[S-SS10] 地震発生の物理・断層のレオロジー

[SSS10-19] 跡津川断層系の断層ガウジ中の酸化グラフェン：断層運動と酸化還元反応の関係性

*島田 知弥¹、長濱 裕幸¹、武藤 潤¹、中村 教博² (1.東北大学大学院理学研究科地学専攻、2.東北学院大学高等教育開発室)

キーワード：酸化グラフェン、ラマン分光法、X線光電子分光法（XPS）、酸化還元反応、断層運動

The Atotsugawa Fault System in central Japan exhibits low seismic activity to depth of 7-8 km. Low-friction graphite (μ ~0.1) is believed to reduce fault strength and contribute to this peculiar seismicity (Oohashi et al., 2012). This study focuses on graphene oxide, derived from the oxidation and exfoliation of graphite. Graphene oxide exhibits a very low friction coefficient of approximately 0.01 (Bouchet et al., 2017); therefore, it can reduce the fault strength more effectively than graphite. We discovered graphene oxide for the first time in the fault gouge of the Atotsugawa Fault System, using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Both spectroscopies identified the presence, chemical state and distribution of graphene oxide in the fault gouge and surrounding Tetori Groups. Although small amounts of graphene oxide were partially confirmed in the Tetori Groups, most graphene oxide was concentrated along cracks within the fault gouge, promoting fault slip and influencing frictional properties. Raman spectroscopy revealed that the fault gouge exhibited a lower intensity ratio (I_D/I_G) compared to rocks from the Tetori Groups, suggesting that this change was induced by strain accumulation during fault movement. Additionally, in each fault gouge, smaller D'_inf − G_app correlated with higher I_D/I_G. The D'_inf − G_app decreases with oxidation and correlates with the carbon-to-oxygen (C/O) ratio (King et al., 2016). Therefore, the degree of oxidation in carbonaceous materials within the fault gouge correlates with the intensity ratio, indicating a relationship between fault motion and redox reactions. In this presentation, we discuss the relationship between fault movement and redox reactions in the Atotsugawa Fault System and further consider the formation process and origin of graphene oxide.