A suggestion to add the correction of Ps moveout before estimating crustal anisotropy

[Zekun Li]

Dear Dr. Xu,

Thanks for your seispy code, it's a great work.

I have a suggestion about rfani function. Before using the joint analysis method from（Liu and Niu, 2012 GJI), the moveout caused by the difference between the ray parameters of P and Ps should better be computed and corrected. For example, Liu and Niu employed a revised IASP91 velocity model with a modified crust to correct the moveout in（Liu and Niu, 2012 GJI). (Sun et al., 2012) used the H-k results to compute the moveout, (Cai et al., 2016) did the same.

But in the current seispy, rfani doesn't include the correction of moveout yet. Could you fix this problem at your convenience？
Thanks for a lot!

Zekun Li