摘要
苏锡常断裂是长三角地区一条重要的NW向隐伏断裂。文中利用浅层地震勘探和钻孔联合剖面探测方法,对苏锡常断裂的展布特征及其第四纪活动性进行了系统研究。浅层地震勘探成果表明:在苏州地区,苏锡常断裂南支整体倾向NE,倾角约60°,基岩断距3~5m,以正断活动为主;在常州地区,苏锡常断裂北支以正断活动为主,倾向S,倾角约55°~70°,基岩断距4~12m。在地震剖面上,苏锡常断裂的各个断点都以断错基岩面为特征,第四系内部层位断错不明显。苏州东桥镇场地上,苏锡常断裂南支断错的最新地层为下更新统上部;常州朝阳路场地上,苏锡常断裂北支断错的最新地层为中更新统底部。综合判断苏锡常断裂的最新活动时代为中更新世早期。苏锡常断裂在前第四纪总体以左旋正断活动为主,早更新世后则在多处转变为左旋逆断性质,第四纪内部层位断错量约3m,判断苏锡常断裂最大潜在地震震级为6. 0级。
Running across the urban areas of Changzhou,Wuxi and Suzhou,the NW-trending Su-Xi-Chang Fault is an important buried fault in Yangtze River Delta. In the respect of structural geomorphology,hilly landform is developed along the southwest side of the Su-Xi-Chang Fault,and a series of lakes and relatively low-lying depressions are developed on its northeast side,which is an important landform and neotectonic boundary line. The fault controlled the Jurassic and Cretaceous stratigraphic sedimentary and Cenozoic volcanic activities,and also has obvious control effects on the modern geomorphology and Quaternary stratigraphic distribution.Su-Xi-Chang Fault is one of the target faults of the project "Urban active fault exploration and seismic risk assessment in Changzhou City "and "Urban active fault exploration and seismic risk assessment in Suzhou City". Hidden in the ground with thick cover layer,few researches have been done on this fault in the past. The study on the activity characteristics and the latest activity era of the Su-Xi-Chang Fault is of great significance for the prevention and reduction of earthquake disaster losses caused by the destructive earthquakes to the cities of Changzhou,Wuxi and Suzhou.Based on shallow seismic exploration and drilling joint profiling method,Quaternary activities and distribution characteristics of the Su-Xi-Chang Fault are analyzed systematically. Shallow seismic exploration results show that the south branch of the Su-Xi-Chang Fault in Suzhou area is dominated by normal faulting,dipping to the north-east,with a dip angle of about 60° and a displacement of 3 ~5 m on the bedrock surface. The north branch of the Su-Xi-Chang Fault in Changzhou area is dominated by normal faulting,dipping to the south,with a dip angle of about 55° ~ 70° and a displacement of 4 ~ 12 m on the bedrock surface. All breakpoints of Su-Xi-Chang Fault on the seismic exploration profiles show that only the bedrock surface was dislocated,not the interior strata of the Quaternary.On the drilling joint profile in the Dongqiao site of Suzhou,the latest activity of the south branch of Su-Xi-Chang Fault is manifested as reverse faulting,with maximum displacement of 2. 9 m in the upper part of Lower Pleistocene,and the Middle Pleistocene has not been dislocated by the fault. The fault acts as normal fault in the Pre-Quaternary strata,with a displacement of 3. 7 m in the Neogene stratum. On the drilling joint profile in the Chaoyang Road site of Changzhou,the latest activity of the north branch of Su-Xi-Chang Fault is manifested as reverse faulting too,with maximum displacement of 2. 8 m in the bottom layer of the Middle Pleistocene. The fault acts as normal fault in the PreQuaternary strata,with a displacement of 10. 2 m in the bedrock surface.Combining the above results,we conclude that the latest activity era of Su-Xi-Chang Fault is early Middle Pleistocene. The Su-Xi-Chang Fault was dominated by the sinistral normal faulting in the pre-Quaternary period,and turned into sinistral reverse faulting after the early Pleistocene,with displacement of about 3 m in the Quaternary strata. The maximum magnitude of potential earthquake on the Su-Xi-Chang Fault is estimated to be 6. 0.
作者
张鹏
张媛媛
许汉刚
刘建达
陈建强
李丽梅
李金良
顾勤平
蒋新
ZHANG Peng;ZHANG Yuan-yuan;XU Han-gang;LIU Jian-da;CHEN Jian-qiang;LI Li-mei;LI Jin-liang;GU Qin-ping;JIANG Xin(College of Transportation Science&Engineering,Nanjing Tech University,Nanjing 210009,China;Jiangsu Earthquake Agency,Nanjing 210014,China;School of the Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)
出处
《地震地质》
EI
CSCD
北大核心
2019年第5期1172-1184,共13页
Seismology and Geology
基金
苏州市政府项目“苏州市活动断层探测与地震危险性评价”
常州市政府项目“常州市城区活动断层探测与地震危险性评价”
“南京工业大学引进人才科研专项启动经费”共同资助
关键词
苏锡常断裂
第四纪活动性
浅层地震勘探
钻孔联合剖面
Su-Xi-Chang Fault
Quaternary activities
shallow seismic exploration
drilling joint profiling
