Tsunami Wave Height Estimation from GPS‐Derived Ionospheric Data

Abstract

Large underwater earthquakes (Mw>7) can transmit part of their energy to the surrounding ocean through large seafloor motions, generating tsunamis that propagate over long distances. The forcing effect of tsunami waves on the atmosphere generates internal gravity waves that, when they reach the upper atmosphere, produce ionospheric perturbations. These perturbations are frequently observed in the total electron content (TEC) measured by multifrequency Global Navigation Satellite Systems (GNSS) such as GPS, GLONASS, and, in the future, Galileo. This paper describes the first inversion of the variation in sea level derived from GPS TEC data. We used a least squares inversion through a normal‐mode summation modeling. This technique was applied to three tsunamis in far field associated to the 2012 Haida Gwaii, 2006 Kuril Islands, and 2011 Tohoku events and for Tohoku also in close field. With the exception of the Tohoku far‐field case, for which the tsunami reconstruction by the TEC inversion is less efficient due to the ionospheric noise background associated to geomagnetic storm, which occurred on the earthquake day, we show that the peak‐to‐peak amplitude of the sea level variation inverted by this method can be compared to the tsunami wave height measured by a DART buoy with an error of less than 20%. This demonstrates that the inversion of TEC data with a tsunami normal‐mode summation approach is able to estimate quite accurately the amplitude and waveform of the first tsunami arrival.

IonoSeis: A Package to Model Coseismic Ionospheric Disturbances

“…Acoustic waves in the atmosphere associated with TIDs are common and can be caused by a variety of sources, including volcanic eruptions [18], earthquakes [19][20][21], tsunamis [22], large storms [5,23], solar flares [23], meteorite impacts [23], interplanetary shocks [24], and human-caused sources such as explosions [25] and rocket launches [26] (see [23,27] for comprehensive lists). There is now compelling evidence that the ionosphere is sufficiently affected by earthquake-related ground motion and tsunami waves, the latter of which can be tracked with TEC [28,29].…”

Upper Atmospheric Responses to Surface Disturbances: An Observational Perspective

“…With GNSS TEC observations, researchers have also attempted to retrieve tsunami characteristics, primarily the wave heights, from the tsunami‐induced ionospheric TEC perturbations. The first and only effort was reported by Rakoto et al (), who assumed that the tsunami wave height, tsunami‐induced atmospheric gravity waves, and their respective ionospheric TEC perturbations could be expressed by a normal‐mode summation with momentum tensor and Legendre polynomials defined in Phinney and Burridge (). By using a least‐squares approach, they successfully inverted the GPS‐derived TEC data to tsunami wave heights for three events.…”

“…As the example given by Rakoto et al (), the inversion of the observed ionospheric signatures back to quantitative characteristics of surface disturbances relies on numerical modeling tools that simulate the response of the upper atmosphere to atmospheric acoustic‐gravity waves generated from surface disturbances. However, modeling approaches contain caveats that limit their capability to represent realistic acoustic‐gravity wave propagation.…”

Ocean Observations Required to Minimize Uncertainty in Global Tsunami Forecasts, Warnings, and Emergency Response

“…Tsunamis also create disturbances in the ionosphere and are being captured by the ever-increasing arrays of GNSS, such as the Global Positioning System (GPS), Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS), and, in the future, Galileo (Occhipinti et al, 2018;Rakoto et al, 2018). The ability of tsunamis to excite internal gravity waves in the atmosphere has been recognized since the early seventies (Hines, 1972).…”