山西交城断裂北端及中段3个大型探槽全新世断错现象分析  

ANALYSIS OF HOLOCENE FAULTING PHENOMENA REVEALED IN THE THREE TRENCHES ALONG THE NORTHERN AND CENTRAL JIAOCHENG FAULT,SHANXI

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,北京100085

出　　处：《地震地质》2012年第1期76-92,共17页Seismology and Geology

基　　金：中国地震重点监视防御区活动断层地震危险性评价项目"山西交城断裂带活断层1/5万填图"资助

摘　　要：前人在山西交城断裂带上开挖过多个探槽,揭露出全新世3次古地震事件,但其研究结果尚不能确定该断裂带全新世活动段的北部边界。近期在该断裂带北端和中段又开挖了3个大型探槽,其中在阳曲县泥屯盆地西界开挖的龙王沟探槽,是一个由多个探槽组合成的大探槽,该探槽揭示的地层断错信息,将交城断裂带全新世活动的范围向北延伸了20km。另外2个大型探槽分别为交城断裂带中段瓦窑沟东侧台地前缘的瓦窑探槽与市儿口沟西侧T1阶地前缘的新民探槽。这3个大探槽均揭示出全新世中期(14C测年值为距今5～6ka)的垆土和淤泥层,以及多组平行分布的断面,所揭示的全新世3次古地震事件具有断错事件活动的同步性,可与前人探槽揭示的全新世断层活动事件相对比。3次断错活动时间分别距今3.06～3.53ka、5.32ka左右或6.14ka左右、8.36ka左右;3次事件的时间间隔分别为2.02～2.84ka和2.22～3.04ka。这些断错事件的同震垂直位移为1.5～4.7m,显示了7级以上地表破裂型的强震活动。最后讨论了探槽中14C测年样品的影响因素。Several trenches were excavated in the previous work along the Jiaocheng Fault zone,which revealed three paleoearthquake events.But the northern boundary of the Jiaocheng Fault zone cannot be confirmed by the previous studies.The paper discussed the fault activities revealed in the three trenches excavated in the northern and central Jiaocheng Fault.Among them,Longwanggou trench is a combination which includes several trenches excavated in western Nitun Basin,Yangqu County.The paper introduced the trench profiles which cross the two right-stepped faults.As is shown in Longwanggou trench,the range of Holocene activity of the Jiaocheng Fault is extended 20km northward.The Wayaogou and Xinmin trenches are located in the central segment of the fault.One is at the foreplatform margin on the east of Wayaogou.The other is in front of the terrace T1 on the west of Shierkougou.Loam and mud layers of mid Holocene（with 14C ages of 5 ～ 6ka BP） and multi-parallel fault planes were observed in all the three trenches.In conclusion,the three Holocene faulting events as revealed in the three trenches are synchronous,which is consistent with previous trenching results.The time of the three events is 3.06 ～ 3.53ka,about 5.32ka or 6.14ka,and about 8.36ka B.P.The recurrence interval of the three events is about 2.02 ～ 2.84ka and about 3.04 ～ 2.22ka.The coseismic vertical displacement of these events is 1.5 ～ 4.7m,which shows surface faulting earthquake activity with magnitude greater than 7.0.This paper concludes with a discussion of the effect of 14C dating samples collected from the trenches.

关 键 词：探槽 古地震期次 全新世 交城断裂带 

分 类 号：P315.2[天文地球—地震学]