COVID-19 pandemic causes seismic noise quiet period in 2020
Research published in the journal Science has shown that lockdown measures to combat the spread of COVID-19 led to a 50% reduction in seismic noise observed around the world in early to mid 2020.
Seismic noise is measure by seismometers. These are sensitive scientific instruments to record vibrations travelling through the ground – known as seismic waves. Traditionally, seismology focuses on measuring seismic waves arising after earthquakes. Seismic records from natural sources however are contaminated by high-frequency vibrations (“buzz”) from humans at the surface – walking around, driving cars, public transport, heavy industry and construction work all create unique seismic signatures in the subsurface that are recorded on seismometers. The buzz is stronger during the day than at night and weaker on weekends than weekdays.
The year of silence
By comparing lockdown seismic noise to months-to-years long datasets from over 300 seismic stations around the world, the study was able to show the seismic noise reduced in many countries and regions, making it possible to visualise the resulting “wave” moving through China, then to Italy, and around the rest of the world. The seismic lockdown sees the total effect of physical/social distancing measures, reduced economic and industrial activity and drops in tourism and travel. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record.
While 2020 has not seen a reduction in earthquakes, the drop in the anthropogenic “buzz” has been unprecedented. The strongest seismic noise reductions were found in urban areas, but the study also found signatures of the lockdown on sensors buried hundreds of metres into the ground. Not only in densely populated areas, but also in more remote areas, such as in Sub-Saharan Africa, a noise reduction was observed.
The study found a strong match between seismic noise reductions and human mobility datasets drawn from mapping apps on mobile phones and made publicly available by Google and Apple. This correlation allows open seismic data to be used as a broad proxy for tracking human activity in near-real-time, and to understand the effects of pandemic lockdowns and recoveries without impinging on potential privacy issues.
The environmental effects of the pandemic lockdowns are wide and varied, including reduced emissions in the atmosphere and reduced traffic and noise pollution impacting wildlife. This period of time has been coined “anthropause”. This new study is the first global study of the impact of the anthropause on the solid Earth beneath our feet.
The study was spawned after the lead author, seismologist Dr. Thomas Lecocq of the Royal Observatory of Belgium, decided that the best way to tackle the problem of analysing data from all around the globe was to share his method with the seismological community. This started a unique collaboration involving 76 authors from 66 institutions in 27 countries.
There are many thousands of seismic monitoring stations around the world, and it took a team effort to download, process, and analyse the many terabytes of data available. Data came from high-end seismic monitoring networks, as well as citizen seismic sensors which individuals and schools have installed themselves, sharing data to a global community.
Seismologists Thomas Lecocq and Koen Van Noten of the Royal Observatory of Belgium led this study. The seismometer data of the Uccle station UCCS was at the origin of the study. They contributed by including seismometer data of the Belgian national seismic network in the study. Benoît Fauville of Brussels Environment participated with audible data from microphones installed in Brussels. The sound drop in the audible data during lockdown (i.e. a quieter city) correlated with the noise drop.
Importance of the study
Will the 2020 seismic noise quiet period allow new types of signals to be detected? The study has shown the first evidence that previously concealed earthquake signals, especially during daytime, appeared much clearer on seismic sensors in urban areas during lockdown. The study’s authors hope that their work will spawn further research on the seismic lockdown. Finding previously hidden signals from earthquakes and volcanoes will be one key aim.
With growing urbanisation and increasing populations globally, more people will be living in geologically hazardous areas. Therefore it will become more important than ever to characterise the anthropogenic noise humans cause so that seismologists can better listen to the Earth, especially in cities, and monitor the ground movements beneath our feet.
T. Lecocq et al., Global quieting of high-frequency seismic noise due to COVID-19 pandemic lockdown measures. Science (2020).
Main contact and contact for French press (first & corresponding author of the paper, available for English and French comments): Thomas Lecocq (thomas.lecocq AT seismology.be), Royal Observatory of Belgium.
Contact for Dutch press: Koen Van Noten (koen.vannoten AT seismology.be), Royal Observatory of Belgium.
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Visualisations: see in the link to the Science paper
- Figure 1 – showing the global seismic stations analysed in the dataset.
- Figure 2 – showing the global noise reduction affect
- Movie – available to download here – seismic lockdown animation movie.
Main authors’ institutions
- Seismology-Gravimetry, Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium
- Department of Earth Science and Engineering, Imperial College London, London, United Kingdom
- Department of Physics, University of Auckland, New-Zealand
- Department of Earth Sciences, Royal Holloway University of London, Egham, United Kingdom
- Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, Mexico
Full list of coauthors’ institutions
Royal Observatory of Belgium, Belgium.
Imperial College London, UK.
University of Auckland, New-Zealand.
Royal Holloway University of London, UK.
Universidad Nacional Autónoma, Mexico.
Swiss Seismological Service, Switzerland.
University of Helsinki, Finland.
U.S. Geological Survey, US.
Zentralanstalt für Meteorologie und Geodynamik, Austria.
Universidad de Costa Rica, Costa Rica.
Royal Netherlands Meteorological Institute, Netherlands.
Boğaziçi University, Turkey.
GFZ Research Centre for Geosciences, Germany.
Università Degli Studi di Catania, Italy.
Istituto Nazionale di Geofisica e Vulcanologia, Italy.
University of Cologne, Germany.
Univ. Savoie Mont Blanc, France.
Volcanological & Seismological Observatory of Costa Rica.
University of Aberdeen, UK.
Dublin Institute for Advanced Studies, Ireland.
Delft University of Technology, Netherlands.
National Observatory of Athens, Greece.
Brussels Environment, Belgium.
Observatorio San Calixto, Bolivia.
Seismotech S.A., Greece.
Hellenic Mediterranean University, Greece.
Norges Geotekniske Institutt, Norway.
University of Alaska Fairbanks, US.
National Institute for Earth Physics, Romania.
Université de Strasbourg, France.
University of Lausanne, Switzerland.
University of Bristol, UK.
Instituto Geofisico del Peru.
Princeton University, US.
University of Tehran, Iran.
Boston College, US.
California Institute of Technology, US.
Stanford University, US.
SETI Institute, US.
University of British Columbia, Canada.
Ludwig-Maximilians-Universität München, Germany.
Australian National University, Australia.
McGill University, Canada.
GEOTOP Research Centre, Canada.
Raspberry Shake, Panama.
University of Maine, US.
University of California Riverside, US.
Universidad de Chile.
European Center for Geodynamics & Seismology, Luxembourg.
Raytheon BBN Technologies, US.
Université de Paris, France.
Observatoire Volcanologique du Piton de la Fournaise, France.
Victoria University of Wellington, New Zealand.
University of Patras, Greece.
University of Bergen, Norway.
University of California Berkeley, US.
Institut d’Estudis Catalans (LEGEF-IEC), Spain.
University of Michigan, US.
Truro School, UK.
IPG Strasbourg, France.
University of Oxford, UK.
University of California, US.