Double-difference Tomography Of Yunnan Crustal Structure

Yunnan Province is a frequent earthquake disaster area in China.Every year,the economic losses and casualties suffered by earthquakes account for a large proportion of the country.Therefore,it is necessary to increase input and research efforts for the prediction and prediction of earthquake disasters in Yunnan Province.From the view of geological structure,the geological structure of Yunnan is quite complicated.In many geological research concepts,it involves the Yunnan region.For example: Tibet Plateau Dynamics(Yunnan is on the southeastern edge of the Tibet Plateau),the South-North Seismic Belt(Yunnan is in the southern section of the structural belt),and the Sichuan-Yunnan diamond-shaped block.This paper collects the earthquake travel time information for the last ten years in Yunnan.By trying different grid precision divisions,0.5°×0.5° is determined as the best resolution.Solve the damping factor and smoothing factor used for the best inversion by using the large-scale curve method.In terms of data,after processing,28368 events were eventually selected from148,562 earthquake events.In the program operation,the absolute time data used in the joint inversion was 332,612,and the relative-time data was 4,801,551.Three-dimensional crustal velocity structure in Yunnan region was obtained.The relationship between velocity distribution and seismic events was analyzed.Combined with the geological structure background,the velocity structure characteristics and dynamic significance were discussed,providing more seismological data for the study of Yunnan region.Research indicates: Before relocation,the depth distribution of seismic events was mainly concentrated in 0-12 km,and the residuals were large in travel time.After repositioning,the distribution of seismic depths was relatively even and mainly distributed in the middle-upper crust.The lateral distribution of crustal velocity in Yunnan is more heterogeneous.As a whole,the areas in the Tibet Plateau have low-speed anomalies,while in the Shangri-La sub-blocks,high-speed anomalies are present.From a small perspective,the low-speed anomaly in the Tengchong volcanic area is more obvious.The low-velocity anomaly caused by the basin structure in the Simao area is also obvious.In the 10 km,15 km,20 km,and 30 km zones,low-speed anomalies like strips appeared,echoing the concept of the recently proposed crustal flow channel.