Lateral resolution and lithological interpretation of surface-wave profiling

O’Neill, Adam; Campbell, Tristan; Matsuoka, Toshifumi

doi:10.1190/1.3011028

Cited by 25 publications

(10 citation statements)

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“…These approaches use, e.g., an offset-dependent windowing of the data to extract local 1D subsurface models that are afterward combined to a pseudo-2D structure (Bohlen et al, 2004). However, the resolution of the derived subsurface models is limited (O'Neill et al, 2008), and in strongly heterogeneous geologic settings in which no continuous dispersion curves can be extracted from the data, these concepts break down. In contrast, full-waveform inversion (FWI) has the potential to reconstruct high-resolution subsurface models even for 2D and 3D structures.…”

Section: Introductionmentioning

confidence: 98%

The role of attenuation in 2D full-waveform inversion of shallow-seismic body and Rayleigh waves

et al. 2014

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Full-waveform inversion (FWI) of Rayleigh waves is attractive for shallow geotechnical investigations due to the high sensitivity of Rayleigh waves to the S-wave velocity structure of the subsurface. In shallow-seismic field data, the effects of anelastic damping are significant. Dissipation results in a low-pass effect as well as frequency-dependent decay with offset. We found this by comparing recorded waveforms with elastic and viscoelastic wave simulation. The effects of anelastic damping must be considered in FWI of shallow-seismic Rayleigh waves. FWI using elastic simulation of wave propagation failed in synthetic inversion tests in which we tried to reconstruct the S-wave velocity in a viscoelastic model. To overcome this, Q-values can be estimated from the recordings to quantify viscoelasticity. Waveform simulation in the FWI then uses these a priori values when inferring seismic velocities and density. A source-wavelet correction, which is inevitable in FWI of field data, can compensate a significant fraction of the residuals between elastically and viscoelastically simulated data by narrowing the signals' bandwidth. This way, elastic simulation becomes applicable in FWI of data from anelastic media. This approach, however, was not able to produce a frequency-dependent amplitude decay with offset. Reconstruction, therefore, was more accurate when using appropriate viscoelastic modeling in FWI of shallowseismic Rayleigh waves. We found this by synthetic inversion tests using elastic forward simulation as well as viscoelastic simulation with different a priori values for Q.

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Section: Introductionmentioning

confidence: 98%

The role of attenuation in 2D full-waveform inversion of shallow-seismic body and Rayleigh waves

et al. 2014

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“…The lateral extent of the anomaly on the half-spread models is consistent with shot gathers showing distinct changes in apparent velocity of surface waves and delays in direct P-waves over the same range of stations. O'Neill et al (2008) reported a similar displacement and asymmetry of anomalies in synthetic models generated with spread lengths greater than the anomaly width. The abrupt decrease in apparent velocity (increase in slope) for the surface waves from STA 78 to 87 indicates a lowvelocity zone spanning approximately 9 m. A slightly Figure 8.…”

Section: Incorporation Of Borehole Data Into the Inversionmentioning

confidence: 57%

“…For the first active survey, a sledge-hammer was used as the seismic source, and four hammer blows were stacked for each record. The array aperture also controls lateral resolution; features smaller than roughly half the array width cannot be fully resolved (O'Neill et al, 2008). Ultimately, the maximum depth of penetration is determined by the maximum wavelength resolved by the geophone array; this is equal to the array aperture.…”

Section: Field Acquisitionmentioning

confidence: 99%

“…Inversion for most of the mid-points required 2-5 iterations. As noted earlier, depending on the distribution and magnitude of lateral variations in velocity, the models may contain distortions that represent departures from simple lateral averages of the actual subsurface structure (Lin and Lin, 2007;O'Neill et al, 2008). Layer thicknesses increased with depth and were held fixed during inversion.…”

Section: Inversion Of Dispersion Curves For Velocity Modelsmentioning

confidence: 99%

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Multi-channel Analysis of Surface Waves (MASW) in Karst Terrain, Southwest Georgia: Implications for Detecting Anomalous Features and Fracture Zones

Parker

Hawman

2012

JEEG

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Multi-channel analysis of surface waves (MASW) was used to map bedrock topography, image anomalies in the soil overburden, and detect variations in the degree of limestone weathering in covered, karst terrain near Albany, Georgia. Surface-wave data were acquired along seven parallel lines and two perpendicular cross-lines. Two surveys using a hammer and moving van-source were conducted to address the trade-off between lateral resolution and depth penetration. Resolution matrices show that the depth ranges most effectively imaged are 0.5-4 m for half-spread hammer data, 3-12 m for full-spread hammer data, and 8-20 m for van-source data. A steep S-velocity gradient marked by the 350 m/s contour at depths of 9-12 m is interpreted as the bedrock surface, in agreement with coincident borehole data. The models indicate variations within limestone bedrock (S-velocity: 350-700 m/s) and anomalous zones within the sandy-clay overburden. Standard penetration tests at two locations 45-m apart confirm variations in limestone rigidity suggested by the velocity models. At one location, a dissolution feature (N-value: 0) within highly weathered, saturated limestone (N-values: 12 and 19) correlates with low S-velocities (,350 m/s). Borehole data from the second location shows more rigid limestone (N-values: 25 and 34) that correlates with S-velocities between 350-400 m/s. A zone of weathered rock at depths of 12-20 m imaged along a suspected fracture zone is consistent with borehole data and sinkhole formation at the ground surface. An anomaly associated with a burn pit at the intersection of two perpendicular profiles was imaged at two different scales. S-velocity models and distinct changes in apparent velocity of direct P-waves and surface waves across shot gathers constrain the lateral and vertical extent of the anomaly, and borehole data verify changes in soil composition and depth (5 m) to the base of the anomaly.

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“…Measuring higher-mode dispersion is difficult, mainly because of the coalescing of the energy bands in the f-k domain. Other approaches have then been proposed such as the high-resolution linear Radon transform ͑Luo et al, 2008͒ or a different representation of the full wavefield ͑Forbriger, 2003;O'Neil and Matsuoka, 2005;O'Neil et al, 2008͒. Here, we propose an alternative method by using a time-f-k analysis technique developed more than 30 years ago in earthquake seismology.…”

Section: Introductionmentioning

confidence: 99%

Improving the analysis and inversion of multimode Rayleigh-wave dispersion by using group-delay time information observed on arrays of high-frequency sensors

et al. 2010

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Near-surface shear-velocity structure can be inferred from multimode dispersion data. Several methods have been developed to isolate the different modes from seismic signals observed on linear arrays of sensors. Most techniques analyze the wavefield through a frequency-wavenumber ͑ f-k͒ transform, paying little attention to group-delay-time information. Moreover, classical analyses are generally restricted to fundamental-mode dispersion, limiting the resolution power at depth. We have overcome the limitations of classical f-k analysis by using a wavefield representation in the group-velocity/phase-velocity ͑U-c͒ domain. We have then set up a nonlinear inversion procedure, easily tractable on a common field computer, to constrain the 1D vertical profile of shear velocities. Applications to synthetic data and to a set of actual records show that U-c diagrams greatly help to separate dispersion information between different modes, even when they are not detectable on usual f-k diagrams. Tests on synthetic and actual data confirm that the inversion procedure quickly converges to the expected model.

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Lateral resolution and lithological interpretation of surface-wave profiling

Cited by 25 publications

References 0 publications

The role of attenuation in 2D full-waveform inversion of shallow-seismic body and Rayleigh waves

The role of attenuation in 2D full-waveform inversion of shallow-seismic body and Rayleigh waves

Multi-channel Analysis of Surface Waves (MASW) in Karst Terrain, Southwest Georgia: Implications for Detecting Anomalous Features and Fracture Zones

Improving the analysis and inversion of multimode Rayleigh-wave dispersion by using group-delay time information observed on arrays of high-frequency sensors

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