海洋大地电磁场的特征与测量技术

探测海洋大地电磁场可推知海底的地质构造 ,借助于先进的仪器方可实现探测目的 ,海洋环境特殊而又复杂 ,表现为对电磁信号的衰减、对设备的破坏以及测量过程难以实时监控。针对所列问题 ,从理论上分析海洋大地电磁场的特征。归纳表明 ,海水对大地电磁场具有低通特性 ;通过测取两个水平方向的电场分量和三个相互垂直的磁场分量 ,即可全面了解海底的场源分布。仪器设计方案中 ,采用专用密封舱对电路器件进行保护 ;以声控方式实现海底设备的回收 ;采集电路由嵌入式计算机、2 4位 A/ D及闪存电子盘等组成 ,信号测量过程全自动化。用新研制的仪器首次获取了我国海域的大地电磁数据 ,所测资料证实与理论预测相符。

The Characteristic and Prospecting Technology of the Marine Magnetotelluric Field

Geologic structure under the seafloor can be known by prospecting the marine magnetotelluric field. Advanced instrument is needed for this purpose. The marine environment is special and complex: it attenuates the magnetotelluric signal, destroys the equipments and makes the measurement uncontrollable. To solve these problems the characteristic of the marine magnetotelluric field is analyzed. The field distribution under the seafloor can be generally deduced by prospecting the two horizontal geoelectric components and the three geomagnetic components that are perpendicular to each other. In the design of the instruments the data collection circuit is composed of embedded computer, 24-Bit A/D and flash memory, and the signal acquisition is automatic. Special pressurized capsule is used to protect electronic devices and the instruments are reclaimed by sonar control method. By using the instruments, the magnetotelluric data have been collected for the first time in Chinese sea area and the acquired data are verified to meet the theoretics.