Comprehensive Analysis Of The Multi-layer Seismic Hazard Model Along The Traffic Corridor Of The Sichuan-Tibet Railway

The Sichuan-Tibet Railway is located in the western Sichuan Basin and the central part of the Qinghai-Tibet Plateau seismic tectonic area.Affected by the uplift of the Qinghai-Tibet Plateau,which is one of the most active areas of modern tectonic activity in our country.The seismic activity is strong,widely distributed,and focal depth Shallow,also the disaster effect is significant.Faced with the potential threats of earthquake disasters to the construction and safe operation of the Sichuan-Tibet Railway,it is very important to analyze the seismic hazard along the railway and give one reasonable seismic zoning.At present,the fifth generation seismic zonation map in China adopts the non-point source model with Poisson distribution of seismicity and G-R relationship of magnitude frequency.However,a large amount of seismic activity data shows that seismic activity below M6.0 is spatial.It is random and discrete,while the high-magnitude seismic activity above M7.5 is closely related to the fault.The traditional horizontal plane source model does not take into account the magnitude classification and can not reflect the actual seismic activity very well.For this reason,this article takes the Sichuan-Tibet Railway as the typical strong earthquake tectonic area.According to the difference in seismic activity characteristics and seismological mechanism,the magnitude has been divided into three levels,and a multi-layer model seismic hazard analysis model is used to conduct earthquakes on different magnitude levels,risk analysis and calculation.Finally,the results of the three models are merged to give the seismic zoning results within 20 km along the Sichuan-Tibet Railway.The research content mainly includes:(1)A variety of publicly published earthquake catalogues were systematically compiled,with the historical earthquake catalogues along the Sichuan-Tibet Railway and modern medium and small earthquake catalogues,and historical earthquake influence field analysis and seismic activity temporal and spatial distribution characteristics analysis in the study area were also carried out.(2)According to the difference in seismic activity characteristics and seismological mechanism,the organized earthquake catalog has been divided into three levels according to magnitude:M4.0-5.9 earthquakes have no structural background,and the occurrence of earthquakes is random and dispersive,with a spatial smooth model;M6.0-7.4 earthquakes have certain structural background,but they are evenly distributed within the potential source and conform to the Poisson distribution,with a structural non-point source model;earthquakes above M7.5 have strong correlation with seismic structures.The three-dimensional fault source model separately calculates the probability of exceeding the field point under the given ground motion conditions.(3)Using the full probability fusion technique,the calculation results of the three models are fused,and the comprehensive results are linearly interpolated to calculate and draw the seismic parameter zoning map within 20km along the Sichuan-Tibet railway,that is the seismic acceleration peak zoning map with 10%exceedance probability in 50 years and 100 years.Based on the multi-model probabilistic seismic hazard analysis method,this article conducts seismic hazard assessment and seismic zoning research along the Sichuan-Tibet Railway,aiming to provide a certain reference value for the seismic zoning of strong earthquake tectonic areas.