VolcaPot Mathieu Poret

Les VolcaPots sont de retour et nous sommes heureux de vous y convier. Le second aura lieu le lundi 23 octobre à 14h : Mathieu Poret (INGV – Bologna) présentera ses travaux sur la dispersion des cendres, notamment appliqués à l’Etna.

Title : Modelling ash cloud dispersion and the impact of ash aggregation during volcanic eruptions

Abstract:

The constant improvement of characterizing the eruption processes is made widely through field analysis, remote-sensing instruments, lab experiments and numerical models. From a computational point of view, the inter-dependency of the main volcanological parameters makes challenging the assessment of the tephra dispersion and sedimentation, from which the total erupted mass and the mass eruption rate are estimated. This study aims at better constraining the Total Grain Size Distribution (TGSD) assessment usually estimated from field sample analysis only. Within the TGSD, the very fine ash (i.e. PM10) suffers from the field based uncertainty induced by their atmospheric residence time. Besides, the particle particle aggregation also affects the ash dispersal and thereby the deposition. Although numerical simulations can account for ash aggregation, they need an accurate TSGD as input. Here, we report the use of the FALL3D model with, first, a study based on the integration of field and satellite data to better estimate the TGSD and especially the PM10 fraction. This application focuses on the February 23rd 2013 Etna paroxysm. This eruption benefited from north-easterly winds which dispersed the tephra towards Brindisi (Puglia region), ~410 km from source. Then, the aggregation feature is studied through the explosive eruption of La Soufrière Saint Vincent on April 26th 1979. During this event, a significant aggregate fraction were observed contributing to a premature tephra fallout from the vent to Bequia Island (36 km southwards). We selected this eruption to investigate the relevance of ash aggregation processes on the tephra fallout through different aggregation schemes.

Venez nombreux,

Les Valentins