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Riduzione dei livelli di rumore sismico ambientale nelle città italiane e stima dell’effetto sulla capacità di rilevamento della Rete Sismica Nazionale a seguito delle misure restrittive COVID-19 del Febbraio-Marzo 2020
Sponsors
Istituto Nazionale di Geofisica e Vulcanologia
Language
Italian
Obiettivo Specifico
Status
Unpublished
Peer review journal
No
Issued date
April 24, 2020
Subjects
Abstract
Ambient seismic noise is the component of the signal discarded in the procedures for interpreting the waveforms of earthquakes.
The Signal / Noise ratio (S / N) is a parameter for assessing the quality of the seismic data in relation to the possibility of detecting the phases of earthquakes useful for their location. The signal is represented by the seismic event, which is a rare transient when seismic sequences are not in progress. Using high-performance seismic equipment, the noise is represented by the ambient seismic noise, which is detected in the form of vibrations imperceptible by humans. In cases where the dynamics of the instrument is restricted and its intrinsic noise is high, the seismic ambient noise cannot be detected, information relating to the medium crossed from the source to measurement point is lost and its variations cannot be revealed.
Ambient seismic noise is a stochastic process from which stationary characteristics can be extracted, related to natural or anthropic sources that generally occur at different frequencies. Rapid vibrations with cycles below one second are well documented in the literature and are generally linked to anthropogenic activities, caused by industrial plants, domestic appliances, vehicular traffic and any transfer of energy to the ground that propagates seismic waves (Peterson, 1993; McNamara and Buland, 2004).
The restrictive measures issued by the Italian Government in year 2020 due to the contagion from COVID-19 (http://www.governo.it/it/coronavirus-normativa) have significantly reduced the sources of cultural seismic noise that transmit seismic waves into the ground, which are not perceived by people but only detectable by seismic instruments.
In Italy, the territory is monitored in real time and continuously by the National Seismic Network (RSN) of the National Institute of Geophysics and Volcanology (INGV Seismological Data Center, 2006). Some works show how it is possible to characterize the variability of seismic noise on the national territory, identifying the origin and nature of seismic waves of background vibrations (Marzorati and Bindi, 2006; Marzorati, 2007; Marzorati and Bindi, 2008; Li et al., 2010 ; Vassallo et al., 2012).
This report shows the reduction of the average levels of seismic noise in the frequency range between 2 and 8 Hz, so as to be able to exclude natural sources at lower frequency and to analyze signals that have the ability to propagate at significant distances from the sources, in order to reach seismic stations located in large italian cities or in their surroundings.
The seismic data of seismic stations of the RSN were analyzed by extracting the seismic noise values from the web services (INGVWS) of the National Earthquake Observatory (ONT) INGV (http://webservices.ingv.it).
The Signal / Noise ratio (S / N) is a parameter for assessing the quality of the seismic data in relation to the possibility of detecting the phases of earthquakes useful for their location. The signal is represented by the seismic event, which is a rare transient when seismic sequences are not in progress. Using high-performance seismic equipment, the noise is represented by the ambient seismic noise, which is detected in the form of vibrations imperceptible by humans. In cases where the dynamics of the instrument is restricted and its intrinsic noise is high, the seismic ambient noise cannot be detected, information relating to the medium crossed from the source to measurement point is lost and its variations cannot be revealed.
Ambient seismic noise is a stochastic process from which stationary characteristics can be extracted, related to natural or anthropic sources that generally occur at different frequencies. Rapid vibrations with cycles below one second are well documented in the literature and are generally linked to anthropogenic activities, caused by industrial plants, domestic appliances, vehicular traffic and any transfer of energy to the ground that propagates seismic waves (Peterson, 1993; McNamara and Buland, 2004).
The restrictive measures issued by the Italian Government in year 2020 due to the contagion from COVID-19 (http://www.governo.it/it/coronavirus-normativa) have significantly reduced the sources of cultural seismic noise that transmit seismic waves into the ground, which are not perceived by people but only detectable by seismic instruments.
In Italy, the territory is monitored in real time and continuously by the National Seismic Network (RSN) of the National Institute of Geophysics and Volcanology (INGV Seismological Data Center, 2006). Some works show how it is possible to characterize the variability of seismic noise on the national territory, identifying the origin and nature of seismic waves of background vibrations (Marzorati and Bindi, 2006; Marzorati, 2007; Marzorati and Bindi, 2008; Li et al., 2010 ; Vassallo et al., 2012).
This report shows the reduction of the average levels of seismic noise in the frequency range between 2 and 8 Hz, so as to be able to exclude natural sources at lower frequency and to analyze signals that have the ability to propagate at significant distances from the sources, in order to reach seismic stations located in large italian cities or in their surroundings.
The seismic data of seismic stations of the RSN were analyzed by extracting the seismic noise values from the web services (INGVWS) of the National Earthquake Observatory (ONT) INGV (http://webservices.ingv.it).
References
INGV Seismological Data Centre. (2006, January 1). Rete Sismica Nazionale (RSN). Istituto Nazionale di Geofisica e Vulcanologia (INGV), Italy. https://doi.org/10.13127/SD/X0FXNH7QFY
Li H., Bernardi F., Michelini A. (2010), Surface wave dispersion measurements from ambient seismic noise analysis in Italy, Geophys. J. Int., 180, 1242–1252, doi: 10.1111/j.1365-246X.2009.04476.x
Marzorati S. (2007), Fenomenologia del Noise Sismico Ambientale: dalla conoscenza del segnale alle applicazioni empiriche, Tesi di dottorato, hdl.handle.net/2122/7960
Marzorati S. and Bindi D. (2006), Ambient Noise Levels in North Central Italy, Geochem. Geophys. Geosyst., 7, doi:10.1029/2006GC001256.
Marzorati S. and Bindi D. (2008), Characteristics of ambient noise cross correlations in northern Italy within the frequency range of 0.1-0.6 Hz, Bull. seism. Soc. Am., 98, 1389–1398
Marzorati S. e Cattaneo M. (2016), Stima automatica della magnitudo minima rilevabile dalla rete sismica ReSIICO, Quaderni di Geofisica, 136, http://editoria.rm.ingv.it/quaderni/2016/quaderno136
McNamara D. E. and Buland R.P. (2004), Ambient Noise Levels in the Continental United States, Bull. Seismol. Soc. Am. 94, 4, 1517–1527
Peterson J. (1993), Observation and modeling of seismic background noise, U.S. Geol. Surv. Open-File Rept. 93-322, 94 pp.
Vassallo M., Festa G., Bobbio A. (2012), Seismic Ambient Noise Analysis in Southern Italy, Bulletin of the Seismological Society of America, 102, 2, pp. 574–586, doi: 10.1785/0120110018
Li H., Bernardi F., Michelini A. (2010), Surface wave dispersion measurements from ambient seismic noise analysis in Italy, Geophys. J. Int., 180, 1242–1252, doi: 10.1111/j.1365-246X.2009.04476.x
Marzorati S. (2007), Fenomenologia del Noise Sismico Ambientale: dalla conoscenza del segnale alle applicazioni empiriche, Tesi di dottorato, hdl.handle.net/2122/7960
Marzorati S. and Bindi D. (2006), Ambient Noise Levels in North Central Italy, Geochem. Geophys. Geosyst., 7, doi:10.1029/2006GC001256.
Marzorati S. and Bindi D. (2008), Characteristics of ambient noise cross correlations in northern Italy within the frequency range of 0.1-0.6 Hz, Bull. seism. Soc. Am., 98, 1389–1398
Marzorati S. e Cattaneo M. (2016), Stima automatica della magnitudo minima rilevabile dalla rete sismica ReSIICO, Quaderni di Geofisica, 136, http://editoria.rm.ingv.it/quaderni/2016/quaderno136
McNamara D. E. and Buland R.P. (2004), Ambient Noise Levels in the Continental United States, Bull. Seismol. Soc. Am. 94, 4, 1517–1527
Peterson J. (1993), Observation and modeling of seismic background noise, U.S. Geol. Surv. Open-File Rept. 93-322, 94 pp.
Vassallo M., Festa G., Bobbio A. (2012), Seismic Ambient Noise Analysis in Southern Italy, Bulletin of the Seismological Society of America, 102, 2, pp. 574–586, doi: 10.1785/0120110018
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