SEISMOLOGICAL STUDY ON THE CRUSTAL STRUCTURE OF TENGCHONG VOLCANO-GEOTHERMAL AREA
Wang Chunyong 1) Lou Hai 1) Wu Jianping 1) Bai Zhiming 1) Huangfu Gang 2) Qin Jiazheng 2) 1) Institute of Geophysics, China Seismological Bureau, Beijing 100081, China 2) Seismological Bureau of Yunnan Province, Kunming 650041, C
Based upon the deep seismic sounding profile conducted in the Tengchong volcano-geothermal area, a two-dimensional crustal P velocity structure is obtained by use of the finite-difference inversion and the forward travel-time fitting method. The crustal model shows that there is a low velocity abnormal body in upper crust in the Tengchong area, which may be related with volcano-geothermal activities, and two intracrustal faults (the Longling-Ruili fault and Tengchong fault) exist on the profile, where the Tengchong fault may cut through the Moho discontinuity. Meanwhile, in view of teleseismic data recorded by the mobile network, S-wave velocity structures beneath the Rehai-Retian region of the Tengchong area show the low S-wave velocity anomaly in upper crust. The authors discuss the genesis of Tengchong volcano based on the deep crustal structure. The crust of Tengchong volcano-geothermal area is characterized by low P-wave and S-wave velocity, low resistivity, high heat-flow value and low Q value. There is also a feature of low P-wave velocity in the upper mantle. For this information, it can be induced that the magma in the crust is derived from the upper mantle, and the low velocity abnormal in upper crust in the Tengchong area may be related to the differentiation of magma. Like many other active volcanoes on the earth, the Tengchong volcano is close to an active plate boundary and belongs to ″plate boundary″ volcano.