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arXiv 1601.05232physics.geo-phcs.NAmath.NA
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全波形反演与延拓低频数据

Full waveform inversion with extrapolated low frequency data

Massachusetts Institute of Technology(麻省理工学院)

Yunyue Elita Li, Laurent Demanet

AI总结:

本文提出通过计算合成低频数据以提升全波形反演效果,利用相位追踪方法分离事件并验证延拓方法的可靠性,展示了在低频数据不准确情况下方法的鲁棒性。

摘要:

低频数据的可用性是声学领域全波形反演(FWI)成功的关键因素。低频有助于确定速度模型的动能相关低波数成分,从而避免FWI收敛到虚假局部极小值。然而,从现场获取低于2或3Hz的数据是一项具有挑战性和昂贵的任务。本文探讨了通过高频频数据计算合成低频数据的可能性,并利用由此产生的缺失数据预测来初始化FWI的频率扫描。作为信号处理问题,带宽扩展是一个非常非线性和精细的操作。它需要将带限地震记录高级解释为单个事件,每个事件可以从非色散的波传播模型中延拓到更低(或更高)的频率带。我们提出使用相位追踪方法进行事件分离任务。所得到的延拓方法的保真度通常在相位上比在振幅上更高。为了在FWI背景下验证带宽扩展的可靠性,我们首先使用延拓带中的低频数据作为数据替代物,以创建低波数背景速度模型,然后在可用带中切换到记录数据进行其余迭代。所得到的方法,简称EFWI,在延拓低频数据的不准确性下表现出令人惊讶的鲁棒性。通过两个校准的例子,证明了基于延拓[1,5]Hz带的FWI,该带本身由[5,15]Hz带中的数据生成,能够产生合理的低波数速度模型估计。

英文摘要:

The availability of low frequency data is an important factor in the success of full waveform inversion (FWI) in the acoustic regime. The low frequencies help determine the kinematically relevant, low-wavenumber components of the velocity model, which are in turn needed to avoid convergence of FWI to spurious local minima. However, acquiring data below 2 or 3 Hz from the field is a challenging and expensive task. In this paper we explore the possibility of synthesizing the low frequencies computationally from high-frequency data, and use the resulting prediction of the missing data to seed the frequency sweep of FWI. As a signal processing problem, bandwidth extension is a very nonlinear and delicate operation. It requires a high-level interpretation of bandlimited seismic records into individual events, each of which is extrapolable to a lower (or higher) frequency band from the non-dispersive nature of the wave propagation model. We propose to use the phase tracking method for the event separation task. The fidelity of the resulting extrapolation method is typically higher in phase than in amplitude. To demonstrate the reliability of bandwidth extension in the context of FWI, we first use the low frequencies in the extrapolated band as data substitute, in order to create the low-wavenumber background velocity model, and then switch to recorded data in the available band for the rest of the iterations. The resulting method, EFWI for short, demonstrates surprising robustness to the inaccuracies in the extrapolated low frequency data. With two synthetic examples calibrated so that regular FWI needs to be initialized at 1 Hz to avoid local minima, we demonstrate that FWI based on an extrapolated [1, 5] Hz band, itself generated from data available in the [5, 15] Hz band, can produce reasonable estimations of the low wavenumber velocity models.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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