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Research Required to Support Comprehensive Nuclear Test Ban Treaty Monitoring (1997) / Chapter Skim
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Appendix F: Infrasonics
Pages 125-130

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From page 125...
... For example, normal wind speeds from 5 to 15 m/s can generate quasi-static dynamic pressures from two to three orders of magnitude greater than most infrasonic signals. 125 Atmospheric acoustic or gravity waves are lower-frequency infrasonic waves indicating that dual processes can influence atmospheric propagation.
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From page 126...
... 100 ,~'1 1 1 1 1 1 1 1 ~ I I I I I I I I I I I I I J I I I I I 4`o _ I I I I I I I 1 1 1 1 1 1 ~ I I ~ I I I I ~ I I I I I I I 1 l ~ J r 5-0 6.M.T. 5 _ ~tS 20 25 30 35 Si0 o ao FIGURE F.2 Sample infrasound record of an atmospheric explosion showing a low-frequency Lamb wave arriving before the main acoustic signal.
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From page 127...
... More recently, using pipes or porous garden hose, 8 or 16 m radial tubes from a central sensor have allowed cost-effective areal sampling. Such filters greatly reduce unwanted noise, but 127 there is still a need to distinguish true infrasonic signals from the remaining local noise, which does not propagate at acoustic frequencies.
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From page 128...
... This part of the spectrum is of interest in explosion monitoring because it is close to the frequency of the main acoustic arrival for 1 kt explosions. The adopted pressure range curve that the United States presented in Geneva was based on nuclear detections from 0.2 to 112 kt and conventional chemical explosions of less than 1 to 6 kt free air equivalent.
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From page 129...
... However, seismic and infrasound signals from the event must be compared to address the possibility that signals from a conventional surface explosion have been used to mask a buried nuclear explosion. In cases where seismic and infrasound stations are colocated, the infrasound stations may be useful in identifying signals recorded by seismic instruments that arise because the passage of the infrasound signal causes the Earth's surface to move.
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From page 130...
... These values are approximate heights of total refraction as given in a ray picture and are reflected in the range of average travel speeds. With wind propagation, as described above, larger measured signals from a source can be observed downwind than would be measured in the opposite direction, against the wind.
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Key Terms

  • main acoustic
  • infrasonic signals
  • pressure signals
  • sources include
  • acoustic signal

  • infrasound signal
  • nuclear explosions
  • ctbt monitoring
  • gravity waves
  • wind speed

  • acoustic signals
  • local noise
  • various signal
  • nuclear test
  • approximate frequency

  • nuclear explosion
  • signal types
  • surface explosion
  • test ban
  • atmospheric propagation

  • infrasound monitoring
  • lamb waves
  • wind speeds
  • comprehensive nuclear
  • average travel

  • frequency ranges
  • pressure changes
  • atmospheric nuclear
  • ban treaty
  • infrasonic sources


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