**Appendix B. Near-Surface Model Generation Method**

For an elastic wave numerical simulation, the model is established mainly to determine the spatial distribution of the elastic parameters. It includes five parameters of the medium involved: the P-wave velocity (*vp*), S-wave velocity (*vs*), density (*ρ*), Lame constant *μ* and *λ*. The relation among these parameters can be given by:

$$\nu\_p = \sqrt{\frac{\lambda + 2\mu}{\rho}}, \ \nu\_s = \sqrt{\frac{\mu}{\rho}} \tag{A18}$$

in which three of the five parameters must be chosen to determine the other two parameters. Here, we control *vp*, *vs*, and *ρ* and determine the Lame constant according to these parameters.
