沧州地区NWW向隐伏断裂存在依据及其地震地质意义
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摘要
经过对河北沧州地区中强地震和小震空间分布分析发现,存在NNE向条带分布,与大规模的河北平原地震带的走向一致;同时也呈现了明显的NWW向条带,与NNE向组成共轭构造图象。对比2次中强地震,其震源机制解基本相同,有近于直立的NWW向节面做左旋走向滑动;3次地震烈度的极震区长轴方向也是NWW;1967年河间6.3级地震之后5天的余震分布也是NWW方向。这和历史上5级地震分布方向一致。虽然没有浅表断层的对应,多种资料的相互验证表明沧州地区深部存在一条NWW向的隐伏断层,对于判别区内地震危险性具有重要意义。
Based on the analysis of earthquakes distribution in Cangzhou area,it is found that there exists a NNE belt of small earthquakes,which is consistent with strike of the Hebei plain seismic belt.In addition,middle and strong earthquakes show obvious NWW-striking distribution,constructing conjugate structure image with the NNE striking belt.Comparing the focal mechanisms of 2 moderate-strong earthquakes,they are similar and have a nearly vertical NNW fault plane doing left-lateral strike-slip movement.The long axis directions of intensity in the meizoseismal area for 3 earthquakes are NWW.The aftershocks distributed in NWW direction within 5 days after the 1967 Hejian M6.3 earthquake.This character coincides with the distribution direction of historical earthquakes with M≥5.Although there is no relevant shallow fault,mutual verification of many kinds of information reflects that there exists a deep buried fault with NWW striking in Cangzhou area.Therefore it can be regarded as the potential seismic source of seismic risk analysis.
Based on the analysis of earthquakes distribution in Cangzhou area,it is found that there exists a NNE belt of small earthquakes,which is consistent with strike of the Hebei plain seismic belt.In addition,middle and strong earthquakes show obvious NWW-striking distribution,constructing conjugate structure image with the NNE striking belt.Comparing the focal mechanisms of 2 moderate-strong earthquakes,they are similar and have a nearly vertical NNW fault plane doing left-lateral strike-slip movement.The long axis directions of intensity in the meizoseismal area for 3 earthquakes are NWW.The aftershocks distributed in NWW direction within 5 days after the 1967 Hejian M6.3 earthquake.This character coincides with the distribution direction of historical earthquakes with M≥5.Although there is no relevant shallow fault,mutual verification of many kinds of information reflects that there exists a deep buried fault with NWW striking in Cangzhou area.Therefore it can be regarded as the potential seismic source of seismic risk analysis.
引文
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[2]邓起东,闵伟,晁洪太,等.渤海地区新生代构造与地震活动[A]∥卢演畴,等主编.新构造与环境[G].北京:地震出版社,2001:218-233.
[3]汪素云,许忠淮,余言祥,等.中国及其邻区周围板块作用力的研究[J].地球物理学报,1996,39(6):764-771.
[4]嘉世旭,张先康,方盛明.华北裂陷盆地不同块体地壳结构及演化研究[J].地学前缘,2001,8(2):259-266.
[5]陈大贤.沧东断裂的地质结构分析[J].石油学报,1989,10(1):20-26.
[6]高战武,徐杰,宋常青,等.华北沧东断裂的构造特征[J].地震地质,2000,22(4):125-133.
[7]王椿镛,王贵美,林中洋.用深地震测深方法研究邢台地震区地壳细结构[J].地球物理学报,1993,36(4):434-444.
[8]尤惠川,徐锡伟,吴建平,等.唐山地震深浅构造关系研究[J].地震地质,2002,24(4):571-581.
[9]张家茹,邵学钟,殷秀华,等.深部构造背景和深部的孕震环境[A]∥高文学,马谨,编.首都圈地震地质环境与地震灾害[G].北京:地震出版社,1993:52-86.
[10]刁桂苓,张四昌,赵军,等.用现今小地震研究历史强震的震源断层——以1830年河北磁县721级地震为例[J].地震地质,1999,21(2):121-126.
[11]周斌,邓志辉,晁洪太,等.营潍断裂带走滑构造特征、演化及动力学机制[J].西北地震学报,2008,30(2):117-123.
[12]都昌庭,李文巧,卢宁,等.2006年青海玉树地震类型和发震构造分析[J].西北地震学报,2007,29(3):271-274.
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