Tengchong Volcanic Area Of ​​crust-mantle Dimensional S-wave Velocity Structure And Magma Chambers Detection

In this study, with the3-component teleseismic waveform date recorded by9broadband stations (QK,MZ,MIZ,TC,SB,RH,RS,XH,CZS) of the Digital Seismic Network in Tengchong volcano area (Jun.2007-Dec.2011), we first use the linear inversion method of receiver functions (Ammon,1990) to investigate the lateral heterogeneity and the S-wave velocity structure of the crust and upper mantle in Tengchong volcano area respectively. Furthermore, based of the anomaly areas of the S-wave velocity structure obtained from receiver function inversion, the locations and shapes of the magma chambers in Tengchong volcano area are described. In this paper, firstly, we research the problem about how to build a more reasonable initial model for receiver function linear inversion by theoretic numerical simulation. Secondly, we consider the variation characteristic changing with different azimuths and the horizontal sweeping ranges of receiver function, and divide the teleseismic waveform dates into different groups according to a certain ranges of back azimuths and epicentral distances. Thirdly, the effective constraint parameters of receiver function inversion in different groups are estimated by using the H-K stacking method and other method. Finally our results show the higher spatial resolution than former studies in the same area.The results of this study are as follows:S-wave velocity fine structures of the same stations achieved by the receiver function inversion in different back azimuths and epicentral distances show obvious lateral heterogeneity. So if the structure of the crust and upper mantle is complicated, it is essential to study the teleseismic waveform date recorded by the same station according to the variation characteristic changing with different back azimuths and the horizontal sweeping ranges of receiver function.The structures of the crust and upper mantle are very complicated and show obvious lateral heterogeneity in Tengchong volcano area. The S-wave low velocity abnormal zones and high velocity abnormal zones exist at some depths obviously. And because of the influence of complicated geologic structure, the locations of the abnormal zones vary largely. The S-wave low velocity abnormal zones located to the local areas may be related to the existent magma chambers.There exist4magma chambers in Tengchong volcano area and their locations and depths are:between TC and RH, about9-12km; the east of MZ, about11-18km; between TC and SB, about16-20km; the east of XH and the south of CZS, about8-11km.To confirm the activity and the heat flow channel of magma chambers in Tengchong volcano area, more researches combined with other methods are needed.