NH32C-01
Ionospheric seismology: The last step before true contributions to seismology?
Abstract:
Ionospheric seismology, which was at most seen as an exotic way to record doubtful signals in the early 2000 has gain maturity, especially after the worldwide observations made during the Tohoku 2011 earthquake and tsunami. The last steps for important contributions in seismology will request however these data to be modeled and inverted in a way precise enough for new and original constraints on the seismic sources, amplitude of tsunamis and atmospheric/interior seismic/acoustic velocities profiles.Ionospheric observations are now able to provide time depending maps of the ionospheric waves, enabling the location of the sources, measurement of the wave speed and amplitude, for both acoustic waves above or close the epicenter or remotely observed Rayleigh and Tsunami waves. Are these data good enough for inversions? Are the modelling techniques good enought for inversions?
We therefore first compare and illustrate the different observation techniques: ground, air-based and space-based GPS and airglow, focusing on the Tohoku 2011 and Haida Gwai earthquake and tsunamis, discuss the physics enabling the conversion of seismic waves into electron perturbation (for GPS data) and light emission (for airglow) and signal to noise issues.
Comparison between data and waveforms modelling are then shown by using either Normal Mode summations for remote detections or Spectral Element techniques for local detections, with an emphasis in the later case on non-linear effects and TEC post-seismic depletions. A special attention is made on the sensitivity of the waveforms to the various parameters of the models, including the sensitivity of the conversion of the seismic to atmospheric signals with the atmosphere structure, the crust subsurface and the ocean thickness and the sensitivity of the conversion of the atmospheric to ionospheric signal with respect to local time, ionospheric state and magnetic latitude.
We then present the perspectives in term of inversion for both the source location, early estimation of the maximum uplift generated by oceanic mega Earthquakes and the remote observations of tsunami and discuss the limitation of ionospheric seismology for future near real time measurement of the ocean vertical displacement associated to tsunami. Some directions on the future needs are given in conclusion.