Water vaporization promotes coseismic fluid pressurization and buffers temperature rise

• Published in: Geophysical research letters Vol. 44; no. 5; pp. 2177 - 2185
• Main Authors: Chen, Jianye, Niemeijer, André, Yao, Lu, Ma, Shengli
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.03.2017
• Subjects: Anomalies; Buffers; Carbonates; Earthquakes; Endothermic reactions; Environmental monitoring; Experiments; Fluid dynamics; Fluids; Geophysics; High temperature; high‐velocity friction; Interfaces; Marine; phase transition; Phase transitions; Plate tectonics; Plateaus; Pore pressure; Pore water; Porosity; Pressure; Pressurization; Pressurizing; Seismic activity; Seismology; Slip; slip‐weakening mechanism; Temperature; Temperature anomalies; Temperature effects; Temperature rise; Thermodynamics; Vaporization; water vaporization
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL071932

We investigated the frictional properties of carbonate‐rich gouge layers at a slip rate of 1.3 m/s, under dry and water‐saturated conditions, while monitoring temperature at different locations on one of the gouge‐host rock interfaces. All experiments showed a peak frictional strength of 0.4–0.7, followed by strong slip weakening to steady state values of 0.1–0.3. Experiments which used a pore fluid with a constant drainage path to the atmosphere showed the development of a temperature plateau beyond 100°C, contemporaneous with the dynamic slip weakening and consistent with thermodynamic considerations of ongoing vaporization of pore water. Upon pore fluid vaporization, the pore pressure increases, while the temperature is buffered endothermically, such that the pore water moves along the liquid‐vapor transition curve in a pressure‐temperature phase diagram. Pore fluid phase transitions of this kind are expected to occur in natural earthquakes at relatively shallow crustal levels, enhancing fluid pressurization while impeding the achievement of high temperatures. Therefore, the operation of vaporization may help explain the low downhole temperature anomalies obtained shortly after large earthquakes. Key Points Water vaporization was “observed” in high‐velocity friction experiments Water vaporization promotes fluid pressurization during coseismic slip Water vaporization limits the temperature rise during coseismic slip