Fig. 5
From: Characteristics of foreshock activity inferred from the JMA earthquake catalog
Comparison of b-value differences. a–d Comparison of the magnitude of the mainshock and b-value differences. The magnitude of the mainshock is shown on the horizontal axis; the vertical axis shows the b-value difference. a, b Foreshocks–aftershocks (with 200 foreshocks and 200 aftershocks), c, d foreshocks—background (with 200 foreshocks, red circle), and aftershocks–background (with 200 aftershocks, black circle). e, f Histogram of b-value differences. The frequency of the b-value differences is on the left axis, and the cumulative probability is shown on the right axis. a, c, e Mc was chosen as MAXC + 0.2 for the entire magnitude range, b, d, f Mc was chosen as MAXC + 0.2 for Mmain < 5.5; Mmain − 3.5 for Mmain ≥ 5.5. The b-value of the background was calculated using hypocenters other than the target cluster within the range of ± 0.4 degree of the mainshock of the target cluster