Abstract:
Studying of the temporal distribution of earthquakes is very important for understanding the physics of the earthquake generation process. In the present study the time distribution of the fore-aftershock sequences before and after the 2020 Plovdiv earthquake, with moment magnitude MW4.5 is analyzed. Foreshocks are one of the few well-documented precursors of large earthquakes. Aftershocks are defined as seismicity above the background activity following a main shock. The properties of aftershock sequences (distinct cluster in space and time) allow time-dependent prediction of aftershock probabilities. We analyze the temporal pattern of earthquake distribution of the foreshock and aftershock sequences of the main event. The temporal distribution of foreshocks shows non-random features. Although dominated by the classic power law decay in time, the aftershocks suggest the existence of secondary aftershock sequence. The attenuation of aftershock activity is well described by the modified Omori formula. Aftershock sequence is best modelled by the combination of one ordinary and two secondary aftershock sequences. Transition from aftershock activity to background seismicity is observed about 62 days after the main shock.