Abstract
Abstract. Spectral analysis has been applied to almost thousand seismic events recorded at Vesuvius volcano (Naples, southern Italy) in 2018 with the aim to test a new tool for a fast event classification. We computed two spectral parameters, central frequency and shape factor, from the spectral moments of order 0, 1, and 2, for each event at seven seismic stations taking the mean among the three components of ground motion. The analyzed events consist of volcano-tectonic earthquakes, low frequency events and unclassified events (landslides, rockfall, thunders, quarry blasts, etc.). Most of them are of low magnitude, and/or low maximum signal amplitude, therefore the signal to noise ratio is very different between the low noise summit stations and the higher noise stations installed at low elevation around the volcano. The results of our analysis show that volcano-tectonic earthquakes and low frequency events are easily distinguishable through the spectral moments values, particularly at seismic stations closer to the epicenter. On the contrary, unclassified events show the spectral parameters values distributed in a broad range which overlap both the volcano-tectonic earthquakes and the low frequency events. Since the computation of spectral parameters is extremely easy and fast for a detected event, it may become an effective tool for event classification in observatory practice.
Highlights
Active volcanoes are complex systems characterized by heterogeneous geological structure and by a variety of phenomena that may generate seismic waves
The results of our analysis show that volcanotectonic earthquakes and low frequency events are distinguishable through the spectral moments values, at seismic stations closer to the epicenter
In the present work we try a step forward in the analysis of seismic signals through the estimation of spectral parameters obtained from statistical moments of the power spectrum
Summary
Active volcanoes are complex systems characterized by heterogeneous geological structure and by a variety of phenomena that may generate seismic waves. Internal sources produce volcano-tectonic (VT) earthquakes, low frequency (LF), long period (LP) events and volcanic tremor, while external sources include landslides, rockfalls, thunders and other atmospheric phenomena Artificial sources such as quarry blasts and other events related to human activity often produce transient seismic signals detected by the monitoring seismic networks. Understanding the origin of the low frequency signals observed on active volcanoes (LF events and volcanic tremor) is of fundamental importance because this type of seismicity often precede eruptions and, it can be indicative for evaluating the potential eruption of a volcano (Chouet, 2003) For this reason, an efficient classification of the seismic events recorded on volcanoes can be achieved only taking into account both the signal shape in time domain, and their spectral characteristics (Chouet, 1996; McNutt, 2005; Zobin, 2017). The proposed approach has been tested by analyzing almost a thousand seismic events recorded at Vesuvius volcano in 2018
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