ABSTRACT An important cause of seismic anisotropic attenuation is the interbedding of thin viscoelastic layers. However, much less attention has been devoted to layer‐induced anisotropic attenuation. Here, we derive a group of unified weighted average forms for effective attenuation from a binary isotropic, transversely isotropic‐ and orthorhombic‐layered medium in the zero‐frequency limit by using the Backus averaging/upscaling method and analyse the influence of interval parameters on effective attenuation. Besides the corresponding interval attenuation and the real part of stiffness, the contrast in the real part of the complex stiffness is also a key factor influencing effective attenuation. A simple linear approximation can be obtained to calculate effective attenuation if the contrast in the real part of stiffness is very small. In a viscoelastic medium, attenuation anisotropy and velocity anisotropy may have different orientations of symmetry planes, and the symmetry class of the former is not lower than that of the latter. We define a group of more general attenuation‐anisotropy parameters to characterize not only the anisotropic attenuation with different symmetry classes from the anisotropic velocity but also the elastic case. Numerical tests reveal the influence of interval attenuation anisotropy, interval velocity anisotropy and the contrast in the real part of stiffness on effective attenuation anisotropy. Types of effective attenuation anisotropy for interval orthorhombic attenuation and interval transversely isotropic attenuation with a vertical symmetry (vertical transversely isotropic attenuation) are controlled only by the interval attenuation anisotropy. A type of effective attenuation anisotropy for interval TI attenuation with a horizontal symmetry (horizontal transversely isotropic attenuation) is controlled by the interval attenuation anisotropy and the contrast in the real part of stiffness. The type of effective attenuation anisotropy for interval isotropic attenuation is controlled by all three factors. The magnitude of effective attenuation anisotropy is positively correlated with the contrast in the real part of the stiffness. Effective attenuation even in isotropic layers with identical isotropic attenuation is anisotropic if the contrast in the real part of stiffness is non‐zero. In addition, if the contrast in the real part of stiffness is very small, a simple linear approximation also can be performed to calculate effective attenuation‐anisotropy parameters for interval anisotropic attenuation.

中文翻译：

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分层粘弹性介质的各向异性衰减

摘要 地震各向异性衰减的一个重要原因是薄粘弹性层的互层。然而，很少有人关注层引起的各向异性衰减。在这里，我们通过使用 Backus 平均/升尺度方法从零频率极限内的二元各向同性、横向各向同性和正交层状介质推导出一组统一的加权平均形式，并分析了区间参数对有效衰减的影响。衰减。除了相应的区间衰减和刚度实部外，复刚度实部的对比度也是影响有效衰减的关键因素。如果刚度实部的对比度非常小，则可以获得一个简单的线性近似值来计算有效衰减。在粘弹性介质中，衰减各向异性和速度各向异性可能具有不同的对称面取向，前者的对称性等级不低于后者。我们定义了一组更通用的衰减各向异性参数，不仅可以表征来自各向异性速度的不同对称类别的各向异性衰减，还可以表征弹性情况。数值试验揭示了区间衰减各向异性、区间速度各向异性和刚度实部对比度对有效衰减各向异性的影响。具有垂直对称性的区间正交衰减和区间横向各向同性衰减（垂直横向各向同性衰减）的有效衰减各向异性类型仅由区间衰减各向异性控制。具有水平对称性的区间TI衰减的一种有效衰减各向异性（水平横向各向同性衰减）由区间衰减各向异性和刚度实部的对比度控制。区间各向同性衰减的有效衰减各向异性类型由所有三个因素控制。有效衰减各向异性的大小与刚度实部的对比度正相关。如果刚度实部的对比度不为零，则即使在具有相同各向同性衰减的各向同性层中，有效衰减也是各向异性的。另外，如果刚度实部的反差很小，