Strong Earthquake Prediction Research Based On Seismic Activity And Deformation Data In The Northern Margin Of West Qinling Fault And Its Vicinity

The northern margin of West Qinling fault is a regional deep large active fault inthe northeastern margin of Qinghai-Tibet Plateau. After Wenchuan8.0earthquake in2008, the strong earthquake risk of West Qinling areas arouses strong concern,especially the West Qinling fault. Based on the seismic activity and cross-faultdeformation data, this article analyses the characteristics of regional stress field andconfirm strong earthquake risk and possible seismogenic faults in the northern marginof West Qinling fault in the future. The article makes some attempts in the long,medium and short term prediction.Seismic activity parameter b-value is a long-medium term prediction index ofstatistical earthquake forecasting. The stress value is inversely proportional to theb-value in magnitude-frequency relationship. We can infer the nowadays relativelevels of stress accumulation in different sections of the active faults according tospatial and temporal distribution of b-value. This paper uses the latest accuratelocation directory in Gansu seismic network to make the space-time scanning ofb-value in the northern margin of West Qinling fault and adjacent areas. The papercarries out a multi-parameter combinations analyzed combined with a value, TLvalueand PLvalue. The results show that b-value is anomaly low value area inZhangxian-Huangxianggou, Tianshui-Baoji surrounding area. They may have formedasperity and we need to pay more attention to these areas in the future.Cross-fault deformation is one of the long-medium term prediction indexes. Inthis paper, we consider the two walls as non-deformable rigid body and analysequantitative relationship between the relative sliding on fault plane and the relativedisplacement of two walls’ point location. Vertical displacement of each measuringpoint was also calculated and preliminarily analysed the relationship to seismicactivity. The results show that some cross-fault deformation measuring points have amore significant change in the timing curve before or after moderate earthquakes,such as Naizigou, Majietan and Bashagou. It shows that the cross-fault deformationmeasurement is the most direct way to reflect the crustal deformation.The research results of this paper: The obtained b-value scanning results andcross-fault deformation observations have a nearly consistent correspondence. Thelow b-value segment is also the relatively large change segment in cross faultdeformation curve of measuring points, such as Naizigou, Majietan, Bashagou,Liujiagou, Panguchuan and so on. It goes to show that the deformation and seismicitydata correspond well. And it also shows that long-medium term and middle-short termprediction indexes can be combined organically, which provides a more powerfulcriterion for earthquake risk judgment.The main innovation points of the thesis:1. Use the mode of man-machinedialogue, determining the unit of Mc one by one, and improve the accuracy of b-valuecalculation.2. Use the latest seismic relocation catalog, the data quantity is better andthe result is more reliable.3. Combine the analysis of cross-fault deformation data,and obtain the relatively accurate earthquake risk assessment of the northern marginof West Qinling fault and adjacent areas.