Rosario Peluso

Seismological insight into the kinematics of the 5 April 2003 vulcanian explosion at Stromboli Volcano (southern Italy)

[1]xa0On 5 April 2003 at 07:13 GMT (09:13 local time) a violent vulcanian explosion occurred at Stromboli volcano. At the time of the event an eruptive crisis was ongoing at the volcano with a lava flow outpouring along the Sciara del Fuoco flank. The seismic signals related to the event were recorded by 8 permanent broadband stations and gives information about the eruption kinematics. An ultra-long-period signal (period > 20 s), that we interpret as the effect of the ground tilt on the broadband sensors, starts about 4 min before and terminates about 1 min after the explosion. On the basis of the radial pattern of tilt directions we conclude that this signal is the effect of the deformation of the volcanic edifice, due to the rapid rising of a batch of magma, its ejection and the magma column readjustment. About 1 min before the explosion we observe an high frequency signal (period < 0.1 s) that we believe to be related to the vesiculation of the rising batch of gas-rich magma. At 07:13:35 GMT a powerful very-long-period signal (period 2 ÷ 20 s), marking the onset of the explosive fragmentation, is recorded. This is confirmed by a blast wave following few seconds later. The remaining seismic signal (more than 3 min), shows an higher frequency content being related only to the fall of ballistic ejecta and to landslides along Sciara del Fuoco. We propose the implementation of an early warning system for the short-term forecast of such explosions, based on the real-time automatic detection of the tilt signals preceding such events.

The 7 September 2008 Vulcanian explosion at Stromboli volcano: Multiparametric characterization of the event and quantification of the ejecta

This paper was partially supported by a research project (project INGV-DPC Paroxysm V2/03, 2007–2009) funded by Istituto Nazionale di Geofisica e Vulcanologia and by the Italian Civil Protection.

Automatic Recognition of Landslides Based on Neural Network Analysis of Seismic Signals: An Application to the Monitoring of Stromboli Volcano (Southern Italy)

In the last 9xa0years, the amount and the quality of geophysical and volcanological observations of Strombolis activity have undergone a marked increase. This new information highlighted that the landslides on the Sciara del Fuoco flank are tightly linked to the volcanic activity. Actually, at the beginning of the December 28, 2002, effusive eruption, the seismic monitoring network was less dense than now, and therefore it is not known if there was an increase in the landslide rate before the eruption. Despite this, it is known that a big landslide occurred 2xa0days after the beginning of the eruption which caused a tsunami (December 30, 2002). More recently, the effusive eruption in February 2007 was preceded by an increase in landslides on the Sciara del Fuoco flank, which were recorded by the seismological monitoring system that had been improved after the 2002–2003 crisis. These episodes led us to believe that monitoring the Sciara del Fuoco flank instability is an important topic, and that landslides might be significant short-term precursors of effusive eruptions at the Stromboli volcano. To automatically detect landslide signals, we have developed a specialized neural algorithm. This can distinguish between landslides and the other types of seismic signals usually recorded at the Stromboli volcano (i.e., explosion quakes and volcanic tremor). The discrimination results show an average performance of 98.67xa0%. According to the experience of the crisis of 2007, to identify changes that can be considered as precursors of effusive eruptions, we set up an automatic decision-making method based on the neural network responses. This method can operate on a continuous data stream. It calculates a landslide percentage index (LPI) that depends on the number of records that are classified by the net as landslides over a given time interval. We tested the method on February 27, 2007, including the beginning of the effusive phase. The index showed an increase as early as at 09:00 UTC on that day and reached its maximum value (100xa0%) at 12:00, about 40xa0min before the onset of the eruption. After the beginning of the effusive phase, the index remains high due to the blocks that roll down along the slope from the front of the lava flow. On the basis of these tests, we propose a decision-making method that is able to recognize a trend in the LPI similar to that of 2007 eruption, allowing the identification of precursors of effusive phases at the Stromboli volcano.

Data acquisition for volcano monitoring

In the past decade, systems and techniques for volcano monitoring activities have improved rapidly. The scientific community focused on the development of new methods and techniques, while the electronic systems for experimental activity and monitoring networks were developed mainly by commercial companies. n nHowever, these commercial systems often do not fit simultaneously all the needs of geophysical research. A new project, led by the Italian Institute of Geophysics and Volcanology (INGV) ‘Osservatorio Vesuviano’ (OV) in Naples is trying to fill this niche with the development of data acquisition systems for multiparametric volcanic monitoring.

Seismological Insights on the Shallow Magma System

We present an overview of the volcanic seismicity recorded at Stromboli from January to September 2003. The data set starts a few weeks after the onset of the eruption and covers most of the effusive phase and the subsequent recovery of the explosive activity. The most important variations occurred between May and July coinciding with the waning of the lava flow and the reappearance of Strombolian activity at the summit craters. All the parameters indicate that the shallow magmatic system has not undergone permanent changes during this period. The only significant variation related to the shallow conduit is the increase in volcanic tremor amplitude and the change in the spectral content of long-period events during the transition between effusive and explosive activity. A slight increase in the very long period (VLP) events source elevation seems to mark the rise of the magma at the end of the effusive phase. The variations in the VLP events occurrence rate are more likely to be attributed to changes in the gas flow rate and the bubble coalescence mechanism, therefore, to a deeper portion of the magmatic system. The 5 April paroxysm is associated only with a small increase of the activity in the following days.

The Seismicity of Ischia Island

This work benefited of the project “Sale operative integrate e reti di monitoraggio ndel futuro: l’INGV 2.0,” Fondo integrativo speciale per la ricerca (FISR) anni 2016 e 2017 (Delibera n. 78/2017). nFurthermore, this work benefited of the agreement between Istituto Nazionale di Geofisica e Vulcanologia and Italian Department of Civil Protection (DPC).

A FORTRAN Code for the Sensitivity Estimate of a Seismic Network: An Application to Campi Flegrei

The resolution power of a seismic network is a crucial point both for scientific and legal reasons. Firstly it allow to understand whether an area is not affected by seismicity or we are just not able to detect it; consequently it is an important parameter when the possible seismicity is eventually associated with human activities. When subsoil exploitation is planned a certain minimum level of sensitivity to earthquake location is indeed usually required for the monitoring network to be installed. The sensitivity of a seismic network is its ability to detect or locate earthquakes. Here we present free downloadable and friendly software to define the sensitivity of a seismic network. Input to the program are the station positions, the seismic noise level of the area and the mean elastic properties of the area and the output is a grid with the minimum magnitude of earthquakes which are localizable or detectable at a certain depth.