Anomaly index of weak seismicity before the M_L5.0 earthquakes in Henan Province and its vicinity

This paper studied the patterns of weak seismicity before all the 16 earthquakes with ML≈5.0 occurred during 1970—2006 in Henan Province and it vicinity.The results indicate that there are some anomalous seismicity patterns,such as the seismic window effect,weak seismic gap,seismic swarming,small earthquake swarm activity,weak seismic band and earthquake-free segment and so on.Among them,the recurrence rate of seismic window effect and weak seismic gap is highest(both are 0.75);the rate of small earthquake swarm activity and seismic swarming is middle(0.56 and 0.53,respectively) and the rate of earthquake-free segment and weak seismic band is the lowest(0.38 and 0.33,respectively).Besides,based on analysis of time process of those anomalies,the future earthquakes with ML≈5.0 are predicted.The weak seismic gap and seismic swarming can be used as the index for annual anomaly.The small earthquake swarms can be regarded as the mark for short term earthquake prediction.And there is anomaly of seismic window,which can be regard as entrance of short term earthquake prediction.Therefore,the activity pattern of weak seismicity is of significance in prediction of earthquakes with ML≈5.0 in Henan Province and its vicinity.