Abstract:
We analyze the seismic spatial-temporal evolution characteristic in Hebei and adjacent area by using the earthquakes catalog from January 1970 to November 2015 recorded by The China earthquake networks center. The result shown that prior the 1976 Tangshan earthquake the Zhangjiakou-Bohai-Weihai earthquake zones appeared 1-2 year's sparse distribution of small earthquake and it preparation area had experienced a seismic gap lasted for 2-3 years. In Zhangjiakou-Bohai-Weihaiearthquake zone, the earthquake of magnitude greater than 4 spatial-temporal distribution map show a "dense-sparse-expansion" distribution and piecewise seismically active features.The small earthquakes distribution do not show any abnormal feature in this earthquake zonesafter 1999 Zhangbei
M5.6 earthquake. The small earthquakes appeared "dense-spare" abnormal distribution phenomenon before the moderately strong earthquakes happened in Xingtai earthquake zone. Noteworthiness, in Hebei basin the small earthquakes occurred in Xingtai earthquake zone appeared a sparse distribution abnormal since 2014 year.