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Tsunamis generated by the Hunga Tonga–Hunga Ha'apai volcanic eruption on January 15, 2022 were recorded on ocean bottom pressure and tide gauges around the Pacific Ocean, earlier than the expected arrival times calculated by tsunami propagation speed. Atmospheric waves from the eruption were also recorded globally with propagation speeds of ~ 310 m/s (Lamb wave) and 200–250 m/s (Pekeris wave). Previous studies have suggested that these propagating atmospheric waves caused at least the initial part of the observed tsunami. We simulated the tsunamis generated by the propagation of the Lamb and Pekeris waves by adding concentric atmospheric pressure changes. The concentric sources are parameterized by their propagation speeds, initial atmospheric wave amplitudes that decay with the distance, and a rise time. For the Lamb wave, inversions of the observed tsunami waveforms at 14 U.S. and nine New Zealand DART stations indicate the start of the positive rise at 4:16 UTC, the peak amplitude of 383 hPa, and the propagation speed of 310 m/s, assuming a rise time of 10 min. The later phases of the observed tsunami waveforms can be better reproduced by adding another propagating concentric wave (Pekeris wave) with a negative amplitude (− 50 hPa) and propagation speeds of 200–250 m/s. The DART records around the Pacific indicate that the Pekeris wave speed is faster toward the northwest and slightly slower toward the northeast. The synthetic waveforms roughly reproduced the far-field tsunami waveforms recorded at tide gauge stations, including the later phases, suggesting that the large amplitude in the later phase may be due to the coupling of the Pekeris wave and the tsunami, as well as resonance around tide gauge stations. [ABSTRACT FROM AUTHOR]

The Hunga Tonga–Hunga Ha'apai volcanic eruption on January 15, 2022 generated a tsunami that affected the entire Pacific Ocean. Tsunami waves 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 of ~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 (southeastern coast of Kamchatka). Using numerical simulation and data analysis methods, we were able to separate oceanic "gravity" tsunami waves from propagating atmospheric pressure waves. In general, we found that on the outer (oceanic) coasts and 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. [ABSTRACT FROM AUTHOR]

The massive eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano in Tonga on 15 January 2022 at 04:15 UTC had a global impact and triggered an atmospheric wave and a tsunami. We first analyzed observation data from meteorological stations and tide gauges at 12 locations. Low-frequency trends in the observation data were removed by using a high-pass filter. Fourier and wavelet spectral analyses were applied to determine the frequency characteristics of the filtered data. Modal analysis was developed and used to investigate natural oscillation periods based on bathymetry. The results showed that the Lamb wave generated by the atmospheric pressure wave arrived ~ 7 and ~ 44 h after the eruption. The tsunami arrived ~ 11 and ~ 45 h after the eruption, which corresponded to the arrival time of the Lamb wave. The dominant periods of the Lamb waves were ~ 7.7 and ~ 7.5 min, and for the tsunamis they were ~ 9.9 and ~ 28.7 min. The periods derived from the spectral analysis matched the natural oscillation of the eigenperiod derived from the modal analysis, in eight out of the twelve stations. This study provides valuable insight and information regarding the nonseismic and far-field effects of tsunamis generated by volcanic eruptions. [ABSTRACT FROM AUTHOR]

The 2022 Hunga Tonga-Hunga Ha'apai eruption generated tsunamis that propagated across the Pacific Ocean. Along the coast of Japan, nearshore amplification led to amplitudes of nearly 1 m at some locations, with varying peak tsunami occurrence times. The leading tsunami wave can generally be reproduced by Lamb waves, which are a type of air-pressure wave generated by an eruption. However, subsequent tsunamis that occurred several hours after the leading wave tended to be larger for unknown reasons. This study performs multi-scale numerical simulations to investigate subsequent tsunami waves in the vicinity of Japan induced by air pressure waves caused by the eruption. The atmospheric pressure field was created using a dispersion relation of atmospheric gravity wave and tuned by physical parameters based on observational records. The tsunami simulations used the adaptive mesh refinement method, incorporating detailed bathymetry and topography to solve the tsunami at various spatial scales. The simulations effectively reproduced the tsunami waveforms observed at numerous coastal locations, and results indicate that the factors contributing to the maximum tsunami amplitude differ by region. In particular, bay resonance plays a major role in determining the maximum amplitude at many sites along the east coast of Japan. However, large tsunami amplification at some west coast locations was not replicated, probably because it was caused by amplification during oceanic wave propagation rather than meteorological factors. These findings enhance our understanding of meteotsunami complexity and help distinguish tsunami amplification factors. [ABSTRACT FROM AUTHOR]

On January 15, 2022 the Hunga Tonga Hunga Ha'apai volcano erupted violently, generating a significant tsunami that was observed around the world. This is the first volcanic tsunami that has been observed worldwide by the modern deep- and shallow-water hydrodynamic instrument network. Here we study deep water DART buoy and coastal tide gauges recordings using waveform stacking, amplitude analysis, and spectral analysis. We find that there are potentially as many as three distinct phases to the tsunami each corresponding to different generation mechanisms. Most sites observed an arrival with a propagation speed of ~ 305–310 m/s that we deduced is likely to be an atmospheric Lamb wave with a ~ 40 min period. We find that this feature has a weakly azimuthally-dependent radiation pattern. We also find secondary phases which range in propagation speed from ~ 150 to 205 ms−1. Analysis of their amplitudes and variability in propagation speeds in the waveforms tacks, their decay, and their frequency domain behavior leads us to posit that they represent a complex amalgam of traditional tsunami and atmospheric effects such as internal gravity waves. Overall, from this analysis we find no evidence that processes at the volcanic edifice, such as caldera collapse, land sliding, or pyroclastic density currents, are the dominant tsunamigenic source in the far field. Finally, we also argue that amplification of tsunami wave heights around the coastal areas of the Pacific basin may be due to the combined effects of processes like those seen in meteotsunamis such as Proudman resonance induced by the Lamb wave front, with various coastal areas seeing also effects from Greenspan and shelf resonance. We show a comparison of the event to the last great basin tsunami the M9 Tohoku-oki earthquake, and discuss how, while the amplitudes of the Hunga Tonga tsunami are smaller than other basin-wide events, the worldwide nature, and atmospherically driven forcing of it pose unique challenges to hazards forecasts and warning. [ABSTRACT FROM AUTHOR]

At 12:15 on January 15, 2022 (Beijing time), a massive eruption of the Hunga Tonga-Hunga Ha'apai volcano produced violent atmospheric fluctuations, which in turn generated a global tsunami through an abrupt air pressure shock upon the sea surface. Two main components of tsunami waves, phase-locked waves and free gravity waves, were identified by significant differences in propagating speeds across the deep ocean. The phase-locked wave propagated through the ocean basin synchronously with the atmospheric Lamb wave at an average speed of approximately 306 m/s, followed by the free gravity wave at a slower speed. The locked wave reached the coast of eastern Taiwan Island at about 20:00 on January 15, in coincidence with the Lamb wave arrival. However, on the coast of Chinese mainland, tidal gauges did not record tsunami signals until at least 2 h after the Lamb wave arrivals. Theoretical analyses and numerical experiments both suggested that as a result of the incoming wave shoaling above the vast continental shelf of Chinese mainland, the locked wave was no longer trapped by the air pressure shock and gradually transformed into freely-propagating shallow water waves by slowing down its propagation. Due to the long-lasting planetary atmospheric fluctuations circling the earth many times, the sea level oscillations continuously propagated onto the Chinese shelf, which resulted in the tsunami waves excited along the Chinese coasts for at least 36 h. The maximum wave amplitude recorded on the coast of eastern Taiwan Island was 44 cm at Wushi, while on the coasts of eastern and southern Chinese mainland, the maximum amplitudes were 22 cm at Shipu and 13 cm at Zhuhai. Fourier and wavelet analyses were performed to identify the major components of the tsunami waves on the Chinese coasts. The results indicated that eastern Taiwan Island was impacted mainly by the waves with periods of approximately 10–40 min. Chinese mainland was hit by the evolved shallow water waves and subsequent free waves, with periods of approximately 40–100 and 16–20 min, respectively. [ABSTRACT FROM AUTHOR]

The 2022 eruption of the Hunga Tonga-Hunga Ha'apai volcano excited an atmospheric Lamb wave, which induced a fast-traveling tsunami. This tsunami was driven by the pressure-forced wave traveling at the speed of the Lamb wave and, thus, was much faster than conventional tsunamis. This was the first case in which ocean bottom monitoring systems widely observed an air pressure-induced tsunami. We found that the pressure-forced waves split and generated ocean gravity waves after passing the Japan Trench based on the S-net data. Our simulations show that changes in water depth can amplify or decrease the pressure-forced wave. Simultaneously, an ocean gravity wave is generated due to the conservation of water volume. Because the ocean gravity wave was slower than the pressure-forced wave near Japan, it was separated from, and traveled behind, the pressure-forced wave. We explained the wave separation phenomenon and reproduced the waveforms of different splitting stages observed by the stations near the Japan Trench. [ABSTRACT FROM AUTHOR]

Tsunamis are commonly generated by earthquakes beneath the ocean floor, volcanic eruptions, and landslides. The tsunami following the Tonga eruption of 2022 is believed to have been excited by atmospheric pressure fluctuations generated by the explosion of the volcano. The first, fast-traveling tsunami was excited by Lamb waves; however, it has not been clarified observationally or theoretically which type of atmospheric fluctuations excited more prominent tsunami which followd. In this study, we investigate atmospheric gravity waves that possibly excited the aforementioned subsequent tsunami based on observations and atmosphere-ocean coupling simulations. The atmospheric fluctuations are classified as Lamb waves, acoustic waves, or gravity waves. The arrival time of the gravity wave and the simulation shows that the gravity wave propagated at a phase speed of 215 m/s, coinciding with the tsunami velocity in the Pacific Ocean, and suggesting that the gravity wave resonantly excited the tsunami (Proudman resonance). These observations and theoretical calculations provide an essential basis for investigations of volcano-induced meteotsunamis, including the Tonga event. [ABSTRACT FROM AUTHOR]

The synchronous response of the lower and upper ionosphere to the propagation of the atmospheric Lamb wave and tsunami that were generated by the mega-eruption of the Hunga submarine volcano on January 15, 2022, has been studied for the first time using data from very low frequency radio sounding in the Far East area of Russia and the Japanese–Australian network of receivers of global navigation satellite system signals. It has been found that wave-like variations of very low frequency and global navigation satellite system signals not only appear at the intersection of radio paths by Lamb waves and tsunamis but also demonstrate nonlocal effects owing to the geomagnetic field. Such variations are caused by the action of internal gravity waves generated by these sources and the dust component of eruption on the ionosphere. The energy of the main eruption has been estimated and detected ionospheric perturbations have been interpreted. [ABSTRACT FROM AUTHOR]

The anomalous variations of a very low frequency (VLF) signal recorded after the eruption of the Hunga-Tonga-Hunga-Ha'apai volcano on January 15, 2022, have been investigated. It is shown that the intensification of the phase and amplitude variations of the VLF signal was caused by the crossing of radio paths by the atmospheric Lamb wave and the tsunami propagating after the volcanic eruption. [ABSTRACT FROM AUTHOR]

On 15 January 2022, the Tonga-Hunga submarine volcano erupted in the southwest Pacific Ocean and created strong tsunami waves that had a dual generation mechanism: "direct" (caused by the explosion) and "atmospheric" (induced by propagating atmospheric Lamb waves). Trans-oceanic waves spread across the ocean and were clearly recorded in marginal seas of the northwestern Pacific, including the Sea of Japan. The two distinct types of incoming waves produced a variety of effects in the sea as determined by the wave origin, propagation features and local topographic properties. Statistical and spectral properties of the tsunami waves recorded in the Sea of Japan and vicinity, including the adjacent part of the northwestern Pacific, are the main subject of the present study. The Sea of Japan is a semi-isolated basin connected to the Pacific Ocean through several straits. The features of these straits (widths, depths, and geometry) significantly affected the arriving waves, strongly modifying their statistical characteristics and spectral content. As discussed in detail in this paper, the two types of incoming tsunami waves are consequently transformed in substantially different ways. [ABSTRACT FROM AUTHOR]

The manifestations of the Hunga Tonga–Hunga Haʻapai volcano explosive eruption on January 15, 2022, in the Pacific region were investigated using the data of the DART deep ocean sea level stations and the IRIS ground-based barographs. It was found that the atmospheric Lamb wave, caused by the explosion of the volcano, was formed at 04:27 UTC ± 4 min and propagated over the Pacific Ocean at a speed of 312 ± 4 m/s. It is shown that the leading distinct pulse recorded by all DART deep ocean sea level stations is a direct manifestation of the atmospheric Lamb wave. Theoretical estimations of the amplitude manifestations of the Lamb wave in the bottom pressure variations have been made. It is shown that the amplitude of bottom pressure variations in the deep ocean is a few times larger than the amplitude of pressure variations in the Lamb wave. Theoretical estimates of the amplitude of surface gravity waves excited in the ocean by traveling atmospheric disturbance passing a depth jump are carried out. [ABSTRACT FROM AUTHOR]

Meteotsunamis (forced waves) triggered by atmospheric disturbances of Lamb waves due to the 2022 Hunga–Tonga volcanic eruption have been observed in coastal areas surrounding the Pacific Ocean. However, the spatiotemporal evolution of the wavefield of meteotsunamis and meteotsunami-induced free waves remains elusive. Here, we show the detailed spatial distribution of the propagation velocities and directions of these waves in the bathymetric slope area between the Japan Trench and nearshore, using a dense array of 150 absolute pressure gauges deployed at water depths of 100–8000 m. Records show that free wave components (i.e., tsunamis) were generated when the forced wave was propagating over the slope area. Amplitudes of the generated free waves are large in the southern half of the slope area, where the equi-arrival time contour lines are densely paralleled. Such amplifications occur due to the relationship between the incoming direction of Lamb waves and the gradient of the bathymetric slope. This indicates that, if meteotsunamis excited by Lamb waves due to future volcanic eruptions come from different directions to this region, a different spatial pattern of free wave amplification on a regional scale is obtained in the bathymetric slope areas. [ABSTRACT FROM AUTHOR]

The characteristics of acoustic-gravity waves (waveforms, time durations, amplitudes, azimuths and horizontal phase speeds) from the eruption of the Hunga-Tonga-Hunga-Hapai volcano detected at different infrasound stations of the Infrasound Monitoring System and at a network of low-frequency microbarographs in the Moscow region are studied. Using the correlation analysis of the signals at different locations, six arrivals of signals from the volcano, which made up to two revolutions around the Earth, were detected. The Lamb mode of acoustic gravity waves from the volcano eruption is identified and the effect of this mode on generation of tsunami waves and variation of aerosol concentration is studied. The energy released from an underwater volcano into the atmosphere is estimated from the parameters of the Lamb wave and compared with the energy released from the most powerful nuclear bomb of 58 Mt TNT. [ABSTRACT FROM AUTHOR]