On the use of a seismic sensor as a seismic source

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. A39-A43
Author(s):  
David F. Halliday ◽  
Taiwo Fawumi ◽  
Johan O. A. Robertsson ◽  
Ed Kragh
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Group Velocity ◽  
Seismic Source ◽  
Body Waves ◽  
Seismic Sources ◽  
Wave Group ◽  
Seismic Sensors ◽  
Voltage Signal ◽  
Seismic Wavefield

We investigated the use of seismic sensors as small seismic sources. A voltage signal is applied to a geophone that forces the mass within the geophone to move. The movement of the mass generates a seismic wavefield that was recorded with an array of geophones operating in the conventional sense. We observed higher-frequency (25 Hz and above) surface and body waves propagating from the geophone source at offsets of 10 s of meters. We further found that the surface waves emitted from geophone sources can be used to generate a surface-wave group velocity map. We discuss potential developments and future applications.

Shallow tunnel detection using converted surface waves

Geophysics ◽  
2021 ◽  
pp. 1-45
Author(s):  
Shelby L. Peterie ◽  
Julian Ivanov ◽  
Erik Knippel ◽  
Richard D. Miller ◽  
Steven D. Sloan
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Body Wave ◽  
Seismic Source ◽  
Body Waves ◽  
Detection Methods ◽  
Imaging Method ◽  
Real World Data ◽  
Processing Methods ◽  
Novel Processing

Seismic surface waves that were likely converted from incident body waves were used to detect a 3 m deep tunnel using two novel processing methods. In data acquired at a tunnel test site, a unique forward-propagating wave (travelling away from both the tunnel and seismic source) was identified as an early-arriving surface wave converted at the tunnel from an incident body wave. To our knowledge, this paper represents the first time converted surface waves have been documented as originating from a tunnel. We developed two novel processing methods targeting this unique wavefield component for detecting tunnels, cavities, or other shallow anomalies. The first is a time-domain imaging method that takes advantage of the unique kinematic characteristics of converted surface waves to produce a cross-section with a coherent, high-amplitude signature originating from the horizontal location of the tunnel. The second method uses frequency-domain analysis of surface-wave amplitudes, which reveals increased amplitudes (primarily from converted surface waves) at locations expected for the tunnel. These proposed approaches for analysis of converted surface waves were successfully used to detect the tunnel and accurately interpret its horizontal location in real world data. These novel methods could be key for detecting shallow tunnels or other subsurface anomalies and complement existing seismic detection methods.

Application of Conformal Mapping in Regional Surface Wave Group Velocity Inversion

2001 ◽  
Vol 44 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Liang-Bao ZHU ◽  
Qing XU ◽  
Xiao-Fei CHEN
Keyword(s):  
Surface Wave ◽  
Conformal Mapping ◽  
Group Velocity ◽  
Wave Group ◽  
Velocity Inversion

Azimuthal multiple signal classification of dispersive and aliased surface waves recorded in 3D seismic acquisition

Geophysics ◽  
2021 ◽  
pp. 1-84
Author(s):  
Chunying Yang ◽  
Wenchuang Wang
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Body Waves ◽  
Signal Classification ◽  
Dispersion Pattern ◽  
Velocity Spectrum ◽  
Low Velocity ◽  
Surface Wave Dispersion ◽  
Multiple Signal Classification ◽  
Multiple Signal

Irregular acquisition geometry causes discontinuities in the appearance of surface wave events, and a large offset causes seismic records to appear as aliased surface waves. The conventional method of sampling data affects the accuracy of the dispersion spectrum and reduces the resolution of surface waves. At the same time, ”mode kissing” of the low-velocity layer and inhomogeneous scatterers requires a high-resolution method for calculating surface wave dispersion. This study tested the use of the multiple signal classification (MUSIC) algorithm in 3D multichannel and aliased wavefield separation. Azimuthal MUSIC is a useful method to estimate the phase velocity spectrum of aliased surface wave data, and it represent the dispersion spectra of low-velocity and inhomogeneous models. The results of this study demonstrate that mode-kissing affects dispersion imaging, and inhomogeneous scatterers change the direction of surface-wave propagation. Surface waves generated from the new propagation directions are also dispersive. The scattered surface wave has a new dispersion pattern different to that of the entire record. Diagonal loading was introduced to improve the robustness of azimuthal MUSIC, and numerical experiments demonstrate the resultant effectiveness of imaging aliasing surface waves. A phase-matched filter was applied to the results of azimuthal MUSIC, and phase iterations were unwrapped in a fast and stable manner. Aliased surface waves and body waves were separated during this process. Overall, field data demonstrate that azimuthal MUSIC and phase-matched filters can successfully separate aliased surface waves.

A model study of elastic waves in a layered sphere

1967 ◽  
Vol 57 (5) ◽  
pp. 959-981
Author(s):  
Victor Gregson
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Elastic Waves ◽  
Wave Dispersion ◽  
Flat Space ◽  
Dispersion Curves ◽  
Body Waves ◽  
Surface Wave Dispersion ◽  
Steel Sphere ◽  
Long Wave

abstract Elastic waves produced by an impact were recorded at the surface of a solid 12.0 inch diameter steel sphere coated with a 0.3 inch copper layer. Conventional modeling techniques employing both compressional and shear piezoelectric transducers were used to record elastic waves for one millisecond at various points around the great circle of the sphere. Body, PL, and surface waves were observed. Density, layer thickness, compressional and shear-wave velocities were measured so that accurate surface-wave dispersion curves could be computed. Surface-wave dispersion was measured as well as computed. Measured PL mode dispersion compared favorably with theoretical computations. In addition, dispersion curves for Rayleigh, Stoneley, and Love modes were computed. Measured surface-wave dispersion showed Rayleigh and Love modes were observed but not Stoneley modes. Measured dispersion compared favorably with theoretical computations. The curvature correction applied to dispersion calculations in a flat space has been estimated to correct dispersion values at long-wave lengths to about one per cent of correct dispersion in a spherical model. Measured dispersion compared with such flat space dispersion corrected for curvature proved accurate within one per cent at long wave lengths. Two sets of surface waves were observed. One set was associated with body waves radiating outward from impact. The other set was associated with body waves reflecting at the pole opposite impact. For each set of surface waves, measured dispersion compared favorably with computed dispersion.

scholarly journals Similarity of lithospheric structure of central and northwestern part of the Indian Peninsula inferred from observed surface wave forms

MAUSAM ◽  
2021 ◽  
Vol 43 (1) ◽  
pp. 51-58
Author(s):  
S. N. BHATTACHARYA
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Group Velocity ◽  
Synthetic Seismograms ◽  
Lithospheric Structure ◽  
Northwestern Part ◽  
Indian Peninsula ◽  
Wave Forms

Observed surface wave forms across the central part of the Indian Peninsula and across northwestern part of the Peninsula have been considered. In a previous work, using group velocity of surface waves across former religion revealed model lithosphere IP 11. Observed surface wave forms across these two regions have been compared with synthetic seismograms  using  model  IP 11. Observed wave forms are found to agree with synthetic one. This suggests that the average lithospheric structure of central and northwestern parts of the Indian Peninsula is similar and the Lithospheric model  IP 11 is an approximation to it

scholarly journals Estimation of Surface Wave Group Velocity beneath the Chukyo Area, Japan

2014 ◽  
Vol 66 (4) ◽  
pp. 127-145 ◽  
Author(s):  
Takumi HAYASHIDA ◽  
Masayuki YOSHIMI ◽  
Haruo HORIKAWA
Keyword(s):  
Surface Wave ◽  
Group Velocity ◽  
Wave Group
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