Temporal rates of major explosions and paroxysms at Stromboli: data and
statistical models
Abstract
The study focuses on the estimation and modeling of the temporal rates
of major explosions and paroxysms at Stromboli volcano (also named
small-scale and large-scale paroxysms respectively). The analysis was
further motivated by the paroxysm of July 3rd 2019, which raised, once
again, the attention of the scientific community and civil protection
authorities on the volcanic hazards of Stromboli. In fact, at the
present state of knowledge, major explosions and paroxysms cannot be
forecasted based on monitoring data, and a full probabilistic assessment
based on past eruption data would be quite useful for scientific and
civil protection purposes. In the study we perform a time series
analysis either considering the last ~150 years of
reconstructed activity and the most recent 35 years. We included the
estimation of event rates and rate changes in time. Results clearly
highlight that the activity is non-homogeneus in time, with a
significant low of activity between about 1960 and 1990. Maximum values
of event rates were computed during the first half of last century, for
both major explosions and paroxysms, whereas the rate of paroxysms is
significantly lower in the last decades with respect to maximum rates.
We also accomplish a statistical analysis of the inter-event times,
enabling us to determine if the data can be modeled as a Poisson process
or not, e.g. if it shows time dependent distributions, recurring cycles,
or temporal clusters. The uncertainty quantification on the current and
future rates is mainly related to the choice of the modeling
assumptions. The study represents a crucial progress towards
quantitative hazard and risk assessments at Stromboli, which is
particularly relevant for the thousands of people (e.g. tourists, guides
and volcanologists) that regularly climb the volcano every year.