Fig. 5

Estimated non-stationary ETAS model, where the MLEs of the ETAS model, as shown in Fig. 4, were used as the reference parameters (see Additional file 1: S4). The background rate μ(t) (red) and the triggering coefficient K₀(t) (blue) in the ordinary time; the envelopes of the twofold standard errors of the estimations are indicated by dotted lines. The gray curve shows the whole intensity λ(t). The first vertical dashed line shows the change-point (1-Oct-2018) as also shown in Fig. 4, and the pink shade indicates the span of the following 4 days. The second vertical dashed line is at the occurrence of the M5.8 largest aftershock (iv). The thick + signs indicate magnitude of the main shock (iii) and the largest aftershock (iv), against occurrence times. See Additional file 1: Table S5 for the fitting configurations and results of model comparisons