Analysis of magma chamber at the Tianchi volcano area in Changbai mountain

According to South Korean media's comments that the Tianchi volcano in Changbai Mountain is likely to erupt in coming 2 years, we carried out an MT sounding observation profile about 103 km long at Tianchi volcano area for detecting the deep electrical structures. Since the electromagnetic interference from unknown sources is very strong in the research area, we used a number of advanced data processing techniques including remote reference, Robust processing, Rhoplus analysis, impedance tensor decomposition, and a mutual approximate calculation method between apparent resistivity and phase, finally obtained high-quality and more reliable electromagnetic data in the strong interference areas. Then we analysed the two dimensional structural trend and characteristics of induction vector at Tianchi volcano area in Changbai Mountain, using NLCG inversion technique to interpret the inversion data, then compared the inversion results with previous exploration results. The results show that there is an obvious magma channel at the bottom of Tianchi volcano, the magma channel is closed in depth about 5 8 km. At the bottom of the crater, near the north direction about 7 km deep exists an obvious low resistance body, the resistivity is less than 10 Omega m, connected with the magma channel. It is inferred that it may be the developing magma chamber in shallow surface. The abnormal region is between stations C07-009 near the entrance gate of Changbai mountain and between C04-C05 station, there are two obvious nearly vertical low resistivity zones existing in the depth of about 7 similar to 17 km, connecting with below low resistance body directly, it is inferred that the low resistivity zone contains the magma. As the depth increases, the crust low resistivity anomaly bodies are widely developed in the depth of 13km to 30km, north to the position of 20 km south from Tianchi volcano, which may be the active magma chamber. Comparing the inversion results with the previous exploration results, the electrical characteristics are overall similar, but locally different.