The presence of partial melt in the Earth is often assumed to lower the velocity, increase attenuation and if aligned, enhance anisotropy of seismic waves. However, to date the relationship between the amount and distribution of partial melt and the transmission of seismic waves is poorly constrained. Many studies estimate melt fraction from seismic velocities using relationships based on a single experiment showing melt distribution in 2D. However, recent studies have shown that seismic anomalies are more sensitive to the geometry of melt distribution rather than the melt fraction. This means that current relationships are not applicable to the wide range of magmatic systems seen on Earth.
The project will develop analogue models (using 3D printing facilities at the UCL Institute of Making) and numerical models of realistic 3D melt distributions determined from SEM and X-ray microtomography images. By varying the composite materials, shapes of the melt distributions and frequency content of acoustic waves we will develop new relationships between melt distribution and seismic velocity, anisotropy and attenuation. These can be applied to volcanic settings around the world to better characterise their magmatic systems.