VOLCEXPLOSEIS · Experimental reconstruction of volcanic explosions: understanding the fragmentation energy balance and seismic signals

Volcanic explosions can have devastating effects on their surrounding area and communtiies, so it is important to improve our understanding of the controls on how energetic volcanic explosions are and the interpretation of the seismic signals that they generate. Volcanic explosions are driven by ascent and depressurisation of magma, which result in the exsolution of large volumes of gas. If the gas cannot escape through permeable pathways, pressure in the magma will build up, resulting in fragmentation and explosion of the magma. Recent work by the host has identified the influence of permeability, pressure, and magma properties on whether and how the magma will fragment. They have also developed methods to assess the energy used to fragment the magma from the size distribution of the fragments. In this project, the fellow will extend this work by conducting fragmentation experiments on natural and synthetic melts with a range of physical properties at a range of temperatures and pressures. The fragment size distribution will be analysed in order to calculate the energy partitioning between fragmentation of magma and ejection and propulsion of the fragments. This will be compared between different magmas in different states. During these experiments acoustic emissions, which are laboratory scale earthquakes, will be recorded. These can be scaled for comparison with seismic events recorded during volcanic explosions. Changes in the size and characteristics of these acoustic emissions with explosion energy, magma state and energy partitioning will be analysed. These results will inform the interpretation of seismic events associated with volcanic explosions, revealing links between the nature of explosion earthquakes and the potential impact of the volcanic explosion. This will be the first time an energy partitioning analysis has been done on natural and synthetic magmas above and below the glass transition temperature and the first time that acoustic emissions have