一维大地电磁和地震数据联合反演方法研究
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摘要
针对江汉盆地海相地层的地电结构特点，对区内5口探井的物性数据作了统计，给出了一维层状介质模型。大地电磁数据是采用一维层状介质递推关系式模拟，差商法求其偏导数；地震数据是以水平界面为基础进行快速射线追踪正演，运用解析法求偏导数。理论数据采用典型HAK型曲线5层地球物理模型试算。在上述基础上，本文着重阐述了大地电磁和地震联合反演方法，首先引入模型空间向量，其参数由各层的速度、电阻率和厚度构成，并给出此模型的响应函数，然后将响应函数和数据向量建立统一的映射关系。由于不同的数据集具有不同的物理空间和数量级，必须作归一化处理，引入相对预测误差向量，为此，文中给出一种求解不适定问题的方法。理论模型和实际数据联合反演结果表明，它优于任何一种单一的地球物理反演方法。
1-D layered medium model has been designed by analysing both the actual geo-electric structure of marine sediments in Jianghan basin and the statistical physicaldata taken from 5 boreholes there. The magnetotelluric data are simulated by usingrecursion formula for 1-D layered medium, and partial derivatives are computed bytaking difference quotient method. The forward computation of seismic data isachieved by doing fast ray tracing on horizontal interface, and the partial deriva-tives are estimated by adopting analytic method- The theoretical data are derivedfrom typical HAK curve and 5-layer geophysical model.Then, the joint inversion of magnetotelluric and seismic data is described in de-talil. The inversion involves the following steps: Introducing the space vector of model, whose parameters consist of velocity,resistivity and thickness of each layer.. Offering the response function of the model.. Determining the mapping relation between the response function and datavector.Different data sets have different physical spaces and magnitudes, so that wemust do normalization, for which we introduce relative prediction error vector thatinvolves the use of the method for solving an ill-posed problem.Theoretical model and joint inversion of real data show that it is better than theinversion of any single kind of geophysical data.
1-D layered medium model has been designed by analysing both the actual geo-electric structure of marine sediments in Jianghan basin and the statistical physicaldata taken from 5 boreholes there. The magnetotelluric data are simulated by usingrecursion formula for 1-D layered medium, and partial derivatives are computed bytaking difference quotient method. The forward computation of seismic data isachieved by doing fast ray tracing on horizontal interface, and the partial deriva-tives are estimated by adopting analytic method- The theoretical data are derivedfrom typical HAK curve and 5-layer geophysical model.Then, the joint inversion of magnetotelluric and seismic data is described in de-talil. The inversion involves the following steps: Introducing the space vector of model, whose parameters consist of velocity,resistivity and thickness of each layer.. Offering the response function of the model.. Determining the mapping relation between the response function and datavector.Different data sets have different physical spaces and magnitudes, so that wemust do normalization, for which we introduce relative prediction error vector thatinvolves the use of the method for solving an ill-posed problem.Theoretical model and joint inversion of real data show that it is better than theinversion of any single kind of geophysical data.
引文
1Backus G E and Gilbert F. Uniqueness in the inversion of inacuriate gross earth data. phil,Trans R soc,London ser, 1970,V266,123～192
2杨文采.地球物理反演和地震层析成像,地质出版社,1989
3Alekseev A S.联合反演问题解的定量描述及其一般特性.第 61届 SEG年会论文集,石油工业出版社,1993,595～596
4Hering A, Mlslek R, etc. A Joint inversion algorithm to process geoelectric and surface wave seismicdata,Part l:basis idea Geophysical Prospecting,1995,43(2):135～156
5周辉,刘财,渠广学.地震-大地电磁数据非线性联合反演方法研究.长春地质学院学报,1995,25(2)
6Anhu, Ginzburg etc. Automatization interpretation of resistivity sounding on direct current. Pure andApplied Geophysics,1976,V114
7Wu F T.The inverse problem of magnetotelluric sounding(least-squares).Geophysics,1968,33(6):972～979
8王家映.地球物理中的反演理论,武汉地质学院物探系,1986
9Llnes L R and Treitel S. Tutorial: A review of least squares inversion and its spplication to geophysicalproblems.Geophysical Prospecting,1984,32(2):159～186
10Jupp D L B and Vozoff K. Stable iterative methods for the inversion of geophysical data. Geophysics,Reprint series, Edited by Vozoff, No 5, P440～ 459, received 1974
11徐义贤.大地电磁多尺度反演方法研究.中国地质大学博士学位论文(摘要),1996
2杨文采.地球物理反演和地震层析成像,地质出版社,1989
3Alekseev A S.联合反演问题解的定量描述及其一般特性.第 61届 SEG年会论文集,石油工业出版社,1993,595～596
4Hering A, Mlslek R, etc. A Joint inversion algorithm to process geoelectric and surface wave seismicdata,Part l:basis idea Geophysical Prospecting,1995,43(2):135～156
5周辉,刘财,渠广学.地震-大地电磁数据非线性联合反演方法研究.长春地质学院学报,1995,25(2)
6Anhu, Ginzburg etc. Automatization interpretation of resistivity sounding on direct current. Pure andApplied Geophysics,1976,V114
7Wu F T.The inverse problem of magnetotelluric sounding(least-squares).Geophysics,1968,33(6):972～979
8王家映.地球物理中的反演理论,武汉地质学院物探系,1986
9Llnes L R and Treitel S. Tutorial: A review of least squares inversion and its spplication to geophysicalproblems.Geophysical Prospecting,1984,32(2):159～186
10Jupp D L B and Vozoff K. Stable iterative methods for the inversion of geophysical data. Geophysics,Reprint series, Edited by Vozoff, No 5, P440～ 459, received 1974
11徐义贤.大地电磁多尺度反演方法研究.中国地质大学博士学位论文(摘要),1996
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