Finite Difference Numerical Simulation Of Seismic Wave Field Based On MPI

As a critical technology in exploration seismology,seismic wave numerical modeling plays an important role thoughtout the process of surving design,acquisition,processing and interpretation of seismic data.Finite difference method becomes the best choice to simulating seismic wave,for it is easy to improving accuracy and realizing.The existing numerical simulation methods have been able to meet the requirement of traditional exploration.But with the development of the industry,it not only requests to gain seismic data with high resolution,but also to complete exploration task quickly and efficiently.Even use workstation or cluster,traditional serial technique can't achieve the ideal effect.So to implement parallel algorithmin numerical simulation of seismic waves is imperative.According to the Foster's parallel algorithm,this paper realizes finite difference numerical simulation of seismic wave based on MPI(message passing interface).In order to realize parallel processing of seismic modeling,this paper will discuss from the following aspects:Firstly,the paper study and deduce seismic wave equation.Based on the elastic dynamic theory,the equations of acoustic wave,elastic wave and SH wave are studied and the effects of quality factor in viscoelastic model is also discussed.Meanwhile,the wave equations of the three kinds of seismic wave based on Kelvin model and standard linear solid(SLS)model in viscoelastic media are deduced.By the comparation of the difference precision between ordinary grid and staggered grid,the advantages of staggered grid is verifed.High order difference coefficients and the discretization of the seismic wave equation are also deduced.Secondly,some critical questions in parallel computing of finite difference seismic wave modeling are discussed,such as why does the numerical dispersion occur and how to suppress them,what's the stability condition of difference equation and how to judge them in programming,how to load the seismic source and what's the difference of different wavelet,how to realize the absorption boundary in programming,etc.Some significant processes in parallel computing are outlined,such as region decomposition,coordinate transformation,region communication,wave field combination and so on.Lastly,through seismic wave filed modeling of layered model,fault model and salt model,the relationships between different number of CPU and simulation efficiency are compared and discussed.Simultaneously,the propagation law of acoustic wave,elastic wave and SH wave in different media are studied.Through comparing the single trace record of elastic model with that of viscoelastic model,the influence of quality factor to seismic wave is analyzed.Simulation results show that the parallel scheme in finite difference seismic wave simulation,which promotes the advantages of high order staggered grid finite difference method,can greatly increase the calculation efficiency.However,the number of CPU in parallel computing depends on the scale of the problem being studied and the performance of selected computer system.An appropriate number of CPU need to be selected properly.The quality factor has a great influence on the amplitude and phase of seismic waves.The calculation cost and acceleration ratio of SLS viscoelastic model in parallel computing are better than that of Kelvin viscoelastic model.So,it is suggested that SLS viscoelastic model should be adopted in the actual data processing.