Downward and upward continuation of 2-D seismic data to eliminate ocean bottom topography's effect  

消除海底起伏影响的海洋地震波场正反向延拓(英文)

作　　者：王祥春[1] 夏常亮 刘学伟[1] 

机构地区：[1]地下信息探测技术与仪器教育部重点实验室(中国地质大学),北京100083 [2]中石油集团东方地球物理勘探有限责任公司研究院海外业务部,河北涿州072750

出　　处：《Applied Geophysics》2010年第2期149-157,194,共10页应用地球物理（英文版）

基　　金：sponsored by the National 973 Program of China(Grant No.2009CB219505);International Science&Technology Cooperation Program of China(Grant No.2010DFA21630)

摘　　要：In order to eliminate the effect of ocean bottom topography on seismic wave field,we transformed curved（x,z）coordinate system grids into rectangular（ξ,η）coordinate system grids and derived a 2-D scalar acoustic wave equation in theξ,ηdomain.The seismic wave field collected at the sea surface was downward continued to the ocean bottom by the inverse finite difference method with the water velocity and then was reversely continued to the ocean surface by the finite difference method using the layer velocity from just below the ocean bottom in the（ξ,η）domain.Simulation calculations and practical application show that this method can not only remove the reflection travel time distortion but also correct the dynamic parameter changes caused by the ocean bottom topography.The inverted velocity after wave field continuation is much more accurate than before continuation and the image section was greatly improved compared to the original wave field.为了解决海底起伏变化对地震波场的影响问题,本文提出将(x-z)域中的曲网格映射成(ξ,η)域中的矩形网格,推导出(ξ,η)域中的二维标量声波方程,根据推导出来的波动方程采用逆时有限差分法将海面上采集到的地震波场在(ξ,η)域中向下延拓至海底面,延拓时采用海水的速度,然后采用顺时有限差分法将延拓后的地震波场再反延拓到海面上,延拓时采用海底面以下地层的速度,从而消除了海底起伏带来的负面影响。模型及实际地震资料的计算分析表明该方法不但能够校正由于海底起伏所引起的海底面下地层反射波场的不连续性还能够校正由于海底起伏所引起的地震波的动力学特征的变化。对延拓前后的地震波场进行速度反演,延拓后反演的地层速度比延拓前反演的地层速度的精度提高很多,延拓前后地震波场的叠加剖面对比表明该延拓方法能够明显提高地震波场的成像质量。

关 键 词：wave equation CONTINUATION ocean bottom topography TRANSFORMATION 

分 类 号：P631.4[天文地球—地质矿产勘探]