Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet

Abstract In this paper, we analyse the seismic noise at Ischia Island (Italy) with the objective of detecting the hydrothermal source signals taking advantage of the Covid-19 quiescence due to lockdown (strong reduction of anthropogenic noise). We compare the characteristics of the background noise...

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Autores principales:	Mariarosaria Falanga, Paola Cusano, Enza De Lauro, Simona Petrosino
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/af1da54722f94a99902e11bfda5cd747
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spelling	oai:doaj.org-article:af1da54722f94a99902e11bfda5cd7472021-12-02T15:27:05ZPicking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet10.1038/s41598-021-88266-92045-2322https://doaj.org/article/af1da54722f94a99902e11bfda5cd7472021-04-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-88266-9https://doaj.org/toc/2045-2322Abstract In this paper, we analyse the seismic noise at Ischia Island (Italy) with the objective of detecting the hydrothermal source signals taking advantage of the Covid-19 quiescence due to lockdown (strong reduction of anthropogenic noise). We compare the characteristics of the background noise in pre-, during and post-lockdown in terms of spectral content, energy release (RMS) and statistical moments. The continuous noise is decomposed into two independent signals in the 1−2 Hz and 2−4 Hz frequency bands, becoming sharpened around 1 Hz and 3 Hz respectively in lockdown. We propose a conceptual model according to which a dendritic system of fluid-permeated fractures plays as neighbour closed organ pipes, for which the fundamental mode provides the persistent whisper and the first higher mode is activated in concomitance with energy increases. By assuming reasonable values for the sound speed in low vapor–liquid mass fraction for a two-phase fluid and considering temperatures and pressures of the shallow aquifer fed by sea, meteoric and deep hydrothermal fluids, we estimate pipe lengths in the range 200–300 m. In this scheme, Ischia organ-like system can play both continuous whisper and transients, depending on the energy variations sourced by pressure fluctuations in the hydrothermal fluids.Mariarosaria FalangaPaola CusanoEnza De LauroSimona PetrosinoNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-11 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Mariarosaria Falanga Paola Cusano Enza De Lauro Simona Petrosino Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet
description	Abstract In this paper, we analyse the seismic noise at Ischia Island (Italy) with the objective of detecting the hydrothermal source signals taking advantage of the Covid-19 quiescence due to lockdown (strong reduction of anthropogenic noise). We compare the characteristics of the background noise in pre-, during and post-lockdown in terms of spectral content, energy release (RMS) and statistical moments. The continuous noise is decomposed into two independent signals in the 1−2 Hz and 2−4 Hz frequency bands, becoming sharpened around 1 Hz and 3 Hz respectively in lockdown. We propose a conceptual model according to which a dendritic system of fluid-permeated fractures plays as neighbour closed organ pipes, for which the fundamental mode provides the persistent whisper and the first higher mode is activated in concomitance with energy increases. By assuming reasonable values for the sound speed in low vapor–liquid mass fraction for a two-phase fluid and considering temperatures and pressures of the shallow aquifer fed by sea, meteoric and deep hydrothermal fluids, we estimate pipe lengths in the range 200–300 m. In this scheme, Ischia organ-like system can play both continuous whisper and transients, depending on the energy variations sourced by pressure fluctuations in the hydrothermal fluids.
format	article
author	Mariarosaria Falanga Paola Cusano Enza De Lauro Simona Petrosino
author_facet	Mariarosaria Falanga Paola Cusano Enza De Lauro Simona Petrosino
author_sort	Mariarosaria Falanga
title	Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet
title_short	Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet
title_full	Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet
title_fullStr	Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet
title_full_unstemmed	Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet
title_sort	picking up the hydrothermal whisper at ischia island in the covid-19 lockdown quiet
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/af1da54722f94a99902e11bfda5cd747
work_keys_str_mv	AT mariarosariafalanga pickingupthehydrothermalwhisperatischiaislandinthecovid19lockdownquiet AT paolacusano pickingupthehydrothermalwhisperatischiaislandinthecovid19lockdownquiet AT enzadelauro pickingupthehydrothermalwhisperatischiaislandinthecovid19lockdownquiet AT simonapetrosino pickingupthehydrothermalwhisperatischiaislandinthecovid19lockdownquiet
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Picking up the hydrothermal whisper at Ischia Island in the Covid-19 lockdown quiet

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