Geophysics at the Interface: Response of Geophysical Properties to Solid-Fluid, Fluid-Fluid, and Solid-Solid Interfaces

Laboratory studies reveal the sensitivity of measured geophysical properties to solid‐fluid, fluid‐fluid, and solid‐solid interfaces in granular and fractured materials. In granular materials, electrical properties and nuclear magnetic resonance relaxation times exhibit a strong dependence on the size and properties of the solid‐fluid interface. The electrical and seismic properties of granular materials and the seismic properties of fractured materials reveal a dependence on the size or geometry of fluid‐fluid interfaces. Seismic properties of granular and fractured materials are affected by the effective stress and cementing material at solid‐solid interfaces. There have been some recent studies demonstrating the use of field‐scale measurements to obtain information about pore‐scale interfaces. In addition, a new approach to geophysical field measurements focuses on the geophysical response of the field‐scale interface itself, with successful applications in imaging the water table and a redox front. The observed sensitivity of geophysical data to interfaces highlights new ways in which geophysical measurements could be used to obtain information about subsurface properties and processes.