在勘探地震频带范围内，我国陆相沉积的含煤地层均是典型的薄互层。含煤地层中各向同性薄层叠置，在不同地震波长尺度下呈现长波长地震各向异性特征，地震勘探中一般做横向各向同性(Transverse Isotropy with a Vertical Axis of Symmetry，VTI)等效或均匀各向同性(Isotropy，ISO)等效简化处理。但是针对不同弹性性质的地层，长波长等效理论的适用条件不同。以淮南煤田的含煤地层为例，利用钻孔声波和密度测井曲线建立二维水平层状薄互层模型，分析含煤地层的长波长地震各向异性的多尺度效应。通过不同平均长度均化测井曲线，重点分析了2种等效建模方法在不同平均长度下所建立的等效模型弹性参数的差异及其各向异性特征；最后通过不同等效模型弹性波场的数值模拟分析不同等效模型的适用性。结果表明：随着平均长度增加，等效模型的速度、密度和各向异性参数的单点数据异常减弱；ISO等效P波速度大于VTI等效；存在某个临界窗长(本次淮南含煤地层为λ_min/L≈3)使等效模型的层状各向异性开始减弱；当平均长度与地层厚度比(L/d)和最小主波长与平均长度比(λ_min/L)都满足长波长假设条件时，含煤薄互层等效模型弹性波传播特征才能逼近原始模型。研究结果有助于厘定含煤地层长波长地震各向异性特征，为含煤地层的正演模拟和反演模型建立提供理论指导，以进一步提高煤田地震勘探精度。

Terrestrial coal-bearing strata in China are all typical thin interbeds given the seismic frequency bands of coal exploration. The isotropic thin interbeds are superimposed in the coal-bearing strata, exhibiting seismic anisotropy at long wavelengths among different seismic wavelengths, for which simplified equivalent processing, such as vertical transverse isotropy (VTI) or isotropy (ISO) approximation, is generally adopted in seismic exploration. However, the long-wave approximation has different applicable conditions for strata with different elastic properties. Taking the coal-bearing strata in the Huainan Coalfield as an example, this study established two-dimensional models of horizontal thin interbeds using acoustic and density logging curves of boreholes and explored the multiscale effect of the seismic anisotropy of coal-bearing strata at long wavelengths. Based on logging curves homogenized with different window lengths, this study emphatically investigated the differences in the elastic parameters and their anisotropy of the equivalent models that were established at different window lengths using the two equivalent modeling methods. Finally, this study analyzed the applicability of different equivalent models through numerical simulations of the elastic wave fields of the models. The results are as follows: (1) the single-point anomalous data of velocity, density, and anisotropy parameters of the equivalent models decreased with an increase in the window length; (2) the ISO approximation yielded high P-wave velocities than the VTI approximation; (3) there existed a critical window length (λ_min/L≈3 for the coal-bearing strata in the Huainan Coalfield) at which the laminar anisotropy of the equivalent models began to weaken; (4) the propagation characteristics of elastic waves of the equivalent models of the coal-bearing thin interbeds approximated those of the original model only when both the ratio of the average length to the stratum thickness (L/d) and the ratio of the minimum principal wavelength to the average length (λ_min/L) satisfied the assumptions of the long-wavelength approximation. The results of this study help determine the seismic anisotropy characteristics of coal-bearing strata at long wavelengths and provide theoretical guidance for the forward simulation and inverse modeling of coal-bearing strata, thus further improving the accuracy of the seismic exploration of coal fields.