly due to closure of preexisting cracks and then decrease due to nucleation and growth of microcracks as the sample approaches failure, with agreement of changes in seismic velocity. Change in amplitude of shear wave tends to be larger than compressional wave, similar to those observed in fluid-saturated sandstone, suggesting that inter-crack fluid flow acts as a main source of energy dissipation. We use these wavelets to estimate attenuation (quality factor) using the spectral ratio method described by Toksoz et al. (1979); the results will be presented during the meeting.