Observations of Tsunami Waves on the Pacific Coast of Russia Originating from the Hunga Tonga-Hunga Ha'apai Volcanic Eruption on January 15, 2022

The Hunga Tonga-Hunga Ha´apai volcanic eruption on January 15, 2022 generated a tsunami that affected the entire Pacific Ocean. Tsunami from the event have been generated both by incoming waves from the source area, with a long-wave speed in the ocean of ~ 200–220 m/s, and by an atmospheric wave propagating at a sound speed ~315 m/s. Such a dual source mechanism created a serious problem and was a real challenge for the Pacific tsunami warning services. The work of the Russian Tsunami Warning Service (Yuzhno-Sakhalinsk) during this event is considered in detail. The tsunami was clearly recorded on the coasts of the Northwest Pacific and in the adjacent marginal seas, including the Sea of Japan, the Sea of Okhotsk and the Bering Sea. We examined high-resolution records (1-min sampling) of 20 tide gauges and 8 air pressure stations in this region for the period of January 14–17, 2022. On the Russian coast, the highest waves, with a trough-to-crest wave height of 1.3 m, were recorded at Malokurilskoe (Shikotan Island) and Vodopadnaya (the southeastern coast of Kamchatka). Using numerical simulation and data analysis methods, we were able to separate the oceanic “gravity” tsunami waves from propagating atmospheric pressure waves. In general, we found that on the outer (oceanic) coasts and the southern coast of the Sea of Okhotsk, oceanic tsunami waves prevailed, while on the coast of the Sea of Japan, oceanic and atmospheric tsunami waves had similar heights.