海洋涡旋地震成像的时域有限差分仿真

Ocean eddy imaging based on time domain finite difference

传统的水声建模方法只考虑水中声波的折射影响,忽略了水层间的声反射,因此不能对反射波地震勘探的海水分层结构成像结果进行分析。文章首先建立了基于时域有限差分的低频宽带脉冲信号传输预报模型,该模型考虑海水分层结构的声反射影响,通过数值求解波动方程计算低频宽带脉冲信号近距离传播过程中的时域波形;其次将某次海上多道地震测量的水文条件作为输入环境参数,计算了近海面地震勘探接收阵所接收的气枪低频脉冲信号时域波形;最后按照反射波地震勘探处理流程,对接收阵信号在共反射点进行相干累加和地震成像,所得到的海水分层结构成像结果与海上多道测量成像结果符合较好。仿真结果验证了水层声反射对海水分层结构反射波地震成像的影响。

The traditional underwater acoustic modeling methods only consider the influence of the refraction of sound waves in the water and ignore the acoustic reflection between the water layers,therefore the imaging results of seawater layered structure in the reflection seismology cannot be analyzed.A sound propagation model of low-frequency broadband pulse based on time-domain finite-difference is established in this paper.This model takes the acoustic reflection effects of the seawater layered structure into account,and the time-domain waveform of the low-frequency broadband signal in the process of short-distance propagation is calculated by numerically solving the wave equation.Then,by considering the hydrological conditions of a maritime multi-channel seismic survey as the input environmental parameters,the air-gun signal waveforms received by the near sea-surface receiving arrays in seismic exploration are simulated.Finally,according to the processing procedure of reflection seismology,the received array signals at the co-reflection points are sorted for coherent accumulation and seismic imaging.The obtained imaging result of seawater layered structure is in good agreement with that of the marine multi-channel survey,which validates the effect of the acoustic reflection of water layer on seismic imaging of the reflection waves of seawater layered structure.