East–west asymmetry of Lamb wave amplitude generated by the HTHH eruption and its effect on GPS-TEC variation

The eruption of the Tonga submarine volcano on January 15, 2022 generated a strong pressure wave, so-called Lamb wave, which orbited the Earth a few times. From high-time resolution pressure observation, it was found that the mean amplitude of the pressure waves separately averaged for the stations on the west-side and on the east-side of the volcano at the first three passages of the waves has a clear east–west asymmetry. That is, the westward propagating waves show larger amplitude than the eastward propagating waves. The structure of Lamb wave front observed on the westside is more complex than that on the eastside. The mean energy flux of westward propagating wave is about 80% larger than that of eastward propagating wave. Enhancement of short period fluctuations, i.e., shorter than about 30 min, in GPS-TEC (Total Electron Content) variation was globally observed around the passages. Their amplitude also tends to be larger for the westward traveling waves than that for the eastward traveling waves. A possible asymmetry of the initial blast wave effect on a Lamb wave formation caused by a vertical component of the Coriolis force is suggested. Similarities with a case at the 1883 Krakatoa volcanic eruption are also presented.