【摘要】 河北省数字地震台网在2013年5月19日至7月15日记录到河北赞皇县发生震群活动,ML-0.9级以上地震229次。震群附近30km之内之前没有发生过5级以上地震,1966年邢台7.2级地震区呈北北东向分布,在其南部存在北西向分支,抵达赞皇附近,发生过少量ML1~2级小震。与较为平静的地震活动背景相比,赞皇震群尤为突出。通过分析震级—频度关系,震群呈现低b值特征;利用振幅比法反演震群ML2级以上11个基本一致的震源机制解,并进一步反演震源区应力场,结果与华北构造应力场完全吻合。结果显示,震群呈北北东方向分布,震源机制也有相应的节面对应,大多数倾向北西西,表明震群为右旋走向滑动。同时,低b值和震源机制一致属于震兆现象,应注意加强赞皇附近区域的震情跟踪研究。更多还原

【Abstract】 According to the records of the Hebei digital seismic network,an earthquake swarm including229 ML≥-0.9earthquakes occurred in Zanhuang County of Hebei Province from May 19 th,2013to July15 th,2013.Historical records show that there is no earthquake of magnitude 5occurred within 30 km.The earthquake regions of the 1966 xingtai M7.2strong earthquake distributed in direction of NNE,but one NW trending branch in the south of the earthquake regions extended near the Zanhuang County,along which,a small quantity of ML1~2earthquakes occurred.Compared with the relatively calm background of earthquake activity,the Zanhuang earthquake swarm activity is very outstanding.Analysis of relationship between earthquake magnitude and frequency shows that the b-value of the earthquake swarm is lower than the normal.On the basis of the 11 focal mechanism solutions of ML≥2earthquakes of the swarm inverted using the wave amplitude ratio method and seismic waveform fitting technique,the stress field in the source area is calculated which is fully consistent with the tectonic stress field of North China Region.It can be proved that the earthquake swarm was triggered by right strike-slip faults through which the earthquake swarm distributed in NNE and was correspond with the nodal planes of the focal mechanism solutions and most of them are NWW-dipped.Owing to the fact that the similar focal mechanism solutions and the low b-value both belong to the phenomenons of earthquake precursor,the research about seismic situation tracing of Zanhuang area should be strengthened.更多还原