11:45 AM - 12:00 PM
[SSS05-20] Estimation of Rate- and State-Dependent Friction Parameters
at Subseismic Loading Rate
Keywords:Rate- and state-dependent friction law, Subseismic slip velocity, Velocity step change, Fujian granite
We conducted rock friction experiments to estimate the values of the parameters a , b and Dc of the rate- and state-dependent friction (RSF) law in the range of subseismic loading rate from 10-3 to 10-1m/s where not much data have been reported to date. The experiments were conducted using Fujian granite, China, which may have similar properties to those of Westerly granite. All the experiments were conducted using a rotary-shear friction apparatus at National Research Institute for Earth Science and Disaster Prevention (NIED) under room temperature and room humidity condition. We conducted velocity step change test between 5.0×10-3 and 1.5×10-2m/s for 10 successive times. The normal stress was kept at 3MPa. The estimation of friction parameters was conducted following steps. First, we estimated the "a" value from the jump of the friction coefficient waveform data at each velocity step. Then, we appropriately set the search range for the parameters "b" and "Dc" for the grid search. For all the parameters in the search range, we numerically calculated friction curve based on the RSF law with the aging law, which we used as the evolution law of the RSF law. Finally, we compared these computations with the measurements and estimated the values of "b" and "Dc" that minimize the weighted root-mean square errors as the optimal solution. Since the experiments data represented sufficient reproducibility, we think the estimated friction parameters were accurate enough. The estimated values of a , a-b and Dc are 0.002~0.007, -0.06~-0.04, 0.2~0.4 m, respectively. These values were different values from other shear friction experiments conducted at low slip velocity of 10-7 to 10-4m/s. In particular, the value of Dc was close to that obtained when high-velocity friction experiments conducted at ~1m/s.