The Numerical Simulation Of Seismic Wave Propagation Based On FEPG Finite Element Analysis System

The numerical simulation of seismic wave field is an effective auxiliary means for researching on the acquisition, processing and interpretation of seismic data in complex area. The main methods of numerical simulation of seismic wave field are wave equation method and geometry ray tracing method. The method of wave equation numerical simulation is solving seismic wave equations, so the seismic wave field simulated with this method includes all the information of seismic wave traveling. The abundant information can supply more evidences for researching on mechanism of transmission of seismic wave and interpretation of complex stratum. So the wave equation method is a very important method of seismic forward modeling.The main numerical simulation methods of seismic wave equation have finite inference method, finite element method (FEM), reflectivity method and Fourier pseudo-spectrum method. These methods are all have advantage and disadvantage. In this paper, using FEM method to numerical simulate the elastic wave equation. The primary advantage of FEM is that it is suitable for simulating any shape of geologic body and arbitrary triangle approximating stratum interface. So it can guarantee the fidelity of simulation of complex stratum interface. But the disadvantages of FEM are that it requires mass memory and that different boundary conditions have to be set to meet different research requirements.In this paper, FEPG finite element analysis system is adopted. Finite element calculation program is generated automatically by differential equation of elastic wave propagation based on virtual work principle and algorithm files. The procedure is simulated of elastic wave propagating in several typical geologic models. Thework on programming is reduced by using the FEPG system, so greater efforts can be made to find right physical model and correct algorithm. The FEM algorithm of this paper uses interpolating function of discrete polynomial to discrete spatially, then transforms the partial differential-coefficient equation's initial and boundary value problem of elastic wave to ordinary differential-coefficient equation's initial and boundary value problem, and uses Newmark direct integral method and iterative method to solve the equation. In addition, attenuation absorbing boundary is applied. Consequently, the algorithm and boundary condition reduce the demand of memory of computer and accelerate computing speed. The graphs of wave field indicate that simulation result is clear and visual and it shows the principle of elastic wave propagating objectively.