Study on the Grouped Occurrence Characteristics of Earthquakes with M≥4 in the Southeast Coastal Seismic Zone

WANG Xiaona; SHAO Ye; CHEN Daqing; XU Binbin; ZHONG Qiu

doi:10.13512/j.hndz.2025.02.01

Abstract：The study analyzes the temporal patterns of M≥4 earthquakes(removing aftershocks)in the southeast coastal seismic zone since 1974.The results reveal that these earthquakes exhibit a pattern of grouped occurrence.Firstly,the paper establishes the criteria for identifying the onset and termination of such grouped episodes:If an M≥4 earthquake occurs within 0.75 years after the end of the previous group of seismic activities,the new group of seismic activities is considered to have started,and the occurrence time of the first earthquake(initial earthquake)is taken as the start time of the group of seismic activities.If no earthquake occurs within 417 days(the maximum time interval between earthquakes within the group)after an earthquake,the group of seismic activities is considered to have ended,and the occurrence time of the last earthquake within the group is taken as the end time of the group of seismic activities.At the same time,this paper summarizes three prediction indicators.Indicator 1∶Within 4.1 years following the first earthquake,multiple M≥4 earthquakes,potentially including M≥5 events,may occur in this seismic zone.Indicator 2:Between 25 and 275 days after the first earthquake,there is potential for another M≥4 earthquake in the zone.Indicator 3:An M≥5 earthquake may occur within 53 to 320 days after the first earthquake.Finally,by integrating the criteria for determining the onset and termination of such grouped activity with these three prediction indicators,this paper proposes an evaluation and prediction plan for M≥4 earthquakes in the Southeastern Coastal Seismic Belt,along with implications of the Qingyuan M4.3 earthquake for evaluating subsequent seismic activity patterns.