Study Of The Gravitational Field And Deep Tectonic Characteristics In Sichuan-Yunnan Region

Sichuan-Yunnan region is located in the eastern margin of Qinghai-Tibet Plateau, the south section of the north-south seismic belt. Frequent earthquakes occurred around this area The Long-men Mountains, the An-ning River and the Xian-shui River three active faults coupled together at the surface, which was "Y" shaped. They constitute the boundaries the South China block, the Bayanhar block and the Sichuan-Yunnan block. It was an important geological structure and affected the stability of this area. The others active faults in the region are also densely developed regularly. However, It did not clearly understand the distribution case of these activities structures deep in the crust. Fine structure of the crust in the area was also far from being recognized. These are essential to the study of fault movement and earthquake preparation. Bouguer gravity anomaly data is a superposition of the crustal layers structure and extension effects. It can reflect the density differences of crustal rocks in all directions. Then it revealed the development status of the deep geological and tectonic belt to provide the basis for the research on the fine crustal structure.In this paper, the gravity field on the Sichuan-Yunnan region was effectively separated by multi-scale wavelet analysis and upward continuation method. It find that regional gravity anomalies have more obvious zoning characteristics. This reflects the lithosphere macro density differences and moho depth landscape fluctuation situation. The distribution characteristics of the Local gravity anomalies present a huge arc step belt. The beit strike is north-east turn to nearly north-south from north to south. And anomalous features are obviously different on both sides of The step belt. These Clearly show the distribution characteristics of the fault in the deep crust. On the other hand, the application 3D Parker density interface inversion method and the variable density model were applied to inversion moho interface in the Sichuan-Yunnan region. Meanwhile, comprehensive existing earthquake geological and geophysical data find that moho depth in research region is gradually deepened from southeast to northwest and it is deepest in the northwest. More, the sichuan-yunnan block exists crustal thickening phenomenon. Finally, this paper discusses seismic activity of the active tectonics in Sichuan-Yunnan region based on the seismic tectonic background.