Application of a perfectly matched layer in seismic wavefield simulation with an irregular free surface

2015 ◽  
Vol 64 (1) ◽  
pp. 112-128 ◽  
Author(s):  
Haiqiang Lan ◽  
Jingyi Chen ◽  
Zhongjie Zhang ◽  
Youshan Liu ◽  
Jianguo Zhao ◽  
...  
Author(s):  
Xiang Li ◽  
Gang Yao ◽  
Fenglin Niu ◽  
Di Wu

Abstract The irregular free surface topography has a significant impact on simulations of seismic wave propagation. Therefore, an accurate representation of the irregular free surface is required for an accurate wavefield simulation. We propose an immersed boundary method used in fluid dynamics calculation to simulate acoustic waves with finite-difference in media with irregular surfaces. First, we set the number of ghost layers to half the length of the finite-difference stencil. Then, we define mirror points by orthogonally projecting the ghost points to fractional points below the free surface. We calculate the wavefield at these mirror points using an iterative symmetric interpolation method. Finally, we set the wavefield at the ghost points to the negative value of the wavefield of their corresponding mirror points. The proposed iterative symmetric interpolation method allows computing the wavefield at the mirror points more accurately and stably than the conventional immersed boundary methods. Numerical examples validate the accuracy and stability of this method in seismic forward modelling with strongly varying topography.


2013 ◽  
Vol 353-356 ◽  
pp. 1858-1866
Author(s):  
Wu Jian Yan ◽  
Yu Cheng Shi

In this paper, we simulated two-dimension numerical on the strong ground motion through the hybrid scheme based on the pseudo-spectral method (PSM) and finite difference method (FDM). We based on the same focal depth, and 2 different thick deposition layers are used as models to analyze the relationship between site situation and the peak displacement of strong ground motion. The results show that the hybrid PSM/FDM method for seismic wavefield simulation combines with advantages of the pseudospectral method and the finite difference method and makes up for the disadvantage of the pseudospectral method and the finite difference method, so this method can process well the calculation of the discontinuous medium surface, then the calculation accuracy is similar to the pseudospectral method. Through the wavefield simulation it is known that the range of the seismic wavefield the peak ground displacement (PGD) of the thicker deposition is larger and the influence of the secondary surface wave at the basin edge is more obvious. The thicker deposition amplitude of strong ground motion in the basin is larger and the duration is longer, and the reflected wave of which is more obvious and stronger. However, the difference of the site condition has little influence to strong ground motion in the horizontal direction.


2012 ◽  
Vol 594-597 ◽  
pp. 1840-1848 ◽  
Author(s):  
Wu Jian Yan ◽  
Yan Bin Wang ◽  
Yu Cheng Shi

Abstract: In this paper, we simulated two-dimension numerical on the strong ground motion in Lanzhou basin through the hybrid scheme based on the pseudospectral method (PSM) and finite difference method (FDM). We base on a focal of 20 km deep and a profile of 5 layers is used as model to analyze the site response and the peak displacement of strong ground motion. The results show that the hybrid PSM/FDM method for seismic wavefield simulation combines with advantages of PSM and FDM and makes up for the disadvantage of them, so this method can process well the calculation of the discontinuous medium surface, then the calculation accuracy is similar to PSM. Through the wavefield simulation it is known that the peak ground displacement (PGD) of the vertical is larger and the influence of surface wave at the basin edge is more obvious than the horizontal.


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