[H-DS10] Tsunami and tsunami forecast

[HDS10-P12] Tsunami source inversion using atmospheric pressure waves generated by earthquake fault movement.

*Hidee Tatehata¹, Kenji Hayashi¹, Masashi Takagi¹, Kentaro Uehara¹ (1.Japan Weather Asociation)

Keywords:Tsunami, inversion analysis, Atmospheric pressure waves, Lamb waves, jet stream

Three years have passed since the tsunami caused by the atmospheric-pressure wave form the Tonga volcanic eruption (January 15, 2022). We are conducting research to predict tsunamis by observing atmospheric-pressure waves generated by crustal movements of earthquake origin, performing inverse analysis to determine the initial water level distribution in the wave source area, and using that data. For example, in source process analysis using seismic waves, the amount of slip is calculated by determining two physical quantities: the source time function and the slip velocity. However, Lamb wave, that is a sort of atmospheric-pressure wave, are strongly related to the initial water level at the tsunami wave source, and less affected by the rise-velocity of sea surface. Then inverse analysis using atmospheric-pressure waves requires only one type of physical quantity and has potential of well convergence of the solution. In another words, this methodology can obtain accurate results only using a few observation points. Another advantage is this methodology can obtain results with shorter observation time-length. It is because that atmospheric-pressure wave has propagation speed of sound with straight course from the source to observation-points, while average speed of tsunami is only about half the speed of sound. As a result, even if barometers are only installed on land, the necessary data can be obtained more quickly than with ocean-floor tsunami gauges installed offshore. The results of atmospheric-pressure wave inversion analysis show that, even when observation data is only available for about five minutes after the earthquake, the initial water level distribution in the wave source area can be determined with better accuracy than the analysis results using ocean-bottom tsunami gauges. We will introduce the results of this methodology and the effect of natural weather disturbances such as typhoons and westerly winds (jet stream).