A survey of the microseisms recorded at Aberdeen in 1955, together with a review of the meteorological conditions under which they may have arisen

1958 ◽  
Vol 48 (1) ◽  
pp. 65-76
Author(s):  
A. E. M. Geddes
Keyword(s):  
Fast Moving ◽  
Rayleigh Waves ◽  
Standing Waves ◽  
Meteorological Conditions ◽  
Love Waves ◽  
Norwegian Coast ◽  
Pressure Distributions ◽  
Moving Storm ◽  
Set Up ◽  
Rocky Coast

Abstract As observations of microseisms at Aberdeen appeared to indicate that microseisms may arise from a cause or causes other than from standing waves set up by reflection from a steep rocky coast or by a mixture of waves in a fast-moving storm, a survey of Aberdeen records for 1955 has been carried out and a comparison made with the meteorological conditions prevailing at the time. A noticeable feature on the weather charts was the frequent occurrence of pressure distributions with two centres, while the occasions on which fast-moving storms occurred, or reflection from rocky coasts, were rare. Consequently there seemed to be grounds for supposing that the standing waves arose from the interference of two sets of wave systems generated by double low-pressure centres. Further, single low centres off either the Norwegian coast or that of America produced very little effect at Aberdeen. The survey suggests that the principal regions where such microseisms were produced appeared to be in the Atlantic north of 50° N and off the rocky coast of northwest Scotland. From a comparison of the displacements on the E-W and N-S records there is some support for the hypothesis that microseisms are due to a mixture of Rayleigh waves and Love waves.

scholarly journals Excitation of mantle Love waves and definition of mantle wave magnitude

1969 ◽  
Vol 59 (2) ◽  
pp. 923-933
Author(s):  
James N. Brune ◽  
Gladys R. Engen
Keyword(s):  
Rayleigh Waves ◽  
Love Wave ◽  
Strike Slip ◽  
Love Waves ◽  
Excitation Curve ◽  
Kamchatka Earthquake ◽  
Set Up ◽  
Definition Of ◽  
Large Earthquakes ◽  
Slip Motion

abstract A study is made of the excitation of mantle Love waves of 100 seconds period as a function of magnitude. 153 measurements of Love wave spectral density for earthquakes since 1930 ranging in magnitude from 6.0 to 8.9 are used to determine an excitation curve. The observations were first corrected to a standard distance of 90°. The excitation curve supports earlier results for mantle Rayleigh waves and, for strike-slip motion, an earlier curve for seismic moment versus mantle-wave magnitude. For dip-slip motion, the moments should be multiplied by a factor of about 212. A definition of mantle wave magnitude MM, is set up, and the largest earthquake since 1930 found on this scale is the Alaskan earthquake of March 28, 1964 where MM = 8.9. Other comparably large earthquakes, MM = 8.8, were the Kamchatka earthquake of November 4, 1952 and the Chilean earthquake of May 22, 1960. It is suggested that mantle-wave magnitudes be used as a diagnostic aid in estimating the Tsunami potential of earthquakes.

scholarly journals Surface waves in multilayered elastic media I. Rayleigh and Love waves from buried sources in a multilayered elastic half-space

1964 ◽  
Vol 54 (2) ◽  
pp. 627-679
Author(s):  
David G. Harkrider
Keyword(s):  
Surface Waves ◽  
Frequency Domain ◽  
Half Space ◽  
Rayleigh Waves ◽  
Elastic Half Space ◽  
Love Waves ◽  
Displacement Fields ◽  
Matrix Formulation ◽  
Total Displacement ◽  
Rayleigh And Love Waves

ABSTRACT A matrix formulation is used to derive integral expressions for the time transformed displacement fields produced by simple sources at any depth in a multilayered elastic isotropic solid half-space. The integrals are evaluated for their residue contribution to obtain surface wave displacements in the frequency domain. The solutions are then generalized to include the effect of a surface liquid layer. The theory includes the effect of layering and source depth for the following: (1) Rayleigh waves from an explosive source, (2) Rayleigh waves from a vertical point force, (3) Rayleigh and Love waves from a vertical strike slip fault model. The latter source also includes the effect of fault dimensions and rupture velocity. From these results we are able to show certain reciprocity relations for surface waves which had been previously proved for the total displacement field. The theory presented here lays the ground work for later papers in which theoretical seismograms are compared with observations in both the time and frequency domain.

Study of the Pressure Distribution between the Piston Rings in Reciprocating Compressors

2011 ◽  
Vol 383-390 ◽  
pp. 6048-6052
Author(s):  
Dian Bo Xin ◽  
Jian Mei Feng ◽  
Yan Jing Xu ◽  
Xue Yuan Peng
Keyword(s):  
Pressure Distribution ◽  
Piston Ring ◽  
Dynamic Pressure ◽  
Threshold Value ◽  
Piston Rings ◽  
Premature Failure ◽  
Root Cause ◽  
Pressure Distributions ◽  
Start Up ◽  
Set Up

Piston ring is one of the most important sealing components that can be easily damaged in reciprocating compressors. The severe non-uniformity of the pressure distribution was suggested to be the essential reason for the premature failure of the piston rings. Therefore, a test rig was set up to measure the pressure distributions as well as the build-up of the dynamic pressure difference, which could reveal the root cause for the non-uniformity of the pressure distributions. The results showed that the build-ups of the pressure differences between different rings were not simultaneous; there existed a threshold pressure, and the latter ring could work only when the pressure before the former ring reached to the threshold value. The pressure distributions were also investigated at the start-up and shut-down of the compressor, which further validated the cause of the premature failure of the first ring.

THE ATMOSPHERIC POTENTIAL GRADIENT AT OTTAWA, CANADA

1937 ◽  
Vol 15a (8) ◽  
pp. 119-148 ◽  
Author(s):  
D. C. Rose
Keyword(s):  
Diurnal Variation ◽  
Potential Gradient ◽  
Meteorological Conditions ◽  
Fine Weather ◽  
Points Of View ◽  
Set Up ◽  
A Site

The atmospheric potential gradient was observed continuously at the National Research Laboratories at Ottawa for a year ending December 1, 1935, and at a country station about nine miles northwest of Ottawa, for four months ending November 1, 1936. The country station was set up on a site as free as possible from man-made pollution of the atmosphere. The records were studied from two points of view, the diurnal variation and disturbances in the normal fine weather value of the potential gradient. The results indicate that the diurnal variation is similar to that of other similarly situated stations. The study of disturbances in the potential gradient shows that all disturbances can be correlated with local meteorological conditions. The disturbances were for the most part associated with the stormy conditions usual at the passage of a front. The effect of city pollution on potential gradient records is clearly shown.

Structure of microseismic waves: estimation of direction of approach by comparison of vertical and horizontal components

1954 ◽  
Vol 223 (1152) ◽  
pp. 96-111 ◽  
Keyword(s):  
Rayleigh Waves ◽  
Vertical Component ◽  
Correlation Coefficients ◽  
Love Waves ◽  
The North ◽  
Wave Interference ◽  
Rayleigh And Love Waves ◽  
The Mean ◽  
East West ◽  
Phase Differences

Analysis of microseisms recorded at Kew Observatory on 8 to 10 October 1951 affords further confirmation of the wave-interference theory of microseism generation, and allows those of 8 to 10 October to be attributed to a fast-moving depression between the Azores and Iceland. Although the bearing of the microseism-generating area changes by more than 90° during the period investigated, there is no appreciable difference in the ratio of the mean ampli­tudes of the north-south and east-west horizontal components as would be expected if the microseisms consisted entirely of Rayleigh waves. An investigation of the phase differences between the three components, using Lee’s method, suggests that the microseisms consist of Rayleigh and Love waves in comparable proportions. Making use of this assumption, the vertical component, which is not affected by the Love waves, is correlated with the two horizontal components with an electronic correlating device, and the bearing of the microseism area can be deduced from the correlation coefficients. The calculated bearings agree reasonably well with those obtained from the meteorological charts. The bearing of a storm on 12 to 15 November 1945, studied in a previous paper, was also calculated satisfactorily.

scholarly journals Study of Love and Rayleigh waves from earthquakes with fault plane solutions or with known faulting Part 3. Table of source phase differences between Rayleigh and Love waves

1964 ◽  
Vol 54 (2) ◽  
pp. 559-570
Author(s):  
Keiiti Aki
Keyword(s):  
Rayleigh Waves ◽  
Fault Plane ◽  
Love Waves ◽  
Fault Plane Solutions ◽  
Rayleigh And Love Waves ◽  
Source Phase ◽  
Phase Differences

ABSTRACT The table of source phase differences between Rayleigh and Love waves which was described in Part 1 and used in Part 2 is presented in a concise form for the case of a surface focus.

scholarly journals Velocities of mantle Love and Rayleigh waves over multiple paths

1963 ◽  
Vol 53 (4) ◽  
pp. 741-764 ◽  
Author(s):  
M. Nafi Toksöz ◽  
Ari Ben-Menahem
Keyword(s):  
Rayleigh Waves ◽  
Great Circle ◽  
Love Waves ◽  
Period Range ◽  
Phase Velocities ◽  
Multiple Paths ◽  
Lateral Variations ◽  
Phase Spectra ◽  
Group Velocities ◽  
Good Agreement

Abstract Phase velocities of Love waves from five major earthquakes are measured over six great circle paths in the period range of 50 to 400 seconds. For two of the great circle paths the phase velocities of Rayleigh waves are also obtained. The digitized seismograph traces are Fourier analyzed, and the phase spectra are used in determining the phase velocities. Where the great circle paths are close, the phase velocities over these paths are found to be in very good agreement with each other indicating that the measured velocities are accurate and reliable. Phase velocities of Love waves over paths that lie far from each other are different, and this difference is consistent and much greater than the experimental error. From this it is concluded that there are lateral variations in the structure of the earth's mantle. One interpretation of this variation is that the mantle under the continents is different from that under the oceans, since the path with the highest phase velocities is almost completely oceanic. This interpretation, however, is not unique and variations under the oceans and continents are also possible. Group velocities are computed from the phase velocities and are also directly measured from the seismograms. The group-velocity curve of Love waves has a plateau between periods of 100 and 300 seconds with a shallow minimum at about 290 seconds. The sources of error in both Fourier analysis and direct time domain methods of phase velocity measurement are discussed.

Anomalous surface waves from underground explosions

1979 ◽  
Vol 69 (6) ◽  
pp. 1995-2002 ◽  
Author(s):  
Eivind Rygg
Keyword(s):  
Rayleigh Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Major Part ◽  
Wave Generation ◽  
Love Waves ◽  
Phase Reversal ◽  
Wave Phase ◽  
Anomalous Surface

abstract The Rayleigh waves at Δ ∼40° from an eastern Kazakh explosion are shown to be polarity reversed and delayed relative to the Rayleigh waves from two other explosions of comparable magnitudes in the same area. The event generating the anomalous Rayleigh waves excited very strong Love waves which were not delayed. The Rayleigh wave phase reversal is shown to be a source phenomenon and it is suggested that in this particular case, spall closure was responsible for a major part of the Rayleigh-wave generation.

Farm Opinion Leaders

2017 ◽  
Vol 13 (1) ◽  
pp. 75-78
Author(s):  
Baljeet Singh
Keyword(s):  
Decision Maker ◽  
Fast Moving ◽  
Opinion Leaders ◽  
New Method ◽  
Opinion Leadership ◽  
Market Selection ◽  
Product Categories ◽  
The Family ◽  
Set Up ◽  
S Model

This book endeavours to help the readers identify the farm opinion leaders and to understand the characteristics of farm opinion leaders and farm opinion seekers. Beside this motivation, satisfaction and effectiveness of farm opinion leaders and farm opinion seekers are also demystified for a rural set up. The study of influence of family members on the head decision maker of the family is initiated. A theoretical 4 P’s model of farm opinion leadership is proposed and a new method for identification of farm opinion leaders is conceptualised. Agriculture marketing decisions for four agriculture product categories i) agri input consumables (seed, fertilizer and pesticides) the fast moving agriculture goods (FMAGs), ii) agri input capital (farm machineries) the agriculture durables, iii) agri input credit (formal and informal sources) and iv) agri output (price, packaging, transport, storage and market selection) were studied.

4. Seismic waves

2018 ◽  
pp. 53-61
Author(s):  
Mike Goldsmith
Keyword(s):  
Seismic Wave ◽  
Rayleigh Waves ◽  
Seismic Waves ◽  
Shear Waves ◽  
Free Vibrations ◽  
Love Waves ◽  
Sound Waves ◽  
P Waves ◽  
Tectonic Plates ◽  
S Waves

Sound waves travel very easily underground, often for many thousands of kilometres. These are usually referred to as a kind of seismic wave and are most often triggered by earthquakes, which result from a sudden slip of tectonic plates, down to about 700 kilometres below the Earth’s surface. ‘Seismic waves’ describes the four types of seismic wave generated by earthquakes: P-waves (primary waves), S-waves (shear waves), Love waves (usually the most powerful and destructive of seismic waves), and Rayleigh waves, which are created when P and S waves reach the Earth’s surface together, combining to form undulating ground rolls. Free vibrations and star waves are also described.

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