Line-source simulation for shallow-seismic data. Part 1: theoretical background

Forbriger, Thomas; Groos, Lisa; Schäfer, Martin

doi:10.1093/gji/ggu199

Cited by 67 publications

(47 citation statements)

References 24 publications

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“…First, each seismogram is convolved with t −1∕2 , second, tapered with t −1∕2 , where t is the traveltime, and third, scaled with r ffiffi ffi 2 p where r is the receiver offset. This transformation is introduced by Forbriger et al (2014) as a direct-wave transformation.…”

Section: Comparison Of Field Data With Simulated Datamentioning

confidence: 99%

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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: Comparison Of Field Data With Simulated Datamentioning

confidence: 99%

“…Schäfer et al (2014) show that this simple approach performs surprisingly well in application to elastic waves (including P-, S-, and Rayleighwaves) on a 2D structure, except for backscattered waves. Forbriger et al (2014) provide theoretical reasoning for the applicability to the layered elastic case.…”

Section: Comparison Of Field Data With Simulated Datamentioning

confidence: 99%

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

et al. 2014

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“…Forbriger et al (2014) show that this approach is also appropriate in the viscoelastic case (both vertical and radial component) for 1-D structures with source and receiver at the free surface.…”

Section: Single-trace Transformations For Non 1-d-structuresmentioning

confidence: 96%

Line-source simulation for shallow-seismic data. Part 2: full-waveform inversion—a synthetic 2-D case study

Schäfer

Groos

Forbriger

et al. 2014

Geophysical Journal International

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S U M M A R YFull-waveform inversion (FWI) of shallow-seismic surface waves is able to reconstruct lateral variations of subsurface elastic properties. Line-source simulation for point-source data is required when applying algorithms of 2-D adjoint FWI to recorded shallow-seismic field data. The equivalent line-source response for point-source data can be obtained by convolving the waveforms with √ t −1 (t: traveltime), which produces a phase shift of π/4. Subsequently an amplitude correction must be applied. In this work we recommend to scale the seismograms with 2r v ph at small receiver offsets r, where v ph is the phase velocity, and gradually shift to applying a √ t −1 time-domain taper and scaling the waveforms with r √ 2 for larger receiver offsets r. We call this the hybrid transformation which is adapted for direct body and Rayleigh waves and demonstrate its outstanding performance on a 2-D heterogeneous structure. The fit of the phases as well as the amplitudes for all shot locations and components (vertical and radial) is excellent with respect to the reference line-source data. An approach for 1-D media based on Fourier-Bessel integral transformation generates strong artefacts for waves produced by 2-D structures. The theoretical background for both approaches is presented in a companion contribution. In the current contribution we study their performance when applied to waves propagating in a significantly 2-D-heterogeneous structure. We calculate synthetic seismograms for 2-D structure for line sources as well as point sources. Line-source simulations obtained from the point-source seismograms through different approaches are then compared to the corresponding line-source reference waveforms. Although being derived by approximation the hybrid transformation performs excellently except for explicitly backscattered waves. In reconstruction tests we further invert point-source synthetic seismograms by a 2-D FWI to subsurface structure and evaluate its ability to reproduce the original structural model in comparison to the inversion of line-source synthetic data. Even when applying no explicit correction to the point-source waveforms prior to inversion only moderate artefacts appear in the results. However, the overall performance is best in terms of model reproduction and ability to reproduce the original data in a 3-D simulation if inverted waveforms are obtained by the hybrid transformation.

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“…In comparison, 2-D full waveform inversion (FWI) is computationally more efficient, preferential for code development and applications. In particular, Forbriger et al (2014), Schäfer et al (2014), and Groos et al (2017) proposed a stable workflow for 2-D FWI of shallow-seismic Rayleigh waves not only for synthetic data but also for real field-recorded data, in which a 3-D/2-D transformation scheme is developed to simulate the response to a line source (i.e., spreading correction) for shallow seismic surface waves. In particular, Forbriger et al (2014), Schäfer et al (2014), and Groos et al (2017) proposed a stable workflow for 2-D FWI of shallow-seismic Rayleigh waves not only for synthetic data but also for real field-recorded data, in which a 3-D/2-D transformation scheme is developed to simulate the response to a line source (i.e., spreading correction) for shallow seismic surface waves.…”

Section: Zhang Et Al 368mentioning

confidence: 99%

Linear Array Ambient Noise Adjoint Tomography Reveals Intense Crust‐Mantle Interactions in North China Craton

et al. 2018

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We present a 2‐D ambient noise adjoint tomography technique for a linear array with a significant reduction in computational cost and show its application to an array in North China. We first convert the observed data for 3‐D media, i.e., surface‐wave empirical Green's functions (EGFs) to the reconstructed EGFs (REGFs) for 2‐D media using a 3‐D/2‐D transformation scheme. Different from the conventional steps of measuring phase dispersion, this technology refines 2‐D shear wave speeds along the profile directly from REGFs. With an initial model based on traditional ambient noise tomography, adjoint tomography updates the model by minimizing the frequency‐dependent Rayleigh wave traveltime delays between the REGFs and synthetic Green functions calculated by the spectral‐element method. The multitaper traveltime difference measurement is applied in four‐period bands: 20–35 s, 15–30 s, 10–20 s, and 6–15 s. The recovered model shows detailed crustal structures including pronounced low‐velocity anomalies in the lower crust and a gradual crust‐mantle transition zone beneath the northern Trans‐North China Orogen, which suggest the possible intense thermo‐chemical interactions between mantle‐derived upwelling melts and the lower crust, probably associated with the magmatic underplating during the Mesozoic to Cenozoic evolution of this region. To our knowledge, it is the first time that ambient noise adjoint tomography is implemented for a 2‐D medium. Compared with the intensive computational cost and storage requirement of 3‐D adjoint tomography, this method offers a computationally efficient and inexpensive alternative to imaging fine‐scale crustal structures beneath linear arrays.

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Line-source simulation for shallow-seismic data. Part 1: theoretical background

Cited by 67 publications

References 24 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

Line-source simulation for shallow-seismic data. Part 2: full-waveform inversion—a synthetic 2-D case study

Linear Array Ambient Noise Adjoint Tomography Reveals Intense Crust‐Mantle Interactions in North China Craton

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