Experimental and numerical investigation of the temperature response to stress changes of rocks

The temperature response to stress changes of rocks is key to understanding temperature anomalies in geoscience phenomena such as earthquakes. We developed a new hydrostatic compression system in which the rock specimen center can achieve adiabatic conditions during the first ~10 s following rapid loading or unloading, and systematically measured several representative sedimentary, igneous and metamorphic rocks sampled from two seismogenic zones [the Longmenshan Fault Zone in Sichuan, and the Chelungpu Fault Zone (TCDP Hole-A) in Taiwan], and several quarries worldwide. We built a finite element model of heat conduction to confirm the measured results of temperature response to stress changes of rocks. The results show that: (1) the adiabatic pressure derivative of the temperature (β) for most crustal rocks is ~1.5 mK/MPa to 6.2 mK/MPa, (2) the temperature response to stress of sedimentary rocks (~3.5-6.2 mK/MPa) is larger than that of igneous and metamorphic rocks (~2.5-3.2 mK/MPa), and (3) there is good linear correlation between β (in mK/MPa) and the bulk modulus K (in GPa): β=(-0.068·K + 5.69) ± 0.4, R2 = 0.85. This empirical equation will be very useful for estimating the distribution of β in the crust, because K can be calculated when profiles of crustal density (ρ) and elastic wave velocities (Vp, Vs) are obtained from gravity surveys and seismic exploration