Acoustic-gravity waves generated by a point source on the ground in a stratified atmosphere-Earth structure

Yongxin Gao, Ting Li, Guanqun Zhou, Chieh Hung Chen, Yang Yi Sun, Xuemin Zhang, Jann Yenq Liu, Jian Wen, Cheng Yao, Xiaodong Bai

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

An analytically based method is proposed to simulate the acoustic-gravity waves in the horizontally stratified atmosphere-Earth structure generated by a point force on the Earth's surface. The method solves the linear momentum, continuity and adiabaticity equations in the atmosphere and elastodynamic equations in the solid Earth in the frequency-wavenumber domain. The time-domain waveforms are obtained by wavenumber integration and fast Fourier transform with respect to the frequency. Numerical simulations are conducted to investigate the properties of the acoustic-gravity waves, including both the high-frequency acoustic-mode waves and low-frequency gravity-mode waves. Simulations of the high-frequency responses show that disturbances in the atmosphere with three apparent horizontal velocities can be identified. They are, namely, the direct acoustic-mode wave generated by source travelling with the sound speed, the head wave generated by the seismic P-wave travelling with apparent horizontal speed identical to the P velocity, and the head wave generated by the Rayleigh wave with a horizontal speed same to the Rayleigh wave velocity. Simulations of the low-frequency responses show that the gravity-mode wave and Lamb wave can be identified. The gravity-mode wave travels with a speed lower than the sound seed and does not reach everywhere, especially the area directly above the source. The Lamb wave travels along the Earth surface with a speed of about 310 m s-1 and its energy decays with the altitude. We also apply our method to explaining the Doppler sounding data observed in Taiwan area during the 2011 Tohoku M 9 earthquake, and find good agreement between the predicted signals and observed data in the arrival time and wave envelope associated with the Rayleigh wave.

Original languageEnglish
Pages (from-to)764-787
Number of pages24
JournalGeophysical Journal International
Volume232
Issue number2
DOIs
StatePublished - 1 Feb 2023

Keywords

  • Acoustic-gravity waves
  • Computational seismology
  • Earthquake ground motions
  • Ionosphere/atmosphere interactions
  • Wave propagation

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