| 对1976年河北唐山MS7.8地震地表破裂带展布及位移特征的新认识 |
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| 引用本文： | 郭慧,江娃利,谢新生.对1976年河北唐山MS7.8地震地表破裂带展布及位移特征的新认识[J].地震地质,2011,33(3):506-524. |
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| 作者姓名： | 郭慧 江娃利 谢新生 |
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| 作者单位： | 中国地震局地壳应力研究所,北京,100085 |
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| 基金项目： | 中国地震局地壳应力研究所基本科研业务专项(ZDJ2007-1)资助 |
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| 摘 要： | 1976年河北唐山MS7.8地震发生之后,诸多资料报道了唐山市南侧展布的长8～11km的地震地表破裂带.该地表破裂带由10余条NE方向、具右旋走滑特征的地表破裂呈左阶形式组成,总体走向N30°E,最大右旋位移2.3m,多数地段的垂直位移为0.5 ～0.7m.近年有学者提出,在更大范围内出现的地表破坏现象.分辨这些地表破...
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| 关 键 词： | 地表破裂带 钻孔 探槽 唐山地震 发震构造 |
NEW EVIDENCE FOR THE DISTRIBUTION OF SURFACE RUPTURE ZONE OF THE 1976 MS 7.8 TANGSHAN EARTHQUAKE |
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| GUO Hui,JIANG Wa-li,XIE Xin-sheng.NEW EVIDENCE FOR THE DISTRIBUTION OF SURFACE RUPTURE ZONE OF THE 1976 MS 7.8 TANGSHAN EARTHQUAKE[J].Seismology and Geology,2011,33(3):506-524. |
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| Authors: | GUO Hui JIANG Wa-li XIE Xin-sheng |
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| Institution: | (Institute of Crustal Dynamics,China Earthquake Administration,Beijing 100085,China) |
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| Abstract: | After the occurrence of the 1976 MS7.8 Tangshan earthquake,some data reported that the surface rupture zone was 8 to 11km long to the south of Tangshan city.The rupture zone was composed by more than ten NE-trending right-lateral strike-slip left-stepping en echelon ruptures,with a general strike of N30°E and a maximum displacement of 1.5～2.3m and a vertical displacement of 0.2～0.7m in most sections.Recently other scholars proposed the surface ruptures appeared in a larger area.An effective way for identifying the tectonic property of the surface ruptures is to use geological method to reveal the distribution and displacement of the strata on the two sides of the surface ruptures.Based on the previous studies and field survey data,we carried out composite borehole profile studies at three sites and trenching at one site across the surface rupture zone of the Tangshan earthquake in a range of 31km to the south of Tangshan city.The three borehole profiles are 4km and 27.5km apart from one another.The total number of boreholes in the three profiles is 28,and the total drilling footage is 1217m.The ages of 51 samples from three borehole profiles have been measured,including seven \{14C\} samples.The drilling investigations on the 3 profiles revealed offset phenomena at the depths of 20～60m beneath the ground surface.The strata consist of sediments of alluvial-proluvial plain,dominated by clay and silty sand,and of littoral plain,dominated by muddy clay and silt.Those offset phenomena show that the displacement amount of stratum increased as multiples of a single displacement with increasing depth.The trenching data verified the fault which was revealed by the drillings.Based on the above,we proved that the surface rupture zone of the 1976 earthquake extends to Xihe in Fengnan County and its total length reaches more than 47km.The 1976 Tangshan earthquake is the newest activity of the Tangshan Fault that had multi-stage activities in the Late Quaternary.The displacement feature of the surface rupture zone is that the north branch is mainly of right-lateral strike-slip motion,and the vertical displacement of the surface is up on the west and down on the east,on the other hand,the vertical displacement on the south branch is up on the east and down on the west,accompanied by some right-lateral slip.Such a faulting style cannot be explained by the movement of a single reverse or normal fault,but is consistent with the vertical displacement field induced by the right-lateral strike-slip of the fault belt.The distribution and rupture style of the newly found surface rupture zone are consistent with the vertical and horizontal displacement field of the Tangshan earthquake.In addition,in the light of the geological structure sections of this area,we discussed the relationship between seismogenic structure of Tangshan earthquake and geological structure,and proposed the suggestions about the next work. |
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| Keywords: | surface rupture zone borehole trench Tangshan earthquake seismogenic structure |
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