MICRO-DOSE RADON MEASUREMENT FOR NEO-TECTONIC ACTIVITY AT PLATE COLLISION ZONES ALONG SICHUAN-TIBET RAILWAY

The geological structure environment of the Sichuan-Tibet railway study area is relatively fragile. There are especially 5 main plate collision zones including Jinshajiang combination zone, Lancangjiang combination zone, Nujiang combination zone, Jiali faults and Yarlung Zangbo River combination zone. They show different tectonic activities. Theirs tectonic activity seriously restricts the construction of Sichuan-Tibet railway. Based on the deep study of geologic characteristics, seismic, deep structure and activity characteristics, this paper uses the method of micro-dose radon measurement to characterize the geochemical characteristics of the collision zone, and obtains the background value through the conventional statistical method. We define the anomalous coefficient(peak value m_max/background value m₀). We then study the relationship between the coefficient and other factors including geological structure, deep features, earthquake and tectonic activity. The results show that there is a "special point" in each profile of radon measurement. The difference among 5 min, 10 min and 15 min radon measurement data is very small. The radon background value is significantly related to the crustal rock construction. The peak value is related to the geotectonic position of the collision zone. The anomalous coefficient of radon decreases from southwest to northeast, which is remarkably related to tectonic activity. The anomalous coefficient has a positive correlation with horizontal displacement velocity, sliding velocity and ground stress. The results are as follows:y=0.869x+0.1278, y=0.7318x+15.1052, y=4.2196x+7.52639. The research results have a great significance to the study of tectonic activity of Sichuan-Tibet railway plate collision zone and the construction of Sichuan-Tibet railway.