The first-order Rytov approximation has be widely used in simulating forward scattering waves and the finitefrequency tomography. However, the Rytov approximation still suffers from the weak-perturbation assumption, which limits the scope of its applicability. To address this problem, we propose a generalized Rytov approximation (GRA) which is valid for arbitrary velocity perturbations as long as the scattering-angles are small. We also show that GRA can be degenerated to the Rytov approximation by taking the first-order approximation of the model perturbation function. Based on GRA, we derive a new finite-frequency traveltime sensitivity kernel which has the potential to produce an improved result over the conventional finite-frequency inversion methods. Theoretical derivation and numerical tests demonstrate that both GRA and the first-order Rytov approximation belongs to small scattering-angle approximations. Therefore, both methods are not valid for dealing with the large scattering-angle propagations.
Presentation Date: Wednesday, September 18, 2019
Session Start Time: 1:50 PM
Presentation Start Time: 3:05 PM
Presentation Type: Oral