Wave train characteristics of long-range, high-frequency Pn,Sn crossing an ocean bottom hydrophone array

1980 ◽  
Vol 70 (2) ◽  
pp. 437-446
Author(s):  
Charles S. McCreery ◽  
George H. Sutton
Keyword(s):  
Long Range ◽  
High Frequency ◽  
Velocity Structure ◽  
Wave Train ◽  
Ocean Bottom ◽  
Near Wake ◽  
Magnetic Type ◽  
Wave Trains ◽  
Hydrophone Array ◽  
Plane Wave Front

abstract During February and March 1976 high-frequency Pn,Sn phases from several earthquakes in the distance range 18° to 29° were recorded on magnetic type from an array of bottom mounted hydrophones near Wake Island. Large discrepancies were found between the actual arrival sequences of these phases and those expected for uniform propagation of a plane wave front across the array. Furthermore, the signal envelopes of the wave trains were dissimilar on different hydrophones for any given Pn,Sn phase. Comparisons between arrival sequences on the different hydrophones and between the signal envelopes on a given hydrophone from groups of earthquakes with nearly identical hypocenters indicate that differences in velocity structure near individual hydrophones cannot explain these observations. They are more likely the result of either the mechanism of generation or of long-range propagation for Pn and Sn, or both.

scholarly journals On the scattering of X- and γ- rays by rings of electrons.—The effect of damping of the incident radiation

1923 ◽  
Vol 104 (724) ◽  
pp. 153-164 ◽  
Keyword(s):  
High Frequency ◽  
Previous Investigation ◽  
Wave Train ◽  
Harmonic Wave ◽  
Incident Radiation ◽  
The Other ◽  
Other Hand ◽  
Γ Rays ◽  
Wave Trains

1. The object of the present investigation is to examine whether damping of the incident radiation can account for the abnormally small scattering of hard γ -rays by aluminium, iron and lead, which was observed by Ishino and was left unexplained in a previous investigation, based on the hypothesis that scattering is a phenomenon of the diffraction by electron rings in the atom of undamped simple harmonic wave-trains of high frequency. It may be stated at once that the result of the enquiry is negative: it is true that damping of an amount small enough to be consistent with the generation of moderately sharp lines in the X- and γ -ray spectrum diminishes the scattering of long waves, but it increases that of short waves, and in each case the change is far too small to explain Ishino’s result. On the other hand, very large damping probably diminishes the scattering of all waves, but it is practically certain that it does not diminish it below the amount required by the Simple Pulse theory, whilst Ishino’s values are only of the order of one-quarter of that amount. This result was to be expected, since an infinitely damped wave-train may be regarded as equivalent to a pulse.

LONG DURATION ECHOES FROM AURORA, METEORS, AND IONOSPHERIC BACK-SCATTER

1953 ◽  
Vol 31 (2) ◽  
pp. 171-181 ◽  
Author(s):  
D. W. R. McKinley ◽  
Peter M. Millman
Keyword(s):  
Long Range ◽  
High Frequency ◽  
The Other ◽  
Very High Frequency ◽  
Long Duration ◽  
E Region ◽  
Very High ◽  
Visual Observations

In the course of the Ottawa meteor program some unusual echoes have been detected on 33 Mc. Echoes from the aurora are discussed and correlated with visual observations. Two mechanisms of radio reflections from the aurora have been proposed but the data here presented are insufficient to favor one over the other. On Aug. 4, 1948, six extremely long duration meteor echoes were observed which may have been due to abnormal ionospheric conditions. From time to time since August, 1948, a weak semipermanent echo has been recorded, usually appearing at a range of about 80 km., and enduring up to an hour. It is suggested that this echo is due to back-scatter from the same sources in the lower E-region that are presumed to be responsible for long-range very high frequency propagation.

Sub-Moho seismic profile in the Mariana Basin — Ocean bottom seismograph long-range explosion experiment

1981 ◽  
Vol 53 (1) ◽  
pp. 93-102 ◽  
Author(s):  
S. Nagumo ◽  
T. Ouchi ◽  
J. Kasahara ◽  
S. Koresawa ◽  
Y. Tomoda ◽  
...  
Keyword(s):  
Long Range ◽  
Seismic Profile ◽  
Ocean Bottom ◽  
Ocean Bottom Seismograph ◽  
Explosion Experiment

scholarly journals Roles of the Synoptic-Scale Wave Train, the Intraseasonal Oscillation, and High-Frequency Eddies in the Genesis of Typhoon Manyi (2001)*

2014 ◽  
Vol 71 (10) ◽  
pp. 3706-3722 ◽  
Author(s):  
Yamei Xu ◽  
Tim Li ◽  
Melinda Peng
Keyword(s):  
High Frequency ◽  
Development Process ◽  
Wave Train ◽  
Wrf Model ◽  
Intraseasonal Oscillation ◽  
Wave Activity ◽  
Weather Research And Forecasting ◽  
Synoptic Scale ◽  
Energy Dispersion ◽  
Multiple Episodes

Abstract Experiments using the Weather Research and Forecasting (WRF) Model were conducted to investigate the effects of multiscale motions on the genesis of Typhoon Manyi (2001) in the western North Pacific. The precursor signal associated with this typhoon genesis was identified as a northwest–southeast-oriented synoptic-scale wave train (SWT). The model successfully simulated the genesis of the typhoon in the wake of the SWT. Further experiments were conducted to isolate the effects of the SWT, the intraseasonal oscillation (ISO), and high-frequency (shorter than 3 days) eddies in the typhoon formation. Removing the SWT in the initial and boundary conditions eliminates the typhoon genesis. This points out the importance of the SWT in the typhoon genesis. It was noted that the SWT strengthened the wake cyclone through southeastward energy dispersion. The strengthening wake cyclone triggered multiple episodes of strong sustained convective updrafts, leading to aggregation of vertical vorticity and formation of a self-amplified mesoscale core vortex through a “bottom up” development process. Removing the ISO flow eliminates the typhoon genesis, as the ISO significantly modulated the strength of the SWT through accumulation of wave activity. In the absence of SWT–ISO-scale interaction, the southeastward energy dispersion was weakened significantly, and thus the strengthening of the wake cyclone did not occur. As a result, the successive strong sustained convective updrafts disappeared. Removing the high-frequency eddies did not eliminate the typhoon genesis but postponed the genesis for about 36 h.

Stability of periodic waves in shallow water

1974 ◽  
Vol 66 (1) ◽  
pp. 81-96 ◽  
Author(s):  
P. J. Bryant
Keyword(s):  
Shallow Water ◽  
Wave Train ◽  
Periodic Wave ◽  
Fundamental Wave ◽  
Cnoidal Waves ◽  
Margin Of Stability ◽  
Fundamental Wavelength ◽  
Stokes Waves ◽  
Wave Trains ◽  
Permanent Shape

Waves of small but finite amplitude in shallow water can occur as periodic wave trains of permanent shape in two known forms, either as Stokes waves for the shorter wavelengths or as cnoidal waves for the longer wavelengths. Calculations are made here of the periodic wave trains of permanent shape which span uniformly the range of increasing wavelength from Stokes waves to cnoidal waves and beyond. The present investigation is concerned with the stability of such permanent waves to periodic disturbances of greater or equal wavelength travelling in the same direction. The waves are found to be stable to infinitesimal and to small but finite disturbances of wavelength greater than the fundamental, the margin of stability decreasing either as the fundamental wave becomes more nonlinear (i.e. contains more harmonics), or as the wavelength of the periodic disturbance becomes large compared with the fundamental wavelength. The decreasing margin of stability is associated with an increasing loss of spatial periodicity of the wave train, to the extent that small but finite disturbances can cause a form of interaction between consecutive crests of the disturbed wave train. In such a case, a small but finite disturbance of wavelength n times the fundamental wavelength converts the wave train into n interacting wave trains. The amplitude of the disturbance subharmonic is then nearly periodic, the time scale being the time taken for repetitions of the pattern of interactions. When the disturbance is of the same wavelength as the permanent wave, the wave is found to be neutrally stable both to infinitesimal and to small but finite disturbances.

On a uniformly valid model for surface wave interaction

1993 ◽  
Vol 247 ◽  
pp. 589-601 ◽  
Author(s):  
Yehuda Agnon
Keyword(s):  
Surface Wave ◽  
Water Waves ◽  
Wave Train ◽  
Wave Interaction ◽  
Shallow Water Waves ◽  
First Order ◽  
Near Resonance ◽  
Wave Trains ◽  
Velocity Changes ◽  
Forced Waves

Nonlinear interaction of surface wave trains is studied. Zakharov's kernel is extended to include the vicinity of trio resonance. The forced wave amplitude and the wave velocity changes are then first order rather than second order. The model is applied to remove near-resonance singularities in expressions for the change of speed of one wave train in the presence of another. New results for Wilton ripples and the drift current and setdown in shallow water waves are readily derived. The ideas are applied to the derivation of forced waves in the vicinity of quartet and quintet resonance in an evolving wave field.

scholarly journals Observations of multiple seismic events

1964 ◽  
Vol 54 (1) ◽  
pp. 19-39
Author(s):  
W. L. Pilant ◽  
L. Knopoff
Keyword(s):  
Amplitude Ratio ◽  
Multipath Propagation ◽  
Wave Train ◽  
Seismic Surface Waves ◽  
Derived Properties ◽  
Beat Phenomenon ◽  
Wave Trains ◽  
The Individual ◽  
Comparable Magnitude ◽  
Resultant Wave

abstract Two or more dispersed wave trains each with constant amplitude will interfere giving a resultant wave train which is amplitude modulated, if the individual waves have their principal energies in a common frequency band and if the trains arrive with time separations small compared to their total length. The dispersive characteristics of the trains need not be the same. If the component trains are of comparable magnitude, the modulation due to interference becomes significant and a “beat” phenomenon occurs. Multiple trains of dispersed seismic surface waves may occur because of a temporal and/or spatial distribution at the source or because of multipath propagation. Each of these causal mechanisms influences the amplitude and phase spectra of the resultant wave train; derived properties such as phase velocities and amplitude ratios are also influenced. In the case of multipath propagation, wavelength dependent time delays may occur. Two cases of twin earthquakes are analyzed, and the significant features of interference are demonstrated. In one case, estimates are obtained for the amplitude ratio and time delay of the second shock with respect to the first. The interpretation of seismograms and spectra influenced by multiple events is discussed.

Sign in / Sign up

Export Citation Format

Share Document