The Numerical Algorithm Perfection Of SDSCD And Simulation On Basin Characteristic Model

Research on seismic waves propagation in complex media is an important part of geophysics. It is an effective means to help people realize the earth medium. In numerical simulations of seismic waves, the wave-equation numerical methods have played an important role. Wave equation simulations can access to plenty of dynamic information, which can provide more evidence for the study of seismic waves propagation and interpretation of complex structures.In the paper, symplectic scheme and discrete singular convolutional differen-tiator(SDSCD)are introduced to wave equation simulations, which fundamentally improve the solution accuracy and credibility. Symplectic algorithm is a struc-ture preserving algorithms, which has strong stability and long-term tracking capability. Discrete singular convolutional differentiator is a short optimization operator.It more highlights the local property of spatial derivative.We do some work to perfect the previous developed SDSCD algorithm, in-cluding to implement the module of plane wave input and the module of perfectly matched layer absorbing boundary conditions. We consider the SH plane wave vertically and obliquely incident from the bottom of model. The module can sat-isfy the incidence with arbitrary angles theoretically. We adopt modified PML boundary conditions for the SDSCD algorithm, which eliminates the third deriva-tive of the variable or convolution process, implement easily and absorb better by introducing differential equations of additional variables. The work lays the foundation on ground motion numerical simulation on basin model.We simulate the two-dimensional elastic wave field of characteristics basin model based on the perfected SDSCD algorithm, and analyze the basin wave field using snapshots, records and response spectrums at surface receiving points. The basin wave field is different from the wave field of homogeneous layered medium from snapshots and theoretical seismograms, because of the structure of the basin, making the surface wave propagation in the basin back and forth and increasing volatility duration.The results show edge effect and focusing effect of basin structure in the central region and hypotenuse region.When we change the wave velocity of basin region, the greater velocity dif-ference between the basin and basement, the peak value of body wave is smaller, and the peak value varies sharply in the hypotenuse region; the greater velocity difference between the basin and basement, the peak value of surface wave is greater, and the peak value varies sharply in the central region. For the same model, the greater cycle from acceleration response spectrum, the spectral value is smaller.When we change the basin depth, the deeper of basin region, the body wave peak value in the hypotenuse corners and the surface wave peak in the central region are greater and change sharply as the incidence of Ricker wavelet, and the body wave peak in the central region does not change with depth; the relationship between the basin depth and peak values is complex as the incidence of earthquake records.