Microseismic And Infrasound Waves

Microseismic and Infrasound Waves

Microseismic and Infrasound Waves

In the early 1950s microseisms, with characteristic amplitudes of several micro meters, were considered insignificant relative to powerful destructive earthquakes. They were understood to be noise, as natural fluctuations, not carrying any in formation and distorting recordings on seismograms. Intensive investigations over subsequent decades have shown, however, that microseisins are only a single facet of a huge complex of phenomena comprising cyclone movement over oceans, sea roughness, infrasound, geomagnetic micropulsations, terrestial of these phenomena proved to be confined in time currents, etc. The source and space, whereas their effects propagated over global distances. This could be interpreted as a case of natural "remote sensing". It should be mentioned that all of the evidence gathered in the last few decades supports the theory of M. S. Longuet-Higgins published in 1950. The author has been engaged in problems of microseisms since 1955 and is deeply convinced that these phenomena are not only of theoretical interest but may also find practical application in meteorology, oceanology, navigation and other areas. She hopes. that this book will stimulate further research as well as new approaches to practical problems.

Infrasound Monitoring for Atmospheric Studies

The use of infrasound to monitor the atmosphere has, like infrasound itself, gone largely unheard of through the years. But it has many applications, and it is about time that a book is being devoted to this fascinating subject. Our own involvement with infrasound occurred as graduate students of Prof. William Donn, who had established an infrasound array at the Lamont-Doherty Geological Observatory (now the Lamont-Doherty Earth Observatory) of Columbia University. It was a natural outgrowth of another major activity at Lamont, using seismic waves to explore the Earth’s interior. Both the atmosphere and the solid Earth feature velocity (seismic or acoustic) gradients in the vertical which act to refract the respective waves. The refraction in turn allows one to calculate the respective background structure in these mediums, indirectly exploring locations that are hard to observe otherwise. Monitoring these signals also allows one to discover various phenomena, both natural and man-made (some of which have military applications).