No Magnitude, No Glory !!

Abstract:

Surface waves emitted after large earthquakes are known to induce, by

dynamic coupling, atmospheric infrasonic waves propagating upward

through the neutral and ionized atmosphere. Those waves have been

detected in the past at ionospheric heights using a variety of techniques,

such as HF Doppler sounding or GPS receivers. The HF Doppler

technique, particularly sensitive to the ionospheric signature of Rayleigh

waves is used here to show ionospheric perturbations consistent with the

propagation of Rayleigh wave phases R1 and R2 following the Sumatra

earthquake on the 28 March 2005 (M = 8.6). This is in our knowledge

the first time that the phase R2 is detected by ionospheric sounding.

In addition, we prove here that the ionospheric signature of R2 is also

observed by over‐the‐horizon (OTH) Radar (Occhipinti et al., 2010).

Adding the OTH Radar to the list of the “ionospheric seismometers” we

finally introduce the ionospheric magnitude and we apply it to 65 events

observed by “ionospheric seismometers”.