Abstract: Observations of magnetotellurics have been carried out at 46 sites along five profiles in shape of umbrella and along a northwest direction profile in the Tianchi volcano area and its vicinity in Changbaishan Mountain northeast China. There are 61 sites including 15 sites which were done in early time. The data processing has been made by using the Robust technique. High S/N ratio resistivity and phase have been obtained. The Bahr’s impedance tensor decomposition was applied for eliminating distortion. The induction arrow vector was calculated. The two-dimensional inversion method (RRI) is used for data interpretation. The results show that (1)There is low resistivity correspondence Tianchi water pool near the surface. There are four low resistivity zones corresponding to Jingjiang hot spring, Julongquan hot spring, gate of mountain and its vicinity and Shuangmu peak at the depth of above 5 km.(2)Low resistivity body at the depth about 12km is located the carter and its north and east area. The body is 20 to 30km thick and 15～25km wide. It is inferred that this anomaly body may be a magma chamber. (3)The crustal electric conductivity structure has obvious difference in direction of SN in this area. There is a high resistivity zone in the south part and low resistivity zone in the north part.

Key words: Magnetotelluric, Apparent resistivity, Induction arrow vector, Low resistivity body, Magma chamber

摘要： 在长白山火山区及其附近,沿5条伞状测线和1条北西向测线进行了61个大地电磁测深点的观测。用Robust等方法对观测资料进行了处理;应用阻抗张量分解方法消除了局部不均匀体的影响;计算了反映地下横向不均匀性的地磁感应矢量。利用RRI二维自动反演等技术对资料进行了解释。结果表明:在近地表存在低阻体,并分别与长白山天池水体、聚龙泉温泉、锦江温泉及长白山山门附近的地下水相对应。在长白山天池及其以北和以东地区,约12km深处存在电阻率很低的地质体,电阻率为10到几十Ω·m,可能是地壳岩浆囊。在测区范围内,地壳电性结构在南北方向存在着明显的横向变化,而东西方向相对均匀,变化比较平缓。

关键词: 大地电磁测深, 视电阻率, 磁感应矢量, 低阻体, 岩浆囊