1969年渤海7.4级地震区地质构造和发震构造的初步研究

Analysis of Structures in 1969 Bohai Sea M_S 7.4 Earthquake Area and Discussion about the Causative Structure

根据石油地质勘探资料和地震学等研究的成果 ,对 1969年渤海 7 4级地震的构造条件作了具体而较深入的分析 ,填补了华北渤海大震区地震构造研究的空白。震区位于渤海湾新生代裂陷盆地的东部 ,地处北北东向营潍断裂带与北西向北京 -蓬莱断裂带交汇的地区。早第三纪断陷阶段 ,该区于地壳上部主要发育北北东、北西和东西向 3组断裂 ,呈铲状和平面状形态 ,正断性质 ,多属断陷主断裂。晚第三纪以来的拗陷阶段 ,先存断裂有不同程度的活动 ;同时还新发育一条北东向黄河口 -庙西北断裂带。 7 4级地震的震源断层走向为北东 4 5° ,倾向南东 ,近于直立 ,呈右旋走滑性质 ,埋藏于 15～ 34km的深度范围。大震的发震断裂不是营潍断裂带 ,而是黄河口 -庙西北新生断裂带。

We have made a concrete and deep analysis of structures in 1969 Bohai Sea M-S 7.4 earthquake area based on the data of petroleum exploration and seismology.This is the first time to analyse structures in the earthquake area. The area lies in the east part of the Bohai Gulf Cenozoic rifting basin,and the jointed area of the Yingkou-Weifang fault zone and the Beijing-Penglai fault zone.In the Palaeogene rifting stage,three groups of faults with strike of NNE,NW and EW had developed in the upper crust,these faults were listric and plane normal faults,and main faults of the rifting basins almost.In the depressing stage since Neogene,the exist faults activity are different.Huanghekou-Miaoxibei newly generated fault zone have developed.The fault of the M-S 7.4 earthquake is NE 45° trending,dipping SE,nearly vertical,dextral slip,15～34km in the crust.The causative fault of the earthquake is not Yingkou-Weifang fault zone,but Huanghekou-Miaoxibei newly generated fault zone.