Manzo, Roberto (2024) The microseismicity of Mt. Vesuvius (southern Italy): A new approach based on detection and inversion of low frequency seismic events. [Tesi di dottorato]

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Abstract

The seismicity at Mt. Vesuvius has been characterized in recent decades by low magnitude local earthquakes (MD < 3.0) While shallow volcano-tectonic (VT) events at Mt. Vesuvius are well-documented, the detection of low-frequency (LF) events at greater depths is a recent study. Previous seismic source studies have focused primarily on VT events, revealing a diverse range of focal mechanisms. The present PhD thesis aims to provide a robust and detailed study of the microseismicity of Mt. Vesuvius (southern Italy) focusing on low frequency seismic events that occurred during the period 2012-2021. Due to the large number of issues in the volcanic area under consideration, an innovative approach based on an automatic procedure to detect these signals hidden in the background noise is proposed. The detection methodology is based on the computation of two spectral parameters, the central frequency Ω and the shape factor δ, at selected sites, and on the coherence of the seismic signals. The procedure shows that the low-frequency activity of Mt. Vesuvius occurs more frequently than previously supposed. Subsequently, the seismic source of LF seismic events is characterized by implementing a specific inversion approach that integrates seismogram fitting in the time domain and amplitude spectrum fitting in the frequency domain within a Bayesian statistical framework. A strong heterogeneity of LF signals is found which is attributed to both complex source processes and wave propagation in a strongly heterogeneous medium.

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