Structural Movement And Risk Analysis Of Kepingtage Block And Its Adjacent Areas

Tianshan mountain,as the largest regenerated orogenic belt in Eurasia,is under the dual influences of plate remote pushing and basin near-field convergence,and the tectonic activity in Tianshan mountain is relatively strong,which is extremely favorable for the occurrence of large earthquakes.Among them,Kepingtage nappe and its adjacent areas are prone to frequent earthquakes.However,due to the insufficient density of GPS stations,geodynamics has been seldom used to study the tectonic deformation and strain accumulation of Kepingtage nappe.To this end,this paper uses the encrypted GPS station data and IGS observation data to analyze the geological environment and structural characteristics of the study area.The research contents mainly include:1)Collection,processing and fusion of Keping block multi-source GPS site data: For the problem that the reference frame is difficult to unify for multi-source data,integrate old and new observation data(GPS encryption point and IGS observation data)to recalculate and obtain Keping Detailed velocity field information of the block;Based on the geological data,the formation mechanism of the SN-Puchang fault perpendicular to the Keping block and the cause of the seismic activity difference between the east and the west of the fault are analyzed.Finally,the cross-fault profile is analyzed to find the area with large horizontal motion difference along the active fault.It has a band-like distribution and strong structural deformation,which makes it have a strong background of seismogenic earthquakes;2)Quantitative analysis of strain accumulation in the region: Two methods are used to obtain different scale strain field states and cross-test method is used to verify the optimal solution method of strain rate in the study area.By analyzing the maximum principal strain,shear strain and surface expansion distribution diagram,the strain accumulation state in the study area was analyzed by faults,and it was concluded that the shear strain and surface expansion abnormal area was the frequent area of medium-strong earthquakes,further revealing the potential relationship between earthquake occurrence and strain state..3)Seismic risk analysis of the study area: the paleoseismic recurrence period of active faults was summarized according to the seismic catalog of the study area,and the seismic recurrence rate of the study area was solved by linear fitting using g-r relation and risk analysis was carried out.The results show that the study area is still in the state of seismic moment deficit and the quiet period has exceeded the theoretical maximum,indicating that the seismic risk in these areas is on the rise.