It is well known that seismic data that have been recorded in complex geological environments must be compensated for geometrical spreading before AVO/AVA analysis, in order to avoid erroneous imaging interpretation. By investigating analytically both the effect of the geometrical spreading and the effect of the reflector curvature on amplitude and phase changes for reflected and transmitted waves between anisotropic media, using ray theory, we show that these data should be compensated for interface effects as well. In order to gain insight more specifically in the focusing effect of the interface, the special case of homogeneous isotropic media separated by a curved interface of syncline type is discussed and compared to the case of a plane interface. 3D numerical simulations of wave reflection from curved interfaces using a Spectral-Element Method validate our analytical derivations. In particular, numerical seismograms obtained at a vertical receiver array highlight that the effect of interface curvature on the reflected events is much more pronounced in a restricted area associated with the existence of caustics, which is consistent with our analytical predictions. Moreover, comparisons between the numerical and the analytical results confirm the fact that using plane-wave reflection coefficients without correction for the interface effect may lead to wrong interpretation of AVA/AVO analysis.

中文翻译：

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各向异性介质中弯曲界面反射波和透射波的振幅和相位变化

众所周知，在AVO / AVA分析之前，必须对在复杂地质环境中记录的地震数据进行几何扩展进行补偿，以避免错误的成像解释。通过使用射线理论，分析研究了几何扩展的影响以及反射器曲率对各向异性介质之间反射波和透射波振幅和相位变化的影响，我们使用射线理论表明，这些数据也应得到界面效应的补偿。为了更具体地了解界面的聚焦效果，我们讨论了由向斜型弯曲界面分隔的均质各向同性介质的特殊情况，并将其与平面界面的情况进行了比较。使用光谱元素方法从弯曲界面反射波的3D数值模拟验证了我们的分析推导。特别是，在垂直接收器阵列处获得的数值地震图突出表明，界面弯曲对反射事件的影响在与苛性碱存在相关的受限区域中更为明显，这与我们的分析预测一致。此外，数值和分析结果之间的比较证实了以下事实：使用不校正界面效应的平面波反射系数可能会导致AVA / AVO分析的错误解释。在垂直接收器阵列处获得的数值地震图突出表明，界面弯曲对反射事件的影响在与苛性碱存在相关的有限区域中更为明显，这与我们的分析预测一致。此外，数值和分析结果之间的比较证实了以下事实：使用不校正界面效应的平面波反射系数可能会导致AVA / AVO分析的错误解释。在垂直接收器阵列处获得的数值地震图突出表明，界面弯曲对反射事件的影响在与苛性碱存在相关的有限区域中更为明显，这与我们的分析预测一致。此外，数值和分析结果之间的比较证实了以下事实：使用不校正界面效应的平面波反射系数可能会导致AVA / AVO分析的错误解释。