A Study On The Quaternary Activity Characteristics Of The Yanshi Fault In Luoyang City,Henan Province

The disruption of active faults within the urban area poses a threat to the city's high-rise buildings,important engineering facilities,lifeline engineering,and people's lives and property.The exploration and research on active faults developed in and around the city and the accurate understanding of the distribution and hazards of active faults are extremely important basic tasks in the development of urban construction and disaster prevention and reduction work.At the same time,they are of great significance on social stability and economic sustainable development.The Yanshi fault is located at the southern edge of the Mangshan Mountains and is the northern boundary fault of the Luoyang Basin.The fault straddles economic development areas such as Luoyang City and Yanshi City and has an impact on the economic development plan of the area.The determination of the exact spatial distribution and the latest activity time of the Yanshi fault can provide indispensable data for the identification of its activity and evaluation of its seismic risk.In addition,the geo-environmental assessment,urban development planning and regional planning for Luoyang City and surrounding areas Earthquake disaster reduction and other aspects also have important reference significance.The paper analyzes the exact distribution location and activity of Yanshi fault by comprehensive analysis of multi-source remote sensing image data processing and analysis interpretation,a large number of field seismic geological surveys,shallow seismic exploration,and joint drilling profile detection.Based on this,the relationship between historical record earthquakes and this fault is discussed.Based on the lasted survey data,this paper,after a comprehensive analysis of the Yanshi fault suggests that:1.The Yanshi fault is a normal fault with an overall trend of near EW and a dip to S,and it is about 55 Km in length.The fault starts in the east with Chaotinggou of Yanshi City,travelling along the south edge of mangling Ridge westwards through Tangquangou,Yanshichengbei,Pinglezhen and south of Fengtai Village;the fault is completely hidden in Quaternary sediments to west of Fengtai Village,and intersects Shiling-Baihe fault at the Jinshuihe river.2.The Yanshi fault is exposed on the surface of the earth east of Zhangjiawo village.There are obvious traces of faults on the surface,and some faults can be seen in the outcrops.Fractures in the west of Zhangjiawo Village are gradually hidden in loose sediments,and there is an inconspicuous fault scarp in the Fengtai section,while the fault west of the Fengtai Formation is completely hidden in the thicker loose sediments.3.According to the results of shallow seismic exploration and joint borehole profile detection,the latest strata of the Yanshi fault dislocation are Middle Pleistocene,and there is no sign of change in the upper strata.The latest activity era of the fault is early Middle Pleistocene.4.Through the identification of the Quaternary activities of Yanshi fault and the demonstration analysis of the three earthquakes recorded in the historical records,it is thought that the Yanshi fault is likely the seimogenic fault of a magnitude 6 earthquake in 1767 BC and other two destructive earthquakes.