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Results
Brazi(; and Dan Koslof' Tel Aviv University, Israel S-The stress displacement relations are given by, This paper presents an evaluation of multi component depth migration. This type of migration can be carried out by most techniques commonly used for conventional single component acoustic migration. We demonstrate downward continuation by extensions of the phase shift method introduced by Gazdag (1978) and Bolodni et al. (1978)) as well as by the generalized phase shift method (Kosloff and Kessler, 1986). We then evaluate elastic reverse time migration where X and /.L are respectively the rigidity and the (Sun and McMechan, 1986, Chang and McMechan, shear modulus. Specifically we show that when the correct velocity is used reverse time migration is incapable of where UT (&, it*, Gu, szx) is the motion-stress reproducing correct amplitudes. Furthermore, use of the vector, and exact velocity and the free surface boundary condition creates false events in all methods.
Gaussian Beam Migration
da Costa, Carlos Alberto (UFBA) | Raz, Shalom (Technion I.I.T.) | Kosloff, Dan (Tel Aviv University)
The method, though based on a high frequency approximation, operates on whole time sections and not merely on selected digitized horizons as in ray tracing map migration. In order to affect Gaussian beam migration, the The beam coefficients A,, in (1) can be determined via recorded time section is first temporally transformed the so called biorthogonal function rrnn according to: from the z-t domain into the z-w domain. The data is then beam stacked by the Gabor expansion (Raz, 1987). The stacking can be carried out over receiver A mn; -/;n(4 f (4 dz 3 (5) coordinates, or over both receiver and shot coordinates. Each beam is then downward continued into the subsurface. Beam migration can be carried out on both CMP rmn(z) 7(2 - mL)exp(innz) .
In a three-dimensional continuous medium the linearized equations This work presents a new scheme for wave propagation simulation in of momentum conservation are three-dimensional elastic-anisotropic media.