SEISMIC WAVES FROM A HORIZONTAL FORCE

Geophysics ◽  
1956 ◽  
Vol 21 (3) ◽  
pp. 715-723 ◽  
Author(s):  
J. E. White ◽  
S. N. Heaps ◽  
P. L. Lawrence
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Qualitative Agreement ◽  
Seismic Waves ◽  
Shear Waves ◽  
Earth Surface ◽  
Horizontal Force ◽  
The Earth ◽  
Fundamental Research ◽  
The Waves

As part of a program of fundamental research on seismic waves, a generator was built for applying a transient horizontal force at the surface of the ground and the resulting seismic waves were observed in some detail. The force is applied when a mass swinging through an arc strikes a target anchored to the earth. Surface geophones along a line in the direction of the force register vertically polarized shear waves refracted back up to the surface, whereas geophones on a line perpendicular to the force register horizontally polarized shear waves. The speeds of the two types of shear waves are often different, indicating anisotropy. Geophones buried below the target show a down‐going shear wave. Variation of amplitude with angle, and other features, are in qualitative agreement with the results given by Rayleigh and others for the waves due to a force at a point in an infinite solid. Love waves and other surface waves were observed, which of course would not be expected from an nterior force.

STUDIES ON SEISMIC WAVES: III. PROPAGATION OF ELASTIC WAVES IN THE NEIGHBORHOOD OF A FREE BOUNDARY

Geophysics ◽  
1947 ◽  
Vol 12 (1) ◽  
pp. 57-71 ◽  
Author(s):  
C. Y. Fu
Keyword(s):  
Surface Waves ◽  
Elastic Waves ◽  
Seismic Waves ◽  
Classical Method ◽  
Epicentral Distance ◽  
Harmonic Waves ◽  
Inhomogeneous Waves ◽  
Different Types ◽  
Propagation Of Elastic Waves ◽  
The Waves

Continuous and spherical harmonic waves are generated at an internal point of the medium. By use of the classical method of Sommerfeld, the different modes of propagation near a free surface after the arrival of the waves are examined. From the approximate evaluations of the integrals, it is found that in addition to the ordinary types of body and surface waves, there are also inhomogeneous waves and surface waves which are not of the Rayleigh type. The amplitude factors of these latter waves vary inversely as the square instead of as the square root of the epicentral distance. Altogether, there are not less than five different types of waves and they are obtained from integrations in the neighborhood of the singularities of the integrals.

Why Newtonian gravity is an electromagnetic wave

2020 ◽  
Vol 33 (1) ◽  
pp. 23-26
Author(s):  
Nicolus Rotich
Keyword(s):  
Electromagnetic Wave ◽  
Gravitational Waves ◽  
Newtonian Gravity ◽  
Earth Surface ◽  
Speed Of Light ◽  
The Earth ◽  
Planetary Bodies ◽  
The Waves

In this brief communication, we have hypothesized that since Newtonian gravity intimately interacts with classical gravitational waves, it must also be perceivable and mathematically expressible as a wave. It has been shown that Newtonian gravity can be represented as an electromagnetic wave of a particular wavelength <mml:math display="inline"> <mml:mi>λ</mml:mi> </mml:math> , propagating at the speed of light, c and with a radius of <mml:math display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>=</mml:mo> <mml:mi>λ</mml:mi> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> . The waves period is given by T = c/g, and thus acceleration due to gravity is representable as g = cf, where f is position dependent, and thus unique for all orbiting planetary bodies. On the Earth surface, this value is ≅32.71 nHz.

A note on the effect of ripple firing on the spectra of quarry shots

1963 ◽  
Vol 53 (1) ◽  
pp. 79-85
Author(s):  
D. E. Willis
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Seismic Waves

Abstract A series of controlled quarry shots were recorded at a distance of approximately 900 feet to ascertain the effect of ripple firing on amplitude and spectra of the seismic waves. A measurable reduction in the amplitude of compressional and shear wave was observed at some frequencies. This effect was not so pronounced for the surface waves.

scholarly journals Attenuation of shear waves in the upper and lower mantle

1964 ◽  
Vol 54 (6A) ◽  
pp. 1855-1864 ◽  
Author(s):  
Robert L. Kovach ◽  
Don L. Anderson
Keyword(s):  
Lower Mantle ◽  
Seismic Waves ◽  
Wave Amplitude ◽  
Body Wave ◽  
Shear Waves ◽  
Normal Incidence ◽  
Frequency Range ◽  
Spectral Ratios ◽  
The Earth ◽  
Deep Focus

abstract The attenuation of seismic waves is a direct measure of the absorption due to nonelastic processes in the earth. The well known difficulties in obtaining body wave amplitude decrement data have been avoided by studying the spectral ratios of multiple ScS and sScS phases from two deep focus earthquakes recorded at near normal incidence. The average Q, for shear, in the mantle is about 600 for the frequency range 0.015 to 0.07 cps. Assuming that equal radiation occurs upwards and downwards from the source the average Q for the upper 600 km of the mantle is determined to be about 200 and about 2200 for the rest of the mantle. The value for Q at the base of the mantle is at least 5000 for shear waves.

scholarly journals A Seismic Experiment Using Quarry Blasts Near Sydney

1962 ◽  
Vol 15 (3) ◽  
pp. 293 ◽  
Author(s):  
BA Bolt
Keyword(s):  
Seismic Waves ◽  
Shear Waves ◽  
Seismic Experiment ◽  
Time Signals ◽  
The Waves ◽  
Bodily Wave

The seismic waves generated by quarry blasts from 2 to 6 tons in weight, over an interval of 7 months, at Prospect, about 30 kIn west of Sydney, are examined. Shot times at the quarry were measured from radio time signals. The waves were recorded by seismographs at 10 seismological stations ranging in distance from 20 kIn (Riverview) to 380 kIn (Geehi in the Snowy Mountains). Analysis of the seismograms indicated two main bodily-wave phases, called PI and S1" The SI waves, which possess considerable energy relative to the compressional first-arrivals PI' appear to be shear waves generated in part by the unsymmetrical nature of the source.

Seismic waves in a wedge

1975 ◽  
Vol 65 (6) ◽  
pp. 1697-1719
Author(s):  
Z. Alterman ◽  
R. Nathaniel
Keyword(s):  
Free Surface ◽  
Surface Waves ◽  
Particle Motion ◽  
Seismic Waves ◽  
Wedge Angle ◽  
Compressional Wave ◽  
Elastic Wedge ◽  
Compressional Wave Velocity ◽  
Quarter Plane ◽  
The Waves

abstract The equations for elastic-wave propagation caused by an explosive point source are solved, by a finite difference scheme, for the case of an elastic wedge, with free boundary. Varying the wedge angle shows that the amplitude of the motion, at the corner, increases as the wedge angle is decreased. The results indicate that for wedges with angles varying from 0° to 180°, the amplitude decreases with decreasing β/α (shear- to compressional-wave velocity). The corner of the wedge generates surface waves and the elliptical particle motion in the waves is analyzed. The particle motion is elliptic and the major axes of the ellipses are inclined at half the wedge angle to the free surface. The surface wave travels to the corner from where it is “transmitted” and reflected. Surface waves are shifted by 180° - θ after transmission. For the case of a quarter plane, we get the same result as Alterman and Loewenthal (1970).

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