Effect of coronavirus lockdowns on the ambient seismic noise levels in Gujarat, northwest India

Roy, Ketan Singha; Sharma, Jyoti; Kumar, Santosh; Kumar, M. Ravi

doi:10.1038/s41598-021-86557-9

Cited by 12 publications

(13 citation statements)

References 25 publications

(39 reference statements)

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“…Schippkus et al (2020) used the large-N arrays in the Vienna Basin to collect environmental noise signals and analyzed the characteristics of urban environmental noise, including the railway track, windmills and oil pumpjacks. Through the ambient noise analysis, researchers monitored the changes of the urban traffic and human activities during the lockdown due to COVID-19 pandemic (Lecocq et al 2020;Roy et al 2021;Kuponiyi et al 2021). Monitoring traffic activity can also provide information for urban construction and management (e.g., Li et al 2016b).…”

Section: Introductionmentioning

confidence: 99%

Sensing Shallow Structure and Traffic Noise with Fiber-optic Internet Cables in an Urban Area

et al. 2021

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Distributed acoustic sensing (DAS) is a novel seismic observation system developed in recent years that can realize ultrahigh density observations and has attracted extensive attention in the field of seismology. DAS uses fiber-optic cables as sensing units, which are easy to incorporate with urban telecommunication fiber-optic cables for seismological observations. Compared with seismometers, DAS has the advantages of being rapidly deployed and recyclable, being able to acquire dense observations at low cost, and convenient data collection. In this study, a 5.2 km long telecom fiber-optic internet cable was utilized as a DAS array in an urban area to record ambient noise, and the noise cross-correlation function (NCF) was calculated. There are two different distribution types of ambient noise sources along the cable, regular along-road trucks (Taihe Road) and complex ambient noise, including human activities and traffic sources along and across the Jinniu road. In the first case, we constructed a 2D S-wave velocity model down to 100 m depth and a low-velocity zone was revealed. The S-wave model well explained the traffic signal along the Taihe road and the low-velocity zone is also consistent with the results obtained from co-located geophone arrays. In the second case, due to the complexity of the traffic noise distribution, empirical Green's functions were barely achieved. Therefore, we performed a synthetic test obtaining different NCFs with different source distributions, and two specific cases that dominate the NCF results were matched. Finally, we obtained the traffic noise distribution along the road, which is consistent with the power spectra density of the ambient noise. In conclusion, by combining DAS and urban fiber-optic internet cables with urban traffic noise, we can effectively reveal the traffic activities and image shallow structures with high resolution, which could offer a reference for urban construction and disaster prevention. Keywords Distributed acoustic sensing • Urban area • Ambient noise tomography • Ambient noise source distribution Article Highlights• DAS turns the urban fiber-optic internet cables into ultra-dense permanent seismic observation arrays • We revealed a high-resolution shallow structure using urban fiber-optic internet cables • We obtained the distribution of traffic activities along the road

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Section: Introductionmentioning

confidence: 99%

Sensing Shallow Structure and Traffic Noise with Fiber-optic Internet Cables in an Urban Area

et al. 2021

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“…Previous studies showed that during the COVID-19 lockdown there was decrease in noise levels due to the reduction of humanrelated activities, and as recorded by both broadband (Poli et al, 2020;Xiao et al, 2020;Lecocq et al, 2020;Somala, 2020;Dias et al, 2020;Roy et al, 2021;Grecu et al, 2021;Cannata et al, 2021) and strong motion (Yabe et al, 2020;Łukasz Ścisło et al, 2021) stations. These activities were affecting our stations more significantly since several of the RAN stations are located inside or near to the public buildings.…”

Section: Covid-19 Lockdownmentioning

confidence: 94%

Seismic Background Noise Levels in Italian Strong Motion Network

Fornasari

Ertuncay

Costa

2022

Preprint

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Abstract. Italian strong motion network monitors the seismic activity of Italy and its surrounding with more than 700 stations. Thanks to the upgrade of the stations with continuous data acquisition, it is possible to measure the noise level of the strong motion network. In this study, we used the recorded background noise to estimate the variations in the noise levels of the network. Data recorded in 2019 and 1st of January to 30th of April 2022 are used to understand the noise level of the stations and data from the COVID-19 lockdown period are used to see the effect of the anthropogenic sources on the background noise. To do that, power spectrum density is calculated for the continuous stations. It is found that more than half of the stations exceed the background noise model designed for strong motion stations by Cauzzi and Clinton (2013) in at least one of the calculated periods. Considering the characteristics of the instrumentation at the stations and their deployment often near urban areas, we focused on relatively short periods (≤5 s), interested by anthropic noises. Stations can be noisier during the day, up to 14 decibels and during the weekday, up to 5 decibels in short periods. Noise level differences between day-night decrease with an increasing period as the human-related high-frequency effects of humans are attenuated. As expected, the noisiest stations are located in densely populated areas such as center of Naples, whereas the quietest stations are located far away from cities. The swell, sea, and wind effects, on the other hand, are not observed in stations. During the COVID-19 lockdown, noise levels dropped to 6.5 decibels in daytime and 12.5 decibels on weekdays. Noise levels are reduced by around 2 decibels in 0.1 s, in which cultural noise is predominant. Furthermore, we found that the vehicles have measurable effects on noise levels.

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“…In these countries, the government adopted a strict lockdown with a total ban on all non-essential movements. Wherever it has been adopted, this measure caused a net reduction of the seismic noise (e.g., Xiao et al [11], Yabe et al [14], Roy et al [16]) including the countries considered here [13,18]. Thus, for each one of the three countries we consider the earthquakes occurred in a time period across the adoption of the lockdown decree.…”

Section: Methodsmentioning

confidence: 99%

“…After the emergency of the COVID-19, many governments worldwide have adopted some restrictions that, in most cases, caused the reduction of anthropogenic noise. In princi-ple, this reduction implies the increase in the detection capability of smaller events [11][12][13][14][15][16] and, in turn, a net decrease of m c would be expected. However, to our knowledge, the greater part of papers focused on the noise analysis and on the improvement of earthquakes detectability.…”

Section: Introductionmentioning

confidence: 99%

The Signal to Noise Ratio and the Completeness Magnitude: The Effect of the COVID-19 Lockdown

2021

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We analyse the earthquakes catalogues for Italy, South California, and Greece across the COVID-19 lockdown period for each country. The results for Italy and Greece show that, even if the reduction of the signal to noise ratio has improved the earthquake detection capability, the completeness magnitude remains substantially unchanged, making the improved detection capability ineffective from the statistical point of view. A slight reduction (0.2) of the completeness magnitude is observed for South California, likely related to the relatively higher number of seismic stations located close to urban areas. Our findings suggest that—given the present configuration of the seismic network considered here—only an important decrease in the station spacing can produce a significant decrease of the completeness magnitude.

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Effect of coronavirus lockdowns on the ambient seismic noise levels in Gujarat, northwest India

Cited by 12 publications

References 25 publications

Sensing Shallow Structure and Traffic Noise with Fiber-optic Internet Cables in an Urban Area

Sensing Shallow Structure and Traffic Noise with Fiber-optic Internet Cables in an Urban Area

Seismic Background Noise Levels in Italian Strong Motion Network

The Signal to Noise Ratio and the Completeness Magnitude: The Effect of the COVID-19 Lockdown

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