Experimental study on the resetting of IRSL and IRPL signals induced by frictional heating in rocks at seismic slip velocities

Abstract

The challenges in luminescence dating of faulting materials often arise from uncertainties in the extent of signal resetting caused by frictional heating and pressing along the fault. In this study, laboratory friction experiments were performed to simulate the influence of seismic slip rates on rock luminescence signals. High-speed friction generated rapid heating of the frictional interface, with temperatures reaching 500–800 °C. This process effectively reset the infrared-stimulated luminescence (IRSL) signal within the upper ∼1.5 mm of gabbro surfaces, and fully reset the signal up to ∼6 mm inward from surface edges. However, depth information was partly lost because mechanical cutting caused local detachment of thin rock slices. To overcome this limitation, we measured luminescence signals using the Risø luminescence imager, which provides non-destructive and high-resolution IRSL and Infrared Photoluminescence (IRPL) measurements on granite samples. The lack of preheating may preserve some unstable charges and slightly underestimate the resetting ratios. Even so, the patterns are robust. High-speed friction eliminated ∼99 % of IRSL intensities and reset 78 ± 1 % of the IRPL₉₅₅ signals. Low-speed friction reset 83 ± 1 % of the IRSL signals and had only 29 ± 1 % of IRPL₉₅₅ signals. These results confirm that the Risø luminescence imager is highly effective in detecting friction-induced signal resetting. The non-destructive imaging approach preserves depth information and offers higher spatial resolution than measurements on cut rock slices. IRSL and IRPL₉₅₅ signals can potentially constrain the timing of high-velocity seismic slip. Their contrasting responses to different slip conditions may also reflect deformation processes associated with stick-slip and creep, providing additional insight into earthquake behavior.