• 责任者：Deng Ming (School of Geophysics and Information Technology ; China University of Geosciences ; Beijing 100083 ; China) ; Wei Wenbo
• 刊名：Chinese Journal of Geophysics
• 出版年：2013
• 卷期：56(11)
• 关键词：大地电磁测深 ; telluric electromagnetic sounding ; 海洋物探 ; marine geophysical exploration ; 数据采集 ; data acquisition
• 页码：p.3610-3618
• 图表：11 illus., 28 refs.
• 分类号：1600
• issnNo：ISSN0001-5733
• isbnNo：CN11-2074/P

     Magnetotelluric data acquisition in deep water faces some difficulties, such as weak signal, serious attenuation of high frequency components, great ambient pressure on instruments, disadvantages of the bottom currents push drag and adsorption, and highly variable sea conditions which make deployment and retrieval of equipment difficult. Concerning these special issues, this work analyzes theoretically earth electromagnetic field propagation in sea and below layered media, calculates the decay ratios of the electric field to the magnetic field with different water depths, and discusses the physical factors relevant to the upward-floating speed of instruments. The working principles of the seafloor electromagnetic instrument are presented, including the signal sensor, data acquisition, voice release unit and mechanical installation parts. The signal resolution of the instrumentation systems is up to nV level with band width 10~0.3 X 10-a Hz, and the maximum working depth is 4000 m. Not long ago, equipped with the scientific research ship ＂Ocean VI＇, the magnetotelluric data are acquired for the first time at water depth about 4000 m in the Zhongsha Islands of the South China Sea. The results show that the measured electromagnetic field is consistent with theoretical calculations and the instrument has achieved the designed specifications. It demonstrates that the marine magnetotelluric technique of our country has been of completely independent intellectual property rights.