Publication Date:
2020-12-07
Description:
The main aim of this work is to recognize the occurrence of seismic VT activity and its discrimination
among other active and persistent natural and/or artificial sources, such as meteo-marine and anthropogenic
noise. This task is of interest because it would support the routine practices of the observatories, considering
that on the hourly scale events of very small energy are often completely hidden and not even the tedious
work of operators can be resolved. To achieve that goal we adopt a robust automatic method, namely the
Convolutive Independent Component Analysis (CICA), which in involves higher-order statistics in
frequency domain. This technique is successful in seismological framework in the case of seismic signals,
which can be considered as the convolution of time delayed source signals. In this work, we focus on
Volcano Tectonic (VT) activity at Campi Flegrei Caldera (Italy) during the 2006 ground uplift. The activity
is characterized approximately by 300 low-magnitude (Md 〈 2; for the definition of duration magnitude, see
Petrosino et al., [2008]) VT earthquakes. Most of them were concentrated in distinct seismic sequences with
hypocentres mainly clustered beneath the Solfatara-Accademia area, at depths ranging between 1 and 4 km
b.s.l.. CICA is fruitfully applied to massive data on hourly scale obtaining a separation among different
independent sources. Specifically, the identification of meteo-marine (〈 1 Hz), anthropogenic noise (mainly
affecting [8-14] Hz frequency range), and hydrothermal tremor (at about 0.8 Hz) is achieved in absence of
VT activity, defining the background level. Variations of that underlying condition appear in approaching to
the period of intense low-energy VT activity. Namely, a further component in 13-15 Hz compatible with the
typical corner frequency of VTs is extracted. We propose a coarse-grained procedure directly applied to
massive data separated through CICA, which would provide fast alert on the occurrence of even very-small
VTs representing a suitable “observable” to monitor in the observatory practice.
Description:
Published
Description:
Naples
Description:
8T. Sismologia in tempo reale
Keywords:
Campi Flegrei
;
ICA
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Conference paper
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