Tsunami Ionospheric Monitoring Across the Pacific Ocean and the Southern Atlantic

As tsunamis propagate across open oceans, they remain largely unseen due to the lack ofadequate sensors. To help better mitigate the tsunami risk, we use a detection method that takesadvantage of the efficient coupling of tsunami waves with the atmosphere. Tsunami-inducedinternal gravity waves thus travel upward in the atmosphere, where amplitude amplifies by severalorders of magnitude as the air density decreases with altitude. Once the waves reach theionosphere, they put charged particles into motion, creating propagative phenomena known asTraveling Ionospheric Disturbances (TIDs). Thanks to the Global Navigation Satellites Systems(GNSS), such disturbances can be monitored and observed using the Total Electron Content (TEC)derived from the delay that the ionosphere imposes in the electromagnetic signals transmitted tothe Earth’s surface by the GNSS satellites. Here we show ionospheric TEC signatures following thepassage of three ocean-wide tsunami events: the two tsunamis triggered by the March 4th, 20218.1 Mw Kermadec Islands, New Zealand, and the July 29th, 2021 8.2 Mw Perryville, Alaskaearthquakes, as well as across the southern Atlantic following the tsunami generated by theAugust 12th, 2021 8.1 Mw Sandwich Islands earthquake. We classify the observed TEC signaturesbased on detection reliability and the potential connection to the tsunami wavefield. In addition,we utilize an analytical model to investigate the source of these identified TEC signatures. Thus, weensure their gravity-waves origin and assess the characteristics (wavelength, period, etc.) of suchgravity waves, which is necessary to confirm they originate from the tsunami. Finally, to bettermap the tsunami amplitude at the ocean level in various configurations, we examine, compare,and contrast the amplitude of the identified tsunami-induced TEC signatures from geographicallysparse regions. We account for multiple parameters such as the local magnetic field, the azimuth,and the distance to the tsunami source. They all affect the TEC signature detection and theretrieval of the tsunami wavefield and, thus, potentially, the estimated risk.