Fig. 2

Distance change in coda-normalized P-wave amplitudes. a Coda-normalized P-wave amplitudes in the 1–2- and 2–4-Hz bands, as measured from crustal earthquakes (Fig. 1). Values of |F _P | are the magnitudes of the P-wave radiation pattern coefficients expected from the centroid moment tensor (CMT) solutions of the F-net. b The same as a except with a limitation of |F _P | ≥ 0.7