The Numerical Simulation Of Scattering In Random Media And The Analysis Of The Wavefield.

In seismic exploration, especially fine exploration, the medium underground is often with heterogeneous elastic property in local scale. In that medium, there are areas with the disturbance in elastic parameters, which obviously interferers the wave field and influences the results in the fine exploration. It should not be ignored. The impact of heterogeneous media in small scale to the wave field is scattering. Therefore, traditional theory and working method can hardly take effect. Study on the description of the medium and the theory in wave field has been done for the problem mentioned above.Some research on the wave propagation in random medium with Von Karman correlation has been developed in this thesis. It includes the summary of the scattering theory and the development in this field, and focus on the seismic record of point and circular disturbance in homogeneous background and random medium with Von Karman random medium. The research of basic theory on wave propagation in random medium with Von Karman correlation has been done by numerical simulation to the model with finite difference time domain (FDTD) method.Numerical simulation with FDTD method is used in seven homogeneous medium models with point or circular disturbance in elastic parameter to study the influence of disturbance of different scale and the research is also the basis of study the random in different scales. And then, six kind of random medium with Von Karman correlation are constructed, which are of the different scales. The impact of the random to the wave field can be studied by using FDTD to the random medium models. Finally, the random background medium model can be constructed by putting the dielectric objects into random medium model.As the six different kinds of random medium become the background of the dielectric object. The study of the relation between the scale of heterogeneous in background random medium and the impact to the responds of the dielectric objects can be measured by applying the FDTD to random background medium model, and the main influences are: 1. The events of the dielectric objects are serious impacted; even though the scale of heterogeneous in random medium is small.2. While the scale of the heterogeneous of the random medium is equivalent to the wavelength, the heterogeneous can be regarded as a point and there was a positive correlation between the scattering energy and the scale of the heterogeneous. So the bigger the scale of heterogeneous is, the more influence it makes to the dielectric objects.3. While the shape of heterogeneous is layered, the signal to noise ratio of the seismic record of the small offset area is higher than that of big offset. The events can be easier to be recognized in small offset area than in big offset area, where the energy of the scattering is strong.4. In all six kind of random background model, a kind of scattering energy, which is the energy of shear wave and is stimulated by the shear wave form the source, can be received in the ground, and the stimulated point is the of the longest distance to the source in the heterogeneous scale.