Numerical simulation of seismic waves propagation generated by explosions

Boundary conditions are derived for numerical wave simulations that minimize artificial reflections from the edges of the domain of computation. In this way acoustic and elastic wave propagation in a limited area can be efficiently used to describe physical behavior in an unbounded domain. The boundary conditions are based on paraxial approximations of the scalar and elastic wave equations. They are computationally inexpensive and simple to apply, and they reduce reflections over a wide range of incident angles. Complex absorbing boundary conditions are developed for numerical simulations of seismic waves. These methods combines absorbing boundary conditions, based on a characteristic analyze of one – dimensional wave equations, with wavefield modifications approaches. Some of these methods absorb the waves from the surface besides the waves in the body. This study represents some of the methods of the finite – difference and finite – elements to easily understand the spreading of seismic waves in simple and complex models. The numerical simulations have improve our understanding of the scattering of seismic waves in portions of earth where are the lateraly heterogenous, which is the crust also. These methods propagate complex seismic wavefields, through high – complex mediums and include scatterings of waves and converted phases (e.g. P to SV, SV to P, wave from body to surface). The numerical methods have shown as especially useful in cases of moderate and strong scatterings in complex mediums where multiple scattering of waves becomes important. Progress have been made with numerical methods in understanding of that how surface – close, small – velocity basin structures scatters the surface waves and vertically incident waves in the medium. Numerical methods have proven usefulness in evaluating of scattering of surface waves and body waves from the topography of both, the free surface and interfaces deep in the crust. Studies for numerical methods have demonstrated the importance of conversions of waves from the body to the surface (and vice versa) when lateral heterogeneities topographic reliefs are presented in the upper parts of the crust. Recently, some analysis are applied to the numerical methods to study the seismic wave propagations in velocity models that varies differently in the space. - 4 - This stochastic approach seeks to understands the effects of complexity of small – range in the crust that cannot solve deterministically. The experiments have improved the connections between statistic characteristics of different heterogeneity and measurable characteristics of the high – frequency ( ) seismograms. These simulations are made from studies of many features that stands for actual high – frequent seismic waves, including: the amplitude and time step of the seismic wave, the apparent attenuation scattering, velocity of the waves and the variations in wave forms through arrays of receivers