S-S reflection coefficient

The treatment here is analogous to the one for the P-S and S-P coefficients. The final relation is:  

$$R_{SS}(x,z,t) \; = \; {\chi^r(x,z,t) \over \chi^s(x,z,t)} \;... ...eft(\nabla \times {\bf u^s}(x,z,t) \right) \cdot {\bf \hat{y}}}$$ (6)