【摘要】 大地吸收效应主要由地球介质本身的黏滞性所致,黏滞性会影响波场的所有频率成分,且对高频成分的影响更大,从而导致地震垂向分辨率的降低。本文将完全弹性介质中的傅里叶有限差分法推广到黏声波介质的正演领域,该法是一种频率域的单程波方法,较双程波法具有计算效率上的优势,较时间域法更容易模拟衰减和频散效应。文中对Marmousi模型进行了黏声波介质的正演模拟,数值算例表明:①黏声波介质和完全弹性介质的振幅和相位特征只有在传播时间短且距炮点近的部位才较吻合,表明黏滞吸收作用对地震波波形、频带以及振幅等产生很大影响;②随着传播距离(时间)的增加,波场的高频成分明显衰减,波形逐渐变宽,能量逐渐变弱。文中方法适应强空间变速介质的正演模拟,且具有较高的计算效率,为深入研究大地吸收效应进而提高地震分辨率奠定了基础。更多还原

【Abstract】 Earth absorption effect mainly resulted from the viscosity of earth media itself,which can affect all frequency components of wavefield,especially for high-frequency elements,leading vertical resolution of seismic data to reduce.The paper popularizes the Fourier finite-difference method in full-elastic media to the forward field in viso-acoustic media,which is one-way wave method in frequency domain and has superiority in computational efficiency if comparison with two-way wave method,and is easier simulation of attenuation and dispersion effects than in time domain.The paper carried out forward modeling for Marmousi model in visco-acoustic media,and the numeric case showed:①the consistency of feature of amplitude and phase between the viso-acoustic media and full-elastic media is only in the part of short travel time and near shot points at the same time,showing absorption effect by viscosity has large influence on waveform,frequency band and amplitude of seismic wave;②along with increasing of the travel distance(time),the high-frequency components in wavefield show clear attenuation,the waveform is gradually widening and the energy is gradually weakening.The method presented in the paper is suitable for forward simulation in large velocity-changed media in space,and has higher computational efficiency,laying the foundation for deep study of earth absorption effect and further improvement of seismic resolution.更多还原