1976年唐山M_S7.8地震乐亭—滦南地区NW向地裂缝带赵滩点位调查  

Investigation on Zhaotan site in NW-trending ground fissure zone of 1976 M_S7.8 Tangshan earthquake in Laoting-Luannan region

作　　者：郭慧[1] 江娃利[1] 谢新生[1] 

机构地区：[1]中国地震局地壳应力研究所,中国北京100085

出　　处：《地震学报》2016年第4期644-655,658,共12页Acta Seismologica Sinica

基　　金：国家自然科学基金青年基金(41202157);中国地震局地壳应力研究所基本科研业务费专项(ZDJ2013-19)共同资助

摘　　要：1976年唐山M_S7.8地震的早期野外调查结果显示,在乐亭—滦南地区存在一条NW走向的地裂缝带,自滦南县申营村往南断续延伸至乐亭县王滩镇王各庄村,长度大于30km,以右旋走滑为主.该地裂缝是1976年唐山M_S7.8地震形成的,但其地理位置接近1976年唐山地震序列中滦县M_S7.1地震形成的NW向地表破裂带延伸方向上.为进一步研究唐山地震的发震构造,本文拟基于前人资料,对乐亭—滦南地区NW向地裂缝带赵滩点位展开调查,并实施探槽开挖和钻孔探测.探槽揭示出小型砂脉和宽1.0—1.2m的大型砂脉分别为1976年唐山MS7.8地震和该地震之前另一次强震事件的产物;钻孔探测结果表明主砂脉两侧地层不存在明显的垂直落差,这与1976年唐山M_S7.8地震时该点位出现的地裂缝现象是右旋剪切以及赵滩探槽揭示的两侧垂直位移不明显的现象相吻合.Field investigation after the 1976 MS7.8Tangshan earthquake reveals that,in Laoting and Luannan region exists a NW-trending ground fissure zone,which is from Shenying village,Luannan county and extended to Wanggezhuang village,Wangtan town,Laoting county,with more than 30 km in length and mainly in dextral strike slip.Laoting-Luannan ground fissures are formed by the 1976 Tangshan MS7.8earthquake,but its position closes to the extending line of the NW-trending surface rupture zone of Luanxian MS7.1earthquake.In order to further study the seismogenic structure of the Tangshan MS7.8earthquake,based on previous data,we investigated the Zhaotan site on the NWtrending Laoting-Luannan ground fissure zone,implemented the trench excavation and drilling exploration.The trench reveals small sand veins and sand vein approximately 1.0—1.2 m wide,which are formed by the 1976 MS7.8Tangshan earthquake and another strong earthquake before the quake,respectively.The borehole profile shows that there is no clearly vertical displacement between the two sides of the main sand vein,which coincides with the phenomena that the ground fissures of the 1976 MS7.8Tangshan earthquake in this position is of dextral strike slip and the vertical displacement is not obvious that is revealed by the Zhaotan trench.

关 键 词：1976年唐山MS7.8地震 NW向地裂缝带 探槽 钻孔测线 

分 类 号：P315.2[天文地球—地震学]