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Computation of frequency-dependent traveltimes
| Content Provider | Semantic Scholar |
|---|---|
| Author | Koslowski, Oliver Ettrich, Norman |
| Copyright Year | 2019 |
| Abstract | The eikonal equation for modeling ray propagation in inhomogeneous media is frequency independent. Therefore, it cannot correctly model the propagation of seismic waves when rapid variations in velocity cause frequency dispersion of the wavefield. Advantages and disadvantages of three methods which are extensions of frequency independent ray tracing to a frequency dependent process are presented. INTRODUCTION A commonly used method for computing traveltimes is given by the propagation of rays. The asymptotic ray tracing (ART) has advantages over full waveform methods because of its efficiency and the simple interpretation of results. There are many applications, e.g., it is used for modeling, in seismic tomography and in Kirchhoff migration. However, application of ray tracing is limited to seismic signals with wavelengths small compared to characteristic lengths of the medium and of the wavefield itself. Reason is that the eikonal equation is a high frequency approximation and, therefore, frequency independent. This may lead to poor imaging in rather complex models when ray tracing is used for pre-stack Kirchhoff migration, since dispersion, scattering and other effects are neglected. In this case, the process of wave propagation must be described in dependence on frequency as it is done by numerically solving the wave equation or the elastodynamic equation of motion. Since this is not practical for many applications we present three different methods which extend kinematic ray tracing to a frequency dependent process. The methods by (Zhu and Chun, 1994) and (Biondi, 1992) involve solving the frequency dependent eikonal equation while the method by (Lomax, 1994) simulates the propagation for lower frequencies by a smoothing of the model. In this paper these methods are called: perturbation scheme by Zhu extrapolation along the frequency axis by Biondi 1email: ettrich@dkrz.de 169 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.wit.uni-hamburg.de/import/documents/reports/1997/wit1997-koslowski.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
