Fig. 5

Stacked monthly CCFs versus interstation distance for all station pairs: a 1–10-s BB station pairs demonstrate the propagation of main Rayleigh-wave signals with an apparent velocity window of 1.3–3.8 km/s (gray dashed lines); b 0.2–5-s SP station pairs demonstrate Rayleigh-wave signals without a distinct velocity window. Black triangles mark the maximum amplitude of CCFs on the positive-time and negative-time axes separately