We present the framework of the modeling package IonoSeis. This software models Global Navigation Satellite System (GNSS) derived slant total electron content (sTEC) perturbations in the ionosphere due to the interaction of the neutral atmosphere and charged particles in the ionosphere. We use a simplified model to couple the neutral particle momentum into the ionosphere and reconstruct time series of sTEC perturbations that match observed data in both arrival time and perturbation shape. We propagate neutral atmosphere disturbances to ionospheric heights using a three-dimensional ray-tracing code in spherical coordinates called Windy Atmospheric Sonic Propagation (WASP3D), which works for a stationary or non-stationary atmospheric models. The source of the atmosphere perturbation can be an earthquake or volcanic eruption; both couple significant amounts of energy into the atmosphere in the frequency range of a few Millihertz. We demonstrate the output of the code by comparing modeled sTEC perturbation data to the observed perturbation recorded at GNSS station BTNG (Bitung, Indonesia) immediately following the 28 September 2018, Sulawesi-Palu earthquake. With this framework, we provide a software to couple the lithosphere, atmosphere, and ionosphere that can be used to study post-seismic ionospherically-derived signals.

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<p>The third-largest earthquake of this 21st century ruptured the Andes subduction zone offshore of the Maule region in central Chile on 27 February 2010, in the middle of the night (3:35 am local time). This huge event triggered strong and destructive seismic motions accompanied by a devastating local tsunami and a significant transpacific tsunami. We investigate the impact of this earthquake on the ionosphere using Global Positioning System (GPS) satellites and other Global Navigation Satellite System (GNSS) data. Investigations related to ionospheric disturbances induced by mega-earthquakes accelerated with the Mw9.0 Tohoku earthquake of March 2011. The worldwide GNSS network, including the exceptionally dense Japanese GNSS network, observed a complex ionospheric response. With a better understanding of the physical mechanisms behind it and a more exhaustive data collection, we revisit the ionospheric wavefield triggered by the Mw8.8 Chile earthquake and tsunami.</p><p>When a large underwater earthquake occurs, the sudden shaking of an extended region of the sea-floor immediately transfers energy to the water column and the air above through an efficient solid-ocean-atmosphere coupling mechanism. The earthquake at depth thus excites seismic and tsunami waves in the ocean and acoustic-gravity waves in the atmosphere. In the lower frequency range (< 20 mHz), these atmospheric waves can propagate to the upper atmosphere, which shakes the ionosphere. During propagation in the rarefying atmosphere, the wave amplitude drastically increases by about four orders of magnitude. Typically, a tsunami with a height of the order of a meter in an open ocean puts the ionosphere into motion with peak displacement exceeding a kilometer at about 200 km of altitude. The shaken charged particles of the ionosphere plasma eventually induce fluctuations of propagation delays in radio signals, such as those emitted by GPS and GNSS satellites. We convert GNSS measurements into Total Electron Content (TEC) variations to study the ionospheric imprint.</p><p>We revisit the Maule earthquake with an in-depth analysis of the TEC data derived from a worldwide collection of GNSS records. We also compare the observed ionospheric responses to ground or ocean motions derived from high-frequency GNSS receiver data recorded onshore and offshore. Doing so, we further characterize the filtering effect of the atmosphere on acoustic-gravity waves driven from the Earth’s surface. Finally, we use numerical tools specifically developed to investigate the complex seismo-ionospheric wavefield triggered by large seismic ruptures. We focus on the resonant part of the seismo-acoustic response and the tsunami-induced ionospheric response and link them to waveguides in the solid-ocean-atmosphere system. This revisit intends ultimately to shed new and independent light on the 2010 Maule mega-earthquake rupture itself.</p>