What excited tsunami from Tonga 2022 eruption? Observation and theory

Abstract

Tsunamis are commonly generated by earthquakes beneath the ocean floor, volcanic eruptions, and landslides. The mysterious tsunami following the Tonga eruption of 2022 is believed to be excited by the atmospheric pressure fluctuations generated by the explosion of this volcano. However, it is not clarified observationally and theoretically that which atmospheric fluctuations excited the tsunami. We show the atmospheric waves that possibly excited the tsunami based on observations detected by our own-manufactured sensors in Japan. The atmospheric fluctuations are classified into Lamb waves, acoustic waves, and gravity waves. The arrival time of the gravity wave and atmosphere-ocean coupling simulation show that the gravity wave propagated at a phase speed of 200-220 m/s, coinciding with tsunami velocity in the Pacific Ocean and suggesting that the gravity wave resonantly excited the tsunami (Proudman resonance). These observations and theory provide an essential basis for theoretical investigations of volcano-induced meteo-tsunamis, including the Tonga event.

Response of the underground environment of the KAGRA observatory against the air-pressure disturbance from the Tonga volcano eruption on January 15th, 2022

“…The Lamb waves of the Earth's atmosphere are observed around 11:30 UTC and the atmospheric gravity wave at milli-Hz order is observed for a long time. This is consistent with other reports in Japan [12][13][14]. The small transient disturbances in the higher frequency bands that appeared before the arrival of the air-pressure wave signal are understood that be caused by human activities like opening/closing doors in the building.…”

“…3. A transient pressure disturbance of 2 Pa was observed in all barometers, consistent with many reports in Japan [12][13][14].…”

“…The values of the time-shift are approximately proportional to the distance from the volcano, with the horizontal propagation speed of 220 m/s. This value is similar to that for the acoustic waves turning from the lower thermosphere, approximately 230 m/s [12]. This result suggests that the outside air-pressure waves affect the underground environments through the mountain 13/26 Fig.…”

“…The impulsive shock wave caused by the volcanic eruption turned into long-period air-pressure waves and were observed worldwide. These waves also reached Japan, traveling longer than 8,000 km away from the Tonga volcano over the Pacific Ocean, and were observed as disturbances of the air-pressure [12][13][14]. These signals from the volcanic eruption were observed by the environmental sensors of KAGRA, not only outside the tunnel but also inside the underground facility.…”

Ocean‐Ionosphere Disturbances Due To the 15 January 2022 Hunga‐Tonga Hunga‐Ha'apai Eruption

“…An atmospheric pressure wave propagates along the ocean surface and pushes dynamically the water surface, causing a tsunami of atmospheric origin similar to a meteo‐tsunami (Vilibić et al., 2016). The HHTH Lamb wave‐related tsunami was recorded all around the Pacific (e.g., Japan, California) and in the Caribbean (Carvajal et al., 2022; International Tsunami Information Center, 2022; Kubota et al., 2022; Kulichkov et al., 2022; Nishikawa et al., 2022; NOAA, 2022b).…”