Parameters of the infrasonic signal generated by the Kamchatka meteoroid

Abstract

The subject of this study is the infrasonic signal generated by a high-speed (32 km/s), high-energy (173 kt TNT), and large-sized (9.4 m) celestial body, later called the Kamchatka meteoroid, which entered the terrestrial atmosphere and exploded on December 18, 2018. The focus of the study is the parameters of the infrasonic signal launched by the Kamchatka meteoroid. The study is based on the data on temporal dependences of pressure in the infrasonic wave collected by the I53US, I30JP, I59US, I46RU, I57US, and MAAG2 infrasonic stations included in the International Monitoring System (IMS) set up by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). The measurement data initially recorded on a relative scale were converted into absolute values. The temporal dependences of the infrasonic wave pressure were then filtered in the 1–40-s period range and were subsequently subjected to system spectral analysis that included the mutually complementary short-time Fourier transform, adaptive Fourier transform, and the wavelet transform with the Morlet wavelet as the basis function. As a result, it was found that the infrasonic signal amplitude exhibits quite a rapid decrease with distance between an infrasonic station and the meteoroid’s explosion site. The time delay of the infrasonic signal shows an increase with distance between the celestial body explosion and the site of signal detection. The signal celerity exhibits a dependence on the distance and the path orientation; it is estimated to be in the range of 269–308 m/s. The infrasonic signal duration shows virtually no dependence on the distance from the detonation point to an infrasonic station. The infrasonic signal spectra have a wide bandwidth with periods from ∼5 to ∼40 s. At the same time, the greatest energy falls within the isolated periods of 12–15 s and 28–33 s. The scatter diagrams and regressions for the infrasound main parameters were plotted. The celestial body’s kinetic energy (179 kt TNT) and acoustic efficiency (∼4%) were estimated from the prevailing infrasonic period.