基于弹性波动方程的局部尺度走时反演  

Elastic wave-equation-based local-scale traveltime inversion

作　　者：胡勇 黄兴国 符力耘 段超然 HU Yong;HUANG XingGuo;FU LiYun;DUAN ChaoRan(School of Resources and Geosciences,China University of Mining and Technology,Xuzhou Jiangsu 221116,China;State Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao Shandong 266580,China;College of Instrumentation and Electrical Engineering,Jilin University,Changchun 130026,China;School of Civil Engineeringand Architecture,Changzhou Institude of Technology,Changzhou Jiangsu 213000,China)

机构地区：[1]中国矿业大学资源与地球科学学院,江苏徐州221116 [2]中国石油大学(华东),深层油气全国重点实验室,山东青岛266580 [3]吉林大学仪器科学与电气工程学院,长春130026 [4]常州工学院土木建筑工程学院,江苏常州213000

出　　处：《地球物理学报》2024年第10期3874-3890,共17页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42104116,41821002,42374149);中国博士后科学基金(2021M703580);国家留学基金联合资助。

摘　　要：弹性波全波形反演(EFWI)充分利用了地震波的运动学和动力学信息,通过最小化目标泛函来反演地下高精度的纵横波速度参数.但是,当地震数据缺失低频分量时,EFWI易产生周期跳跃问题,严重影响纵横波速度参数的反演精度.为此,本文提出基于弹性波动方程的局部尺度走时反演方法(ELTI),来同步恢复纵横波速度模型的低波数分量,进而实现缓解EFWI周期跳跃的目标.该方法充分利用了弹性波全波场的局部尺度走时信息,能够对纵横波速度参数进行同步反演,很好地解决了常规波动方程走时反演方法只能获得纵波速度参数的缺陷.此外,由于ELTI方法同时利用了弹性波全波场的走时信息,可以有效获得深部区域纵横波速度模型的低波数分量,并为EFWI提供较好的初始速度模型.本文首先,利用局部尺度分解来提取弹性波全波场数据的局部尺度走时信息,并利用观测数据与模拟数据的局部尺度走时差构建ELTI目标函数;其次,结合链式法则和伴随状态法详细推导了ELTI目标函数对应的纵横波速度参数梯度算子;最后,结合L-BFGS优化算法同步更新纵横波速度模型.Marmousi模型测试结果表明,基于弹性波动方程的局部尺度走时反演方法可以很好地获得地下纵横波速度参数的低波数分量,从而缓解EFWI的周期跳跃问题.Elastic Full Waveform Inversion (EFWI) makes full use of the dynamics and kinematic information of seismic waves to invert the P-and S-wave velocity models by minimizing the misfit function with high-resolutions. However, the conventional EFWI may suffer from severe cycle skipping without the low-frequency components in seismic data, which seriously affects the accuracy of P- and S-wave velocity parameters inversion. In this paper, we propose a Elastic Wave-Equation-Based Local-Scale Traveltime Inversion (ELTI) method to simultaneously recover the low-wavenumber components of the P- and S-wave velocity models by using the local-scale traveltime information of elastic full wavefields, which can effectively mitigate the cycle skipping problem of EFWI. The ELTI method makes full use of the local traveltime information of the elastic full wavefields, and is able to invert the P- and S- wave velocity parameters at the same time, which is a good solution to the defect of the conventional traveltime inversion method that can only obtain the P-wave velocity parameter. In addition, because the ELTI simultaneously utilizes the elastic full wavefields traveltime information, it can effectively improve the accuracy of the P- and S- wave velocity parameters inversion and provide a better initial velocity model for EFWI method. In this paper, first, the local-scale transformation is used to extract the local-scale traveltime information of the seismic elastic wave data, and then the local-scale traveltime difference between the observed and synthetic data is used to construct the ELTI misfit function;secondly, the gradient operator of the P- and S-wave velocity parameters corresponding to the ELTI misfit function is derived in detail by combining the chain rule and the adjoint-state method;finally, the P- and S- wave velocity models are updated simultaneously by combining the L-BFGS optimization algorithm. The results of the Marmousi model tests show that the elastic wave-equation-based local-scale traveltime inversion can bet

关 键 词：走时反演 局部尺度 弹性波 全波形反演 目标函数 

分 类 号：P631[天文地球—地质矿产勘探]