Figure 1. (Top) Azimuth-dependent PP arrival time and reflectivity from fracture targets A and B. (Bottom) Azimuth-dependent PS arrival time and reflectivity from the same targets. PP reflectivity changes little with azimuth; PS reflectivity varies significantly. PP arrival time changes by 4 ms between azimuths 50° and 140°, whereas PS arrival time changes by 50 ms. Azimuth 50° is the fast-S mode (S1); azimuth 140° is the slow-S mode (S2).