Publication Date:
2021-01-22
Description:
Phreatic eruptions, although posing a serious threat to people in crater proximity, are often underestimated and have
been comparatively understudied. The detailed eruption catalogue for Ruapehu Volcano (New Zealand) provides an
exceptional opportunity to study the statistics of recurring phreatic explosions at a crater lake volcano. We performed
a statistical analysis on this phreatic eruption database, which suggests that phreatic events at Ruapehu do not follow
a Poisson process. Instead they tend to cluster, which is possibly linked to an increased heat flow during periods of a
more shallow-seated magma column. Larger explosions are more likely to follow shortly after smaller events, as
opposed to longer periods of quiescence. The absolute probability for a phreatic explosion to occur at Ruapehu
within the next month is about 10%, when averaging over the last 70 years of recording. However, the frequency of
phreatic explosions is significantly higher than the background level in years prior to magmatic episodes.
Combining clast ejection simulations with a Bayesian event tree tool (PyBetVH) we perform a probabilistic assessment
of the hazard due to ballistic ejecta in the summit area of Ruapehu, which is frequently visited by hikers. Resulting
hazard maps show that the absolute probability for the summit to be affected by ballistics within the next month is up to 6%. The hazard is especially high on the northern lakeshore, where there is a mountain refuge.
Our results contribute to the local hazard assessment as well as the general perception of hazards due to
steam-driven explosions.
Description:
Published
Description:
6V. Pericolosità vulcanica e contributi alla stima del rischio
Description:
N/A or not JCR
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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