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Theoretical and experimental analyses of the temperature responses of water-saturated rocks to changes in confining pressure
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  • Xiaoqiu Yang,
  • Weiren Lin,
  • Hehua Xu,
  • Osamu Tadai,
  • Xin Zeng
Xiaoqiu Yang
South China Sea Institute of Oceanology, Chinese Academy of Sciences

Corresponding Author:yxq2081@scsio.ac.cn

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Weiren Lin
Graduate School of Engineering, Kyoto University
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Hehua Xu
South China Sea Institute of Oceanology, Chinese Academy of Sciences, PRChina
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Osamu Tadai
Marine Works Japan Ltd.
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Xin Zeng
Key Laboratory of Marginal Sea Geology
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The temperature response of water-saturated rocks to stress changes is critical for understanding thermal anomalies in the crust, because most porous rocks are saturated with groundwater. In this study, we establish a theoretical basis of the adiabatic pressure derivative of the temperature of water-saturated rocks under both undrained (βwet_U) and drained (βwet_D) conditions. The value of βwet_U is linearly correlated with Skempton’s coefficient (B) and βwet_D increases nonlinearly as the pore water volume per unit volume of rock (ξ) increases. The theoretical calculations demonstrate that the thermal effects of pore water predominate in water-saturated rocks with medium to high porosity, especially under undrained conditions. In most cases, the temperature response of rocks with a porosity of ϕ > 0.05 under water-saturated and undrained conditions is greater than that under dry conditions. Experiments were also carried out on a water-saturated typical medium porosity sandstone (sample RJS, ϕ = 0.102) and on a compact limestone (sample L27, ϕ = 0.003) using an improved hydrostatic compression system. The experimental results confirm that the theoretical derivation is correct, and the calculated ranges of βwet_U and βwet_D are reliable for all 15 rocks. Consequently, this study increases our understanding of the thermal anomalies that occur after huge earthquakes, including the negative thermal anomalies, which are probably induced by co-seismic stress release, that were observed in the boreholes that penetrate seismic faults after the Chi-Chi Earthquake, the Wenchuan Earthquake, and the Tohoku Earthquake.