Deep conductivity characteristics of the Longmen Shinto, Eastern Qinghai-Tibet Plateau
青藏高原东缘龙门山逆冲构造深部电性结构特征

By processing, interpreting and inverting the magnetotelluric observation data obtained before the Wenchuan earthquake along the Luqu-Zhongjiang profile passing through Qinling Tectonic Zone, Songpan-Garzê block and Longmen Shan Mountains, as well as Sichaun Basin, this paper reveals the crust architecture above 50 km depth of the Eastern Qinghai-Tibet Plateau and Western Sichuan foreland basin and the relationship between them. The eastward pressing of Qinghai-Tibet Plateau forces the Songpan-Garzê block thrusting upon the Yangzi block, which obstructs the eastward movement of Qinghai-Tibet Plateau. The Longmen Shan is located at the joint of two blocks and it is found that there is a west-inclined low-conductivity layer in the crust at 10~20 km depth beneath the Longmen Shan Mountain, it is deduced as the deep conductivity characteristics of thrust belt structure in Longmen Shan tectonic zone. The three main faults of Maoxian-Wenchaun, Beichuan-Yingxiu and Peng-Guan of Longmen Shan fault belt dip to NW with different dip angles. The two faults of Beichuan-Yingxiu and Peng-Guan seem to converge together in the deep but they are probably separated with the Maoxian-Wenchaun fault. There are different characters between the Sichuan basin and Songpan-Garzê fold belt located at the two sides of Longmen Shan. The Sichuan basin has a thick low-resistance sedimentary layer on a stable high-resistance basement, while Songpan-Garzê block has high resisitivity cover of upper crust with continuous low resistance bed of the crust. Resulted from Songpan-Garzê block thrusting onto the Sichuan Basin stable block, Longmen Shan tectonic zone formed a three-layer geoelectrical structure with high resistance in the upper and lower part and low resistance thrust fault zone in the middle. So the research on the MT profile is important for both continent dynamics in the orogenic zone and deep mechanism of Wenchuan earthquake at Longmeshan fault zone in the east of Qinghai-Tibet plateau.