Find out the magnitude of earthquakes by observing the atmosphere!
A study, published in the journal Nature - Scientific Reports on January 24th 2018, and signed by Giovanni Occhipinti (from the Planetology and Space Sciences team, also a junior member of the Institut Universitaire de France) and two IPGP PhD students, Florent Aden-Antoniow and Aurélien Bablet, introduces a new magnitude, Mi (ionospheric magnitude), capable of transforming oscillations in the ionised layers of the upper atmosphere detected by CEA and ONERA radars into seismic information.
Charles Richter and the magnitude equation (photo montage).
Publication date: 26/01/2018
General public, Press, Research
Related teams :
Planetology and Space Sciences
Related themes : Natural Hazards
Following an earthquake, the atmosphere vibrates with the Earth. By understanding the physical properties of this vibration, it can be converted back into ground motion, transforming the radars into “atmospheric seismometers” that could in future cover ocean areas inaccessible to conventional seismometers and provide a better understanding of the Earth.
Introduced in 1935 by Charles Richter in order to standardise the measurements of 7 seismometers at the Southern California seismology laboratory in Pasadena, the ML magnitude was intended, at the time, simply to measure and estimate the local intensity of Californian seismic events (L for Local in ML). The local magnitude ML was extended the following year, in 1936, by Beno Guttemberg and Charles Richter, to the entire surface of the Earth, by introducing the magnitude MS – a magnitude estimated by measuring the surface waves (S for ‘surface wave’) generated by an earthquake and detectable even at a great distance from the epicentre.
Estimating the magnitude of an earthquake has evolved considerably over the history of seismology, but has always been limited to the use of seismic observations made at the Earth’s surface. With the ionospheric magnitude Mi, this limit has been crossed and the field of vision of seismology on Earth has been broadened (by adding the atmosphere), but also for other planets! Observing the atmosphere of Venus could provide information about the seismicity of the planet, whose surface conditions are too hostile for a seismometer to survive.
With the support of CNES and NASA, the IPGP is currently exploring and proposing ideas for satellites to probe the atmosphere of the Earth and Venus, thereby increasing the number of seismic observables and improving tsunami warnings.
Ref: Occhipinti, G., F. Aden-Antoniow, A. Bablet, T. Farges, J.-P. Molinie, Surface waves magnitude estimation from ionospheric signature of Rayleigh waves measured by Doppler sounder and OTH radar, Scientific Report. Published the 24th January 2018 – https://www.nature.com/articles/s41598-018-19305-1
