Preprints
https://doi.org/10.5194/nhess-2021-119
https://doi.org/10.5194/nhess-2021-119

  12 Jul 2021

12 Jul 2021

Review status: this preprint is currently under review for the journal NHESS.

Robust uncertainty quantification of the volume of tsunami ionospheric holes for the 2011 Tohoku-Oki Earthquake: towards low-cost satellite-based tsunami warning systems

Ryuichi Kanai1, Masashi Kamogawa3, Toshiyasu Nagao4, Alan Smith2, and Serge Guillas1 Ryuichi Kanai et al.
  • 1Department of Statistical Science, University College London, London, UK
  • 2Department of Space and Climate Physics, University College London, London, UK
  • 3Global Center for Asian and Regional Research, University of Shizuoka, Shizuoka, Japan
  • 4Institute of Oceanic Research and Development, Tokai University, Shizuoka, Japan

Abstract. We develop a new method to analyze the total electron content (TEC) depression in the ionosphere after a tsunami occurrence. We employ Gaussian process regression to accurately estimate the TEC disturbance every 30 s using satellite observations from the GNSS network, even over regions without measurements. We face multiple challenges. First, the impact of the acoustic wave generated by a tsunami onto TEC levels is non-linear and anisotropic. Second, observation points are moving. Third, the measured data is not uniformly distributed in the targeting range. Nevertheless, our method always computes the electron density depression volumes, along with estimated uncertainties, when applied to the 2011 Tohoku-Oki Earthquake, even with random selections of only 5 % of the 1,000 GPS Earth Observation Network System receivers considered here over Japan. Also, the statistically estimated TEC depression area mostly overlaps the range of the initial tsunami, which indicates that our method can potentially be used to estimate the initial tsunami. The method can warn of a tsunami event within 15 minutes of the earthquake, at high levels of confidence, even with a sparse receiver network. Hence, it is potentially applicable worldwide using the existing GNSS network.

Ryuichi Kanai et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-119', Anonymous Referee #1, 06 Aug 2021 reply
    • AC1: 'Reply on RC1', Ryuichi Kanai, 03 Sep 2021 reply

Ryuichi Kanai et al.

Ryuichi Kanai et al.

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Short summary
The air pressure created by a tsunami causes a depression in the electron density in the ionosphere. The depression is measured at sparsely distributed, moving, GPS satellite locations. We provide an estimate of the volume of the depression. When applied to the 2011 Tohoku-Oki Earthquake in Japan, our method can warn of a tsunami event within 15 minutes of the earthquake, even when using only 5 % of the data. Thus satellite-based warnings could be implemented across the world with our approach.
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