Unveiling earthquakes: thermoluminescence signal resetting of a natural polymineral sample in laboratory-produced fault gouge

Abstract

Abstract Unravelling a reliable timing of past earthquakes through luminescence dating of fault gouge depends on sufficient frictional heat during a co-seismic event to fully reset the luminescence signal. Laboratory fault-gouge production using a rotary shear apparatus has attracted interest as a method for probing the degree of signal resetting in quartz during friction experiments. However, natural fault gouges are complex, exhibiting a mixture of minerals that are specific to the host rocks. Here, we employed a host rock sample from the Alborz Mountains (Iran) and subjected it to a friction experiment without any chemical treatment, after being reset and irradiated with a known gamma dose. We performed a medium-slip velocity friction experiment with a slip velocity of 0.05 m/s and a normal stress of 12 MPa, while the temperature evolution of the gouge zone was recorded using an infrared camera. The thermographic images show a transient temperature of approximately 296 °C, with the luminescence signal resetting at a small, extremely localised slip patch, confirming the challenges involved in identifying the best spot for signal resetting. However, we identified a high-temperature signal enhancement in the thermoluminescence (TL) curves that might serve as a marker for fault-gouge formation.