Ionospheric response to earthquakes of different magnitudes: Larger quakes perturb the ionosphere stronger and longer

Recently, it has been shown that the ionosphere is capable of showing images of seismic fault shortly after an earthquake. This gives rise to the idea of retrieval of seismic information from ionospheric observations. As the first step toward such inversion, here we study distinctive features of ionospheric response to shallow earthquakes, both submarine and inland, of moment magnitudes Mw7.2-9.1. Using GPS measurements of the ionospheric total electron content, we show that: (1) the amplitude of coseismic total electron content variations in the near-field is larger after more powerful earthquakes, and (2) stronger earthquakes (M>7.9) are in general characterized by a longer negative phase in coseismic perturbations.