Microseismic and Infrasound Waves

ISBN-13: 9783540532934 / Angielski / Miękka / 1992 / 150 str.

V. N. Tabulevich; Valentina N. Tabulevich

Opis

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.

Spis treści

1. Excitation of Microseisms and Infrasound Vibrations.- 1.1 Formation of Microseisms from Sea Waves.- 1.1.1 Hydrodynamics.- 1.1.2 Pressure at the Bottom in the Case of Running Waves.- 1.1.3 Pressure at the Bottom in the Case of Standing Waves.- 1.2 SMS Excitation.- 1.2.1 Coherent Model.- 1.2.2 Noncoherent Model.- 1.3 Comparison of Existing Theories of SMS Excitation.- 1.4 Theories of SMS and Infrasound Generation by Standing Sea Waves.- 1.4.1 Theory of Miche and Longuet-Higgins.- 1.4.2 Hieblot and Rocard Theory on the Origin of SMS.- 1.4.3 Theory of Infrasound Radiation 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.- 3.1.1 Examples.- 3.2 SMS Spectra.- 3.3 Separation of Seismic “Noise” into Components Arriving from Different Sources.- 3.3.1 Measurements.- 4. Determination of Power, Energy and Positions of Sources of MS Excitation.- 4.1 Source Position.- 4.1.1 The Amplitude Field.- 4.1.2 Amplitude Centroid Method.- 4.2 Source Power and Energy.- 4.2.1 Typical Source Strengths (Hydrodynamic Model).- 4.2.2 Seismic Station Measurements of MS Excitation Sources.- 4.2.3 Calibration Curves.- 4.2.4 Estimates of the Power in Actual Cases.- 4.2.5 Comparison of MS Energy with Cyclone Energy.- 4.2.6 Method of Centroids in MS Source Position and Power Determination. An Example.- 4.3 Determination of Position and Power of MS Sources Using the Power Constant.- 4.3.1 Graphical Method.- 4.3.2 Cayley’s Determinant.- 4.3.3 Method of Power Discrepancy.- 4.3.4 MS Sources in the Northern Atlantic and Northwestern Pacific.- 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.- 5.6 Perturbations in the Ionosphere and Fluctuations of the Geomagnetic Field.- 5.7 Geomagnetic Storms, Telluric Currents, Geomagnetic Micropulsations and SMS.- 5.7.1 Geomagnetic Storms and MS.- 5.7.2 SMS, Geomagnetic Micropulsations and Telluric Currents.- 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.