11:00 AM - 1:00 PM
[SSS07-P23] Estimation of parameter values for a slip- and time- dependent friction law using slip-stress relations of the Boso slow slips
Keywords:Friction law, slow slip, abrasion rate, adhesion rate, fractal limit of wave length
Studies on friction law, effective normal stress and shear stress on faults is important for understanding fault behavior and earthquake events. Kobayashi and Sato (JpGU,2019) proposed that relation of slip-rate and stress change for slow slip events can estimate absolute values of effective normal stress on the basis of a rate and state dependent friction law. This presentation proposes an estimation method of parameter values for a slip- and time- dependent friction law from slip-stress relations of slow slip events using that slow slip has similar changes in shear stress and frictional force. This makes it possible to obtain the parameters of the friction constitutive law at these region from the observation.
To obtain slip-stress relations of slow slip events, we used the daily F3 coordinate values of GNSS stations from the Geospatial Information Authority of Japan. The GNSS data were fitted with a time series model that takes account of the liner trend and seasonal variations in the data, and then the fitted data were smoothed. We made every 3 days transient movement from the smoothed data. From the 3 days data, we estimated slip distributions using ABIC inversion method. We calculated stress changes from the slip distributions using Coulomb3.3. We used a slip- and time-dependent friction law proposed by Aochi and Matsu’ura (2002), which considers interaction between statistically self-similar fault surface and abrasion of surface asperities as well as adhesion, which indicates the healing process of the fault surface. Important parameters of this friction law are abrasion rate, adhesion rate, and upper fractal limit of wave length on the fault surface.
From the comparison of observed and theoretical relations between slips and shear stresses for the Boso slow slip events, we estimate about 0.005~0.01 for the abrasion rate, about 10-6~10-5 (cm2/day) for the adhesion rate, and 50 cm for the upper fractal limit of wave length on the fault.
Acknowledgements: We used the daily F3 coordinate values by GSI, and Coulomb 3.3 program by USGS.
To obtain slip-stress relations of slow slip events, we used the daily F3 coordinate values of GNSS stations from the Geospatial Information Authority of Japan. The GNSS data were fitted with a time series model that takes account of the liner trend and seasonal variations in the data, and then the fitted data were smoothed. We made every 3 days transient movement from the smoothed data. From the 3 days data, we estimated slip distributions using ABIC inversion method. We calculated stress changes from the slip distributions using Coulomb3.3. We used a slip- and time-dependent friction law proposed by Aochi and Matsu’ura (2002), which considers interaction between statistically self-similar fault surface and abrasion of surface asperities as well as adhesion, which indicates the healing process of the fault surface. Important parameters of this friction law are abrasion rate, adhesion rate, and upper fractal limit of wave length on the fault surface.
From the comparison of observed and theoretical relations between slips and shear stresses for the Boso slow slip events, we estimate about 0.005~0.01 for the abrasion rate, about 10-6~10-5 (cm2/day) for the adhesion rate, and 50 cm for the upper fractal limit of wave length on the fault.
Acknowledgements: We used the daily F3 coordinate values by GSI, and Coulomb 3.3 program by USGS.