基于FCT校正的OBN资料弹性波逆时偏移

Elastic reverse-time migration method of OBN data based on flux correction transmission algorithm

OBN多分量地震勘探资料具有频带宽和矢量保真性高等特点,现有的弹性波逆时偏移技术难以解决OBN宽频多分量数据的纵横波偏移成像问题。以实现OBN宽频地震勘探资料的纵横波高精度成像为目标,研究一阶速度-胀缩-旋转弹性波方程逆时偏移中的数值频散压制方法,实现了基于FCT校正的OBN资料弹性波逆时偏移。在炮、检波场延拓过程中,依据相邻两个时刻的波场以及漫射因子和反漫射因子构建漫射通量和反漫射通量,并对每一时刻含数值频散的波场进行校正,实现了对由差分离散造成的数值频散的压制,消除了纵横波成像误差。模型测试与实测资料处理试验表明,本文方法能够消除由数值频散造成的偏移剖面同相轴错断或虚假同相轴等现象,可以获取高精度的深度域纵横波成像结果。

Ocean Bottom Nodes (OBN) multi-component seismic data have the characteristics of high frequency bandwidth and vector fidelity. The existing elastic reverse-time migration (ERTM) technique cannot be directly used to solve the problem of P-P and P-S wave imaging problem because of the wide frequency band in OBN data. Aiming at high precision imaging of P-P and P-S waves for OBN broadband seismic data,this paper studies the numerical dispersion suppression method in ERTM of the first order velocity-expansion-rotation elastic wave equation,and realizes the ERTM of OBN data based on flux correction transmission (FCT) algorithm. In the process of wave field continuation of source and receiver fields,diffuse and anti-diffusion fluxes are constructed by using diffusion factor,anti-diffusion factor and the elastic wave field of two adjacent moments,and so the numerical dispersion is corrected at each time step. The numerical dispersion caused by difference discrete is suppressed and the imaging errors of P and S waves are eliminated. Model test and actual data processing test show that this method can eliminate phenomena like the migration profile phase axis breaking and false phase axis caused by numerical dispersion,and obtain high precision depth-domain P-P and P-S wave imaging results.