Observing conduit flow processes during Strombolian Eruptions using Transient Electromagnetics (TEM): a numerical and field approach

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Volcanic eruptions are one of the most fascinating spectacles that can be witnessed on Earth. They are boon and bane to mankind and mitigating the effects of volcanic eruptions is a major societal task. Among other things mitigation strategies involve short term crisis management including short notice eruption warnings. Most crucial in this regard is the understanding of processes inside volcanic conduits preceding an eruption. In situ observations of magma transport processes in the conduit are still nearly impossible. So far almost all measurements rely on remote sensing techniques like seismological observations, tilt measurements or ground based InSAR observations. All processes in the conduit prior to an eruption involve the nucleation and growth of bubbles. In case of strombolian eruptions these bubbles are usually quite elongated with a length to width ratio being much larger than 1. They are called gas slugs. One of the goals of this proposal is to explore the potential of transient electromagnetics (TEM) to monitor the final rise of such gas slugs in the volcanic conduit passing through the last 100 m prior to the eruptions. Electromagnetic methods in general show a high potential in volcanic environments due to inductive coupling and the high conductivity contrast between magma, gas and host rock. By running virtual experiments using a highly sophisticated three-dimensional TEM forward simulation software we will explore the sensitivity of the subsurface response taking especially into account real topography and subsurface features like hydrothermal systems as well as a magma filled conduit including a gas slug. We will investigate the effect of various setups including different source/receiver configurations on the TEM response in a realistic volcanic setting. This will allow us to determine characteristic signals that we would expect to record at an active volcano using TEM prior to an eruption. In order to do so, we will expand an existing software with an adaptive meshing and sophisticated geomodeling tools to properly describe the volcanic edifice leading to novel modeling techniques and results in geoelectromagnetics.Applying a detailed sensitivity study using geophysical information available for Stromboli volcano, Italy, we will carry out a set of virtual experiments to constrain possible measurement configurations to optimize a field experiment at Stromboli. We propose to carry out a field experiment using TEM for monitoring processes within the volcanic conduit. These TEM measurements will be complemented by monitoring the eruptions using cameras and Doppler radar. Combining those data hopefully enables us to better constrain slug rise and benchmark numerical models for the rise of gas slugs in volcanic conduits thereby improving volcanic hazard mitigation.