Mechanochemical Effect on Maturation of Carbonaceous Material: Implications for Thermal Maturity as a Proxy for Temperature in Estimation of Coseismic Slip Parameters
S. Kaneki, T. Ichiba, T. Hirono
Geophysical Research Letters
Because shear stress in a fault is directly related to the frictional heat generated during slip, the thermal maturity of carbonaceous material has been used as a proxy for fault‐rock temperature. We used infrared and Raman spectroscopic analyses and friction and heating experiments to investigate enhancement of the maturation of lignite by shear damage (the mechanochemical effect) and explored the resultant implications for the use of the thermal maturity of lignite as a proxy for temperature. We showed that higher shear stress applied to lignite samples resulted in greater progression of the thermal destruction of aliphatic C─H chains and the survival of the stronger C─C bonds. Thus, we demonstrated that shear damage during earthquake slip causes mechanochemical enhancement of organochemical reactions related to the aromatization of lignite. Our results suggest that shear stress estimated from Raman spectroscopic analyses in previous studies might have been overestimated.
Mechanochemistry, Seismic slip, FTIR Microscopy