Akihiro Takeuchi

Frictional melting can terminate seismic slips: Experimental results of stick‐slips

[1] The appropriate setting of sensors and the use of a high speed data acquisition system enabled us to detect the exact time of melting of the slip surfaces during a stick-slip event (fault displacement of 0.32 mm, stress drop of 230 MPa, rise time of 23 μs and maximum slip velocity of 40 m/s) in triaxial apparatus at 150 MPa confining pressure. Once slip started, the friction coefficient decreased continuously from 0.55 to 0.3, after which the frictional resistance recovered promptly and remarkably. This strengthening can be attributed to the highly resistive initial melt, a potential mechanism for arresting seismic slips.

Milling-Induced Reset of Thermoluminescence and Deformation of Hydroxyl Species in the Near-Surface Layers of Quartz Grains

Milling-Induced Reset of Thermoluminescence and Deformation of Hydroxyl Species in the Near-Surface Layers of Quartz Grains Reset mechanisms of thermoluminescence (TL) signals in the near-surface layers (~500 nm thick) of quartz grains during milling are discussed on the basis of the dependence of TL glow-curves and infrared absorption spectra on grain diameter. TL measurements (heating to 370°C at 1°C/s) indicate that the near-surface layer does not seem to emit TL at ~250-400°C, especially in the blue range, even in TL measurements after re-irradiation. In contrast, the layer seems to emit more TL at ~130°C than the inner original quartz. On the other hand, diffused reflection infrared Fourier transform spectrometry indicates that hydroxyl species (e.g. Al-OH, Li-dependent OH and molecular H2O species) are deformed in the near-surface layer. These two series of data suggest that TL recombination sites in the near-surface layer are deformed or broken during milling and contribute to TL emission unusually strongly.