Activity Analysis Of The Southern Segment Of Fuyu/Songyuan Zhaodong Fault

The southern segment of Fuyu/Songyuan-Zhaodong fault occurred an earthquake of magnitude 5 in 2006,and the 5.8 magnitude earthquake group occurred in 2013.It is an important seismogenic fault in the Songliao basin,and also the most active fault structure in the Northeast seismic area.The fault is located in the south of Songliao Basin,and it is in a concealed state.Based on the results of active faults detection in Songyuan(2012)and analysis of previous studies on the fault,we found that the Fuyu/Songyuan-Zhaodong fault has obvious segmentation and independence.According to geometrical structural features and seismicity,the Fuyu/Songyuan-Zhaodong fault can divide into Fuyu-Zhaodong segment fault,Fuyubei fault,Gudian fault and Chaganhua segment fault.In recent years,seismic activities occurred mainly in the southern segment of the fault,but the study of the fault is relatively few.The southern part of the fault is composed of Gudian fault and Chaganhua segment fault.We deployed shallow artificial seismological lines in the area of Chaganhua area and the west side of Songyuan city to study the activity of the southern segment of the fault.According to the result of the exploration,the Chaganhua segment fault is an early Quaternary fault,and the fault strike is near SN direction in the survey area.The Gudian fault that probed in the west side of Songyuan city is quite different from that of petroleum.In order to accurately determine the characteristics and activity of fault structures,we used shallowartificial seismic exploration and joint borehole detection to study the fault in the original position.Comparing the results of the two surveys,we determined that the Gudian fault is distributed toward NE and tends to SE.Through the analysis of the borehole joint section,we considered that the latest active age of the fault is late Late Pleistocene.At the same time,we made high-precision aerial photography for the exploration area and completed the DSM.We studied the microtopography changes in Songyuan area.Combining with the borehole joint section,we thought that the uplift was caused by the late Pleistocene activity of the fault,and there was no activity since the Holocene.The structural inversion in Songliao basin occurred in the late stage of the depression,and it strongly reformed the fault structure in the basin.The Fuyu/Songyuan-Zhaodong fault is located in the central depression inversion structure belt.Through analyses of the evolution and characteristics of the fault structure and studies of other faults inversion structures in the inversion zone,the paper holds that the fold inversion structure developed by the compression of the fault leads to the change of the fault properties,and controls the occurrence of the earthquake in the region.The inversion structures have obvious effect on the activity of fault.In addition,this paper discusses the seismogenic structure of the 5.8 earthquake swarm in Chaganhua area.The5.8 earthquake swarm in the area of Chaganhua area has particularity.