| Abstract Submission No. | ABS-3.1-0163 |
| Title of Abstract | Characterization of the Rayleigh Surface WaCharacterization of the Rayleigh Surface Waves from Ionospheric Observations during the Mw 9.1 Tohoku-Oki Earthquakeves from Ionospheric Observations during the Mw 9.1 Tohoku-Oki Earthquake |
| Authors | SUNIL SAINI*, MALA S. BAGIYA, PRATHMESH TARI, SATISH MAURYA, SUBRATA KUNDU, A.P. DIMRI |
| Organisation | Indian Institute of Geomagnetism, New Panvel, Navi Mumbai |
| Address | Indian Institute of Geomagnetism, New Panvel, Navi Mumbai Mumbai, Maharashtra, India Pincode: 410218 E-mail: sainisunilkc@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | This study utilized the total electron content measured by nearly 1200 GEONET GPS receivers across Japan to examine ionospheric perturbations mainly generated by Rayleigh-induced acoustic waves (RAWs) following the Tohoku-Oki earthquake (2011). Earthquakes release wide range of seismic energy, which propagates as seismic waves through the Earth's surface and interior. During these events, vertical surface movements caused by propagating Rayleigh surface waves (RSWs) induce acoustic waves that travel into the atmosphere through dynamic coupling. Their amplitudes increase with altitude due to decreasing atmospheric neutral density. When these waves reach the ionosphere, they alter the plasma density, resulting in co-seismic ionospheric perturbations (Perevalova et al., 2014). We analyzed data from various GPS satellites to estimate the propagation velocity and amplitudes of these perturbations. Subsequently, we examined seismic waveforms recorded by 64 seismic stations of the NIED F-net system across Japan to determine the period-dependent group velocities of RSWs using their energy dispersion curves and their amplitudes. While correlating the ionospheric response with ground observations, we found that RSWs with periods, 10-50 s effectively manifested at the ionospheric heights, as their mean propagation velocity correlates with that of ionospheric perturbations, and their amplitudes correspond fairly well (Sunil et al., 2025, under review). Furthermore, we extended this analysis to large earthquakes worldwide, aiming to identify a more specific period range of RSWs that predominantly manifest in the ionosphere. Major events, such as the Tokachi-Oki earthquake, 2003 (Japan), Illapel earthquake, 2015 (Chile), and Iquique earthquake, 2014 (Chile), were selected for detailed analysis, as they exhibited notable perturbations caused by RAWs. This extended work further confirms our earlier conclusion that RSWs with periods, 10-50 s are most prominent at ionospheric heights. Therefore, it is emphasized that the low-frequency RSWs could be characterized from the ionospheric observations, as they manifest effectively in the ionosphere. Reference: Perevalova, N. P., Sankov, V. A., Astafyeva, E. I., & Zhupityaeva, A. S. (2014). Threshold magnitude for Ionospheric TEC response to earthquakes. Journal of Atmospheric and Solar-Terrestrial Physics, 108, 77⿿90. https://doi.org/https://doi.org/10.1016/j.jastp.2013.12.014. |
| Keywords | Comparative assessment between Rayleigh wave-generated ionospheric perturbations and Rayleigh waves was performed for Tohoku-Oki Earthquake, Rayleigh waves with periods of 10-50 s predominantly manifested in the ionosphere during the Tohoku-Oki Earthquake |