反射地震道的反演—问题和限制

INVERSION OF REFLECTION SEISMIC TRACES——Problems and Limitations

地矿部北京计算中心

经过处理的反射地震数据,可以逐道地反演地下岩石的波阻抗或速度的垂向变化。本文讨论应用一维声波方程反演法、广义线性反演和线性规划反演法的假设条件和由此产生的局限性,它们与反问题解的存在性有关。由于大地的滤波作用,检波器与大地的耦合和地震仪中滤波器的作用,地震记录与地面振动之间有很大的差别。在反演前对地震信号进行衰减补偿、频带展宽和相位改正等预处理,是提高反演效果的关键之一。

The processed reflection seismic data can be used trace by trace for inversion of the vertical variation of acoutic impedance or velocities of the subsurface media. This paper deals with the limitations of the following inversion approaches of seismic traces namely,·1-D wave equation inversion·The generalized linear inversion · Inversions by linear programmingThese limitations are due to mathematical assumptions in simplification of a geophysical model and have a bearing on the solution of inverse problems. The seismic data for inversion differ significantly from ground vibration in a wave equation due to the earth filtering, coupling between geophones and the earth, analog filters in a seismograph and digital filters used during data processing. It is advised that to perform the Q compensation, expand the frequency band arid the phase correction on seismic data must be done before they are used for inversion. Anyway, preprocessing should be considered as one of the essentials for obtaining the desirable results out of inversion.