The Significance of Crust Structure and Continental Dynamics Inferred from Receiver Functions in West Yunnan

摘要

In our study we collected the teleseismic record of 31 broadband stations and 9 PASSCAL stations in West Yunnan, as well as extracted more than a million receiver functions. Using the waveform model and stacking techniques, we calculated the earth crust thicknesses and Vp/Vs ratios below the stations and obtained 35 valid data points. At the same time, we evenly stacked the receiver functions at the same station and superimposed the two profiles' cross sections of the main tectonic units. The results show a clear difference between the crust thicknesses of different tectonic units. Because of the magma underplatting and delimanition of the lower crust in the role of deep process, the West Yunnan's crust can be divided two kinds-mafic-ultramafic and feldspathic crusts. The research also shows that the mafic-ultramafic crust corresponds to a good background of mineralization. The delamination of the lower crust is one of the leading causes for moderate to strong earthquake prone in central Yunnan. The thinner crust and high velocity ratio as well as the multimodal structure of Ps in the Tengchong volcanic area confirms existence of a deep process of the strong magma underplating. Due to the basic crust structure and nature, it is believed that the Honghe fault is a main suture of the Gondwana and Eurasia continents.