Experimental study on the thermal response of rocks to stress change and its significance

Bedrock temperature contains effective information about changes in the crustal stress. A new method of detecting crustal stress change by bedrock temperature (DSCT) has been proposed. Understanding the stress-induced temperature response characteristics of loaded rocks is fundamental for applying DSCT. In this study, temperature observation experiments of different rocks and water-saturated sandstones subjected to tiered cyclic loading were conducted to investigate the temperature–stress relationship throughout the whole rock deformation and failure process. Through experiments, some valuable results are obtained: (i) temperature changes synchronously with stress and has a very strong linear correlation with it; (ii) the magnitude of temperature response to stress (TRS) is approximately 1 mK MPa−1, ranging from strong to weak are sandstone, marble, diorite and basalt, respectively. The differences in TRS of various rocks are determined by their major rock-forming minerals, textures and structures; (iii) the evolution of TRS experiences three stages: the TRS rises rapidly in the compression stage, slowly in the acoustic emission quiet period and a significant increase in TRS before rock failure is observed on marble, sandstone and basalt, consistent with the abnormal bedrock temperature rise preceding earthquakes; (iv) the TRS of water-saturated sandstones is higher compared to the dry ones, and the abnormal sharp increase in TRS before rock failure is also more significant in the former. These findings mentioned above promote the understanding of thermal anomalies preceding earthquakes.