1.昆明理工大学国土资源工程学院;2.Institute of Geology ,Chinese Academy of Geological Sciences;3.Institute of Land and Resources Engineering Kunming University of Science and Technolody
The Bomi region of Tibet is located in the northeast of the Namche Barwa tectonic junction.It is a key area for studying the evolution of tectonic junctions in the eastern Himalayas.At the same time,it holds great significance for the Sichuan-Tibet Railway project, which is a key transportation initiative during the Fourteenth Five-Year Plan period. Therefore, it is crucial to study the stability and safety of the region"s deep geological structure. However, the scarcity of geophysical data in the area, due to limitations in geological and geomorphological conditions, has resulted in limited research on the relationship between deep density structure and seismic in the Bomi region.This thesis obtains 1:200,000 bouguer gravity data in Bomi region for the first time.First,we used the wavelet transform multi-scale decomposition method, scratch analysis method and gravity 3D inversion method to divide the tectonic activity unit, we obtained the gravity anomalies of different , faults distribution and density structures. The analysis results show that the overall crust density in the Bomi region changes significantly, which is closely related to the fault distribution. At the same time, combined with the regional geological data,our inferred 20 faults in the Bomi area、found 4 large transverse density uneven zones and deduced the occurrence of Jiali fault zone which runs through the study area. In addition, using the seismic and aftershock activity records in the area, analyzing the relationship between deep density structure and earthquake. Finally, according to the transverse variation of fault structure density, seismic activty and gravity anomaly in the study area, it can be seen that the seismic, fault zone and rock density disturbance are closely related to the transverse unevenness, and the earthquakes are mainly located in the high-density area of the density difference zone. Based on the above analysis, We discussed the potential influence of deep density structure on major railway projects----Sichuan-Tibet Railway in Bomi area is discussed, and corresponding suggestions are put forward.