Seismicity And Crustal Structure In Tengchong And Its Adjacent

In this paper,we collected 187 teleseismic waveform data from 26 portable seismographic stations and 4 fixed stations in Tengchong and surrounding area of Yunnan,during 2 September 2011 to 6 January 2014,P receiver functions were calculated by the time domain iterative deconvolution technique using Gauss parameter of 1.0 and 2.5,respectively.Selecting 3408 receiver functions with high signal-noise ratio from them,and choosing a simple initial model to invert each event twice.The Bootstrap resampling technology is used to count and analyze velocity structures,the fine S-velocity structures in the crust and upper mantle beneath 30 stations were obtained finally.And obtaining 2769 relocation seismic events located in Tengchong area during 1 January 2009 to 30 June 2015 with a double-difference earthquake location algorithm.Then,based on S-velocity structure and relocated results,discussing the seismicity and crustal structure of Tengchong and adjacent areas.The main conclusions:1?Inverting receiver functions with different Gauss parameters twice can effectively reduce the dependence of inversion results on the initial model,and reduce the non uniqueness of the solution.Using the Bootstrap technique to analyze velocity structures and return the most reliable velocity result,can overcome the shortcomings of the superimposed receiver functions,and obtain more precise and reliable crustal structure features.2?The Moho depth in Tengchong area is 34?40km,and the change is relatively flat.Near the surface there is the 3?5km deposition,the Baoshan basin is 8km.The high velocity structure at 4-12km depth in the volcanic area may be less volatile high-density remnants or cooled intrusions in the early volcanic eruption.3?Significant low velocity zones at 14?34km depth below Tengchong town-Chengzishan,at 18?30km depth below the confluence of Nu River fault and Longling-Ruili fault,and at 20?36km depth below Mingguang area in Tengchong's north,respectively,probably represent magma chambers in the crust.They are connected at 24km depth,may originate from the same magma source.4?Between January 2009 and June 2015,the seismicity is relatively calm in Tengchong volcano region,tectonic earthquakes are active around the vocalno area,is characterized of small magnitude and shallow focal depth.The seismic activity is very active at Sudian fault,Yingjiang fault,the southern segment of Nu River fault,Longling-Ruili fault and around the Baoshan basin.5?The seismicity in the south of the volcanic area is stronger than that in the northern region,which may be related to the geothermal activity in Hot sea and magmatic activity in the south.The small earthquake swarms around Tengchong town and Chengzishan may belong to the magma-impact type caused by magmatic activities in the crust.6?The low velocity column in the upper mantle of Baoshan may be a channel for hot material upwelling from the mantle.Longchuan River fault,Tengchong fault,Yingjiang fault,Nu River fault,Longling-Ruili fault and their junction may be transmission channels between crust and the deep magma source.The mantle material from the upper mantle of Baoshan to the lower crust,along these deep faults to the crust of Tengchong area,form molten or semi molten chambers after mixing with crustal material.