长江谷地安庆-马鞍山段新构造和断裂活动特征  

NEOTECTONICS AND FAULT ACTIVITY IN THE ANQING-MA'ANSHAN SECTION OF THE CHANGJIANG RIVER VALLEY

作　　者：宋方敏[1] 邓志辉[1] 马晓静[1] 祖金华[1] 楚全芝[1] 尹功明[1] 周庆[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地震地质》2008年第1期99-110,共12页Seismology and Geology

摘　　要：根据地面地质调查、浅层地震勘探、钻探等成果,分析了长江谷地安庆—马鞍山段的新构造运动和断裂活动特征。资料表明,该段谷地及其两侧新构造时期总体以弱的间歇性隆升运动为主,其中无为、安庆一带受NE,NNE向断裂活动的影响,古近纪—新近纪有较强烈的垂直差异运动,并一直持续到早、中更新世。谷地及其两侧基岩中发育NE—NNE向与NW向2组断裂,前者主要形成于印支期,后者主要形成于燕山期,其中控制新生代盆地发育且规模较大的断裂最新活动时代为中更新世,而发育在前新生界内部且规模较小的断裂最新活动时代为前第四纪。谷地中第四系厚度为10-50m,主要为晚更新世—全新世堆积,等厚线总体分布平稳,为正常的河谷堆积。沿谷地及其两侧地震活动较弱,历史上仅发生4次破坏性地震,最大地震为1585年巢湖南534级地震,另有1次541级地震、2次43/4级地震,1970年有仪器记载以来,记录到的最大地震为ML3.7。这些特征有利于该段谷地的地壳稳定性评价。The neotectonic movement and characteristics of fault activity in the Anqing-Ma＇anshan section of the Changjiang River valley are analyzed on the basis of data obtained from field investigation,shallow seismic prospecting and drilling. The results show that during neotectonic time this river valley section and its both sides as a whole was dominated by weak and intermittent uplift movement. As a consequence, owing to the effect of the activity of NE- and NNE-trending faults,relatively strong vertical differential movement occurred in Wuwei-Anqing area during Paleogene-Neogene, and had continued to early and middle Pleistocene. The NE- NNE-trending and NW-trending faults were developed in the bed rocks of the valley and its both sides. The former was formed during Indo-Chinese epoch,while the later was formed during Yanshan epoch. The most recent active period of the larger faults controlling the development of Cenozoic Basins is middle Pleistocene, while the newest activity of the relatively small faults developed within pre-Cenozoic group is pre-Quaternary. The Quaternary system in the valley is 10 - 50m thick,consisting mainly of Pleistocene-Holocene deposits. The isopach of these deposits is smoothly distributed, indicating normal valley deposition. Seismic activity along the valley and its both sides is relatively weak,and historically only 4 destructive earthquakes have been recorded. Among these events,the largest one is the M 53/4 earthquake occurring at Chaohu in 1585 ,and the other events including one with M 51/4 and two with M 43/4. Since the beginning of instrumental records in 1970,the largest magnitude that has been recorded so far is ML 3.7. All these results may provide better constraints on the assessment of the crustal stability for this river valley section.

关 键 词：长江谷地 断裂 新活动时代 第四系厚度 

分 类 号：P315.2[天文地球—地震学]