Abstract
Theoretically, the Green's function can be used to calculate the wavefield response of a specified source and the Frechet derivative with respect to the model parameters for crosshole seismic full-waveform inversion. In this paper, we apply the finite-element method to numerically compute the 2.5-D Green's function for an arbitrary acoustic medium by solving a composite boundary-valued problem in the wavenumber-frequency domain. The composite boundary condition consists of a 2.5-D absorbing boundary condition for the propagating wave field and a mixed boundary condition for the evanescent field in inhomogeneous media modeling. A numerical experiment performed for a uniform earth (having a known exact solution) shows the accuracy of the computation in the frequency and time domain. An inhomogeneous medium test, involving an embedded low-velocity layer, demonstrates that the permissible range of ky at each frequency can be determined rationally from the critical wavenumber value of the medium around the source. Furthermore, it shows that the frequency-domain solution is not improved continuously by increasing the number of ky samples because of the complicated nature of the wavefield. Both experiments show that the proposed method is effective and flexible for computing the 2.5-D Green's function for arbitrary acoustic media.
Original language | British English |
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Pages (from-to) | 1813-1823 |
Number of pages | 11 |
Journal | Geophysics |
Volume | 63 |
Issue number | 5 |
DOIs | |
State | Published - 1998 |
Keywords
- Green function
- Seismic method