Abstract:

An advection-diffusion model describing tephra transportation can be used to quantitatively evaluate eruption parameters, e.g., plume height, total eruptive mass, tephra grain size distribution (e.g., Bonadonna et al. Bonadonna et al. 2005; Mannen et al. 2020). If a similar evaluation is performed for each of subunit sediments of an erupted event, it may be possible to know the time history of the event in an quantitative way. The eruption parameters obtained from this evaluation can also be applied for predicting future eruption history and eruption impact assessment. In this presentation, I will introduce that we have developed an inversion analysis system to estimate the outline of eruptive events from irregularly spaced data of tephra fall thickness, and have verified the usefulness of the system by adopting it to the tephra data of Tarumai volcano, Hokkaido, Japan. It has been confirmed that the constructed inversion system is able to predict the volume of ejecta comparable with geological estimation, and to reproduce the tephra fall thickness at each point within an error of less than ~5-30%, from proximal ~15-20 point data of tephra fall thickness. However, further verification is necessary to confirm the consistency with the grain size distribution at each data point and the distal tephra thickness, for which more variety of case study are necessary in future study to improve the quality of the system.

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