基于起伏地形平化策略的弹性波逆时偏移成像方法  

Elastic reverse time migration using a topography flattening scheme

作　　者：侯爵 刘有山[2] 兰海强[2] 徐涛[2,3] 白志明[2] HOU Jue1 , LIU YouShan2 , LAN HaiQiang2 , XU Tao2,3 , BAI ZhiMing2(1 Institute of Geophysics, China Earthquake Administration, Beijing 100081, China 2 State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 3 CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, Chin)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [3]中国科学院青藏高原地球科学卓越创新中心,北京100101

出　　处：《地球物理学报》2018年第4期1434-1446,共13页Chinese Journal of Geophysics

基　　金：国家重点研究发展计划(2016YFC0600201;2016YFC0600101;2016YFC0600302);中国地震局地球物理研究所基本科研业务专项(DQJB17B08);国家自然科学基金(41774097;41404073;41604076;41674095;41504074)联合资助

摘　　要：随着能源和资源勘查开采工作的深入,地形强烈起伏的盆山耦合地区的地震资料处理解释技术正日益成为山地地震勘探面临的重要挑战.逆时偏移方法作为精确的地震偏移成像方法之一,能对地下结构进行高精度成像.逆时偏移的核心是地震波场延拓,由于传统的地震波场延拓技术往往基于水平地表条件,相应的方法在直接处理强地形起伏条件下的地震资料时往往存在一定的精度损失.本文引入一种精度无损的处理起伏边界的模型参数化方法:基于贴体网格的地形"平化"策略发展了与地形有关的地震波波动方程数值模拟方法,采用零延迟归一化互相关成像条件实现了起伏地表条件下的弹性波场逆时偏移成像.对工业界的标准Marmousi模型和盐丘模型进行改造,获得了相应起伏地形条件下的复杂几何模型,开展了起伏地表下的地震偏移成像数值试验.结果表明基于贴体网格"平化"策略的逆时偏移成像方法具有较高的灵活性,可适应不同类型起伏地表采集的地震资料,显示出该方法在地震勘探领域的良好应用前景.With the steady development of energy and resource exploration,the data processing and interpretation of seismic surveys in rugged mountains,plateaus and basins and other is facing serious challenges.Reverse time migration is one of the most accurate migration methods,which can image the crust and upper mantle structure with high precision.Seismic wavefield extrapolation is the core part of this approach.Because the conventional wavefield extrapolation method is based on the flattening-surface assumption,it often brings loss of precision when dealing with the seismic data acquired in mountainous areas with large topographic relief.To solve this problem,we introduce a parametric method for dealing with the irregular boundary without loss of accuracy：a flattening scheme based on the boundary conforming grid.We study the topography-dependent wave equation,apply the zero-lag normalized cross-correlation imaging condition,and implement the reverse time migration of the elastic wavefield under the irregular surface conditions.First,the standard industrial Marmousi and SEG/Salt models are modified to adapt to undulating surface cases to verify the presented reverse time migration method based on the flattening scheme.Next,we make numerical tests on the Marmousi and SEG/Salt models to show the feasibility of the reverse time migration method based on the boundary conforming grid under the flattening irregular topography.The results indicate that this method can deal with seismic data collected from different types of irregular surfaces,exhibiting agood prospect in the seismic exploration.

关 键 词：起伏地表 弹性波 逆时偏移 贴体网格 有限差分 

分 类 号：P631[天文地球—地质矿产勘探]