Publication Date:
2021-01-18
Description:
A statistical analysis of explosive eruptive events can give important clues on the behaviour
of a volcano for both the time- and size-domains, producing crucial information for hazards
assessment. In this paper, we analyse in these domains an up-to-date catalogue of eruptive
events at Galeras volcano, collating data from the Colombian Geological Survey and from
the Smithsonian Institution. The dataset appears to be complete, stationary and consisting of
independent events since 1820, for events of magnitude ≥2.6. In the time-domain, Inter-Event
Times are fitted by various renewal models to describe the observed repose times. On the basis
of the Akaike Information Criterion, the preferred model is the Lognormal, with a characteristic
time scale of ∼1.6 years. However, a tendency for the events to cluster in time into ”eruptive
cycles” is observed. Therefore, we perform a cluster analysis, to objectively identify clusters
of events: we find three plausible partitions into 6, 8 and 11 clusters of events with magnitude
≥ 2.6 the 6-cluster partition being the preferred. The Inter-Event Times between cluster onsets
(inter-cluster) and between events belonging to the same cluster (intra-cluster) are also modelled
by renewal models. For inter-cluster data, the preferred model is the Brownian Passage Time,
describing a periodical occurrence (mean return time ∼ 36 years) perturbed by a Gaussian noise.
For the intra-cluster explosions, the preferred model is the Lognormal, with a characteristic time
scale of ∼ 0.9 years. In the size-domain, we analyse only single events, due to the low number of
clusters. Considering two independent parts of the catalogue, we cannot reject the null hypothesis
of the erupted mass being described by a power law, implying no characteristic eruption size.
Finally, looking for time- and size-predictability, we find a significant inverse linear relationship
between the logarithm of the erupted mass during a cycle and the time to the subsequent one.
These results suggest that, presently, Galeras is still in the eruption cycle started in 2007; a new
eruptive cycle may be expected in a few decades, unless the present cluster resumes to activity
with magnitude ≥2.6.
Description:
This research has been partially funded by project EXACT (Progetto 29 di Ricerca Libera INGV 2019 Delibera 53/2020).
Description:
Published
Description:
583703
Description:
6V. Pericolosità vulcanica e contributi alla stima del rischio
Description:
JCR Journal
Keywords:
stochastic modelling
;
Galeras
;
Volcanic eruption
;
Clusters
;
04.08. Volcanology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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