Fig. 4

ETAS model fittings to the restricted regions. ETAS model (1) is fitted to the seismicity in Region A, including the narrow aftershock Region B of the 2000 M5.0 earthquake, beneath which the aftershocks of the 2016 M6.5 and M7.3 Kumamoto earthquakes are plotted as gray circles. The red circles indicate earthquakes from January 1, 1990, until the M6.5 Kumamoto earthquake on April 14, 2016 (blue disk), and its aftershocks prior to the M7.3 mainshock, with a threshold magnitude of M _c  = 2.0, are plotted as gray circles. The dashed rectangles indicate the fault models of the 2016 Kumamoto earthquakes listed in Table 3. The seismicity in Region B is from 09:32, June 8, 2000, when the mainshock of M5.0 (marked by a thick circle) occurred, and consists only of its aftershocks. The right panels show the ETAS model fitted before the change-point MLE (dashed vertical line) for Region A (top panels) and for the narrower Region B (bottom panels). The estimated cumulative curves are superimposed (red curves) on the observed values (black curves) versus the ordinary time (the left side of each pair) and the transformed time (the right side of each pair). The corresponding M–T plots are attached under the corresponding panels