Step-by-Step... Getting Remote Infrasound Into Real-Time Estimate of Eruption Dynamics.

Abstract:

In recent years, much effort has been focused on using remote sensing to characterise and identify explosive volcanic events. It has ranged from the use of space-based technology to the use of regional infrasound sensors. While we do not advocate for the use of only one technology, we concentrate on the potential advantage of including remote infrasound. Infrasound technology has been used in volcano monitoring for years now and has proven to be a valuable source of information to identify different types of surface volcanic activity. From identification to localisation, this technology allows for a unique way to characterize the source. A key parameter that can be retrieved is the exit gas velocity which can be further used in the modelling of the plume dynamics and used to estimate the potential height at which volcanic products could be transported. While recent work focused on calculating such parameter from locally recorded infrasound signals, we show that with certain assumptions, similar analysis can be done with infrasound sensors located thousands of kilometres away. While it still remains a challenge to identify signals associated to large explosions at these distances, we show how film sound audio postproduction techniques, like spectral subtraction, can be used to improve detections. We will also discuss the key controlling parameters involved in this type of filtering. Following this procedure, we demonstrate that from this enhanced detection and associated acoustic energy, we can retrieve reasonable estimates of plume height and signal duration at the source. In parallel, we review the effect and contribution to the uncertainties of each different step that goes into this computation. Each phases of the process could be automated and included into a real time framework. The current procedure has been benchmarked with current understanding and could be upgraded with new understanding and improvements within the field of infrasound and physical volcanology. This modular step-by-step approach allows for immediate use of remote infrasound for eruption characterization, as well as the flexibility to reduce uncertainties by improving individual blocks in the future. Retrieving source parameters, with high level of certainty, is key to better estimating and mitigating the associated hazards.