Detection of low frequency earthquakes at Mt. Vesuvius by using a frequency domain approach

The most common and recognised typologies of seismic events occurring in volcanic environments can be classified as: high frequency (HF) events, often identified as volcano-tectonic earthquakes (VT), earthquakes associated with explosive activity (explosion quakes), low frequency (LF), long period LP seismic events and volcanic tremor. The assessment of a volcano’s eruptive potential, and the variation of its internal dynamics, can be provided through detection, identification and analysis of the different typologies of seismicity. In particular, the onset of low frequency events (LF or LP) or volcanic tremor is considered as a potential indicator of the awakening of volcanic activity related to in-depth magma movement or injection of fluids. Although high volcanic risk areas are monitored by modern high-sensitivity seismic instrumentation, the background noise compromises the detection and study of low-energy earthquakes. In this framework, a new multi-methodological analysis approach is provided to overcome this critical issue. In particular, in this note we present the results of the proposed approach applied to the densely urbanized area of Mt. Vesuvius, where low amplitude seismic signals due to local seismicity are recorded by a monitoring network equipped by broad band high sensitivity seismic stations. Our aim is to detect small low frequency events into the background noise by means of methodologies that operate in the frequency domain.