The Quarantine as seen by the IPGP seismometer
The seismometer installed in the basement of the IPGP's Pavillon Curie has recorded the "signature" of human activity since the beginning of March, and its evolution since the containment was put in place.
Publication date: 08/04/2020
General public, Press
Long intended simply to record earthquakes, seismometers are now used to pick up all kinds of vibrations, whether related to an earthquake, ocean storms, wind in trees or even human activity.
The most accurate seismometers are so-called ‘broadband’ instruments, which can detect a wide range of signals. One of these devices, part of the Résif-RLBP national network, has been in operation since the beginning of 2020 in the basement of the Curie1 building at the Institut de Physique du Globe in Paris.
This seismometer, known as the “CURIE station”, continuously records displacements in the Paris subsoil, with an accuracy of the order of one nanometre2 (one millionth of a millimetre). The signal recorded is known as “seismic noise” if no major event such as an earthquake is detected.
The seismologists in charge of this station have analysed the evolution of seismic noise recordings since the beginning of March in the figure below (click to enlarge).
This figure shows the evolution of high-frequency noise (4-14 Hz) recorded by the CURIE station from 1 March to 5 April. This frequency band is particularly sensitive to human activity in and around the IPGP, particularly car, bus and metro traffic.
The recording shows a spectacular reduction in high-frequency noise from 12 noon on 17 March, when containment measures were put in place following the COVID-19 epidemic. There was a further slight drop from 26 March, when public transport in Paris was drastically reduced.
The human origin of this noise and its evolution can be confirmed by several clues:
- The day-night alternation of the signal.
- A slight drop in noise during the lunch break.
Before confinement:
- Daytime noise is higher during the week (grey bands) than at weekends.
- Night-time noise was higher at weekends than on other days of the week (reflecting the neighbourhood’s night-time life).
From the implementation of the confinement :
- Much less difference between weekdays and weekends.
- Reduction in daytime and night-time noise from 26 March, following the reduction in public transport.
The sharp reduction in seismic noise at this station clearly shows the effect of confinement on human activity at the IPGP and more generally in the capital (scientific instrumentation at the IPGP, traffic in the area, metro, etc.).
#RestezChezVous !
Ref:
1- Building used by Marie Curie from 1906 to 1914 for her radium research and now part of the IPGP’s Cuvier site.
2- The thickness of a human hair is around 100,000 nanometres!
Further reading
- Pascal Bernard, Pourquoi la terre tremble, Éditions Belin, 2017
