Japan Geoscience Union Meeting 2014

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Oral

Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS30_28AM2] New perspective of great earthquakes along subduction zones

Mon. Apr 28, 2014 11:00 AM - 12:42 PM Main Hall (1F)

Convener:*Kyuichi Kanagawa(Graduate School of Science, Chiba University), Takashi Furumura(Center for Integrated Disaster Information Research (CIDIR) Interfaculty Initiative in Information Studies, The University of Tokyo), Shuichi Kodaira(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Masanobu Shishikura(Active Fault and Earthquake Research Center, GSJ/AIST), Chair:Saneatsu Saito(Japan Agency for Marine-Earth Science and Technology)

11:00 AM - 11:15 AM

[SSS30-P14_PG] Effects of frictional heating and comminution on coal maturation

3-min talk in an oral session

*Hiroyuki FURUICHI1, Kohtaro UJIIE1, Tsubasa SAITO1, Arito SAKAGUCHI2, Akito TSUTSUMI3 (1.Life and Env., Sci., Univ. Tsukuba, 2.Sci., Yamaguchi Univ., 3.Sci., Kyoto Univ.)

Keywords:vitrinite reflectance, frictional heating, comminution, Nankai Trough

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.