Rapid Estimation of 2022 Tonga Erupted Volume from the Remote Seismo-Acoustic Resonance

The powerful acoustic waves generated by the major eruption on January 15, 2022 on Hunga Tonga Hunga Ha’apai (HTHH) of Tonga were unambiguously recorded in Taiwan by several infrasonic stations and Formosa array, which consists of 146 broadband seismic stations with an average spacing of ~5 km in northern Taiwan. Based on the carefully analyses of the broadband frequency-wavenumber method (BBFK) and the Fast Fourier Transform (FFT), it was interesting to see that both data sets consistently showed a resonant frequency of ~0.0117 Hz persisted for more than 25 minutes after the first major eruption. Such a long-duration resonance of the remote seismo-acoustic waves provides a rapid estimation of the erupted magma volume of 0.215 ± 0.015 if the volcanic cavity produced by the erupting magma is considered as a classic Helmholtz resonator. Thus, we may obtain that the first major eruption alone of HTHH rated a 4 on the VEI scale. But the total erupted volume could reach up VEI 5 or even 6 if we consider all of the accumulated magma from the following eruptions.