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.

Contenu

1. Excitation of Microseisms and Infrasound Vibrations.- 1.1 Formation of Microseisms from Sea Waves.- 1.2 SMS Excitation.- 1.3 Comparison of Existing Theories of SMS Excitation.- 1.4 Theories of SMS and Infrasound Generation by Standing Sea Waves.- 1.5 Hasselman Theory.- 1.6 Nanda Theory of SMS Generation.- 1.7 Primary and Secondary Shore Microseisms.- 2. Sources of Excitation of SMS and IS.- 2.1 Observations on the Caspian Sea. Establishment of Fundamental Relations.- 2.2 Observations of SMS on Lake Baikal.- 2.3 Microseismic Storms on the Okhotsky Sea.- 2.4 Observations of Hydrometeorological Conditions and SMS on Oceans. Recording of Alternating Pressures on the Ocean Bottom.- 2.5 Recording Infrasound Vibrations in the Atmosphere and Microseisms.- 2.6 Observations on SMS in the Shore Zone and on the Ocean Bottom.- 2.7 Experimental Confirmation of the Theory of Standing Waves, MS and Infrasound.- 3. Decomposition of MS Noise into Discrete Sources of MS Excitation.- 3.1 Separation of MS Noise According to Frequency Synchronism.- 3.2 SMS Spectra.- 3.3 Separation of Seismic Noise into Components Arriving from Different Sources.- 4. Determination of Power, Energy and Positions of Sources of MS Excitation.- 4.1 Source Position.- 4.2 Source Power and Energy.- 4.3 Determination of Position and Power of MS Sources Using the Power Constant.- 4.4 Shape and Size of MS Sources.- 5. MS as an Indicator of Storm Phenomena, Water Wave Regimes, Infrasound Waves and Geometric Excitations.- 5.1 Phenomena Which Arise with SMS.- 5.2 Formation of Standing Sea Waves and SMS.- 5.3 Influence of the Velocity of a Cyclone Center on MS Formation.- 5.4 Directionality of SMS and IS Radiation by an Array of Standing Sea Waves.- 5.5 Velocity of a Cyclone Center, SMS and Magnetic Storms.- 5.6Perturbations in the Ionosphere and Fluctuations of the Geomagnetic Field.- 5.7 Geomagnetic Storms, Telluric Currents, Geomagnetic Micropulsations and SMS.- 5.8 Variations of Global MS Vibrations.- 5.9 Propagation of Radiowaves and MS Storms on Oceans.- 6. MS Vibrations in Engineering Seismology.- 6.1 Use of MS in Estimating the Seismic Response of Soils. Electrodynamic Analogy.- 6.2 High Frequency MS.- 6.2.1 Spontaneous MS.- 6.2.2 Mechanical Vibrators.- 6.3 Low Frequency MS.- 6.4 Further Possible Applications of MS.- References.