关键词: 首都圈, 极低频电磁台网, 大地电磁, 电性结构

Abstract: Carrying out the detection of the underground background electric structure in the CSELF network area/station is of great significance to play its role in the study of earthquake prediction and forecast. A short magnetotelluric (MT) profile was deployed at each station of the CSELF network in the Capital Circle region and a total of 60 broadband MT sites was collected using ADU-07e systems. All the time series data were processed to MT transfer functions and analyzed in detail with different impedance tensor decomposed methods. On the one hand, one-dimensional (1D) subsurface electrical resistivity structures at each station and MT site were derived from 1D MT inversion. On the other hand, we also imaged the electric structures along the short MT profile by 2D inversion at each station. In addition, the 3D inversion of 15 stations was performed to produce a 3-D crustal electrical resistivity model for the entire network. The combined results show: the crustal electrical structures are mainly characterized by high resistivity beneath the Yinshan-Yanshan orogenic belt in the north of North China, the Taihangshan area in the middle, the Jiao-Liao block in the east, while the North China Plain and Shanxi depression areas have relatively lower resistivity in the crust; There are obvious electrical resistivity difference on both sides of the gravity gradient of Taihang Mountain and the Tanlu fault zone, which indicates they could be manifested as an electric structure boundary zone, respectively. The electric structure characteristics of the entire network area are related to the regional geological structure and seismic activity to some extent. Implementing the detection of the underground electrical resistivity structure in the CSELF network of the Capital Circle region will provide important foundations for the researches on the regional seismogenic, the generation mechanism of seismic electromagnetic anomaly signals, and earthquake prediction and forecast.

Key words: Capital Circle Region, CSELF network, magnetotelluric, electric structure