金塔南山断裂中东段古地震特征初步研究  

PRELIMINARY STUDY OF PALEOEARTHQUAKES ON THE MIDDLE-EASTERN SEGMENT OF JINTA NANSHAN FAULT

作　　者：庞炜[1] 张波[2] 何文贵[2] 吴明 PANG Wei;ZHANG Bo;HE Wen-gui;WU Ming(The Second Monitoring and Application Center,CEA,Xi an 710054,China;Lanzhou Institute of Seismology,CEA,Lanzhou 730000,China;Shaanxi Earthquake Administration,Xi an 710068,China)

机构地区：[1]中国地震局第二监测中心,西安710054 [2]中国地震局兰州地震研究所,兰州730000 [3]陕西省地震局,西安710068

出　　处：《地震地质》2018年第4期801-817,共17页Seismology and Geology

基　　金：国家自然科学基金(41602225;41590860);中国地震局地震预测研究所基本科研业务专项(2013IESLZ07)共同资助

摘　　要：金塔南山断裂位于河西走廊酒泉盆地北侧,是青藏块体与阿拉善块体的边界断裂之一。前人仅对该断裂西段开展过古地震研究。文中基于古地震探槽研究和光释光测年等传统地震地质工作方法,定量研究了金塔南山断裂中东段的古地震特征。通过对断裂进行系统的野外调查,发现沿断裂沿线地层以早更新世至晚更新世洪积物为主,全新世洪积物厚度仅几十cm。选取发育在全新世洪积物相对较厚的洪积扇上的断层陡坎进行工作,获得了一些初步的认识:金塔南山断裂中东段晚第四纪以来持续活动特征明显,全新世洪积扇上发育高0.5~1m的断层陡坎表现出了很新的活动性。多个探槽揭露出晚更新世晚期以来的4次古地震事件,分别发生在(15.16±1.29)ka之前、(9.9±0.5)ka之前、6ka左右、(3.5±0.4)ka之后。全新世中期以来,发生过2次事件,且2次古地震均造成断裂全段破裂。Hexi Corridor is located at the northeastern margin of the Tibetan plateau.Series of late Quaternary active faults are developed in this area.Numerous strong earthquakes occurred in history and nowadays.Jinta Nanshan fault is one of the boundary faults between the Qinghai-Tibet block and the Alxa block.The fault starts from the northwest of Wutongdun in the west,passes through Changshan,Yuanyangchi reservoir,Dakouzi,and ends in the east of Hongdun.Because the Jinta Nanshan fault is a new active fault in this region,it is important to ascertain its paleoearthquakes since late Pleistocene for the earthquake risk study.Previous studies were carried out on the western part,such as field geomorphic investigation and trench excavation,which shows strong activity in Holocene on the western segment of Jinta Nanshan fault.On the basis of the above research,in this paper,we carried out satellite image interpretation,detailed investigation of faulted landforms and differential GPS survey for the whole fault.Focusing on the middle-eastern part,we studied paleoearthquakes through trench exploration on the Holocene alluvial fan and optical luminescence dating.The main results are as follows:Early Pleistocene to late Pleistocene alluvial strata are widely developed along the fault and Holocene sediment is only about tens of centimeters thick.The Jinta Nanshan fault shows long-lasting activity since late Quaternary and reveals tens of centimeters of the lowest scarp which illustrates new strong activity on the middle-east segment of this fault.Since late Pleistocene,4 paleoearthquakes happened respectively before(15.16±1.29)ka,before(9.9±0.5)ka,about 6ka and after(3.5±0.4)ka,revealed by 4 trenches,of which 2 are laid on relatively thicker Holocene alluvial fan.Two events occurred since middle Holocene,and both ruptured the whole fault.

关 键 词：古地震 金塔南山断裂 探槽 OSL测年 

分 类 号：P315[天文地球—地震学]