ABSTRACT In this work, we describe an experiment concerning global–local full‐waveform inversion, carried out on a P‐wave seismic reflection profile that was acquired at Luni, an archaeological site in Italy. The global full‐waveform inversion makes use of a two‐grid genetic algorithm scheme and recorded refraction and diving waves, to build an initial velocity model of the subsurface. Two important pieces of a priori information which help to better constrain the inversion results are the refraction velocity model and the Dix‐converted semblance velocity field obtained from time processing. A good match between observed and predicted data allows us to use the estimated velocity field as the starting point for a local, gradient‐based full‐waveform inversion that inverts the recorded data (except the surface waves). The final estimated velocity field shows two main discontinuities: one is very shallow and related to the refractor velocity model used and the other corresponds to the strongest reflection event observed in the pre‐stack depth‐migrated section, at a depth of 100 m. The pre‐stack depth‐migrated common image gathers provide evidence of a good horizontal alignment of this reflection, indicating an accurate velocity estimation down to 100 m depth that corresponds to the maximum offset used in the acquisition.

中文翻译：

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用于意大利 Luni 采集的近地表地震数据 p 速度估计的声学全局-局部 FWI

摘要 在这项工作中，我们描述了一项关于全球-局域全波形反演的实验，该实验是在意大利卢尼考古遗址获得的 P 波地震反射剖面上进行的。全局全波形反演利用双网格遗传算法方案并记录折射波和潜波，建立地下初始速度模型。有助于更好地约束反演结果的两个重要先验信息是折射速度模型和从时间处理中获得的 Dix 转换的相似速度场。观测数据和预测数据之间的良好匹配使我们能够使用估计的速度场作为局部、基于梯度的全波形反演的起点，该反演对记录的数据（表面波除外）进行反演。最终估计的速度场显示了两个主要的不连续性：一个非常浅，与使用的折射镜速度模型有关，另一个对应于在叠前深度偏移剖面中观察到的最强反射事件，深度为 100 m。叠前深度偏移的普通图像道集提供了这种反射的良好水平对齐的证据，表明精确的速度估计低至 100 m 深度，对应于采集中使用的最大偏移。