Declustering of the catalogue after 2002. (a) The magnitude against time with scaled colours based on background probability from 2002 to 2018 September. Orange probability of being background (near 1.0) and black aftershock seismicity (close to 0.0). Dotted line denotes M_c = 1.8. (b) Cumulative number of observed events with M_c ≥ 1.8 (black line) and cumulative number of background events (grey line). Background rate of subperiod 3 (Sbr3), subperiod 4 (Sbr4) and subperiod 5 (Sbr5) are depicted in solid, dotted–dashed and dashed lines. The ETAS result is shown in the grey box.