THE ACOUSTOELASTIC EFFECT: MEASURING THE EFFECT OF STRESS ON P- AND S- WAVE VELOCITIES

Knowledge of the elastic properties of minerals is critical for understanding the structure and composition of Earth's interior and interpreting seismic data. This study investigates the effect of a materials stress state on P- and S-waves velocities, known as the acoustoelastic effect. This material property is well known in metals and has been measured at ambient to low pressure conditions. The acoustoelastic effect was recently evaluated in olivine at high pressure conditions relevant to Earth’s interior (Traylor et al., 2021, JGR: Solid Earth, DOI: 10.1029/2021JB022494). A measurable acoustoelastic effect was observed in olivine that was nearly insensitive to changes in temperature and showed a minor pressure dependence. The current study seeks to expand the study of the acoustoelastic effect by investigating other minerals relevant to Earth’s lower crust and lithospheric mantle.

Our method employs the DIASCoPE ultrasonic system, incorporated into the D-DIA multi-anvil apparatus, at the APS 6-BM-B beamline to obtain in-situ longitudinal (P) and shear (S) wave velocities at high pressure and high temperature. We use elastic-plastic self-consistent (EPSC) numerical modeling to forward model X-ray diffraction data collected in D-DIA experiments to obtain the macroscopic stress on our sample. The acoustoelastic effect is then derived from the relationship between the relative elastic wave velocity change (ΔV/V) and macroscopic stress. This study will aid in our understanding of the acoustoelastic effect and provide a new experimental technique to measure the stress state in elastically deformed geologic materials at high pressure conditions.