摘要
野马河-大雪山断裂位于青藏高原东北缘祁连山西端,处于NEE向的阿尔金断裂向NW向的祁连山断裂转换的部位,是1条全新世活动断裂,全长170km。依据断裂几何学和活动特征可把该断裂分为3段,即肃北段、野马河段和大雪山段。野马河段是野马河-大雪山断裂带上活动性最强的段,断裂活动性质以左旋走滑为主,兼具正断层性质,至今保存了新鲜的断层陡坎,高度只有几十cm。通过野外地质调查,在扎子湖一带开挖了2个大探槽,清理了1个前人探槽。对这3个探槽进行了古地震事件分析和年代学样品的采集,最终确定有3次古地震事件发生,野马河断裂最后1次古地震事件的离逝时间为(2 010±30)a。
A series of NWW striking faults are obliquely intersected by the NEE striking Altyn Tagh fault zone in the western Qilian Mountains.These faults were mostly active in late Quaternary and play an important role in accommodating regional lateral extrusion by both reverse and sinistral slip.Detailed studies on late Quaternary activity,tectonic transformation,paleoseismology,and strain partitioning not only significantly affect our recognition on seismogenic mechanism and zones of potential large earthquakes,but also provide useful information for exploring tectonic deformation mechanism in the northern Tibetan plateau.The Danghenanshan Fault,Yemahe-Daxueshan fault,and Altyn Tagh Fault form a triplet junction point at southwest of Subei county.The Yemahe-Daxueshan fault is one important branch fault in the western Qilian Mountains that accommodated eastward decreasing slip of the Altyn Tagh Fault,which was active in late Holocene,with a length up to 170km.Based on geometry and late Quaternary activity,the Yemahe-Daxueshan fault was subdivided into 3 segments,i.e.the Subei fault,Yemahe fault and Daxueshan Fault.The Yemahe Fault has the most prominent appearance among them,and is dominated by left-lateral slip with a little normal component.The heights of fresh scarps on this fault are only several tens of centimeters.We dug 2 trenches at the Zhazhihu site,and cleaned and reinterpreted one trench of previous studies.Then we interpreted trench profiles and paleoseismic events,and collected\{14 C\}and Optical Stimulated Luminescence samples to constrain event ages.Finally,we determined 3 events on the Yemahe fault with ages(6 830±30)a BP-(6 280±40)a BP,(5 220±30)a BP,(2 010±30)a BP,respectively.The elapsed time of most recent earthquake is(2 010±30)years before present,which is very close to the recurrence interval,so the possibility of major earthquakes on the Yemahe fault is relatively large.
作者
何文贵
张波
吴明
王朋涛
邹小波
高效东
HE Wen-gui;ZHANG Bo;WU Ming;WANG Peng-tao;ZOU Xiao-bo;GAO Xiao-dong(Lanzhou Institute of Seismology,China Earthquake Administration,Lanzhou 730000,China;Shaanxi Earthquake Administration,Xi an 710068,China)
出处
《地震地质》
EI
CSCD
北大核心
2018年第1期261-275,共15页
Seismology and Geology
基金
中国地震局地震行业科研专项(201408023)
国家自然科学基金(41602225)共同资助
