Figure 10. (a) Low-frequency (1–5 Hz) S-wave spectral amplitudes plotted in the format described in Figure 6. Backazimuths between 120° and 124° (events 17–22) exhibit a spike at station 11. A caustic (equation 9) is included in the model for events 17–22. (b) High-frequency (5–10 Hz) S-wave spectral amplitudes plotted in the format described in Figure 6. Backazimuths between 120° and 124° (events 17–22) exhibit a spike at station 11. A caustic (equation 9) is included in the model for events 17–22.