Rayleigh waves from a moving thrust fault

1972 ◽  
Vol 62 (3) ◽  
pp. 751-762
Author(s):  
A. K. Mal
Keyword(s):  
Free Surface ◽  
Earthquake Engineering ◽  
Amplitude Modulation ◽  
Rayleigh Waves ◽  
Wave Amplitude ◽  
Thrust Fault ◽  
Arbitrary Orientation ◽  
Period Range ◽  
Epicentral Region ◽  
Made In

Abstract The amplitude of the Rayleigh waves produced by a finite, propagating dip-slip fault of arbitrary orientation in a homogeneous, isotropic half-space is obtained. The fault is assumed to initiate suddenly at depth and to spread unilaterally to the free surface with constant speed. The Rayleigh-wave amplitude ahead of the fault break is shown to be considerably higher than that behind the initial epicenter. There is severe amplitude modulation in the epicentral region caused by the interference of waves traveling in opposite directions. The numerical results indicate that for Rayleigh waves in the period range of interest in earthquake engineering, a number of simplifications can be made in modeling an earthquake source of this type.

Attenuation of Rayleigh-wave amplitudes across Eurasia

1977 ◽  
Vol 67 (3) ◽  
pp. 751-769
Author(s):  
Nazieh K. Yacoub ◽  
Brian J. Mitchell
Keyword(s):  
Rayleigh Wave ◽  
Regional Variation ◽  
Wave Amplitude ◽  
Period Range ◽  
Attenuation Coefficients ◽  
Nuclear Explosions ◽  
Amplitude Data ◽  
Standard Deviations ◽  
Data Yield ◽  
Rayleigh Mode

abstract Surface waves generated by six earthquakes and two nuclear explosions are used to study the attenuation coefficients of the fundamental Rayleigh mode across Eurasia. Rayleigh-wave amplitude data yield average attenuation coefficients at periods between 4 and 50 sec. The data exhibit relatively large standard deviations and in some cases the average attenuation coefficients take on negative values which may be due to regional variations of the attenuative properties of the crust, lateral refraction, multipathing and scattering. A method has been developed to investigate the regional variation in the attenuative properties of the Eurasian crust and its effect on surface-wave amplitude data, employing the evaluated average attenuation coefficients for the fundamental Rayleigh mode. For this investigation, Eurasia is divided into two regions, one considered to be relatively stable, and the other considered to be tectonic in nature. This regionalization shows that the tectonic regions exhibit higher attenuation than the stable regions in the period range below about 20 sec, whereas in the period range above about 20 sec, no clear difference can be observed for the two regions. Although the effects of lateral refraction and multipathing may still significantly affect the observations, the regionalization lowers the standard deviations considerably and eliminates the negative values which were obtained in the unregionalized determinations.

An algorithm for automated tsunami warning in French Polynesia based on mantle magnitudes

1989 ◽  
Vol 79 (4) ◽  
pp. 1177-1193
Author(s):  
Jacques Talandier ◽  
Emile A. Okal
Keyword(s):  
Rayleigh Wave ◽  
Seismic Moment ◽  
Rayleigh Waves ◽  
French Polynesia ◽  
Tsunami Warning ◽  
Period Range ◽  
Wave Duration ◽  
T Wave ◽  
The Moment ◽  
Historical References

Abstract We have developed a new magnitude scale, Mm, based on the measurement of mantle Rayleigh-wave energy in the 50 to 300 sec period range, and directly related to the seismic moment through Mm = log10M0 − 20. Measurements are taken on the first passage of Rayleigh waves, recorded on-scale on broadband instruments with adequate dynamical range. This allows estimation of the moment of an event within minutes of the arrival of the Rayleigh wave, and with a standard deviation of ±0.2 magnitude units. In turn, the knowledge of the seismic moment allows computation of an estimate of the high-seas amplitude of a range of expectable tsunami heights. The latter, combined with complementary data from T-wave duration and historical references, have been integrated into an automated procedure of tsunami warning by the Centre Polynésien de Prévention des Tsunamis (CPPT), in Papeete, Tahiti.

Short-period seismic noise

1967 ◽  
Vol 57 (1) ◽  
pp. 55-81
Author(s):  
E. J. Douze
Keyword(s):  
Surface Waves ◽  
Rayleigh Waves ◽  
Seismic Noise ◽  
Body Waves ◽  
Deep Hole ◽  
Period Range ◽  
Short Period ◽  
The Subject ◽  
Hole Arrays

abstract This report consists of a summary of the studies conducted on the subject of short-period (6.0-0.3 sec period) noise over a period of approximately three years. Information from deep-hole and surface arrays was used in an attempt to determine the types of waves of which the noise is composed. The theoretical behavior of higher-mode Rayleigh waves and of body waves as measured by surface and deep-hole arrays is described. Both surface and body waves are shown to exist in the noise. Surface waves generally predominate at the longer periods (of the period range discussed) while body waves appear at the shorter periods at quiet sites. Not all the data could be interpreted to define the wave types present.

Ellipticity of Rayleigh waves recorded in the Midwest

1977 ◽  
Vol 67 (2) ◽  
pp. 369-382
Author(s):  
John L. Sexton ◽  
A. J. Rudman ◽  
Judson Mead
Keyword(s):  
Local Structure ◽  
Rayleigh Waves ◽  
Signal To Noise Ratio ◽  
Interference Effects ◽  
Signal To Noise ◽  
Period Range ◽  
Model Studies ◽  
Single Station ◽  
Special Value ◽  
The Time Domain

Abstract Measurements of ellipticity of Rayleigh waves recorded in the U.S. Midwest have been examined for azimuth dependence, effects of interference, and repeatability, as well as the hypothesis that a single station may be used to determine local structure. Time- and frequency-domain analyses were performed for each event, with more consistent results from the time-domain method. Results indicate that for the period range of 10 to 50 sec, ellipticity depends primarily upon local structure and does not exhibit significant azimuthal dependence. Most ellipticity values for a given period are repeatable within 5 per cent of other measured values from all source regions, with the greatest deviation being about 10 per cent. The cause of the deviations is attributed to interfering waves and/or poor signal-to-noise ratios. Interference effects result in scatter in ellipticity values. An ellipticity peak in the period range of 18 to 22 sec has variable magnitude for different events, depending upon the amount of interference present and the signal-to-noise ratio. Interference effects also manifest themselves as sharp decreases in group-velocity observations even after filtering. Model studies show that ellipticity peaks can exist, which are due to the layered structure and not necessarily to interference effects. Ellipticity measurements (10- to 50-sec-period range) from a single station are useful for determination of a crustal model for the vicinity of the recording station, but should be used in conjunction with other available geophysical and geological data. Ellipticity measurements are shown to be of special value for model determination in areas with sedimentary layering, a result in agreement with the Boore-Toksöz 1969) study.

Analysis of Rayleigh-wave multipath propagation at LASA

1970 ◽  
Vol 60 (5) ◽  
pp. 1701-1731 ◽  
Author(s):  
Jack Capon
Keyword(s):  
Rayleigh Waves ◽  
Multipath Propagation ◽  
Continental Margins ◽  
Period Range ◽  
Analysis Technique ◽  
High Resolution Analysis ◽  
Resolution Analysis ◽  
Propagation Paths ◽  
Using Data ◽  
Almost All

Abstract An investigation has been made of the multipath propagation of Rayleigh waves by using data obtained from the large aperture seismic array (LASA). The use of the LASA in conjunction with a high-resolution analysis technique provides a greater angular resolution and accuracy than was previously possible for the analysis of the multipath propagation. Measurements have been made of this phenomenon for the Rayleigh waves of 26 events distributed at various azimuths and distances from LASA. On the bas of these measurements reasonably good conjectures are made concerning the actual propagation paths for groups in the 20- to 40-sec period range. It is shown that in almost all cases these propagation paths can be associated with refractions and reflections at the continental margins.

Enhancing Signal-to-Noise Ratios of High-Frequency Rayleigh Waves Extracted from Ambient Seismic Noises in Topographic Region

2020 ◽  
Vol 110 (2) ◽  
pp. 793-802
Author(s):  
Ping Ping ◽  
Risheng Chu ◽  
Yu Zhang ◽  
Jun Xie
Keyword(s):  
Free Surface ◽  
Correlation Functions ◽  
High Frequency ◽  
Rayleigh Waves ◽  
Vertical Component ◽  
Noise Correlation ◽  
Surface Boundary ◽  
Elastic Wedge ◽  
Signal To Noise ◽  
Surface Boundary Conditions

ABSTRACT High-frequency Rayleigh waves can be extracted from ambient seismic noises through noise correlation functions (NCFs), which provides a useful tool to image shallow structures in topographic regions, for example, landslides. Topography may affect signal-to-noise ratios (SNRs) of extracted Rayleigh waves. It is necessary to investigate the propagation features of Rayleigh waves passing a 3D topography. Based on the incident and scattered waves satisfying the free surface boundary conditions, we first derive the displacement responses of Rayleigh waves across a 3D elastic wedge. The results show that the particle motions of Rayleigh waves are an ellipse whose longer axis is always perpendicular to the topographic free surface. Therefore, the Qg component, perpendicular to the topographic free surface, is a better choice to extract high-frequency Rayleigh waves than the conventional vertical component. To verify the choice, we carry out numerical simulations to extract high-frequency NCFs for a typical 3D massif model. Finally, we apply this approach to extract high-frequency Rayleigh-wave NCFs on the Xishancun landslide in southwestern China. The NCFs obtained using the Qg component have more coherent waveforms and higher SNRs than those using the vertical component. We conclude that the Qg component has advantages in extracting high-frequency Rayleigh waves over the conventional vertical component.

Near-perfect terahertz wave amplitude modulation enabled by impedance matching in VO2 thin films

2018 ◽  
Vol 112 (8) ◽  
pp. 081103 ◽  
Author(s):  
Hong-Fu Zhu ◽  
Liang-Hui Du ◽  
Jiang Li ◽  
Qi-Wu Shi ◽  
Bo Peng ◽  
...  
Keyword(s):  
Thin Films ◽  
Amplitude Modulation ◽  
Wave Amplitude ◽  
Impedance Matching ◽  
Terahertz Wave ◽  
Vo2 Thin Films

A Numerical Model for the Evaporation of a Nanoliter Droplet on a Solid, Heated Substrate

2007 ◽  
Author(s):  
Rajneesh Bhardwaj ◽  
Daniel Attinger
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Evaporation Time ◽  
Flat Substrate ◽  
Lagrangian Framework ◽  
Thermodynamic Conditions ◽  
Isothermal Case ◽  
Evaporative Flux ◽  
Temperature Levels ◽  
Made In

A finite-element numerical model is developed to study the evaporation of a sessile nanoliter droplet on a flat substrate in the isothermal and non-isothermal case. All equations are expressed in a Lagrangian framework, which provides accurate modeling of the free surface motion and the associated Laplace stresses. The evaporative flux at the free surface is defined as a function of the drop geometry and thermodynamic conditions. The boundary conditions at free surface are the mass and energy jump conditions. Results for fluid dynamics, evaporation time and evaporative flux are described for substrate temperature levels of 27°C (ambient), 82°C and 122°C. Comparisons with experiments are made, in terms of the evolution of volume, wetting angle and wetted radius.

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