Marine sediment shear velocity structure from the ratio of displacement to pressure of Rayleigh waves at seafloor

2014 ◽  
Vol 119 (8) ◽  
pp. 6357-6371 ◽  
Author(s):  
Youyi Ruan ◽  
Donald W. Forsyth ◽  
Samuel W. Bell
Keyword(s):  
Marine Sediment ◽  
Rayleigh Waves ◽  
Velocity Structure ◽  
Shear Velocity

Rayleigh waves in southern New Guinea

1969 ◽  
Vol 59 (2) ◽  
pp. 945-958 ◽  
Author(s):  
J. A. Brooks
Keyword(s):  
Rayleigh Waves ◽  
Velocity Structure ◽  
Group Velocity Dispersion ◽  
Focal Depth ◽  
New Guinea ◽  
Shear Velocity ◽  
Stationary Wave ◽  
Period Range ◽  
Mode Group ◽  
Path Lengths

abstract A shear velocity structure having features similar to the Gutenberg model for the upper 200 km of the mantle is consistent with features of higher mode Rayleighwave group-velocity dispersion curves in the period range 4 to 30 seconds, for paths across southern New Guinea. Pronounced discontinuities appear to be absent within the crust where shear velocities are expected to gradually increase with depth. Clearly dispersive second mode (M21) Rayleigh waves, well separated in time from the fundamental mode, are shown for path lengths less than 2000 km. Frequencies excited show some dependence on focal depth. Stationary wave groups of period 10-20 seconds, very like the Sa phase, and generated by earthquakes of focal depth between 100 and 160 km coincide with expected normal mode group arrivals.

scholarly journals Shear velocity structure in the Aegean area obtained by inversion of Rayleigh waves

2004 ◽  
Vol 160 (1) ◽  
pp. 127-143 ◽  
Author(s):  
E. E. Karagianni ◽  
C. B. Papazachos ◽  
D. G. Panagiotopoulos ◽  
P. Suhadolc ◽  
A. Vuan ◽  
...  
Keyword(s):  
Rayleigh Waves ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Aegean Area

scholarly journals Mantle Rayleigh waves from the Kamchatka earthquake of November 4, 1952*

1954 ◽  
Vol 44 (3) ◽  
pp. 471-479
Author(s):  
Maurice Ewing ◽  
Frank Press
Keyword(s):  
Internal Friction ◽  
Rayleigh Waves ◽  
Shear Velocity ◽  
Velocity Curve ◽  
The Core ◽  
Long Period ◽  
A Value ◽  
The Earth ◽  
Dispersion Data ◽  
Kamchatka Earthquake

Abstract Mantle Rayleigh waves from the Kamchatka earthquake of November 4, 1952, are analyzed. The new Palisades long-period vertical seismograph recorded orders R6–R15, the corresponding paths involving up to seven complete passages around the earth. The dispersion data for periods below 400 sec. are in excellent agreement with earlier results and can be explained in terms of the known increase of shear velocity with depth in the mantle. Data for periods 400-480 sec. indicate a tendency for the group velocity curve to level off, suggesting that these long waves are influenced by a low or vanishing shear velocity in the core. Deduction of internal friction in the mantle from wave absorption gives a value 1/Q = 370 × 10−5 for periods 250-350 sec. This is a little over half the value reported earlier for periods 140-215 sec.

scholarly journals Imaging New Zealand's Crustal Structure Using Ambient Seismic Noise Recordings from Permanent and Temporary Instruments

2021 ◽  
Author(s):  
◽  
Yannik Behr
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Ambient Seismic Noise ◽  
Uppermost Mantle ◽  
Noise Sources ◽  
Noise Field ◽  
Rayleigh And Love Waves ◽  
Noise Cross Correlation

<p>We use ambient seismic noise to image the crust and uppermost mantle, and to determine the spatiotemporal characteristics of the noise field itself, and examine the way in which those characteristics may influence imaging results. Surface wave information extracted from ambient seismic noise using cross-correlation methods significantly enhances our knowledge of the crustal and uppermost mantle shear-velocity structure of New Zealand. We assemble a large dataset of three-component broadband continuous seismic data from temporary and permanent seismic stations, increasing the achievable resolution of surface wave velocity maps in comparison to a previous study. Three-component data enables us to examine both Rayleigh and Love waves using noise cross-correlation functions. Employing a Monte Carlo inversion method, we invert Rayleigh and Love wave phase and group velocity dispersion curves separately for spatially averaged isotropic shear velocity models beneath the Northland Peninsula. The results yield first-order radial anisotropy estimates of 2% in the upper crust and up to 15% in the lower crust, and estimates of Moho depth and uppermost mantle velocity compatible with previous studies. We also construct a high-resolution, pseudo-3D image of the shear-velocity distribution in the crust and uppermost mantle beneath the central North Island using Rayleigh and Love waves. We document, for the first time, the lateral extent of low shear-velocity zones in the upper and mid-crust beneath the highly active Taupo Volcanic Zone, which have been reported previously based on spatially confined 1D shear-velocity profiles. Attributing these low shear-velocities to the presence of partial melt, we use an empirical relation to estimate an average percentage of partial melt of < 4:2% in the upper and middle crust. Analysis of the ambient seismic noise field in the North Island using plane wave beamforming and slant stacking indicates that higher mode Rayleigh waves can be detected, in addition to the fundamental mode. The azimuthal distributions of seismic noise sources inferred from beamforming are compatible with high near-coastal ocean wave heights in the period band of the secondary microseism (~7 s). Averaged over 130 days, the distribution of seismic noise sources is azimuthally homogeneous, indicating that the seismic noise field is well-suited to noise cross-correlation studies. This is underpinned by the good agreement of our results with those from previous studies. The effective homogeneity of the seismic noise field and the large dataset of noise cross-correlation functions we here compiled, provide the cornerstone for future studies of ambient seismic noise and crustal shear velocity structure in New Zealand.</p>

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