【摘要】 为研究起伏地表、复杂构造以及复杂速度分布条件下地震数据的精确成像方法,本文采用有限元法完成观测波场的声波方程逆时外推,并提出了以节点波场最大振幅出现时间作为成像时间的最大振幅成像条件。该成像条件不同于激发时间成像条件,它基于波动理论而不是射线理论,可使能量更好地聚焦。有限元法采用六节点三角形单元,对单元内的场和速度均作二次插值以提高模拟精度;用对角化的集中质量矩阵代替协调质量矩阵,避免了矩阵求逆,提高了计算效率。通过对带地形的凹陷模型、Mormousi模型及带地形的Mormousi模型等三个理论模型的计算,结果表明该方法能够有效处理复杂地质条件下的地震成像问题,对于复杂地质体中的断层、断块、背斜构造、高速体和目标体成像都比较清晰,位置准确。尤其对于基于起伏地表直接进行偏移的模型数据也得到了较好的成像结果。更多还原

【Abstract】 In order to study the preciously imaging method of seismic data in conditions of relief surface,complex structure and velocity distribution,the paper used finite-element algorithm to finish the wave-equation reverse-time extrapolation of surveyed wavefield,and proposed taking the time the max amplitude appeared in node wavefield for the imaging condition of max amplitude,which is different from the imaging condition of shooting time.This imaging condition is based on the wave theory rather than on ray theory,which can focus energy better.The finite-element method used 6-node triangular element,quadratic interpolation of field and velocity in element is carried out to improve the precision of simulation; Diagonal lumped mass matrix was used to replace consistent mass matrix to avoid matrix inverse and improve computation efficiency.It’s shown by computing three theoretical models: sag model with topography,Marmousi model and Marmousi model with topography that the method can effectively handle the issue of seismic imaging in complex geologic condition.The imaging in such complex geologic bodies as fault,faulted block,anticline structure,high-velocity body and targets is characterized by identification and accurate position.Especially,the imaging results of model data based on ragged surface by direct migration are also better.更多还原