Počet záznamů: 1  

Nonlinear coseismic infrasound waves in the upper atmosphere and ionosphere

  1. 1.
    0484705 - ÚFA 2018 RIV US eng A - Abstrakt
    Chum, Jaroslav - Liu, J. Y. - Cabrera, M. A.
    Nonlinear coseismic infrasound waves in the upper atmosphere and ionosphere.
    AGU Fall Meeting. s. l.: American Geophysical Union, 2017. NH51C-02.
    [AGU Fall Meeting 2017. 11.12.2017-15.12.2017, New Orleans]
    Grant CEP: GA ČR(CZ) GC15-07281J
    Institucionální podpora: RVO:68378289
    Klíčová slova: acoustic waves * upper atmosphere * ionosphere
    Obor OECD: Meteorology and atmospheric sciences
    https://agu.confex.com/agu/fm17/meetingapp.cgi/Paper/210599

    Vertical motion of the ground surface caused by seismic waves generates acoustic waves that propagate nearly vertically upward because of supersonic speed of seismic waves. As the air density decreases with height, the amplitude of acoustic waves increases to conserve the energy flux. If the initial perturbation is large enough (larger than ~10 mm/s) and the period of waves is long (>10 s), then the amplitude reaches significant values in the upper atmosphere (e.g. oscillation velocities of the air particles become comparable with sound speed) and the nonlinear phenomena start to play an important role before the wave is dissipated. The nonlinear phenomena lead to changes of spectral content of the wave packet. The energy is transferred to lower frequencies, which can cause the formation of roughly bipolar N-shaped pulse in the vicinity of the epicenters (up to distance about 1000-1500 km) of strong, M>7, earthquakes.
    The nonlinear propagation is studied on the basis of numerical solution of continuity, momentum and heat equations in 1D (along vertical axis) for viscous compressible atmosphere. Boundary conditions on the ground are determined by real measurements of the vertical motion of the ground surface. The results of numerical simulations are in a good agreement with atmospheric fluctuations observed by continuous Doppler sounding at heights of about 200 km and epicenter distance around 800 km. In addition, the expected fluctuations of GSP-TEC are calculated.
    Trvalý link: http://hdl.handle.net/11104/0279840

     
     
Počet záznamů: 1  

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