Andrea Cannata

Multidisciplinary investigation on a lava fountain preceding a flank eruption: The 10 May 2008 Etna case

A multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of the erupted products to volcanic tremor, long-period events, and tilt and gravity signals is used to investigate the source depth and magma dynamics of the 10 May 2008 lava fountain at Southeast crater (SEC) of Mount Etna. The investigation was undertaken in the framework of the previous 2007 explosive activity as well as the subsequent effusive eruption beginning 13 May 2008 and lasting up to July 2009. All the data concur in indicating that the 10 May lava fountain was generated by the fragmentation of a foam layer trapped at the top of a shallow reservoir, about 1500–1700 m below the summit of SEC. The shift from the episodic strombolian/lava fountain activity occurring in 2007 at SEC to the more powerful 10 May 2008 lava fountain is explained by the intrusion of a new more primitive magma into the shallow reservoir. Data also indicate that an attempted magma intrusion east of the summit area occurred during the 10 May fire fountain. This event caused the fracturing and weakening of the surrounding rocks and created a preferential pathway for the penetration of the magma that, only 3 days later, started to feed the 2008–2009 effusive eruption.

Multiparametric study of the February-April 2013 paroxysmal phase of Mt. Etna New South-East crater

European FP7 MED-SUV (MEditerranean SUpersite Volcanoes). Grant Number: 308665 European Research Council European FP7 (FP/2007-2013)/ERC. Grant Number: 279802 SIGMA (Sistema Integrato di sensori in ambiente cloud per la Gestione Multirischio Avanzata)

Monitoring Seismo-volcanic and Infrasonic Signals at Volcanoes: Mt. Etna Case Study

Volcanoes generate a broad range of seismo-volcanic and infrasonic signals, whose features and variations are often closely related to volcanic activity. The study of these signals is hence very useful in the monitoring and investigation of volcano dynamics. The analysis of seismo-volcanic and infrasonic signals requires specifically developed techniques due to their unique characteristics, which are generally quite distinct compared with tectonic and volcano-tectonic earthquakes. In this work, we describe analysis methods used to detect and locate seismo-volcanic and infrasonic signals at Mt. Etna. Volcanic tremor sources are located using a method based on spatial seismic amplitude distribution, assuming propagation in a homogeneous medium. The tremor source is found by calculating the goodness of the linear regression fit (R2) of the log-linearized equation of the seismic amplitude decay with distance. The location method for long-period events is based on the joint computation of semblance and R2 values, and the location method of very long-period events is based on the application of radial semblance. Infrasonic events and tremor are located by semblance–brightness- and semblance-based methods, respectively. The techniques described here can also be applied to other volcanoes and do not require particular network geometries (such as arrays) but rather simple sparse networks. Using the source locations of all the considered signals, we were able to reconstruct the shallow plumbing system (above sea level) during 2011.

Pressurization and depressurization phases inside the plumbing system of Mount Etna volcano: Evidence from a multiparametric approach

During 2013 Mount Etna volcano experienced intense eruptive activity at the summit craters, foremost at the New Southeast Crater and to a minor degree at the Voragine and Bocca Nuova (BN), which took place in two cycles, February–April and September–December. In this work, we mainly focus on the period between these cycles, applying a multiparametric approach. The period from the end of April to 5 September showed a gradual increase in the amplitude of long-period (LP) events and volcanic tremor, a slight inflation testified by both tilt and GPS data, and a CO2 flux increase. Such variations were interpreted as due to a gradual pressurization of the plumbing system, from the shallowest part, where LP and volcanic tremor are located, down to about 3–9 km below sea level, pressure source depths obtained by both geodetic and CO2 data. On 5 September, at the same time as a large explosion at BN, we observed an instantaneous variation of the aforementioned signals (decrease in amplitude of LP events and volcanic tremor, slight deflation, and CO2 flux decrease) and the activation of a new infrasonic source located at BN. In the light of it, the BN explosion probably caused the instantaneous end of the pressurization, and the opening of a new vent at BN, that has become a new steady source of infrasonic events. This apparently slight change in the plumbing system also led to the gradual resumption of activity at the New Southeast Crater, culminating with the second lava fountain cycle of 2013.

A comprehensive interpretative model of slow slip events on Mt. Etna's eastern flank

Starting off from a review of previous literature on kinematic models of the unstable eastern flank of Mt. Etna, we propose a new model. The model is based on our analysis of a large quantity of multidisciplinary data deriving from an extensive and diverse network of INGV monitoring devices deployed along the slopes of the volcano. Our analysis had a twofold objective: first, investigating the origin of the recently observed slow-slip events on the eastern flank of Mt. Etna; and second, defining a general kinematic model for the instability of this area of the volcano. To this end, we investigated the 2008–2013 period using data collected from different geochemical, geodetic, and seismic networks, integrated with the tectonic and geologic features of the volcano and including the volcanic activity during the observation period. The complex correlations between the large quantities of multidisciplinary data have given us the opportunity to infer, as outlined in this work, that the fluids of volcanic origin and their interrelationship with aquifers, tectonic and morphological features play a dominant role in the large scale instability of the eastern flank of Mt. Etna. Furthermore, we suggest that changes in the strain distribution due to volcanic inflation/deflation cycles are closely connected to changes in shallow depth fluid circulation. Finally, we propose a general framework for both the short and long term modeling of the large flank displacements observed.

The unusual 28 December 2014 dike-fed paroxysm at Mount Etna: Timing and mechanism from a multidisciplinary perspective

Between 2011 and 2013, there were 43 lava fountain episodes from Mount Etnas New South-East summit crater (NSEC). In 2014, this intense activity was supplanted by sporadic Strombolian explosions and the opening of an eruptive fissure between July and August. The only lava fountaining episode of the year occurred on 28 December; this was characterized by the emplacement of a shallow dike that, at the surface, fed two distinct lava flows from an ENE-WSW trending eruptive fissure. Here we provide a detailed picture of the onset of the dike emplacement, as well as the mechanism driving its migration, using a multidisciplinary data set based on seismic, geodetic, geochemical, and volcanological observations. The dike emplacement was preceded by a pressurization of the magmatic plumbing system recorded from August 2014 on. This pressurization has been modeled as a vertically elongated magmatic source located beneath the summit craters at ~4.5 km below sea level. From September to October, magma rising was also detected by seismic and geochemical data that highlighted pressurization of the shallower portion of the plumbing system. We suggest that the 28 December 2014 dike emplacement resulted from a modification of the preexisting NSEC shallow plumbing system, largely due to drainage of the main shallow conduit during the July–August 2014 eruptive fissure activity. Such a structural modification might have created the conditions for magma emplacement as a dike-like structure.

Similarity Measures and Dimensionality Reduction Techniques for Time Series Data Mining

© 2012 Cassisi et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Similarity Measures and Dimensionality Reduction Techniques for Time Series Data Mining

How a complex basaltic volcanic system works: Constraints from integrating seismic, geodetic, and petrological data at Mount Etna volcano during the July-August 2014 eruption

The petrological part of this study was supported by the FIR 2014 research grant to Marco Viccaro from the University of Catania (Italy), grant number 2F119B, title of the project “Dynamics of evolution, ascent and emplacement of basic magmas: case-studies from eruptive manifestations of Eastern Sicily”.

Insights into Mt. Etna’s Shallow Plumbing System from the Analysis of Infrasound Signals, August 2007–December 2009

Previous studies performed on Mt. Etna on short and discontinuous time intervals indicate the North East Crater (NEC) as the most active source of infrasound. The source mechanism of NEC infrasound events was modeled as a double resonance. This lead to infer the connection between the NEC and both the southeast crater (SEC) and the eruptive fissure (EF), that opened at the beginning of the 2008–2009 eruption. Nevertheless, there are still several open questions that need to be addressed. For instance, the steadiness of NEC event features should be studied, as well as the orderliness of spectral changes of NEC events time-related to eruptive activity of other vents. The investigation of such topics is strongly enhanced by the possibility of analysing infrasound signals during year-long time periods. With this aim about 40,000 infrasound events, recorded at Mt. Etna from August 2007 to December 2009 were analysed by using spectral and location techniques. It was noted in particular that the NEC events featured periods with very steady waveforms and spectral characteristics lasting from days to months with slow or sudden variations. The most important eruptive episodes occurring at the SEC or the EF were accompanied by significant spectral changes in NEC events. In light of such systematic behaviour the connection between the NEC and the SEC/EF plumbing systems was not considered temporary but rather stable even during a relatively long time interval (2006–2009). Moreover, study of NEC event spectral features and their changes over multiple years supports the double resonance source model. Such a model, together with the inferred connections between NEC and SEC/EF feeding systems, implies that level fluctuations of a magma column inside the NEC conduit correspond to magmastatic pressure decrease/increase inside the main plumbing system. These findings open up new and interesting possibilities for monitoring magma pressure changes inside the Mt. Etna plumbing system.

Probabilistic Reasoning Over Seismic Time Series: Volcano Monitoring by Hidden Markov Models at Mt. Etna

From January 2011 to December 2015, Mt. Etna was mainly characterized by a cyclic eruptive behavior with more than 40 lava fountains from New South-East Crater. Using the RMS (Root Mean Square) of the seismic signal recorded by stations close to the summit area, an automatic recognition of the different states of volcanic activity (QUIET, PRE-FOUNTAIN, FOUNTAIN, POST-FOUNTAIN) has been applied for monitoring purposes. Since values of the RMS time series calculated on the seismic signal are generated from a stochastic process, we can try to model the system generating its sampled values, assumed to be a Markov process, using Hidden Markov Models (HMMs). HMMs analysis seeks to recover the sequence of hidden states from the observations. In our framework, observations are characters generated by the Symbolic Aggregate approXimation (SAX) technique, which maps RMS time series values with symbols of a pre-defined alphabet. The main advantages of the proposed framework, based on HMMs and SAX, with respect to other automatic systems applied on seismic signals at Mt. Etna, are the use of multiple stations and static thresholds to well characterize the volcano states. Its application on a wide seismic dataset of Etna volcano shows the possibility to guess the volcano states. The experimental results show that, in most of the cases, we detected lava fountains in advance.