18:15 〜 19:30
[SSS30-P14] 摩擦発熱と粉砕作用がビトリナイト反射率増加に与える効果：南海トラフ巨大分岐断層ガウジと摩擦実験試料の比較
キーワード：ビトリナイト反射率, 摩擦発熱, 粉砕, 南海トラフ
The detection of friction heating on faults is crucial to estimate frictional heat during earthquakes. Recently, vitrinite reflectance (Ro) has been used to detect friction heating along faults. However, the factors controlling increase in Ro on faults remain poorly understood. Moreover, the application of the commonly used kinetic model to the estimation of temperature rise during short-lived thermal events such as frictional heating on faults has not been convinced. Here, we conducted friction experiments on a mixture of 95 wt% clay-rich material from the host rock of the megasplay fault gouge and 5 wt% coal grains from the forearc basin in the Nankai subduction zone at slip rates of 0.15 mm/s-1.3 m/s under dry (room humidity) and wet (water-saturated) conditions. After the experiments, we examined microstructures, Ro and size of coal grains and then compared with those obtained from in and around the megasplay fault gouge. The results show that Ro does not increase by rapid heating alone; grain-size reduction due to comminution is required for increase in Ro. The combination of comminution and heating is the most effective for increase in Ro, possibly due to enhanced mechanochemical reaction associated with an increase in surface area of coal grains. The application of the results to the Nankai megasplay fault gouge is that increased Ro in the fault gouge results from frictional heating and comminution, while that in adjacent to the gouge are mainly derived from comminution. The Ro calculated from the chemical kinetic model is higher than that measured after the experiments. Ro is an useful tool to detect past frictional heating on faults, but the estimation of temperature rise from Ro is problematic; the new kinetics model considering the effects of frictional heating and comminution is necessary to estimate amount of frictional heat.