A damping method for the computation of the 2.5-D Green's function for arbitrary acoustic media

被引:10
作者
Bing, Z [1 ]
Greenhalgh, S [1 ]
机构
[1] Flinders Univ S Australia, Sch Earth Sci, Adelaide, SA 5001, Australia
关键词
2.5-D Green's function; damping method; frequency domain; full-waveform inversion;
D O I
10.1046/j.1365-246X.1998.1331474.x
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
In acoustic wavefield modelling, the 2.5-D approximation, in which the model parameter is considered to be invariant in the strike direction and the source is assumed to be a point excitation so that the wavefield has 3-D features, is an economical and realistic scheme for seismic full-waveform inversion. On the other hand, according to Parseval's theorem, the least-squares inversion of time-domain seismic data is equivalent to that carried out with frequency-domain data, but the latter has some advantages such as its efficiency and flexibility in non-linear waveform (or diffraction) inversion with single- or multiple-frequency crosshole data. These inverse techniques require the computation of the response of a specified source and the Frechet derivatives in the frequency domain, both of which can be calculated via the Green's function. In this paper, a damping method was applied to the computation of the 2.5-D Green's function for arbitrary acoustic media in the wavenumber-frequency domain. The 2.5-D acoustic and time-damped wave equation was solved with the finite-element method (FEM). The computations for homogeneous and heterogeneous media were performed in the frequency range 100-300 Hz. It was found that the time damper is important to the solution. A linear damper, as in time-domain modelling, can be chosen, but it depends on the frequency, the wavenumber and the width of the absorbing zone in the wavenumber-frequency-domain modelling. An appropriate time damper and a reasonable number of k(y) samples can be determined in terms of the range of frequency and the critical values of the wavenumber of the media. By comparing the numerical solutions with the exact analytic solution for the homogeneous case and the semi-analytic solution for two semi-infinite media in contact, it is shown that the method can yield satisfactory solutions in the frequency domain and the time domain. Finally, a synthetic experiment of crosshole seismic full-waveform inversion is used to illustrate the method.
引用
收藏
页码:111 / 120
页数:10
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