Seismic waves remain impervious to water

Lateral variations of seismic wave speed and attenuation in the Earth’s upper mantle can potentially be used to map its underlying properties. Structurally bound water is thought to affect such seismic measurements substantially. To investigate, Christopher Cline and co-authors assess the effect of water on the seismic properties of olivine, a common mineral in the Earth’s subsurface, and demonstrate that wave speeds and attenuation are strikingly insensitive to water content. Instead, the imposed redox conditions and associated defect chemistry appear to have a substantial influence on seismic properties, indicating that elevated water contents are not responsible for low-velocity/high-attenuation structures observed in the Earth’s upper mantle.