[SSS17-P13] Temperature-dependent frictional strength of dolerite in an argon atmosphere
Keywords:friction, temperature dependence, dolerite
Experiments were conducted on dolerite (Belfast, Northern Ireland) using a rotary shear deformation apparatus at Chiba University. Dolerite samples were sheared at a normal stress of 1 MPa, slip rates of 1 to 300 mm/s, slip displacements of 10 - 20 m at each slip rate and temperatures of 20 - 500oC in an argon atmosphere with an oxygen concentration of 0.2 %. A high-frequency induction coil surrounding the sample holders is used to heat up the sample holders and the rock samples.
At 20oC and 100oC, the dolerite showed velocity weakening at the range of slip velocities 1 - 30 mm/s with µ ranging 0.81 - 0.83 at 1 mm/s and of 0.73 at 30 mm/s. Whereas at high temperatures >300oC, friction is almost constant (µ = 0.81 - 0.85) at < 30 mm/s. At 100 mm/s, the behavior is slight velocity strengthening at 20oC and 100oC with µ = 0.75 - 0.79 and clear velocity-weakening at more than 300oC with µ = 0.67 - 0.76. At 300 mm/s, the dolerite showed strong velocity weakening at all temperatures investigated. The amount of weakening (i.e., the drop in friction, Δµ) increases with increasing temperature (Δµ = 0.1 - 0.38). Thus, the frictional properties of dolerite are affected by not only slip rate but also the ambient temperature. Our results suggest that rocks at depths are energetically favored for earthquake ruptures to propagate deeper.