自适应变差分算子长度正演模拟及在渤海湾地区的应用

Seismic modeling with adaptive variable-length spatial operators and its application in Bohai bay

常规笛卡尔坐标系正演模拟算法,波长随速度而变,为了保证低速区的模拟精度和频散关系,空间差分阶数需要取得较高,常常造成高速区的空间过采样.本文将简化的自适应变差分算子长度算法应用到正演模拟算法的空间导数计算中,在保证相同模拟精度的前提下,低速区采用高阶差分算子,高速区只需低阶差分阶数,有效减小了计算量、提高了计算效率.此外,将卷积完全匹配层技术应用到正演模拟的边界条件处理中,相比常规吸收边界条件,可以在较少的计算量下得到更好的吸收效果.最后,将本文算法应用到渤海湾地区,分析了相应的波场特征和地震响应.

Wavelength varies in space due to velocity variation,and considering the regular spacing in conventional implementations,this could result in uneven spatial representation of wavefields. Specifically,we tend to undersample wavefields in layers with low velocities and oversample them in layers with high velocities. To address these issues,based on previous studies,we introduced the simplified adaptive variable-length spatial operators to calculate the spatial derivatives. Under the premise of ensuring the same simulation accuracy,the high order difference operator is used in the low speed region,and the low order difference precision is needed in the high speed region. Therefore this method reduces the computation and improves the computing efficiency. In addition, the convolution perfectly matched layer technique is applied to the above method,and it can get better absorption effect than the conventional absorbing boundary conditions. Finally,the algorithm is applied to the Bohai bay area,and we analyzed the corresponding wave field characteristics and seismic response.