We present a novel numerical upscaling technique for modeling the wave response of gas-hydrate bearing sediments composed of a rock frame, gas-hydrate and water, where the hydrate consists of ice-like lattice of water molecules with methane trapped inside. These sediments are highly heterogeneous at mesoscopic scales, much smaller than the wavelength but much larger than the pore size, inducing substantial seismic wave attenuation and dispersion due to mode conversions. The proposed numerical upscaling procedure simulates the wave-induced fluid-flow loss mechanism by computing an average effective viscoelastic medium having the same behavior of the original sediment. The method determines the complex stiffness coefficients associated with the viscoelastic medium by solving numerically boundary value problems formulated in the space-frequency domain, representing compressibility and shear experiments. The procedure is applied to composite media with regions of different amounts of hydrate with patchy or periodic-layer distributions, which define an anisotropic effective viscoelastic medium, respectively. The examples demonstrate that variations in hydrate content induce strong attenuation and dispersion effects on seismic waves due to the mesoscopic loss mechanism.

我们提出了一种新的数值放大技术，用于模拟由岩石框架、天然气水合物和水组成的含天然气水合物沉积物的波浪响应，其中水合物由冰状水分子晶格组成，其中含有甲烷。这些沉积物在细观尺度上是高度异质的，远小于波长但远大于孔径，由于模式转换导致地震波衰减和色散显着。建议的数值放大程序通过计算具有与原始沉积物相同行为的平均有效粘弹性介质来模拟波浪引起的流体流动损失机制。该方法通过求解在空间频率域中表示的数值边界值问题来确定与粘弹性介质相关的复杂刚度系数，代表可压缩性和剪切实验。该程序适用于具有不同数量水合物区域的复合介质，这些区域具有不规则或周期性层分布，分别定义了各向异性的有效粘弹性介质。这些例子表明，由于细观损失机制，水合物含量的变化会对地震波产生强烈的衰减和色散效应。分别。这些例子表明，由于细观损失机制，水合物含量的变化会对地震波产生强烈的衰减和色散效应。分别。这些例子表明，由于细观损失机制，水合物含量的变化会对地震波产生强烈的衰减和色散效应。