Extending the reach of FWI with reflection data: Potential and challenges

Gomes, Adriano; Chazalnoel, Nicolas

doi:10.3997/2214-4609.201701714

Cited by 5 publications

(5 citation statements)

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“…In contrast, although the shot gather extracted ~9°40′N (Figure S7) shows bright AML reflector, none or a very small portion of the AML reflection signal is encompassed by the inversion window (the event appears at greater twtt) and thus no information on the AML was included in our waveform inversion modeling. For further, proper evaluation of the AML signal the application of emerging techniques, such as reflection‐based full‐waveform inversion (e.g., Gomes & Chazalnoel, ) or localized full‐waveform inversion (e.g., Yuan et al, ), is recommended. The region south of 9°37′N does not show the presence of the velocity anomaly that could be related to the AML.…”

Section: Discussionmentioning

confidence: 99%

Seismic Signatures of Hydrothermal Pathways Along the East Pacific Rise Between 9°16′ and 9°56′N

et al. 2017

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We apply wave equation‐based techniques to 2‐D seismic data to characterize the nature of zero‐age upper crust at the East Pacific Rise from 9°16′ to 9°56′N. The final velocity model reveals a number of low‐velocity anomalies, complex in shape, extending down to ~1 km below the seafloor. We attribute them to the presence of hydrothermal flow. Depending on their spatial correlation with the previously identified tectonic discontinuities in bathymetry and presence of venting, we classify them as downgoing and upgoing pathways, respectively. This distinction is not always clear; within the third‐order discontinuities at 9°20′ and 9°37′N, both pathways may be present. The region north of 9°44′N, known for its magmatic robustness and volcanic activity, is represented by five low‐velocity perturbations. Three of these anomalies are spatially correlated with the fourth‐order discontinuities and attributed to the presence of the on‐axis recharge zones. The remaining two anomalies underlie two vent clusters, marked as hydrothermally active sites after the last documented eruption event. These velocity anomalies can be thus identified as the up‐flow pathways or at least their remnants. By comparing our results to the available interdisciplinary data sets, we show that the interaction between the tectono‐magmatic and hydrothermal processes is not straightforward due to different timescales at which they operate. However, for developing, maintaining, and driving vigorous, high‐temperature hydrothermal flow, the high crustal permeability and high thermal regime must coexist in time and space.

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Section: Discussionmentioning

confidence: 99%

Seismic Signatures of Hydrothermal Pathways Along the East Pacific Rise Between 9°16′ and 9°56′N

et al. 2017

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“…To further decrease computational costs during wavefield decomposition, the Hilbert transformation is adopted to decompose the wavefields implicitly (Liu et al ., 2011; Fei et al . 2015; Chi et al ., 2017; Gomes and Chazalnoel 2017) by

\begin{matrix} true \\ right g_{v_{0}} ((), x^{''}) & = & left \frac{1}{I_{0} (x^{''}) v_{0}^{2} (x^{''})} \\ left \times \int \int normald x_{s} normald t ({, S, (x^{''}, t; x_{s}), R, (x^{''}, t; x_{r})) \\ left + (}, H_{z}, [S (() x^{''}, t; x_{s})], H_{z}, [R (() x^{''}, t; x_{r})]), \end{matrix}

where

H_{z}

indicates the z ‐direction of the Hilbert transformation, which can be carried with high efficiency, e.g. the discrete convolution.…”

Section: Methodsmentioning

confidence: 99%

“…Chi et al . (2017) and Gomes and Chazalnoel (2017) developed an efficient implicit wavefield separation scheme, which significantly reduced the computational costs of wavefield separation. Because the impedance–velocity parameterization leads to a more natural uncoupling between the two‐parameter classes, it is consistent with the scale separation between the velocity model and the reflectivity (image) model (Zhou et al ., 2015).…”

Section: Introductionmentioning

confidence: 99%

Efficient reflection waveform inversion using a locally normalized zero‐lag correlative objective function

Liu

2020

Geophysical Prospecting

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Full-waveform inversion is characterized by cycle-skipping when the starting background model differs significantly from the true model and low-frequency data are unavailable. To mitigate this problem, reflection waveform inversion is applied to provide a background velocity model for full-waveform inversion. This technique attempts to extract background velocity updates along the reflection wavepath by matching the reflection waveforms. However, two issues arise during the implementation of reflection waveform inversion: amplitude and efficiency. The amplitude is always underestimated due to the complex subsurface parameter (i.e. the source signature, density, attenuation etc.). This makes it unreasonable to match the reflection amplitude involved in waveforms, especially in the filed data cases. In addition, generating the background velocity gradient requires the simulation of the reflection wavefield. However, simulating the reflection wavefield is time-consuming. To address the former, we introduced a locally normalized objective function, while for the latter, we used an efficient strategy by avoiding the explicit generation of the reflection wavefield. Results show that applying the proposed method to both synthetic and field data can provide a good background velocity model for full-waveform inversion with high efficiency.

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“…RFWI (Xu et al, 2012) is effective at providing velocity updates beyond the penetration depth of diving waves. Recent applications of velocity inversion methods driven by RFWI have been implemented by Irabor & Warner (2016), Sun et al (2016), Gomes & Chazalnoel (2017), Gomes & Yang (2018) with promising results. The essence of this method lies in iterating between a migration phase and a tomographic phase, where the migration phase is used to model the synthetic reflected data, and the tomographic phase allows to estimate low-wavenumber updates of the velocity models.…”

Section: Stack-power Wemvamentioning

confidence: 99%