Correlation between eruptions of Mount Etna, Sicily, and regional earthquakes as seen in historical records from AD 1582

Self Cite

Results of studies concerning seismic activity (earthquakes and tremor) and its relation with eruptive events on Mt Etna are briefly discussed.Seismic records collected from 1977 up to 1986 have been analysed and special care was given to observation of changes in some seismic parameters, such as the rate of microseismic activity, the amplitude and dominant spectral peaks of the volcanic tremor, which vary significantly in relation to the occurrence of eruptive events.The systematic nature of variations in the seismic parameters considered allows us to propose a preliminary model which puts all the observations made so far into a wide context giving an interpretative hypothesis of the magma uprise mechanisms preceding either summit or flank eruptions.Summit eruptions are modelled in two stages and occur without changes in the seismic parameters considered, except for a sharp increase in tremor amplitude almost coincident in time with the eruption onset.Flank eruptions are modelled in three stages and follow a simultaneous change of all the mentioned parameters with time. The onset of these eruptions is in fact preceded by an increase in both the daily number of shocks and the amplitude of the volcanic tremor as well as a shifting from relatively high values in the dominant peaks of the tremor spectra, which appear in the pre-eruptive stage, towards usual lower frequency values (1.0-2.3 Hz).

Section: Discussion a N D Conclusionmentioning

confidence: 90%

A Model For Internal Dynamical Processes On Mt Etna

Cosentino

Lombardo

Privitera³

1989

Self Cite

“…Mount Etna has displayed a variety of eruption styles, but since 1500 AD the activity has been predominately effusive eruptions from lateral vents on the volcanoes flanks, or from the central craters. While the catalogue of flank eruptions can be considered complete since 1535 (Wadge 1977), 1582 (Sharp et al 1981) or 1600 (Mulargia et al 1985), the corresponding date for summit eruptions is about 1970 (Wadge et al 1975). Moreover, the eruptive volume of pre‐1970 summit eruptions is impossible to measure accurately (Wadge et al 1975), and the quasi‐continuous nature of the activity makes the durations difficult to define, much less measure.…”

Section: Flank Eruptions At Mount Etnamentioning

confidence: 99%

Identifying volcanic regimes using Hidden Markov Models

Bebbington

2007

S U M M A R YWe examine the application of Hidden Markov Models (HMMs) to volcanic occurrences. The parameters in HMMs can be estimated from data by means of the Expectation-Maximization (EM) algorithm. Various formulations permit modelling the activity level of a volcano through onset counts, the intensity of a Markov Modulated Poisson Process (MMPP), or through the intervals between onsets. More elaborate models allow investigation of the relationship between durations and reposes. After fitting the model, the Viterbi algorithm can be used to identify the underlying (hidden) activity level of the volcano most consistent with the observations. The HMM readily provides forecasts of the next event, and is easily simulated. Data of flank eruptions 1600-2006 from Mount Etna are used to illustrate the methodology. We find that the volcano has longish periods of Poissonian behaviour, interspersed with less random periods, and that changes in regime may be more frequent than have previously been identified statistically. The flank eruptions of Mount Etna appear to have a complex time-predictable character, which is compatible with transitions between an open and closed conduit system. The relationship between reposes and durations appears to characterize the cyclic nature of the volcanoes activity.

“…Several studies have looked for a link between volcanic and seismic activity at Etna volcano (Sharp et al 1981; Nercessian et al 1991; Gresta et al 1994; De Rubeis et al 1997; Hirn et al 1997). Sharp et al (1981) and Nercessian et al (1991) performed statistical analyses using all eruptions and seismic events that occurred since 1582 within 200–300 km of the volcano, independent of their tectonic origin and magnitude. Depending on how they select the events, these authors obtained different results.…”

Section: Time Correlation Between Earthquakes and Eruptionsmentioning

confidence: 99%

“…Depending on how they select the events, these authors obtained different results. Sharp et al (1981) observed that earthquakes are related to flank eruptions in the area surrounding the volcano, with earthquakes preceding eruptions. However, Nercessian et al (1991), found that earthquakes mainly occurred at the end of eruptive periods.…”

Section: Time Correlation Between Earthquakes and Eruptionsmentioning

confidence: 99%

Stress interaction between seismic and volcanic activity at Mt Etna

Feuillet

Cocco

Musumeci

et al. 2006

International audienceMt Etna lies on the footwall of a large normal fault system, which cuts the eastern coast of Sicily and crosses the volcano eastern flank. These faults are responsible for both large magnitude historical earthquakes and smaller damaging seismic events, closer to the volcano. We investigate here the two-way mechanical coupling between such normal faults and Mt Etna through elastic stress transfer. The comparison between eruptive sequences and historical seismicity reveals that the large earthquakes which struck the eastern Sicily occurred after long periods of activity along the Mt Etna rift zone. The larger the erupted lava volumes, the stronger the earthquake. The smaller earthquakes located on the eastern flank of the volcano occur during periods of rift zone eruptions. We point out that the seismicity rates are well correlated with the rate of erupted lava. By modelling elastic stress changes caused by earthquakes and eruptions in a 3-D elastic half-space, we investigate their interaction. Earthquake dislocations create a vertical stress gradient along fissures oriented perpendicular to the minimum compressive stress and compress shallow reservoirs beneath the volcano. This may perturb the magmatic overpressures in the Etna plumbing system and influence the transport and storage of the magma as well as the style of the eruptions. Conversely, the large rift zone eruptions increase up to several tenths MPa the Coulomb stress along the eastern Sicily normal fault system and may promote earthquakes. We show that the seismic activity of the normal faults that cut the eastern flank of the volcano is likely to be controlled by Coulomb stress perturbations caused by the voiding of shallow reservoirs during flank eruptions