镜像法表面多次波正演模拟研究

Free surface multiples modeling with mirror image method

针对海洋地震勘探的海底电缆(OBC)采集系统,提出了一种直接正演表面多次波的方法,其核心思想是采用镜像延拓的思路修改模型,将海底对称映射到海平面之上作为新边界。将原始模型的表面多次波传播路径等效成新模型下一次反射波的传播路径,因此,只需将新模型的表面边界设置成吸收边界就可以方便地计算出多次波的传播特征。将该方法应用于多个地质模型数据,正演出的多次波波场和实际多次波信息较为吻合,证明了方法的有效性和便捷性。

Multiples always exist with the primary seismic reflection for offshore seismic acquisition.Most of the time,the multiples are regarded as noises,which may destroy the seismic imaging results and seismic interpretation.Thence,the removal of seismic multiples is very important to seismic exploration,and seismic modeling helps to know more about the performance of multiples.In this paper,a new method to directly simulate free surface multiples for ocean bottom cable（OBC）data acquisition is proposed.For the OBC data acquisition,the original geophones are placed at the position symmetrically to the sea surface.In that way,the traveling path of the seismic data recorded by those virtual geophones equal to free surface multiples in original acquisition geometry.Thus the free surface multiples can be computed after modifying the velocity model by setting a new boundary,which is the mirror image of the seabed to the sea surface.The free surface multiples modeling with mirror image method was applied on several OBC data acquisition system,and the modeling results indicate that it can simulate the free surface multiples correctly and efficiently.