Search

On 15 January 2022, the largest eruption of the Hunga‐Tonga volcano in recorded history produced a plume registered by multi‐parametric instruments around the world. However, the far‐field hydrogeological responses to Lamb waves from this eruption remain underexplored. We studied the responses of groundwater to the volcanic eruption in the far‐field over 8,700 km, including 274 wells. Results show that the Lamb waves with a speed of 316 m/s affects the groundwater system, leading to similar fluctuations in well water level (WL) and opposite phase fluctuation in borehole strain. Different wells exhibit diverse responses in WL amplitudes, possibly for heterogeneities in local aquifer systems. Gain values of 5 wells that simultaneously measure atmospheric pressure, borehole air pressure, borehole strain and WL are consistent with results obtained through cross‐power spectrum estimation. This work demonstrates a novel response in far‐field groundwater systems induced by Lamb waves and expects application for aquifer parameter estimation. Plain Language Summary: The massive eruption of the Hunga‐Tonga volcano on 15 January 2022 generated shock waves in the Earth's atmospheric layer, known as Lamb waves, which propagated at the boundary of air and the solid Earth. While many studies reported multi‐parameter responses during or after the eruption, the response of the groundwater system has not been studied. In this study, we found that Lamb waves from the volcano eruption induced similar phase responses in the water levels of 256 wells within the 274‐well network and opposite phase responses in borehole strain in mainland China. Additionally, the Lamb wave induced a possible time lag in the response of well water level (WL) and horizontal strain, which may be caused by different hydraulic properties of the wells. In the five wells with common observations, the calculated atmosphere pressure sensitivity is consistent with previous studies. The response of well WL to the Lamb wave is obviously different compared to that observed during co‐seismic events and Earth tides. Key Points: The Lamb wave from the Hunga‐Tonga volcano eruption induces similar phase responses in the water level (WL) of 256 wells in the far fieldResponses of well WL and borehole strain to the Lamb wave show a possible time‐delay relative to that of atmosphere pressureThe incorporation of the WL parameter and horizontal transverse strain is recommended to calibrate the appropriate models [ABSTRACT FROM AUTHOR]

At 04:14:45 UT on 2022 January 15, a powerful eruption of the submarine Hunga Tonga–Hunga Ha'apai volcano occurred at about 30 km south of the Ha'apai Islands in the Kingdom of Tonga (at −20.55° N, −175.39° E). This eruption caused atmospheric waves that spread worldwide. In this study, we investigate the the total electron content (TEC) variation over China using the BeiDou Navigation Satellite System. The particularly interesting feature of the data set compared to other ground-based TEC data is the exclusive use of the BeiDou geostationary satellites, which monitor the TEC variations for fixed ionospheric piercing points and can provide more accurate calculations of the travelling speed of the disturbance. For comparison, atmospheric pressure records were examined, which show that the Lamb wave passed by the same stations four times with a constant speed of 310 m s−1. However, the TEC results show that the ionospheric disturbances passing over China four times with different speeds within four days after the eruption, two travelling along the short-path direction and two along the long-path direction. The primary front of the first short-path event travels with a speed of 340 m s−1, which is higher than the Lamb wave. The faster speed suggests that the primary front cannot be fully attributed to the Lamb wave, and further studies need to explore its mechanism. The second short-path and first long-path events travel with speeds of 301 and 310 m s−1, respectively, close to the speed of the Lamb wave, and they may be caused by upward energy leakage during the propagation of the Lamb wave. The second long-path event travels with a speed of 264 m s−1, possibly induced by the gravity waves. [ABSTRACT FROM AUTHOR]

The Hunga Tonga-Hunga Ha'apai volcano eruption resulted in propagation of tsunamis globally. Atmospheric pressure disturbances and tsunamis were recorded in Lingding Bay, China, situated more than 9000 km from the volcano. We studied the features of tsunamis in Lingding Bay and its surrounding areas by using records from tide gauges and meteorological stations. Lamb waves were observed in the bay approximately 8, 44 and 80 hr after the volcanic eruption. The first and second tsunami waves arrived approximately 11 and 45–47 hr following the eruption, respectively, indicating consistency with the arrival time of Lamb waves. In addition, wavelet and Fourier analyses were applied to the sea level records to investigate the frequency characteristics. The ratio of the tsunami spectra to the background spectra for two tsunami waves was calculated as the source spectra. The source spectra of two tsunami waves were mostly of the same shape, with dominant periods of ∼17 and ∼46 min. Our results provide information for theoretical investigation of the Tonga tsunami event. More efforts should be devoted to relevant research on the generating mechanism and early warning of tsunamis from non-seismic origins. [ABSTRACT FROM AUTHOR]

Objectives: The Tonga volcano erupted violently on January 15th, 2022, which produced atmospheric gravity waves affecting around the world, and was clearly recorded by all ground strain observation stations in Chinese mainland with the distance from 8-736 km to 12-758 km. Methods: The wavelet analysis method is applied to systematically analyze the spatial-temporal response and frequency characteristics of the data recorded by nearly 200 ground strain observations in China. Results: The results show that the duration of change is about 1.5 hours, in which the strongest energy change is occurred at the first 40 minutes. The average amplitude of surface strain is about 186x10-10, showing a single pulse as rise and fall change, and the patterns have highly consistency with Lamb wave propagation properties. The average velocity of event propagation is 310 m/s, which is consistent with the propagation velocity of atmospheric gravity waves. Most stations also record the effect of atmospheric gravity wave signals on the surface as they arrive twice around the Earth. Conclusions: It is the first time to record the traces of atmospheric gravity waves acting on the surface through a large scale high-precision ground strain meters and it is helpful to understand the mechanism of interaction between crustal movement and atmospheric sphere. [ABSTRACT FROM AUTHOR]

The amount to be invested and the timing of clearcutting are central concerns in timber production. To assess the impact of the initial planting density on optimal economic rotation, we explicitly included the distribution of stand diameter classes and price differences representing the quality of stumpage in a model of forest land expected value (LEV). We selected five initial planting densities of 35-year old China fir (Cunninghamia lanceolata (Lamb.) Hook) plantations to fit the distribution of diameter classes along with stand age using a three-parameter Weibull theoretical growth model and then the Faustmann formula was used to calculate LEVs under different conditions. We found that the difference in the values of the growth rate of the stand volume and the discount rate affected the direction of the impact of initial planting density on the optimal economic rotation. If the value of the growth rate of the stand volume exceeded that of the discount rate, then the initial planting density had a negative impact on optimal economic rotation and vice versa. In addition, the quality effect, which means the shift in diameter class to a higher value attributed to the initial planting density, determined the extent of the impact of the initial planting density on the optimal economic rotation. The proportion of large-sized timber increased at a faster pace in accordance with the age of the stand in stands where the planting density was low compared with the proportion of such timber in stands with a higher initial planting density. The corresponding net stumpage price difference resulted in significant differences in LEVs. We concluded that a low-density stand of China fir was a preferred planting option for obtaining the highest LEV. [ABSTRACT FROM AUTHOR]