Continental-Scale Investigation of Underlying Electrical Conductivity Structure in Mainland China Using Geomagnetic Data

Abstract

The magnetotelluric method has been used to fully study regional electrical conductivity structures in different areas in mainland China; however, there is a lack of overall understanding of the electrical structure distribution. A novel insight for the study of continental-scale underlying conductivity structures was proposed in this work via geomagnetic data recorded by permanent stations. To study the underlying electrical structure distribution in mainland China, we mapped the conductors and resistors at a depth range of 4–100 km beneath mainland China using Parkinson vectors through magnetic transfer function. Three-component geomagnetic data within a low artificial disturbance period (local time 23:00–05:00) from 98 stations in 2019 were collected and processed to derive Parkinson vectors in the frequency band of 0.001–0.5 Hz. The distribution of subsurface electrical structures at distinct depths was constructed using corresponding frequency through the skin depth. We compare the consistent results herein with previous magnetotelluric studies, which indicated the reliability of our method. Combining previous multiple geophysical inversion results, we found that large-scale plastic bodies are distributed along the east of the Qinghai-Tibet Plateau and extend to the west of Yunnan. In central mainland China, the areas are mainly highly resistive, indicating that the structures are overall rigid. In north China, there exist high-low-high-low conductive structures from west to east. The separate high- and low-conductive electrical bodies in the North China Craton provide geophysical evidence that the Craton is composed of multiple blocks. The distributions of the underlying electrical structures in this work can provide an overall perspective for studying tectonic evolution and geodynamics in mainland China.