The Study On Quaternary Activity Of Handong Fault

The eastern region of Handan is the main location of the planned new economic area.In order to plan the major infrastructure construction in the new area of Handan.It is of great significance to carry out a detailed investigation and the activity in Handong fault.We carried out cross-fault drilling exploration in the study area based on the previous data of geophysical methods.Through the logging of borehole cores,we draw joint section of drilling hole and divided the Quaternary strata.Then we determined the position of the upper breakpoint and study the specific active age of Handong fault.Finally,the sliding rate of Handong fault is calculated.Achieved the following knowledge:1.The Quaternary strata in the eastern plain area of Handan are divided into Holocene Shuangjing formation(sedimentary strata less than 0.012Ma),Late Pleistocene Mengguan Formation(sedimentary strata within 0.012～0.128Ma),Middle Pleistocene Weixian Formation(sedimentary strata within 0.128～0.78Ma)and Early Pleistocene Yangliuqing Formation(sedimentary strata greater than 0.78Ma).2.The depth of the Holocene bottom boundary at CK2 site is 24.50～25.90 m,the late Pleistocene bottom boundary is 68.20～68.73 m,the middle Pleistocene bottom boundary is 107.14～113.10 m,and the early Pleistocene is not exposed;The depth of the Holocene bottom boundary of XK4 site is 26.30～27.00 m,the late Pleistocene bottom boundary is 65.00～66.40 m,the middle Pleistocene bottom boundary is133.80～138.60 m,and the early Pleistocene is not exposed;The depth of the Holocene bottom boundary of CK5 site is 24.70～25.75 m,the late Pleistocene bottom boundary is 65.05～65.94 m,and the middle Pleistocene bottom boundary is 117.63～122.03 m,and the early Pleistocene is not exposed.3.Handong fault has different breakpoint positions on each site.There are no signs of fault in the strata since the Holocene and Late Pleistocene in the three sites,indicating that Handong fault has not been active since the Late Pleistocene.In the CK2 site,Handong fault dislocated the brownish red clay layer at 101.52～102.53m(the footwall of the fault),and the brownish yellow clay-bearing silty sand layer at93.50～95.0m above it had no obvious dislocation,and the depth of the breakpoint was between 95.0～11.52m;The Handong fault in the XK4 site dislocated the gray-green clay layer at 89.40m～90.0m(footwall),and the light gray fine sand lens at82.0～83.6m above it had no obvious fault phenomenon,and the depth of the breakpoint was between 83.6～89.40m;In the CK5 site,Handong fault dislocated the brownish red clay layer at 86.8～87.68 m(the footwall of the fault),and the brownish red silty clay layer at 78.6～79.10 m above it had no obvious dislocation,and the depth of the breakpoint was 79.10-86.8m.According to comprehensive analysis,the Handong fault has been inactive since the Late Pleistocene,and the depth of the breakpoint has gradually become shallow from north to south.4.At CK2 site,there is an obvious fault dislocation interface in the Middle Pleistocene.The fault displacement is 1.10 m.And there are two obvious fault dislocation interfaces in the Early Pleistocene.The fault displacement is 1.80 m and3.90 m respectively.The fault activity in the site is in the Middle Pleistocene,and there is no obvious activity trace since 499±42ka;At XK4 site,there are four obvious faults interface in the Middle Pleistocene.The fault displacement is 0.75 m,1.55 m,1.60 m and 2.45 m respectively.And there is an obvious fault dislocation interfaces in the Early Pleistocene.The fault displacement is 4.0m.The fault activity in the site is in the Middle Pleistocene,and there is no obvious activity trace since 220.8±16.1ka.At CK5 site,there are three obvious faults interface in the middle Pleistocene.The fault displacement is 1.10 m,1.95 m and 4.40 m respectively.And there is an obvious fault dislocation interfaces in the Middle Pleistocene.The fault displacement is 4.0m.The fault activity in the site is in the early and middle Pleistocene,and there is no obvious activity trace since 183.05±11.4ka.The latest active time of Handong fault is the late Middle Pleistocene,and the latest active time is not later than 183.05±11.40 ka.5.The fault movement rate of CK2 site in the early middle Pleistocene is about0.55cm/ka,and the fault movement rate in the late early Pleistocene is not more than1.45cm/ka;The fault movement rate of XK4 site in the early Pleistocene is about0.4cm/ka,and the fault movement rate in the late Pleistocene is not more than2.2cm/ka;The fault movement rate of CK5 site in the early middle Pleistocene is about 1.73cm/ka,and the fault movement rate in the late early Pleistocene is not more than 2cm/ka.According to comprehensive analysis,the fault movement rate of Handong fault in the late early Pleistocene is not more than 2.2cm/ka,and that in the early Middle Pleistocene is not more than 1.73cm/ka,and the activity is gradually weakened.