Fig. 9

Time-dependent b-value estimates and the 50% detection rate of magnitudes. a Epicenters of the whole aftershocks of M ≥ 1.5; orange and blue dots indicate the deep aftershocks at 23–55 km depth and the shallow aftershocks at 0–23 km depth, respectively. b Hypocenters are plotted as depth vs. longitude. c Time-dependent b-values are estimated with the aftershocks at all depths (black line), shallow aftershocks (blue line), and deep aftershocks (orange line), respectively; these are with twofold error envelopes. d The + signs show M–T plots with colors for corresponding ranges in depth. The black line indicates a 50% detection rate of magnitudes for all depths with twofold errors together with magnitudes of all detected aftershocks. e The blue and orange broken line shows counted numbers of the shallow and deep aftershocks, respectively, counted in bins of 0.05 logarithmic days from the M6.7 main shock. The dashed vertical lines throughout c–e indicate the occurrence of the topical swarm events and the M5.8 largest aftershock (iv), respectively. See Additional file 1: Table S9 for the fitting configurations and results of model comparisons