The impact of the COVID-19 lockdown measures on the seismic monitoring in the Bucharest (Romania) metropolitan area

2021 ◽  
Author(s):  
Bogdan Grecu ◽  
Alexandru Tiganescu ◽  
Natalia Poiata ◽  
Felix Borleanu ◽  
Raluca Dinescu ◽  
...  
Keyword(s):  
Frequency Band ◽  
Urban Areas ◽  
Seismic Noise ◽  
Free Field ◽  
Substantial Reduction ◽  
Urban Traffic ◽  
Ambient Seismic Noise ◽  
Mobility Data ◽  
Short Period ◽  
The Impact

<p>The lockdown measures taken to control and stop the spread of the novel coronavirus (COVID-19) in cities around the globe caused an unprecedented reduction of anthropic activities. The signature of this reduction, different from one place to another, has been captured by the seismic stations installed in the urban areas where lockdown restrictions have been implemented. Bucharest, the capital of Romania, was no exception from this phenomenon.</p><p>In this paper, we investigate the effect of the COVID-19 lockdown measures imposed by the Romanian authorities on the high-frequency ambient seismic noise (ASN) data recorded by the Bucharest Metropolitan Seismic Network (BMSN). BMSN consists of 26 stations of which 19 are equipped with strong motion sensors and 7 have both short-period velocity and accelerometer sensors. All the stations are continuously recording the ground motion and the data is sent in real-time to the data center of the National Institute for Earth Physics.         </p><p>The reduction of ASN was first observed at stations installed in educational units (kindergartens, schools) starting with 11th of March 2020, when the Romanian government decided to close the schools in Romania. For these stations, the largest reduction of ASN, up to 82%, was noticed in the 25-40 Hz frequency band. On 16th of March the state of emergency was imposed in Romania and a few days later, on 25th of March, the stay-at-home order was issued. These new restrictions caused substantial reduction in urban traffic and people’s mobility and reflected in significant reduction of ASN at almost all the other BMSN stations, located either free-field or in buildings. For these stations, we observed a decrease of the noise levels by as much as 66% in the 15-25 Hz frequency band. We also correlated the ambient seismic noise with other types of data that might be affected by human activity, such as the mobility data from Google and Apple, and we found good correlation between ASN in different frequency bands and various mobility data categories. Finally, we showed that the noise reduction due to lockdown measures improved the signal-to-noise ratio of the stations in the Bucharest area, allowing us to record smaller earthquakes which otherwise would not have been recorded.</p>

scholarly journals Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

Solid Earth ◽  
2017 ◽  
Vol 8 (2) ◽  
pp. 531-544 ◽  
Author(s):  
Nikita Afonin ◽  
Elena Kozlovskaya ◽  
Ilmo Kukkonen ◽  
Keyword(s):  
Seismic Noise ◽  
Ambient Seismic Noise ◽  
Seismic Events ◽  
S Wave ◽  
Noise Sources ◽  
Surface Wave Dispersion ◽  
Velocity Models ◽  
Wave Velocities ◽  
Short Period ◽  
Single Station

Abstract. Understanding the inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating the continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in the northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä postglacial fault (SPGF), which was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised an area of about 20 to 100 km and consisted of eight short-period and four broadband three-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September 2011–May 2013. Recordings of the array have being analysed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä gold mine. As a result, we found a number of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single-station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1–1 Hz and to calculate corresponding surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curve inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low-velocity region as a non-healed mechanically weak fault damage zone (FDZ) formed due to the last major earthquake that occurred after the last glaciation.

Variation in microseism power and direction of approach in northeast Greenland

1993 ◽  
Vol 83 (6) ◽  
pp. 1939-1958
Author(s):  
P. E. Harben ◽  
E. Hjortenberg
Keyword(s):  
Surface Waves ◽  
Power Density ◽  
Frequency Band ◽  
Seismic Noise ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Continental Margins ◽  
Greenland Sea ◽  
Seismic Stations ◽  
Short Period

Abstract Previous work on background noise at seismic stations in Greenland has shown minimum seismic noise in the winter months for frequencies around 1 Hz and maximum seismic noise in the winter months for periods around 6 sec. We have analyzed microseism data from three new digital seismic stations installed during the summer of 1991 in northeast Greenland at Nord, Daneborg, and Scoresbysund. We determined seasonal and station-to-station variations in spectral power density between August and December in the frequency band between 10 sec periods and 5-Hz frequencies. These variations are in agreement with previous studies at periods of 1 and 6 sec. During the summer months, all three stations recorded a minimum for the average spectral power density in the microseism band between 10- and 5-sec periods. From about 3-sec periods to at least 5-Hz frequencies, the average spectral power density is at a maximum during the summer at all three stations. Conversely, the winter months have a maximum in spectral power density between 10- and 5-sec periods and a minimum between about 3-sec periods and at least 5-Hz frequencies at all stations. Station-to-station average-spectral-power-density comparisons show that Nord and Daneborg are roughly comparable over most of the frequency band between 10-sec periods and at least 5-Hz frequencies. Scoresbysund has a systematically higher spectral power density between 8-sec periods and at least 5-Hz frequencies. Overall, Nord had the lowest background seismic noise, at some frequencies approaching the values of a low noise model. We determined average direction of approaches in the 8- to 4-sec period band for each station during the months of August and November; these determinations agreed with previous studies. The predominant average direction of approaches were: southwest for Nord, south for Daneborg, and southeast for Scoresbysund. Although the microseism amplitude is larger and the direction-of-approach scatter is smaller during the winter months at all three stations, the direction-of-approach mean is apparently independent of season. A large number of storms develop around Iceland and typically track northeast, giving rise to large amplitude microseisms at Scoresbysund but relatively small amplitude microseisms at Daneborg and no microseism activity at Nord. This complete lack of microseism energy at Nord (and to a lesser degree Daneborg) from known frequent microseism sources in the Greenland Sea is shown for one 5-day period in August 1991. Other studies have shown that thick sediments in the Atlantic Ocean's continental margins are responsible for the absence of short-period surface waves from mid-ocean ridge earthquakes that have paths traversing such continental margins. Thick sediments act to attenuate, scatter, and disperse short-period surface waves. Indirect evidence indicates that the northeast Greenland shelf has thick and variable sediment layers. Because the paths of surface waves to Nord (and to a lesser extent Daneborg) originating from typical storms in the Greenland Sea have long path lengths traversing the northeast Greenland shelf, we conclude that this is the likely explanation for the lack of southeast directions from Nord (and to a lesser degree Daneborg) in the observed microseism direction of approaches.

scholarly journals Nitrogen oxides concentration and emission change detection during COVID-19 restrictions in North India

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Prakhar Misra ◽  
Masayuki Takigawa ◽  
Pradeep Khatri ◽  
Surendra K. Dhaka ◽  
A. P. Dimri ◽  
...  
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Power Plants ◽  
Phase 1 ◽  
Substantial Reduction ◽  
North India ◽  
Nox Emissions ◽  
Top Down ◽  
Monitoring Instrument ◽  
The Impact

AbstractCOVID-19 related restrictions lowered particulate matter and trace gas concentrations across cities around the world, providing a natural opportunity to study effects of anthropogenic activities on emissions of air pollutants. In this paper, the impact of sudden suspension of human activities on air pollution was analyzed by studying the change in satellite retrieved NO2 concentrations and top-down NOx emission over the urban and rural areas around Delhi. NO2 was chosen for being the most indicative of emission intensity due to its short lifetime of the order of a few hours in the planetary boundary layer. We present a robust temporal comparison of Ozone Monitoring Instrument (OMI) retrieved NO2 column density during the lockdown with the counterfactual baseline concentrations, extrapolated from the long-term trend and seasonal cycle components of NO2 using observations during 2015 to 2019. NO2 concentration in the urban area of Delhi experienced an anomalous relative change ranging from 60.0% decline during the Phase 1 of lockdown (March 25–April 13, 2020) to 3.4% during the post-lockdown Phase 5. In contrast, we find no substantial reduction in NO2 concentrations over the rural areas. To segregate the impact of the lockdown from the meteorology, weekly top-down NOx emissions were estimated from high-resolution TROPOspheric Monitoring Instrument (TROPOMI) retrieved NO2 by accounting for horizontal advection derived from the steady state continuity equation. NOx emissions from urban Delhi and power plants exhibited a mean decline of 72.2% and 53.4% respectively in Phase 1 compared to the pre-lockdown business-as-usual phase. Emission estimates over urban areas and power-plants showed a good correlation with activity reports, suggesting the applicability of this approach for studying emission changes. A higher anomaly in emission estimates suggests that comparison of only concentration change, without accounting for the dynamical and photochemical conditions, may mislead evaluation of lockdown impact. Our results shall also have a broader impact for optimizing bottom-up emission inventories.

scholarly journals Changes in Air Quality Associated with Mobility Trends and Meteorological Conditions during COVID-19 Lockdown in Northern England, UK

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 504
Author(s):  
Said Munir ◽  
Gulnur Coskuner ◽  
Majeed Jassim ◽  
Yusuf Aina ◽  
Asad Ali ◽  
...  
Keyword(s):  
Air Quality ◽  
Urban Areas ◽  
Human Life ◽  
Additive Model ◽  
Positive Association ◽  
Air Pollutant ◽  
Back Trajectory ◽  
Generalised Additive Model ◽  
Mobility Data ◽  
The Impact

The COVID-19 pandemic triggered catastrophic impacts on human life, but at the same time demonstrated positive impacts on air quality. In this study, the impact of COVID-19 lockdown interventions on five major air pollutants during the pre-lockdown, lockdown, and post-lockdown periods is analysed in three urban areas in Northern England: Leeds, Sheffield, and Manchester. A Generalised Additive Model (GAM) was implemented to eliminate the effects of meteorological factors from air quality to understand the variations in air pollutant levels exclusively caused by reductions in emissions. Comparison of lockdown with pre-lockdown period exhibited noticeable reductions in concentrations of NO (56.68–74.16%), NO2 (18.06–47.15%), and NOx (35.81–56.52%) for measured data. However, PM10 and PM2.5 levels demonstrated positive gain during lockdown ranging from 21.96–62.00% and 36.24–80.31%, respectively. Comparison of lockdown period with the equivalent period in 2019 also showed reductions in air pollutant concentrations, ranging 43.31–69.75% for NO, 41.52–62.99% for NOx, 37.13–55.54% for NO2, 2.36–19.02% for PM10, and 29.93–40.26% for PM2.5. Back trajectory analysis was performed to show the air mass origin during the pre-lockdown and lockdown periods. Further, the analysis showed a positive association of mobility data with gaseous pollutants and a negative correlation with particulate matter.

scholarly journals Structure of Suasselkä Postglacial Fault in northern Finland obtained by analysis of local events and ambient seismic noise

2016 ◽  
Author(s):  
Nikita Afonin ◽  
Elena Kozlovskaya ◽  
Ilmo Kukkonen ◽  
DAFNE/FINLAND Working Group
Keyword(s):  
Seismic Noise ◽  
Dispersion Curves ◽  
Ambient Seismic Noise ◽  
Seismic Events ◽  
S Wave ◽  
Noise Sources ◽  
Velocity Models ◽  
Wave Velocities ◽  
Short Period ◽  
Single Station

Abstract. Understanding inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä post-glacial fault (SPGF) that was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised the area of about 20 to 100 km and consisted of 8 short-period and 4 broad-band 3-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September, 2011–May, 2013. Recordings of the array have being analyzed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä Gold Mine. As a result, we found several dozens of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green’s functions between pairs of stations in the frequency band of 0.1–1 Hz and to calculate correspondent surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curves inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low velocity region as a non-healed mechanically weak fault damage zone (FDZ) that remained after the last major earthquake that occurred after the last glaciation.

scholarly journals Predicting dengue outbreaks at neighbourhood level using human mobility in urban areas

2020 ◽  
Vol 17 (171) ◽  
pp. 20200691
Author(s):  
Rafael Bomfim ◽  
Sen Pei ◽  
Jeffrey Shaman ◽  
Teresa Yamana ◽  
Hernán A. Makse ◽  
...  
Keyword(s):  
Neural Networks ◽  
Dengue Virus ◽  
Urban Areas ◽  
Human Mobility ◽  
Mechanistic Models ◽  
Mobility Data ◽  
Dengue Transmission ◽  
Neighbourhood Level ◽  
Dengue Outbreaks ◽  
The Impact

Dengue is a vector-borne disease transmitted by the Aedes genus mosquito. It causes financial burdens on public health systems and considerable morbidity and mortality. Tropical regions in the Americas and Asia are the areas most affected by the virus. Fortaleza is a city with approximately 2.6 million inhabitants in northeastern Brazil that, during the recent decades, has been suffering from endemic dengue transmission, interspersed with larger epidemics. The objective of this paper is to study the impact of human mobility in urban areas on the spread of the dengue virus, and to test whether human mobility data can be used to improve predictions of dengue virus transmission at the neighbourhood level. We present two distinct forecasting systems for dengue transmission in Fortaleza: the first using artificial neural network methods and the second developed using a mechanistic model of disease transmission. We then present enhanced versions of the two forecasting systems that incorporate bus transportation data cataloguing movement among 119 neighbourhoods in Fortaleza. Each forecasting system was used to perform retrospective forecasts for historical dengue outbreaks from 2007 to 2015. Results show that both artificial neural networks and mechanistic models can accurately forecast dengue cases, and that the inclusion of human mobility data substantially improves the performance of both forecasting systems. While the mechanistic models perform better in capturing seasons with large-scale outbreaks, the neural networks more accurately forecast outbreak peak timing, peak intensity and annual dengue time series. These results have two practical implications: they support the creation of public policies from the use of the models created here to combat the disease and help to understand the impact of urban mobility on the epidemic in large cities.

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

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ketan Singha Roy ◽  
Jyoti Sharma ◽  
Santosh Kumar ◽  
M. Ravi Kumar
Keyword(s):  
Urban Areas ◽  
Seismic Noise ◽  
Anthropogenic Activities ◽  
Anthropogenic Activity ◽  
Noise Levels ◽  
Geological Conditions ◽  
Northwest India ◽  
Almost All ◽  
Cultural Noise ◽  
The Impact

AbstractThe Covid-19 pandemic created havoc and forced lockdowns in almost all the countries worldwide, to inhibit social spreading. In India as well, as a precautionary measure, complete and partial lockdowns were announced in phases during March 25 to May 31, 2020. The restricted human activities led to a drastic reduction in seismic background noise in the high frequency range of 1–20 Hz, representative of cultural noise. In this study, we analyse the effect of anthropogenic activity on the Earth vibrations, utilizing ambient noise recorded at twelve broadband seismographs installed in different environmental and geological conditions in Gujarat. We find that the lockdowns caused 1–19 dB decrease in seismic noise levels. The impact of restricted anthropogenic activities is predominantly visible during the daytime in urban areas, in the vicinity of industries and/or highways. A 27–79% reduction in seismic noise ground displacement (drms) is observed in daytime during the lockdown, in populated areas. However, data from station MOR reveals a drastic decrease in drms amplitude both during the day (79%) and night times (87%) since factories in this area operate round the clock. The noise at stations located in remote areas and that due to microseisms, shows negligible variation.

scholarly journals GIS-Based Survey over the Public Transport Strategy: An Instrument for Economic and Sustainable Urban Traffic Planning

2021 ◽  
Vol 11 (1) ◽  
pp. 16
Author(s):  
Gabriela Droj ◽  
Laurențiu Droj ◽  
Ana-Cornelia Badea
Keyword(s):  
Network Analysis ◽  
Public Transport ◽  
Public Transportation ◽  
Traffic Congestion ◽  
Urban Areas ◽  
Traffic Accidents ◽  
Urban Traffic ◽  
The Public ◽  
Real Time Traffic ◽  
The Impact

Traffic has a direct impact on local and regional economies, on pollution levels and is also a major source of discomfort and frustration for the public who have to deal with congestion, accidents or detours due to road works or accidents. Congestion in urban areas is a common phenomenon nowadays, as the main arteries of cities become congested during peak hours or when there are additional constraints such as traffic accidents and road works that slow down traffic on road sections. When traffic increases, it is observed that some roads are predisposed to congestion, while others are not. It is evident that both congestion and urban traffic itself are influenced by several factors represented by complex geospatial data and the spatial relationships between them. In this paper were integrated mathematical models, real time traffic data with network analysis and simulation procedures in order to analyze the public transportation in Oradea and the impact on urban traffic. A mathematical model was also adapted to simulate the travel choices of the population of the city and of the surrounding villages. Based on the network analysis, traffic analysis and on the traveling simulation, the elements generating traffic congestion in the inner city can be easily determined. The results of the case study are emphasizing that diminishing the traffic and its effects can be obtained by improving either the public transport density or its accessibility.

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