珠江三角洲西缘西江断裂鹤山-磨刀门段的活动性  

LATEST PROGRESS ON ACTIVITY OF HESHAN-MODAOMEN SEGMENT,XIJIANG FAULT

作　　者：卢帮华[1] 王萍[2] 王慧颖 赖忠平 邓志辉[1] 毕丽思[1] 王万合 LU Bang-hua;WANG Ping;WANG Hui-ying;LAI Zhong-ping;DENG Zhi-hui;BI Li-si;WAN Wan-he(Guangdong Earthquake Agency,Guangzhou 510070,China;State Key Laboratory of Earthquakes Dynamics,Institute of Geology,China Earthquakes Administration,Beijing 100029,China;Shantou University,Shantou 515063,China;Xi’an Research Institute,China Coal Technology and Engineering Group Corp,Xi’an 710077,China)

机构地区：[1]广东省地震局,广州510070 [2]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [3]汕头大学,汕头515063 [4]中煤科工集团西安研究院有限公司,西安710077

出　　处：《地震地质》2020年第6期1370-1384,共15页Seismology and Geology

基　　金：广东省“十二五”防震减灾规划重点项目“西江断裂(珠海—江门段)、吉大断裂探测与地震危险性评价”;国家自然科学基金(U1901602);南方海洋科学与工程广东省实验室(珠海)项目(99147-42080024)共同资助。

摘　　要：西江断裂是位于珠江三角洲西缘的一条重要的NW向断裂,以鹤山为界可划分为南、北2段。其南段为鹤山—磨刀门段,大部分呈隐伏状,由于缺乏系统性的深、浅部探测工作,对于该段断裂的活动性存在着不同的认识,影响了断裂沿线的地震灾害风险评估及防治工作。文中通过地震地质调查、浅层地震勘探、钻孔联合剖面探测、第四纪沉积物年代测试等,对该段断裂的展布与活动性进行了研究。在浅层地震勘探的断点附近,基于有代表性的2个跨断层钻孔联合剖面的探测结果开展了相关分析,均发现了存在基岩断裂。构造岩以断层角砾岩、碎裂岩为主,断层物质已固化。后期沿断层带的部分地段被侵蚀形成凹槽,其上覆晚更新世河流堆积或全新世海侵沉积层内未见断错或地层扰动变形。根据地貌、断层产状以及横向断裂的发育,以竹排岛南的五指山断裂为界将西江断裂划分为南、北2段,没有发现北段晚更新世晚期以来、南段至少自全新世以来活动的证据。The Xijiang Fault is an important NW-trending fault with a length of^200 km,located in the western part of the Pearl River Delta.A M43/4 earthquake occurred at the northern end of the fault(Sihui)in 1445 and a magnitude 5 earthquake occurred at the southern end of the fault(Modaomen Waters)in 1905.Heshan is the boundary between the southern and the northern segments of this fault.The southern segment which is called Heshan-Modaomen segment is mainly hidden faults.The activity of Heshan-Modaomen segment remains controversial due to the lack of systematic studies for the deep and shallow exploration,which affects the assessment and prevention of earthquake disaster risk.In this paper,we concentrate particularly on the distribution and activity of Heshan-Modaomen segment using seismic geological surveys,shallow seismic exploration,joint borehole profile detection,and Quaternary geochronology.Field geological surveys show that the fault zone is prominently normal sinistral strike-slip faults,striking about N310°~330°W,with a width of 10~20 m.Most of them dip northeast at angles of 60°~80°.Observations on typical outcrop show that cataclasite,breccias and siliceous rocks are developed on the faults.Fault planes often have smooth and polished surfaces and no fault geomorphology has been developed along the fault zone.The overlying eluvial weathered soil materials have not been disturbed or cut.We carried out shallow cross-fault sounding of 7 profiles in the hidden section of the fault zone using longitudinal wave reflection method of multifold coverage observation system.As a result,we obtained the reflection time sections of the target stratum and the main structure.A total of13 breaking points to be investigated were explained.We also performed cross-fault drilling at the location of the seismic data interpretation profile and catalogued drilling cores.14C and OSL samples were collected systematically.The 14C dating was performed by the BETA Laboratory in the United States and 16 valid age data were obtained.OSL

关 键 词：西江断裂 断裂活动性 浅层地震勘探 跨断层钻探 地质年代学 

分 类 号：P315.2[天文地球—地震学]